The “Science” behind “Bonking”

It has long been “common knowledge” that endurance exercise is fuel-limited. This is most familiar to general populations as a commonly observed limitation on foot races that says that you will run out of energy, “hit the wall,” or “bonk” at around 20 miles. For common race distances, the effect is most frequently observed in the marathon (26.2 miles). The standard explanation is that you can only store a limited amount of carbohydrate fuel in the form of muscle and liver glycogen, and that you will bonk when the supplies run out. Management of the “problem” is variously accomplished by “carb-loading” before the race to super-fill (“super-compensate”) the glycogen stores, and by various refueling strategies during the race (which support a large industry that provides special drinks, gels, bars, and the like).

At the same time, there is a growing body of evidence that there is no reason to depend on stored carbohydrate fuel which is limited in quantity if you can mobilize your fat stores as a source of fuel. The problem seems to be that anyone who is accustomed (adapted) to eating a high-carbohydrate diet tends to preferentially burn carbohydrates as fuel and does not utilize the energy available from fat in a way that spares carbohydrate use during endurance exercise. These are the so-called “sugar burners” as compared to “fat burners.”

There are a few possible strategies to enhance fat burning. The most commonly discussed strategy is to train at slower, more aerobic paces, to train the body to optimize using fat as fuel. This approach was discussed by Alan Couzens. Although carbohydrate was also restricted, the main emphasis was on low intensity training, with pretty amazing results from the combined approach.

A second strategy, perhaps even simpler, is to change to a low-carbohydrate diet. Maintaining glycogen supplies in a partially depleted state encourages the development of aerobic apparatus via the action of AMP Kinase (increased mitochondria and associated fat burning enzymes such as carnitine palmitoyltransferase, necessary to help transport fatty acids across the mitochondrial membrane). People with deficiencies of carnitine palmitoyltransferase are unable to utilize fat for fuel efficiently, and can even suffer damaged muscles and rhabdomyelosis resulting in kidney failure. There is also evidence that people suffering from obesity and diabetes may have impaired mitochondrial function, which inhibits their fat burning and at least partially explains the origins of their condition. Similarly, a deficiency of carnitine can result in impaired mitochondrial function and even lead to symptoms of metabolic syndrome.

There is an adaptation period of a few weeks to lowering carbohydrate intake during which the appropriate metabolic pathways and aerobic enzymes and cofactors are up-regulated to better utilize fat as a substrate, allowing blood glucose levels during exercise to be more easily maintained. As Alan Couzens explains, lower carb intake should result in a 20% increase in fat burning in a few weeks. Numerous scientific studies bear this out. A recent study, for example, concludes that a high fat diet increased the rate of whole-body and muscle fat oxidation while reducing the rate of muscle glycogenolysis during submaximal exercise, even after restoring high carbohydrate intake. In this study, a high fat diet was followed for up to two weeks (which we know is just long enough to see significant adaptation), during which usual training was followed. A high carbohydrate diet was restored for the last few days along with a taper before racing. The athletes were able to maintain the increased fat oxidation even after reinstating high carbohydrate intake.

There is at least one supplement (Vespa) which is alleged to improve fat-burning during exercise. There is also some evidence that, all else being equal, the athlete that has the most efficient fat-burning ability can consistently beat the athlete with the higher raw power output (higher VO_{2 max}) in endurance competition.

An article in Running Times last year discussed the strategy of carb cutting to increase endurance, though the article suggests mainly forgoing carb supplementation on training runs, not going low carb in the training diet. The Ethiopian runners again are cited as evidence that a high carb diet is necessary to fuel runs, and there is speculation that they are somehow training themselves not to use glycogen as the predominant fuel by not consuming carbs while actually training. This conclusion seems unlikely to us, since it is well known that exercise causes an increase in blood sugar (due to action of epinephrine and glucagon), effectively mimicking the result of taking in supplemental carbohydrate while exercising. A marathoner does not “hit the wall” until they have run ~20 miles at race pace anyway, a condition not likely encountered during routine training runs for most of us.

Despite all that is known about “the wall,” people persist in believing that a high carbohydrate diet is necessary if you hope to be a good runner. A high carbohydrate diet may work well for Ethiopian runners, who are known for running prodigious mileage and training three times per day. At this training intensity, we seriously doubt their glycogen stores are ever completely full, and they may effectively be training in a perpetually glycogen depleted state, which would upregulate the same enzyme systems that occurs in the low carbohydrate condition. Perhaps what they are mainly training is the rapid replenishment of glycogen stores. However, for most of us amateur or older runners, we’re only fooling ourselves if we think we need to fuel exercise with a high carb diet. David does quite well on very minimal carbs (less than 50 g/day), while Cynthia prefers closer to 100 g/day. Since we generally only run once per day and even then usually less than 10 miles, there is no reason to consume any more carbs to fuel our exercise habits.

David has been a low-carb runner for more than two years now, keeping carbohydrate consumption low before, during, and after endurance exercise. While he won’t brag about his speed and has no plans to challenge any course records, he consistently finds that he has even energy levels and rapid post-event recovery with minimal muscle aches and pains. Fat fueling works for him! However, until very recently, while he refueled less often than is typical, he did routinely refuel using protein and fat for any event of more than 3–4 hours.

He was prompted to revisit the issue when he heard about a recent study (“Metabolic Factors Limiting Performance in Marathon Runners”) by Ben Rapoport when he had his fifteen minutes of fame on NPR in October 2010. Ben was attempting to model bonking in the context of marathon runners. David subsequently exchanged e-mail with Ben whose initial reaction was to interpret David’s personal experience as simply confirming Ben’s model, arguing that fat-fueling works, and that you don’t bonk as long as you run sufficiently slowly. David pointed out some flaws in Ben’s interpretation of the scientific data he analyzed and challenged him to define a performance that David might personally be able to achieve that he might consider sufficient to disprove his model, but he never responded to the challenge. We summarize here both a couple of the criticisms of Ben’s model and analysis and some more recent personal experience and experiments.

A key part of the experimental data that Ben used in building his model came from Romijn AJ, Coyle EF, Sidossis LS, Gastaldelli A, Horowitz JF, et al. (1993) “Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration,” Am J Physiol 265: E380–E391. That paper shows (in Fig. 8) the relative amount of particular substrates which are used in short-term exercise at three different intensities. The subject’s dietary habits were not identified, and any changes that might take place over more than a few minutes were ignored. The data show that more intense efforts use primarily muscle glycogen as fuel. They do not show the pathways that feed the muscle glycogen. Glycogen and glucose are rapidly interconverted, and over longer periods of exercise, new supplies of glucose are made by the liver. The liver, in turn, is capable of using any available fuel source via gluconeogenesis to keep blood glucose levels up. These fuel sources include ingested carbohydrates, protein, and fat as well as lactate, glycerol from liver and adipose tissue fat stores, and even body protein stores such as in muscle tissue. Which source predominates depends on availability. Some of the necessary up- and down-regulation of different metabolic pathways can take place on a short time scale to respond to instantaneous demand for fuel from the muscles and other bodily functions. However, there are also some key adjustments that respond more to average demand and supply to deal with changing diet, exercise demand, starvation, and the like, and these are events that tend to have time constants measured in days or weeks, not minutes or hours. The adaptation processes may be numerous and complex (or at least, we fully admit that we don’t understand all of them) and likely include adaptations in the skeletal muscles as well as in the liver. However, we think it is clear that the data extracted from Romijn do not actually show the underlying consumed fuel source for various levels of endurance exercise, and the data cannot reasonably be extrapolated to model and predict bonking.

One factor which Ben cites in favor of the importance of carbohydrate and fueling is the relative stoichiometry of oxygen consumption for each substrate. He states that carbohydrate oxidation typically generates approximately 120 kcal per mole of respired oxygen, whereas fatty acid oxidation typically generates only approximately 100 kcal per mole of oxygen. We would argue that this, while probably correct, is irrelevant in that the difference is relatively small, and the availability of oxygen is never a limiting factor at a typical aerobic marathon pace. There is always an excess of oxygen available. In any case, regardless of the underlying fuel used to generate blood glucose/glycogen, the immediate muscle activity (except for very short term bursts of power) is fueled by glucose.

Notwithstanding the possible flaws, Ben’s model does make predictions as to whether one is likely to bonk in a marathon. In particular, he has provided a calculator for the marathon. Putting in the best estimates David has for his personal situation, the calculator predicts that he should not bonk for finishing times over about 3 hrs. Since he can only sustain a 3-hour marathon pace for about 1 mile or so, he may never be able to really challenge the model experimentally using himself as a test subject.

However, David was inspired to test his need for refueling during running, and now has a significant number of test results that, if not sufficient to explicitly challenge Ben’s model, are at least startling to many people. For some time now, David routinely runs training runs of up to 4–5 hrs without refueling (water alone). This is still true when he runs with his son at faster speeds who typically chooses to refuel using at least a couple of energy bars or gels. David first pushed the envelope a bit on what was supposed to be a planned 18-mile run that stretched to about 26 miles when the route was blocked by an impassable rain-swollen river crossing. That run extended over about 7 hours including some significant rest breaks, so it was not at a strenuous pace, although it did include some significant elevation change. David consumed only water. The next experience was a 50K (31-mile), mostly flat run, again at a very modest pace, finishing in 6:50, again on water alone. Two weeks later, he completed a much more strenuous 50K on rough rocky trails with about 6000 ft of elevation gain (and loss) in 7:28 on water alone. In all three of these runs, David started with a breakfast of a two-egg cheese omelet and bacon about two hours beforehand. He felt some minor hunger around normal lunch time, but otherwise did not experience any significant fluctuations in energy level, and he certainly did not bonk. His overall weight was down about 3–4 lbs at the end of the day compared to the beginning, but looking at beginning-of-day weights across several days, any weight change was pretty much lost in the noise. Of course, it only takes about a pound of fat to fuel a 50K run, anyway. Another week later David ran yet another moderately hilly 50K event which was slower (8:04) due to snowy trail conditions. Due to a late start (10 am), he chose to eat a little at around the 6-hour mark, mostly because it was a long time since breakfast. However, the ability to do three 50K runs in four weekends, certainly confirms that post-event recovery was rapid.

So what’s the take-away message from all this? It’s interesting to compare our reaction and the experiments that David decided to try to others. Greg Crowther also blogged on Ben’s article. Greg’s big concern was inter- and intra-personal variability, and he questioned the validity of extrapolating from some sort of average measurement of performance to the needs of one individual on one particular day. He didn’t ask (as we did) if too many runners are needlessly afraid of bonking but rather, “if ingesting extra carbohydrates before and during a marathon might help you avoid ‘hitting the wall,’ why wouldn’t you do it? Especially after investing all of that time and effort in training, traveling to the race, etc.?” Hey, we’ll even go further: if ingesting fuel (whether carbohydrate, protein, or fat) during a race might help you maintain a faster pace for whatever reason and for whatever limited portion of the race, even it’s just a placebo effect (or tricking your Central Governor), then by all means go for it! But we also stand by our basic conclusions that (1) carbohydrates are simply not necessary before, during, or after endurance exercise, (2) they’re probably not even particularly beneficial, at least if you are suitably adapted to efficient fat-burning (and may be harmful to your long-term health) and not logging very high miles at high intensity, and (3) unless you’re able and motivated to run, say, an entire marathon at a high percentage of your VO_{2 max}, consuming much of any food immediately before, during, or after the event is entirely optional. Moreover, there may be some benefit to having the stomach completely empty while racing, in order to avoid stomach upset, intestinal discomfort/diarrhea or nausea when running at high intensity. (David does continue to believe in significant protein consumption sometime in the 12 hours or so following strenuous exercise as an aid to muscle repair and recovery, but the timing of even that refueling does not appear to be nearly as critical as some authors suggest.) David will probably resume modest consumption of fat and protein on longer events, just because he’s not big on skipping meals entirely, anyway, but it’s reassuring to know that he can easily keep going without any fuel if for any reason he needs to.

Rio Del Lago 100 Mile—A DNF

If you’ve read my previous entry about all my injuries and travails in the past year, you might think it a silly thing to sign up for a 100-miler, and you’d probably be right. But life is short, and sometimes you just have to go for something, even if wiser heads would counsel you otherwise. This attempt was not successful, and not even all that impressive as a first attempt, but has lots of lessons that might be of interest to some.

Prologue
I remember running a series of marathons in the 1980s and hearing about the first running of Western States 100. I was awe-inspired at the difficulty and epic-ness of such a journey and fantasized about someday trying it myself. Life got in the way of such aspirations, but ever since, it’s been in the back of my mind that I wanted to do a 100-miler. I’m now also interested in exercise physiology, and diet and exercise effects on health, and am intrigued by how the body manages energy, so experiencing the highs and lows of energy in ultra events is fascinating to me. So kind of on the spur of the moment, I decided to give Rio del Lago a try.

Now tackling a 100-miler for someone like me is no easy matter. In addition to having a bum and finicky foot, I’m not particularly fast, robust, or tolerant of heat, and my feet get easily blistered (OK, I’m old, frail, slow and whiny, especially if it’s over 70º F). I consulted with Don and Gillian http://www.zombierunner.com/ about strategy and was told to 1) get lots of sleep prior to the race, 2) be comfortable with night running, 3) keep the pace down, walking the hills, and 4) resolve not to give up. Don warned me it would be warm, but I was still glowing from the unseasonable cold front that had just gone through a few days prior. The pace chart indicated that the paces necessary to complete the race are not even that fast—for more than half the race, an 18-minute pace is good enough to make the cutoff times. I felt pretty confident I could manage those factors and that pace and decided to go for it. David agreed to be my crew and pacer if needed, even though his Achilles was not really up to running long distances, but he felt that with the pace I’d be keeping late in the race, it would likely be easy enough that he could pace me without aggravating his injury.

Since I signed up on the last possible day (Thursday) before the race, I didn’t have a lot of time for the reality to sink into my head. As a consequence, Thursday night I barely slept—I dutifully lay there inviting sleep, but my mind had other ideas, namely processing the shock of actually trying to “run” 100 miles (Ok, we all know it’s not all running, but lots of hiking or walking too). This insomnia was unusual and was the first strategic error of many. We drove up on Friday afternoon after frantically trying (and failing) to find our night-running lights, arriving late for the check-in, and then had to go shopping for flashlights. I was such a wreck that my blood pressure and heart rate were abnormally high at the check-in. Of course they were—I was about to do a really challenging and stupid thing, I was terrified! (But at least my valves checked out healthy.) We found several cheap LED flashlights that seemed suitable for the night running portion in a hardware store and proceeded to dinner and finish preparations for the morrow’s race. Dinner was at Denny’s (I had tilapia and mashed potatoes—that and some yogurt with fruit and granola was the extent of my carb loading on Friday). We got my breakfast for the next morning (eggs, sausage, hash-browns and pancakes) as take-out so we would be all set to go.
After dinner, it was time for a shower and foot preparations. I opted for kinesio tape around the balls and heels of each foot and a couple of toes each (but no tincture of benzoin). The middle toe on my left foot seems to blister without fail of late and I was most worried about it, so I taped it and the adjoining one for good measure, and did the same for the right foot. We were in bed by 9:30 and I fell asleep quickly, being already sleep deprived, only to wake up at midnight unable to fall asleep again. Not only could I not sleep, I began to get a nagging headache that I could not ignore. By 4 AM I started in on ibuprofen, and by 5 AM when I was supposed to be eating my hearty breakfast, I was nauseous and unable to eat more than a couple of bites of egg and hashbrowns. This was unpleasant, but not necessarily terrible, since I am used to running fasted or having eaten little. I would have to make do with the Gu in my bottle for fuel (and a few gels) until the aid stations.

A blur of one of the fast runners

The Race
Standing around before the start, I said hello to Stacey and Misty (they looked so cute in their race outfits) and looked around for other people I knew. But conversation would have to wait because in moments we were out the door with our flashlights in the pre-dawn gloom. The first section was nice and cool, and easy with rolling hills on wide trails. I tried to walk the hills, but occasionally ran them anyway since they were shallow and I was way too excited to slow down. It began to warm up as soon as the sun peeked over the other side of Folsom Lake, and I realized then that it was indeed going to be HOT, not just warm. My T-shirt came off and I decided to pick up the pace a little to get as far as possible before being reduced to melting slug pace. This worked for the first few miles, and I ran with a few other runners, trying to navigate the poorly marked section (someone had been removing ribbons). The Twin Rocks section proved difficult—stepping up and over boulders and roots, then back down, never too much elevation change, but tricky footing nonetheless. I ran with Tracy Youngstedt for a while and commented that I knew I was supposed to get through the first third of the race without doing anything stupid (according to Olga), this after nearly doing a face plant from kicking a root. Finally the Twin Rocks section was finished and I finally saw David for the first time at Rattlesnake Bar (mile 11.9). He offered me breakfast, and I took the rest of the eggs and hash-browns in a cup, and attempted to eat them during walking breaks (of course after dropping the cup and spilling the food a couple of times, didn’t manage to eat all that much). On past the power plant and toward Cardiac, all seemed well until the trail began to really heat up in the strengthening sun. At one point I came across a stream and just stared at it incredulous—coolness. I untied by T-shirt, dunked it in the water and draped it across my shoulders—instant relief! At another creek crossing, I refreshed the wetting and so was kept somewhat cool until reaching the aid station at the foot of Cardiac (where ice and Coke was provided). It was now full blown HOT and all I could do was trudge forward toward the flume trail, chewing on bits of ice. The flume provided more shirt wetting and relief, and I managed to jog a bit now and then toward Maidu and then Auburn Dam Overlook. At Maidu (mile 21.2), the aid station volunteer gave me a juicy PB & J sandwich, of which I again only managed to eat half (though it was delicious).

Maidu aid station and the flume trail

I reached Auburn Dam Overlook (mile 22.7) well within the cutoff time (well, 40 minutes to spare), got weighed and was maintaining weight ok, so presumably hydration was ok. David handed me V8 juice in my water bottle, well diluted with ice. I took coke with ice as well, wetted my T shirt again, and proceeded down what I expected to be an easy bit of downhill to No Hands Bridge aid station. Unfortunately, this stretch of trail was not all downhill, not easy, and HOT. There are numerous uphills which appear as innocent little jiggles on the course profile. I was amazed to see both Jean Pommier and Sean Lang already returning from Cool at this stage! They looked so light and fresh trotting up the hill to Auburn Dam Overlook. I set my Garmin to re-charging on this section and so could not see how long it was taking, but it seemed to take forever even though it was net downhill (800 feet).

trotting towards Auburn Dam Overlook

I finally dragged myself into No-Hands Bridge aid station (mile 26.7), barely able to muster a trot on level ground over the bridge in the oppressive heat. One fellow runner sitting at the aid station looked to be suffering from heat exhaustion, as he was trembling and pale and limp. The sympathetic volunteers loaded me up with ice—in my hat, bra and bandana—for the long climb up K2. I got more iced V8 from David and took some grilled cheese sandwich pieces (which I again did not manage to eat). I was prepared for this steep climb and its numerous false summits, and it wasn’t too bad. There was some shade at least and my ice kept me cool enough to keep moving, but slowly. I did pass my first “conquest” at this stage—a man who had been nauseous for the last ten miles, he said. He described himself as an “urban polar bear” and bemoaned the fierce heat radiating up from the trail (if only the clouds from the few days prior had remained), with which I agreed wholeheartedly. I was still moving ok, though mostly just at a walk towards Cool, and passed S Baboo on his return from Cool, all smiling and making it look easy. At this point, my stomach too was beginning to feel funny. There was a suspicious pain and when I pushed on it I realized that my entire belly was distended with liquid—I wasn’t processing fluids anymore! Trouble seemed to be brewing.

unknown runner coming across No Hands Bridge

Finally at Cool (mile 29.8), I switched to ice water only and sucked it down like a fiend. I’ve never experienced thirst like that, and could not get enough water. I also got this idea in my head that I might be getting too much potassium from the V8 juice and was worried about developing a heart arrhythmia (don’t know where this idea came from but it was probably wrong). I tried again to eat some solid foods when David gave me a cup full of “beef bowl” (beef, broth and rice that we brought with us) which I badly needed for fuel. I left this aid station nursing my cup of coke and ice (mostly ice), then drinking ice water. There was very little shade, and at one point I just sat down on the trail in the shade of a tree for a moment. I believed I had plenty of time and just needed to get through the loop without mishap, and hopefully things would be cooling off by the time I had to head back to the hot canyon. There was one other runner that I played leap frog with here. He got ahead of me after the aid station, because he ran while I walked (lazy me), then when I was getting desperate for more water, I ran and passed him again. Finally refilled with ice water at the Knickerbocker Hill aid station (mile 35.3), I ran briefly on the 1.5 mile road section, but just couldn’t bring myself to keep running, even though there was a nice breeze by now and it was plainly cooling off. I practiced a power walk instead and was pleased that it wasn’t too bad.

Refilling with food, ice and water at Cool again (mile 36.9), I left at a leisurely pace crunching on ice, drinking coke and slurping a small cup of beef bowl (only had two hands or I’d have carried more food!), then upon reaching the downhill, trotted along as expeditiously as possible, watching for the trail markers, afraid I would miss the turn like one runner I saw coming the wrong direction down K2. This section was relatively fast and easy, but upon reaching the No-Hands Bridge aid station (mile 40.4) realized that I had run out of buffer time and was going to have to run my tail off back up to Auburn Dam Overlook, 4 miles with an 800 foot climb in a little over an hour! While this section was my least favorite on the way out, it became my favorite on the return trip. Even though it was a long climb, it was broken by brief downhill segments (uphill on the way out), and much of it was of a runnable grade, plus it was cooling off by now. I pulled into Auburn Dam Overlook aid station (mile 44.3) as the volunteer was yelling a three minute warning at me, quickly weighed myself (only 2 pounds down), then had to leave immediately for Maidu. I followed the flume trail feeling good, jogging and passing a couple of other runners, then met David again for another refill on food at Maidu (mile 45.8). This time he added coconut milk with chicken broth to my beef/rice bowl, and the feeling of actual calories going down my throat was amazing. To this point (45 miles) I had eaten a half PB&J sandwich, 3 gels, a few bites of egg leftover from breakfast, 2 bites of grilled cheese, a couple bottles of Gu, 3 bottles of V8 juice, and several small cups of Coke, and I had been on my feet for 13 hours! I guess I was starting to get tired and hungry. David offered to pace me, but I told him I felt surprisingly good and declined his offer (this would turn out to be a mistake). He asked me if I wanted to take a dry T-shirt and I said I was still hot, but at least I didn’t need to wet the T-shirt anymore!

View of American River Canyon

Off along the flume trail again, I turned down the wrong trail (getting behind again) and had to backtrack. It was now becoming dark and the flashlights were necessary, and it was really hard to see the marking ribbons. Going down Cardiac in the dark was also much, much harder than the climb up had been. I couldn’t see far enough ahead on the twisting rooty trail to have any confidence in my footing, so inched down slowly like an old lady (which I guess I am!). There were numerous trail junctions that I hadn’t even noticed on the way up, and each required careful searching for ribbons, which took additional time. At the bottom, all I wanted was to sit and doze for a few minutes as the effects of the sleep deprivation suddenly hit me. But when I got there, the trail sweepers were waiting for me (last again!), and I had to keep moving. I tried to keep the pace up, jogging along occasionally, but the blisters on my feet, which until now had not really been much of a factor, suddenly became noticeable. I was trying to jog along on this overgrown trail, which I could see only poorly with my ghostly LED illumination, when I stumbled on a few rocks and several blisters tore open at once on my right foot. The pain was excruciating, and I suddenly realized for the first time in the whole race that I might not be able to finish, might not want to finish. The pain slowly faded, but now I was afraid of the slightest misstep setting off more blister pain. My jogging became more intermittent. Still, I managed to pass a couple of other runners and tried to keep my pace up, but this section seemed interminable, even though I had been looking forward to it as one of the more runnable sections from before. Finally after passing the power plant again, I encountered David coming in from Rattlesnake bar AS to find me. I had lost track of time, because my Garmin power had run out again and since I neglected to charge it again, it shut off. I didn’t realize it until he told me, but I was too far behind schedule and would not be able to make the cutoff time at Rattlesnake Bar (mile 55) and continue past the AS to finish the race.

Afterwards
I wasn’t too disappointed to have to quit because exhaustion and pain have a way of changing one’s priorities. We left Rattlesnake Bar aid station and returned to Cavitt School for some food (all they had that seemed remotely appetizing was watermelon) and a real bathroom (I was tired of peeing in the bushes). Then David just wanted to get us home. The drive home was uneventful and I slept pretty hard. Upon arriving home, I needed to use the bathroom as soon as I got out of the car, and discovered what exploding diarrhea was all about (just in time to the bathroom)! I don’t know what caused the diarrhea—whether it was a side effect of heat exhaustion and dehydration or a sign that my stomach and intestines just couldn’t absorb fluids as fast as I shoved them in. Perhaps the fiber and minerals in the V8 juice were the problem. A comment from one of the AS volunteers seemed to presage the event, as she pointed out that tomato juice gives her diarrhea. Finally home and cleaned up a bit at 3 AM, I had to eat some real food and opted for a large chicken breast poached in the rest of the coconut milk and chicken broth remaining from our supplies. It was delicious and nourishing and I finally slept, with my burning feet on icepacks.

The next morning, my weight was down a full pound and a half (it was down a pound before eating and drinking more before sleep). The real problem was my blistered foot. Only one foot was in a bad way, though I had taped them both the same. It was hot and inflamed and I finally resorted to just soaking both feet in cool water with a little salt and ice added—for TWO days! The blisters were two layers of skin deep, which is more than I usually experience. The plantar fasciitis as expected was not particularly noticeable. I discovered I had chafing over much of my body, wherever I had neglected to put Vaseline. So I had odd scabs on much of my back from the chafing from the water bottle and clothing. Finally three days after the event, my weight had spiked up two pounds, before the compensatory fluid retention passed. Once my weight declined again, I had lost a full pound of body weight, presumably fat, which stayed off. (For some reason, I’ve continued to lose weight in the aftermath and am now down to 138, a new low since going “low carb.”) However, I don’t recommend running 50 or 100 miles just to lose weight!

Postmortem
I now understand the addictive quality of 100-mile races. The lower key pacing throughout (for us back-of-the-pack-ers at least) was just fun and low stress. I only felt I was close to running hard on one segment (making it back to Auburn Dam Overlook)—the rest was easy going (with heart rate at least 10 bpm below my usual race paces). Instead of a race, it felt like an epic adventure, or a trail party. I always think about Aragorn and company chasing after the Orcs and captured hobbits in ultra events. It always feels like a challenge and an adventure, 100-milers even more so. So even though it was much hotter than I hoped, I had a great time.

Running in the heat is still a huge weakness for me, and even though I’m a lot lighter than I used to be, that problem remains. See the Science of Sport posts for some interesting discussion of the effects of heat on performance. Basically, your brain controls how much muscle gets activated when exercising: it senses the heat accumulation and sets the pace accordingly so that your core temperature doesn’t exceed ~40 C (~102º F). Slender, lightweight people can cool themselves much more efficiently, and accumulate heat more slowly, and so can perform at a higher intensity in the heat than heavier people. I guess I’m still too well insulated to perform well in the heat! It shouldn’t have been a deciding factor in this race, however—if I had managed all the other factors better, I could have made all the cutoffs and finished despite the slower pace. Someone like David with a BMI of 25 still performs much better than me in the heat even though theoretically he should overheat more, but perhaps he has the advantage of so much additional muscle that he only needs to activate a fraction of his muscle fibers to keep a comfortable pace.

I was completely prepared to feel crappy at some point in the event, then to come back to life with the sunrise or coffee or something. I wasn’t prepared at all for how quickly my energy levels could go from “I feel surprisingly good” to “I just wanna take a nap.” Neither was my crew. Advice for crew/pacers out there: don’t listen to your runner when they tell you everything is great. They are in denial and a bad patch is inevitable. So do the thinking for your spaced-out runner and try to foresee what they will need before they fall in a hole.

Even though I only made it to 55 miles, it was much harder on me and especially my feet than any 50 mile race I’ve ever run.* I attribute this to the total “time on the feet” fatigue from the slow pace, the drain of heat on salt and energy stores, and the accumulated damage to the feet (blistering is much worse in the heat), not to mention the sleep debt before the race. It’s also possible that I had not eaten enough calories to keep my energy levels high, since I estimate I’d eaten at most 2230 calories during the whole day (less than half the calories burned). Some of that difficulty was due to extreme thirst during the hot hours of the day, when I craved water, pure cold water, and my stomach was having trouble processing the input as it was.

I am intrigued with the energy requirements of these events. I’m not advising anyone to eat as lightly as I do in ultras, but I wonder why we need all this food. I wonder if it’s not mostly just to trick the body into thinking all is well and to trigger reward systems in the brain (like the study that found that just swishing a sweet drink in your mouth, but not actually drinking it, can improve performance). For myself, I know that when I get hungry while running, which certainly happens, eating some small amount of food fixes the problem, but if I don’t eat, nausea will occur and will not be easy to fix once started. Salty or starchy foods, sodas, protein, even fatty foods such as smoked salmon, cheese or nuts—they all seem to help. But this is more to keep the stomach happy than to provide fueling (though I was once revived by a tamale). Not everyone needs huge amounts of calories to get through ultras, for example, Jean Pommier wrote an account of Skyline 50K where he basically ran on nothing but sports-drink and Vespa (which is supposed to enhance fat burning). But again, fast runners just aren’t out there that long, and perhaps that is an important factor in total energy needs in an event.

In my case, a confluence of factors (getting dark, poor visibility, anti-climax from enduring the hot part of the day, accumulated fatigue and pre-existing sleep debt, blisters) suddenly outweighed all the race enthusiasm and improved conditions that came with the cool of night. It would have been helpful to anticipate these energy level fluctuations. We actually had caffeine pills and energy drinks, but elected to save them for later. Unfortunately, they were needed far sooner than expected. I can also say that night-running in a 100-mile race is not like night-running on familiar trails close to home. The dark makes everything more difficult—finding things that you need (especially if you drop something), keeping track of time, seeing far enough ahead to plan running segments and walking breaks, finding course markers.

I recommend this race to anyone contemplating running a 100-miler. The course is excellent, and the volunteers were amazing—experienced runners themselves, they were helpful and truly wanted runners to succeed. Unlike some races where cutoff times are rigidly enforced, in Rio, they are willing to bend them a little if they think it will help runners succeed. However, they could have improved the race by making sure enough trail markers were present, and that glow lights or reflective/phosphoresecent markers were used on the sections run at night, but if you’re not as slow as me or as slowed down by the heat, this problem could be avoided (the wider trails past Cavitt School would have obviated some of this problem too). On the other hand, if you struggle with heat as I do, perhaps you should wait to run this one on a cloudy day.

Gear
Drymax socks, Montrail Continental Divides, GoLite running shirt and skirt, Kinesiotape, hat, saltstick caps, sunscreen, bandana, ankle braces, Garmin 405, USB battery and charging cable.

What worked:
1. Ice in the hat and clothing cavities really helped in the heat- it offset some of the blast radiating off the sunburnt trails, though my legs and feet were always hot.
2. V8 juice really hit the spot, but perhaps less of it would have been better or I should have waited until later
3. Lubing all moving/touching parts
4. Eating food (most anything works for me) to keep the stomach from getting touchy and queasy. The beef with broth and rice went down well and kept the stomach demons at bay. Liquid calories (Gu) and caffeine (Coke) went down well too (though I don’t advocate for their healthfulness—still fructose intake in the context of exercise and low glycogen reserves is likely to rapidly replenish liver glycogen, so maybe in this limited context, fructose is ok).
5. USB battery successfully charged Garmin 405 on the run, and it continued to take data
6. Except for blisters, I didn’t fall down or get injured (I had sore leg and abdominal muscles a couple days later, but nothing extraordinary). I used about 1 Ibuprofen and 1 saltstick cap per hour, especially after 20 miles.
7. I was successful at not wearing myself out on the initial faster portions of trail or early climbs. I was aiming for an overall 12 minute pace on the “flat and easy” portion up to Cardiac at mile ~20, but this section turned out to be anything but flat and easy and my pace was more like 13–16 min/mile, which was still well within the pace estimated by the pace charts. More walking than running in the heat of the day was good enough to keep to the necessary pace.
8. My crew was excellent, attentive and supportive (Thanks David!).


What didn’t work:
1. My taping job sucked, at least on one foot.
2. My brain—I got serious brain fog once it got dark and the accumulated fatigue and sleep debt hit. I couldn’t seem to think straight or solve problems.
3. Signing up late and going into a panic, getting sleep deprived more than usual.
4. I didn’t leave enough time for any deviation from the plan. You need to keep a bigger buffer of time for shoe changes or brief naps etc. even if it seems you have plenty of time, because it can evaporate quickly on you. I should have pushed harder on the loop at Cool and not just waited until the downhills or the evening to do more running than walking.
5. On paper it may appear to be an “easy” 100-miler, but it was (and is often) too HOT to be easy for the vast majority of people. In my case I managed the heat well enough not to get heat exhaustion, but couldn’t quite muster the energy to move as fast as I wanted to.
6. Inadequate night-time lighting. My 60 lumen LED emitted a ghostly diffuse light that provided very poor contrast and texture, making it difficult to estimate distances and surfaces and slowed me down even further. (I had a second better light but was too spaced to think of using it.)
7. Apparently I had some issues with my intestines not absorbing fluids, though I don’t know whether it was due to fiber in the V8 juice or the heat and dehydration itself impeding intestinal absorption. If I had continued on the trail, it could have become very unpleasant.
8. Going it alone when I was getting tired. I should have accepted the aid of my pacer who could have helped me find the trail and keep to the required pace.
9. Not lubing enough skin surfaces—some nasty abrasions and chafing resulted.

* Well, Firetrails this year beat me up pretty bad too.

The year of running injuriously

Cynthia’s Experience

Ok, silly title, but apt, as you will see. As of late summer of 2009, after running the SF Marathon and wondering why I was so much slower than expected, I intended to increase my mileage and see if I couldn’t improve my running ability. That did not happen as planned obviously, or I would have been happily blogging about my triumphs attempts. For running friends wondering what has happened, here is the sad story of the last year in running.

May 2009 at Quicksilver 50K, I landed badly while jumping across a creek—the embankment was at a steep angle, which I failed to notice until midair. Afterwards, I had swelling and pain in that foot off and on for a couple of months. It never hurt particularly badly and I mostly ignored it, continuing to run on it, even completing Diablo 50K a month later without problem, with my foot at least. Anyone who has done an event at Mt. Diablo knows it will take a lot out of you one way or another. I mentioned this in blog entries in June 2009 and July 2009. I thought I was babying it enough by taking it easy and mostly running uphill, where the foot falls are softer and more controlled. It did feel like there was some structural weakness for a couple of months when I’d try standing on the ball of that foot with my full body weight, but I figured it would pass. Mostly I just congratulated myself on having good recuperative powers, and continued to run as much as I pleased, and never bothered to get any x-ray or medical opinion.

In summer 2009 while training for the SF Marathon, I ran more track workouts and harder road runs, not the varied and softer surfaces of trails. A glimmer of foot pain began, but remained sporadic and mysterious until by August, after the marathon when I got the bright idea to up my mileage, I developed the dreaded plantar fasciitis. I scoured the web for information on treating and training with PF. One of the more useful references I found is from the Sports Medicine Institute, complete with physical therapy recommendations. My symptoms matched those of textbook PF, and I began to treat it as recommended—icing, using arch supports, keeping the fascia stretched, reduced running, using ibuprofen, etc.


When September came around, it was time for Steven’s Creek 50K. This is another charming local race on trails that we often train on, put on by Steve Patt of Steven’s Creek Software, with proceeds to benefit the Audubon Society. In 2008, the first year I ran this event and only my second 50K, I had such a poor time that I was determined to come back and vindicate myself, hurt foot or no. In 2009, the weather was cooperative, cool and even a few sprinkles, and I managed to improve my time by over 2 hours even with the injury! This tells you how terrible I am in the heat. I found myself running slower and scouring the trail ahead for the softest surfaces to run on, but my foot seemed all right afterwards.

So without too much fear, I signed up for a second running of Dick Collins Firetrails 50 Mile. I thought I would be faster since I was fresh from marathon training and significant hillwork and was lighter compared to 2008. Instead, I was slower by 40 minutes (almost a minute per mile slower!). It turned out to be a truly miserable experience, with me fantasizing about using crutches for much of the race, wincing down the long descent to the turnaround and just generally having the motivation sucked out of me by pain. I vowed not to run any other races until it didn’t hurt so much to run.

For the rest of the Fall/early 2010, I was reduced to easy running/rigorous icing, stretching and physical therapy. I could run, but not fast, and not far (nothing new really, but I didn’t enjoy being even slower than usual). There was almost no pain running uphill—this is of course without any kind of energetic bounding, which would likely negate the pain-free aspects. But of course, there is the downhill part to every run, where I would cringe and whimper my way back down. The strange part is how much more it hurt after running than before or during, and more than in the mornings when it is supposed to hurt the most (“first step” pain). On bad days, the arch and entire heel blazed with heat from the resulting inflammation (icing certainly helps with that), and even tingling or buzzing sensations from nerve irritation and entrapment. I also noticed occasional toe numbness and neuroma-like symptoms, but it seemed to be specific to going uphill, and was helped by walking on rocks that would put the pressure on the arch and not the ball of the foot.

During this time, I compared my feet and realized that my injured foot was now noticeably longer than the right (before, the right was larger), and the right calf musculature was better developed. Whatever injury I had sustained caused the foot structure to attempt to adapt and compensate for the weakness. The bone structure in the arch is now noticeably thicker as well, and presumably is stronger. This picture shows the two feet aligned heel to heel (excuse the post-Rio blisters). The plantar fascia can be easily seen when the toes are stretched back, revealing the tautness of the fascia. Unfortunately, the left fascia is still much tauter than the right due to the relative fast growth of the foot. The tautness can be more readily felt than seen, and the right is springier, with more give to it, than the left. Whenever I strain the fascia, such as landing on the toes going downstairs, skipping, running fast, I can feel it yanking on the calcaneus as if it was trying to pull free. In the acute phase, it felt like an ice pick or broken glass in my heel. Now it is merely a dull but persistent pain.

During January, we cut back running in favor of some weight and cross training, but ran the Fremont Fatass 50K anyway. This is a local event organized by Catra Corbett and Mike Palmer, a friendly (mostly) flat run on bike trails between Quarry Lakes and Coyote Hills. My foot wasn’t too bad on the trail part, though the pavement portions were painful. Then we ran the Second Saratoga Fatass 50K in February (where we got lost and only did a marathon) and Adam Blum’s Overgrown Fatass Marathon, where I was feeling better (and won the women’s event—Yea me! I think there were only two of us!). With the rainy winter, the trails were often soft and squishy, and this helped a great deal to soften the impact for my hurt foot.

By March, I was just starting to feel normal again, until I pushed too hard one day. I could feel something in the fascia “ping” and was back to pain and rigorous icing again. It was clear I wasn’t going to race anytime soon. We volunteered at Skyline-to-the-Sea in April, but my foot was killing me just from standing around all day. I went back to track workouts, thinking the soft springy surface would help. I also did running drills, not realizing these would exacerbate the problems. With more PF pain and weird associated pains and numbness, I finally broke down and went to see a podiatrist in an attempt to find out what the heck had happened and whether I had a stress fracture or something serious. Several x-rays and CT scans later, he informed me I had dislocated a bone in my foot nearly a year before! As a consequence, the foot joints had been trying to compensate for the injury by growing larger and stronger, hence the longer left foot. He also said it looked like I was getting some arthritis too. He instructed me to ration my running, run on soft surfaces, use an insole and to take glucosamine/chondroitin sulfate pills. (As an aside, he was also appalled at the looseness of my left ankle ligaments and advised me to run with an ankle brace, which I do- it has saved me from further injuring the ankle at least). So for the next month, I stuck with trails, the softest I could find and ran gently—no more “speed” work!

By May, it was time for Quicksilver 50K again, the scene of the original injury. I was determined to run it again, not sure if it would be the last ultra for a long time. I wanted to look for the offending stream crossing and this time cross it sensibly, but never did find it (I think they put up a bridge). This race was slower than last year by 23 minutes, but my foot didn’t hurt until after 15 miles. The after effects were fine too—less pain if anything. Encouraged, I signed up for the famous and popular Ohlone 50K two weeks later (I got lucky on the wait list), which involved a lot of slow trudging up hills and fast downhills trying to make up time, and I was pleased that my foot wasn’t a limiter, not seriously. We got lucky with a cool spell of weather on this one too. My lack of ability to run those hills was by far the biggest limiter. And again, the after effects were minimal. I was so excited to get through Ohlone without further injury that I went out and injured something else by running too hard (one of the little gemellis or something in the butt—the little bugger still hurts).

David and his son Ethan decided to run the SF Marathon this year. I played “coach,” leading them through a 30 minute time trial to assess training paces, long runs, hills runs, and mile repeats and Yasso 800s on the track. I couldn’t keep up with their pace, but tagged along behind. We did short trail runs at first to keep the impact lighter to help Ethan work up to longer distances without injury, but quickly escalated to 17–25 mile runs (I only did 20 miles that day) when it was clear he was weathering the distance without his previous injuries reappearing. Being injured yet again, I took it pretty slow and used this as a build phase. By marathon day, they were both primed and ready (though as it turns out, David had pushed too hard already and had some limiting injuries), and gave 3:37 and 4:12 performances.

So by August 1st, I was eager for another race, this time Skyline 50K. This race was extremely well organized and fun, with friendly volunteers positioned at trail junctions pointing the right direction frequently during the race, it was not possible to get lost. The course was harder than I expected, even though it is ostensibly completely runnable (just not for me), because some sections are very steep and rugged. I was amazed to read Jean Pommier’s account of running 7 minute miles through the parts that had me picking my way carefully over roots and rocks, averaging 15 minute miles!

Two weeks later marked the August 2010 (instead of September or March) running of the Steven’s Creek 50K. The event was well run this year as well, though our weather was not as considerate and became hot, while last year was unseasonably cool. I met Roger Jensen (“the yo-yo guy”) and Gordy Ansleigh here. Roger planted the seed for running Rio del Lago, saying that he and Barbara Elia would be there. I ended up finishing a little ahead of Roger, and thought Hmmm…

For these races as well, my foot just wasn’t the main limitation—it still hurt sometimes and made me run cautiously and tentatively at times, but after the races seemed better than before, if anything. But by the time the next weekend came around, I had put in 61 miles for the week and everything started to rebel. I had aches at the Achilles insertion into the calcaneus, peroneal brevis (or longus) tendonitis (maybe) in addition to PF (but the buzzing and tingling of nerve entrapment has finally gone for good I think). I blamed running with extra weight for aggravating the ligaments, but I certainly don’t understand what causes it to flare up on occasion still. So, a couple of easy cutback weeks were in order. I watched and pampered the foot during these weeks and then on the last possible day signed up for my first 100 mile race. Stay tuned for this next misadventure!

So the upshot is that over the last year, an impact injury with dislocation resulted in significant remodeling of foot structure, resulting in PF and other aggravations. It’s possible if I had gone to have it checked out right away, all of these problems could have been avoided, although I’ve heard stories about residual effects of injuries in people who were careful to get everything checked out. I now wonder whether PF is generally the result of minor or unnoticed foot remodeling. After all, the fascia is very inflexible, and changes in bone structure in the foot increasing the length of the foot of only a few mm could result in changes in tension in the fascia, possibly in stretching and tearing injuries. I was able to keep running, but not as fast or as far as I wanted. I had to give up my beloved Inov8’s because my feet seemed to hurt more wearing them than my uber-protective Montrail Continental Divides (sadly, no longer available). I also tried La Sportiva Cascadias and Salomon XTs, which are great shoes, but not as easy on my feet. I got into a routine of easy runs with prophylactic ibuprofen, which seemed to help prevent the majority of the inflammation, then I’d have to sit around for several hours icing my foot. It gradually got better so that it no longer hurt after running most of the time, and did not hurt when getting out of bed in the AM, but still requires a lot of maintenance and pampering. I’ve been able to manage mileage of 20 to 50 miles per week throughout the year, but have to be prepared to cut back at signs of aggravation. At various times, the pain has caused me to run with an awkward running gait, twisting of the knee or ankle (trying to avoid direct pressure on the heel), differences in foot falls (midfoot or forefoot on the left while heel strike on the right), all possibly leading to additional injury if not careful. I can really see the difference on potentially fast downhills, where I find myself holding back for fear of re-injury. I am optimistic, but would not be surprised to have to put up with this for another year or more. It’s looking less and less like I will ever run as fast as even a 6:30 (hilly) 50K again, but at least I can still get out there, and I am grateful for that. Luckily for most PF sufferers, their injuries are more minor and will resolve more quickly.

David’s experience

It has been a rough year for both of us in the running area. David strained his popliteus muscle in May 2009 (sprinting on the track in his new VFFs), and shortly thereafter pinched his meniscus, probably as a result of his knee misbehaving due to his first injury (one injury begets another). He ran with a knee brace for months, and as a result of this knee tenderness was not willing to run Steven’s Creek 50K (he volunteered) or Firetrails in 2009, but instead agreed to be my pacer. Sometime in late Fall 2009/early Winter of 2010, David also developed plantar fasciitis, in the same foot as me. We’re not sure why, or if it was related to some adjustments he made due to knee pain he had from the previous injury, or due to excessive strain when adapting to using VFFs. His PF never became as rabid as mine, and he has managed to recover without suffering too much. It didn’t seem to bother him in the Fremont Fatass 50K or the Second Saratoga Fatass 50K, though he was definitely slower at the Overgrown Fatass Marathon because of it (and also something of a real tenderfoot on that rugged trail with his VFFs). So he has spent some of the past year also icing his foot, along with physical therapy exercises too (lots of ankle work and calf raises).

Then while training for the SF Marathon, he injured a psoas muscle and one or two adductors. Though seemingly minor, these became aggravated during the race so that he was unable to run his best pace. Afterwards, we noticed he had a big lump on his Achilles tendon, so he is treating all of these new injuries with caution and easy running. David is convinced that it was speed work that was problematic and led to injuries; he’s never had any problems from the longer, slower distances. I am reminded of one of Gordo Byrn’s posts about how big men (i.e., ≥ 6 ft tall, > 165 lbs) benefit from easier training (“Small women get fast from intensity, big men get fast from volume.”). This certainly seems to be true for David. He seemed indestructible when he first started running with me, but then he never had to strain very hard to keep up with me and was always able to stay within his body’s limits. Avoiding high intensity training doesn’t seem to have prevented him from running faster than me!

Weight Loss Followup

In previous posts, we discussed the first several months of weight loss for Cynthia and David. We’re now about two and a half years into our new eating lifestyle, and it seems like a followup post is overdue.

We have been taking near daily measurements through the period with some more occasional measurements of other parameters, so we have lots of data to misinterpret according to whatever bias or slant you might want to apply. As usual, life is complicated, and the data are subject to a lot of coarse- and fine-grained hypotheses that can be postulated to explain various features. We’ll offer an assortment of hypotheses, some of which are more strongly supported by the data than others. Since it’s all basically post-hoc analysis based on two subjects, none of the hypotheses can really be considered confirmed.

The most striking observation, perhaps, is that the change to lower-carbohydrate consumption continues to be working. (Let’s not call it a “diet” since that seems to mean something that people try to use as a temporary measure that ultimately fails when they revert to “normal” eating habits.) While our weight loss has inevitably slowed and had various “plateaus” and “reversals” or “setbacks,” our weight loss is holding and we are both at or near our lows of recent years some 30 months into our new eating habits. This bodes well for the long term. We are emphatically not counting calories, calorie restricting to the point of gnawing hunger, or otherwise depriving ourselves of the enjoyment of eating. Sure, we are emphasizing some different foods and limiting consumption of sugars of all sorts and simple starches, but, for the most part, we don't crave them and can satisfy what cravings we have with either small portions or satisfactory substitutes. Fortunately, we don’t often share meals with the high-carb/low fat crowd, so we don’t face a lot of peer pressure to “cheat,” and we stay away from the French bakeries. There are some differences between our preferred diets as well. David tends more towards the “Optimal Diet” (lower carb and high in butter and cream) while Cynthia gives in more to carb cravings (more fruit and indulgences such as Chinese dumplings), to which she attributes her various weight stalls and reversals!

And, of course, at least among those who are open-minded enough to have actually investigated the current state of the science, acceptance of the low-carb lifestyle has been increasing steadily. While advertising by the food industry continues to be abysmally misleading, we’ve noticed an increasing number of more positive references to low-carb nutrition in everything from a steadily increasing number of blogs posts, books, and scientific papers to passing references in recent movies (e.g., “She eats CARBS” from The Devil Wears Prada). The mainstream government agencies and medical societies are generally still not recognizing the error of the low fat diet, as seen in the 2010 USDA guidelines. (Quoting from Question 5 in Appendix E-1, “Conclusions”: “No optimal macronutrient proportion was identified for enhancing weight loss or weight maintenance. However, decreasing caloric intake led to increased weight loss and improved weight maintenance. Therefore, diets that are reduced in calories and have macronutrient proportions that are within the ranges recommended in the Dietary References Intakes (IOM, 2002/2005) (protein: 10%-35%; carbohydrate: 45%-65%; fat: 20%-35%) are appropriate for individuals who desire to lose weight or maintain weight loss. Diets that are less than 45 percent carbohydrate or more than 35 percent protein are difficult to adhere to, are not more effective than other calorie-controlled diets for weight loss and weight maintenance, and may pose health risk, and are therefore not recommended for weight loss or maintenance.”) There are, of course, huge entrenched economic interests that will continue to fight the status quo tooth and nail. There is some evidence that they may start to crack in the foreseeable future—for example, the American Diabetes Association now recognizes that a low carb diet may be useful for weight loss in diabetics—but progress continues to be slow.

Then there’s the exercise wild card. We all “know” that increased exercise is a “necessary” part of any “reputable” weight loss program. And yes, we have increased our level of exercise. We were never serious couch potatoes, but we weren’t serious athletes, either. Very roughly, we were running 20–30 mi/wk two and a half years ago, and increased to 30–40 mi/wk, and have often done closer to 50 mi/wk. We also started running ultramarathons of 30–50 mi in one day, averaging more than one such event per month at times. So what did all that exercise do for us? Well, we certainly got stronger and faster. We generally feel good and energetic (aside from the inevitable sore muscles and minor injuries). We also continue to find that more often than not, increased exercise correlates with weight gain, not weight loss! This happens both over the short term
(water weight of up to a few pounds the day after an ultra-marathon that may take a few days to lose), and over the longer term (our weight loss trends reversed for about 4 months after we started doing frequent day runs in excess of about 15 mi). We also tended to see a stalling of any downward trend whenever we increased our weekly mileage significantly. Partly, this is because moderate mileage increases such as this are easily compensated for by eating more. There are exceptions too, for example, during August 2009, Cynthia upped her mileage considerably (>50 mi/wk) and found she could not eat enough to keep her weight stable. However, this amount of mileage was not sustainable (due to an injury in May 2009 that began to cause pain), and eventually she gained it back.

There are, of course, several competing things going on when you exercise a lot. Over the period of the exercise itself, the dominant effect is usually level of hydration, and body weight is often used to monitor endurance athletes for dehydration and/or over-hydration. If you exercise hard enough and long enough, you can also deplete your glycogen stores to account for another pound or so of temporary weight loss (including the accompanying water of hydration). So generally speaking, you usually finish a long, hard bout of exercise down a few pounds. But then, of course, you eat and drink. Your appetite increases, so you may eat more than normal, and there are various reasons why you might retain extra fluid. That’s why we frequently saw a net increase in weight the day after. Interestingly, the size of this effect has generally decreased over time. Probably, as our bodies have become better adapted to the rigors of a long, hard day of exercise, they no longer see it as stressful. This is supported by the evidence of less muscle soreness and edema, as well. In David’s case, there is probably also a nutritional effect. He ran earlier events consuming more than normal carbs during and immediately after the event, and then, in later events, switched to more strict low-carb fueling before, during, and after. Some amount of fluid retention would be expected to be correlated with a temporary increase in carb consumption, and eliminating the carbs apparently eliminates that source of fluid retention. Cynthia tends to push harder into her non-aerobic zone, especially when trying to keep up with David, and chooses to consume more carbs during and after long runs, but she’s been showing smaller post-event weight spikes more recently, too. The effect is a sensitive measure of training, because it is more pronounced when less prepared or perhaps as a response to heat stress. The water retention is most likely due to a complex interplay of hormones that signal the kidneys to retain salt and fluid. Such a response is understandable after the stimulus of long and/or hot conditions.

The increased appetite can generally overcome any predicted weight loss from a purely thermodynamic point of view. The problem is that you have to run on the order of 30 mi or so to burn enough calories to consume a pound of body fat (assuming that you’re actually burning fat for fuel). If you do that over a week, it’s pretty easy to unknowingly increase your daily food Calorie consumption enough to more than offset that burn. It’s not much more than an extra couple of “servings” of something tasty per day. Be careful about rewarding yourself with too many bowls of ice cream or extra double cheesburgers!

An increased level of exercise, if done systematically and with adequate general nutritional support (enough protein, for example), often results in muscle building. This can result in body “recomposition”: loss of body fat and increase in lean muscle mass with no net change in weight. That may explain some of the apparent plateauing of our weights. Running doesn’t build bulky muscles the way, say, weightlifting does, but we have seen some measurable changes in body measurements.



Nevertheless, with a very blurry-eyed look at the weight loss data over 30 months, a simple-minded interpretation and hypothesis is that we both generally lost weight more or less linearly for 8 months until we started seriously increasing our level of exercise and then stalled out, remaining at a more or less constant weight for the following 22 months. (Click on figures to show larger.)



With slightly less blurry eyes, one immediately notices that longer trending period tends to follow more of an exponential curve rather than a straight line. A simple model which can be made to fit the data pretty well is to assume that you are always approaching an asymptote (target weight) exponentially so that your rate of weight loss (gain) gets steadily slower as you approach your target. Fitting such exponentials to the various regions on our graphs gives a pretty good fit (i.e., the data looks like it fits a set of straight line segments on a semi-log plot where an estimated target weight is subtracted out). Measured time constants vary from about half a year to two years. And while our weight loss is now hard to see from day to day or even week to week, we are still losing at an average net rate of about a pound every 2–3 months. We both feel like we should be able to lose another 10–15 pounds, but that could take a few years.


It is interesting to treat the data using some of the technical indicators typically used on financial charts. For example, one can draw upper("resistance") and lower ("support") levels and trend lines. Weight can bounce off or break through these lines as you can see on Cynthia's chart from August 2008 through February 2010. You can also see a downward trending channel or notice triangular patterns with converging oscillations, double bottoms, retracement levels, all very similar to observed price behavior on financial charts.

There are other secondary effects that may also be present in the data. While we have so far explained the weight gain last fall as due to increased exercise, it could also be due, at least in part, to a normal seasonal effect. Some weight gain through the fall and into mid-winter is perhaps genetically programmed to store fuel for the winter. Some of it may also be just increased fluid retention in cooler weather (or just reduced dehydration?—the body probably undergoes larger hydration cycles in hot weather as one sweats and eventually replaces lost fluid—but note that a drop in core body temperature actually has the reverse effect as anyone who dives in cold water can attest: the body naturally sheds excess water when cold).

Cynthia's data also show a pronounced oscillation with an amplitude of 4–6 pounds and a period of 1.5–3 months. We have, so far, been unable to correlate this oscillation with any obvious body cycles, lifestyle cycles, eating, or exercise habits. Being female, one might suspect menstrual cycle effects, but the period is too long and the amplitude is too large. (Menstrual cycles generally result in monthly weight variations with an amplitude of about 2 pounds. In order to see it, you typically have to average several months of data [with the end dates of cycles carefully lined up if the length of the cycle is at all irregular] since the amplitude is comparable to normal day to day fluctuations. It's actually more noticeable as a cyclic change in waist circumference.)

David's data show periods of unexpectedly rapid weight loss (July/August 2008, January/February 2009, May/June 2010). Again, we have not been able to clearly explain these periods, although similar “success” periods seem to be commonly reported anecdotally. Perhaps the body suddenly decides to adjust its natural setpoint in some important way. Fat storage and loss is driven more by hormonal signals than by daily calorie balance anyway.

If you want to keep losing weight, you may need to keep reducing your calorie consumption as well. In principle, this should happen automatically if you basically eat to satiety, but eating habits can often be somewhat independent of satiety if you are in the habit of eating particular portion sizes (e.g., 2 eggs and 2 slices of cheese, etc.). Presumably with a little conscious effort, you should be able to readjust your habits to your new needs as you lose weight, but some portions are a little hard to adjust. (It’s not convenient to cook 1.8 eggs for breakfast…)


Another interesting comparison is to plot David’s weight vs. Cynthia’s weight. This plot is noisier in that David’s and Cynthia’s weight gain and loss have not always been tightly correlated despite similar diet and exercise schedules. Overall, David’s weight is approximately 30% higher than Cynthia’s at any given time, but he has been losing about 1.2 pounds for each pound that Cynthia loses. We're still not sure how much more weight we can (or should) realistically lose. The corresponding weight loss rates are consistent with our college-age weights of about 167/125 pounds respectively, but a more realistic goal may be more like 175/133 pounds.

There are other measures of body composition that are often used to determine “ideal” weights. The most commonly used is the Body Mass Index or BMI. This is based purely on height and weight and does not take skeletal build or musculature into account at all. David is still classed as borderline “overweight” by standard BMI guidelines; Cynthia is “normal” at a BMI of ~23.

However, David is relatively well-muscled and big-boned. At least by current American on-the-street standards, most people would not say he was overweight at this point. Another approach to determining ideal body composition is to estimate percent fat. There are many ways to make this measurement—all approximations based on indirect measurements of one sort or another.
Underwater weighing is the current standard against which other measurements are typically evaluated, but it is imperfect, too. Skin-fold thickness is also popular, because it’s easy, but it can be unreliable. See Lyle McDonald’s post for more in-depth discussion. The two methods that are most readily available to most people (including us) are Bioelectric Impedance Analysis (BIA), a measurement built-in to some digital bathroom scales, and various formulas based on using additional body dimensions such as waist, hip, and neck circumference. Our favorite of these right now is a set of formulas derived by the US Navy based on height, waist, weight, neck, and hip (women only): %Fat=495/(1.0324 - 0.19077(log(waist - neck)) + 0.15456(log(height))) - 450 for men or %Fat=495/(1.29579 - 0.35004(log(waist + hip - neck)) + 0.22100(log(height))) - 450 for women. These give current values of 28.5% fat for Cynthia and 18.5% fat for David. Not surprisingly, these calculations put both of us solidly in the “acceptable” range, but still significantly above the upper end of the target ranges for athletes (presumably based on a young military test population: 20% for women, 13% for men). Just to give you some idea of the uncertainty in these measurements, the BIA method as implemented by a Weight Watchers bathroom scale gives 25.4% for Cynthia and 22.4% for David, showing discrepancies on the order of 3% and in opposite directions for Cynthia and for David.

And finally, just a quick observation about the Weight Watcher brand scale implementation of the BIA measurement: while we have been unable to locate any information on the algorithms implemented in the scale, it is clear that there is more than a little something amiss. First, it tends to report %Water in the mid-50s, while the human body is generally estimated to be closer to 70% water. While the instructions warn you that the data may be inaccurate if you take measurements immediately after heavy exercise or large fluid consumption, it is nevertheless disconcerting that it actually tends to report higher %Water (and lower %Fat) after losing a lot of fluid due to exercise and sweating, and lower %Water after a large drink! Clearly the algorithms and/or measurements fail to accurately account for variations in the distribution of fluid throughout the body. Another anomaly we have noticed is that the scale has reported a slight decrease in %Bone for both of us as we have lost weight, something that is very unlikely to be valid.

So all in all, our way of eating is pretty easy to sustain and requires no weighing or measuring. If we really wanted to lose weight faster, I'm sure it could be done using more discipline, but then we'd have to worry about regaining once the discipline slips. This way the changes are more gradual, and perhaps, more sustainable.

Vibram Five-Fingers, 1200 Miles in

Most reviews of running in Vibram Five-Fingers “shoes” are necessarily based on a few days to a few weeks of experience. Journalists, of course, rarely have any longer time horizon available to them since they need to get something out promptly. My own first review was based on a couple of months of experience; this is a follow-up report now that I’ve been using them for some 8 months and 1200 miles.

“Barefoot” Running?
Do I now consider myself a “habitual barefoot runner”? No! I’ve definitely gotten solidly past a transition period away from conventional running shoes and now run (and do most things where I need shoes and can get by without more complicated foot protection) exclusively in my Five-Fingers. However, my feet don’t have good abrasion resistance yet. I can run 3–4 miles on “good” surfaces such as real or artificial turf, smooth dirt, rubber track surfaces, and the like, and up to about 2 miles on rough surfaces such as gravel or rough asphalt or concrete, but for longer distances, I need to wear something on the bottom of my feet to avoid blisters and hot spots. I have no plans to run any organized events barefoot anytime soon, though I will continue to go barefoot for less strenuous activities whenever I think it is safe to do so.

That said, of course, running in minimalist shoes, whether Five-Fingers, moccasins, sandals, or other commercial attempts to provide a near-barefoot experience, does allow you to mimic a lot of the characteristics of barefoot running with our modern typical fragile foot bottoms. Musculature and fat pads adapt more quickly than abrasion resistance, though these, too, require some real adaptation leading to a lot of early problems for people that try to do too much too soon.

Running Style
Whether running barefoot or in minimalist shoes, you rapidly discover (if no one tells you first), that you probably want to move away from the sort of heel-strike running gait that most shod runners are taught to use or use instinctively for anything beyond short sprint distances. True habitual barefoot runners (such as those who grew up not wearing shoes at all) do not use a heel strike. The high shock associated with landing on your heel without any possibility of shock absorption by the foot causes heel bruises and other unpleasant feelings (such as more strain on the knees) if you don’t have any shoe structure to absorb the shock of heel-strike running. Sprinters run on their forefeet and generally don’t let their heels touch the ground at all. But for longer distances (more than about 30 seconds of running), most runners do allow their heels to touch even if they don’t land on them.

There are many possible variations on the exact gait one can use when running in minimalist shoes. Personally, I strive for efficiency as an endurance runner (I’m definitely not a sprinter), and I find that the gait I use for most routine running keeps my feet low to the ground, and my stride length perhaps a little shorter than it used to be. I land first (just barely) on the inside edge of my forefoot and roll the ground contact across the ball of my foot and then back along the outside edge to my heel which just touches the ground with minimal force and then comes back up to reverse the movement until the foot leaves the ground again. This motion, of course, makes full use of the natural structure of the foot and provides maximum opportunity to use all available ligaments, tendons, and muscles for shock absorption, energy storage and release, and push for the next step. I think this is true regardless of your foot type (within normal variations). I happen to have rather flat arches, but I don’t think my minimalist shoe running style is particularly different from that of someone with very high arches. I haven’t yet seen any data on wear patterns for the soles of minimalist shoe runners. Anecdotally, there is still some variability in the location of maximum wear, though much less so than is observed for “normal” running shoes. I think I am seeing what I think is the most common pattern, finding that the point of greatest wear is on the inside ball of the foot and the big toe.

[Addendum 11 February 2010: (thanks to Tuck for making me look more carefully at Daniel Lieberman’s pressure-plate video) It seems that exactly where you naturally strike on your forefoot depends on your particular foot structure. I have rather flat arches and a tendency to pronate (turn my foot inward) which is manifested in a tendency to wear the inside edge of the heel of shoes when running with a heel-strike gait. In a forefoot gait, I land first on my first metatarsal and then transfer weight to my big toe, then across the rest of my metatarsals. Daniel’s pressure plate video (presumably of himself running) shows initial pressure buildup under the fourth metatarsal with a roll toward the first metatarsal. Presumably he does not tend to pronate and likely has higher arches than I do. If you don’t have access to time-resolved pressure plate data recording equipment and don’t want to wait a few hundred miles to analyze shoe wear patterns, here’s a simple trick I found that should tell you how you should probably land: Stand up (barefoot) with your leg forward. Point your toe (i.e., bend your foot forward), but keep your ankle in a neutral position laterally (don’t consciously turn it either in or out). Now touch your foot to the ground. When I do this test, I touch with my first metatarsal and/or big toe. Cynthia, on the other hand, who has high arches and no tendency to pronate, touches on the fourth metatarsal. While there are some people who try to get everyone to do the “right” thing meaning the same thing they do, it is my belief that there is no right or wrong way to use your foot. You should do what is comfortable and natural for your particular bone and ligament structure. For me, while I could force myself to land on my fourth metatarsal, it would be an unnatural thing to do and likely cause undesirable side effects in the form of muscle strain.]

Landing on your forefoot results in a gentler landing with less force against the ground, less shock on the knees, and less noise. You become the proverbial Indian brave, able to run quietly through the woods in your moccasins (or equivalent). In fact, one of the ways that you can further train yourself to reduce stress is to aim for the quietest running that you can achieve. There is still a range of impact force that can be used with forefront landing, and a good way to aim for lower impact force and greater running efficiency is to listen to your running and try to keep it as quiet as possible. You may need to ramp up the noise a little bit again when you’re out to get maximum speed, but for most routine running, quieter is probably better.

While I am primarily a trail runner by temperament, one surprising (to me) consequence of switching to a forefoot landing habit is that running on hard surfaces such as roads is no longer something that I shun. Since I am now a gentler runner, long distance pavement pounding is just not nearly as stressful as it used to be, and in fact, all else being equal, I now find myself seeking out the smoother harder surfaces rather than running on the adjacent dirt if both are available.

Another aspect of running in minimalist shoes is that you are less constrained to hold your foot in a particular orientation relative to your leg. Most of the time this doesn’t matter all that much. But if you happen to be contouring along a steep hillside or placing your feet on the sides of a deeply rutted trail, you may find yourself needing to adapt to a surface that is far from perpendicular to your leg. In shoes, this can be an unpleasant ankle twisting (and even ankle spraining) experience. But with Five-Fingers shoes you can take up most of the extra bending in the foot rather than the ankle with structures that are much better adapted to the bend than is the ankle. This is an aspect of barefoot/minimalist shoe running about which I’ve seen very little comment. I discovered the phenomenon accidentally one day when I found myself running along the side of a very steep hillside, cutting across an open field. I suddenly realized that the running was much easier and much less stressful on the ankles than I would have expected.

Muscle and other Soft Tissue Development
Any change in running style—whether due to a change in footwear, compensation for injury, change in running surface, distance, or terrain—will stress muscles in new and different ways. Most notably, switching from heel-strike to forefoot running increases the dependence on muscles associated with the feet. The strongest of these muscles are actually located in the lower leg and connected via an elaborate system of ropes and pulleys (a.k.a. tendons, ligaments, and fascia) to the bones of the foot. Runners who transition too rapidly from heel-strike to forefoot running often experience at least pain if not outright injury in their lower leg muscles as well as their Achilles tendons and plantar fascia. As with any transition, the key is to start slowly—less than a mile for the first few days, increasing gradually as muscles allow. Plan on a minimum of 2–3 weeks of gradually increasing distance, speed, and difficulty, and preferably at least twice that long. Back off if you experience any significant pain. If you want to supplement your actual running with other training, then anything that puts you on your toes (calf raises, skipping rope, dance or fencing exercises) can be useful cross training.

How did I fare during my transition? Well enough. I had an enforced reduction in mileage about the same time I made the transition due to an unrelated injury. I’m finally fully recovered from that injury, and I actually think that forefoot running and the associated reduced knee stress helped me recover more quickly and increase mileage again more quickly. I’m presently contending with a mild case of plantar fasciitis in one foot—nothing that is limiting my running at all, but annoying all the same. Again, I find that forefoot running is less stressful on the injured tissues.

Padding
Of course, one of the main things that people wonder about, especially for trail running, is the issue of how you can run on rough surfaces without much cushioning from a shoe. Running on surfaces with a lot of small stones (rocky trails, gravel roads with relatively little actual gravel) is the most challenging. It takes a while to toughen the pads on the balls of your feet, but it does happen. The improvement is gradual and takes easily 3–6 months depending on how you train. Eight months out, I find that surface that used to leave my feet feeling beat-up after a few miles no longer bother me at all. I can run 10+ miles on very challenging trail surfaces and come home feeling unaffected. A recent 50K run that included a lot of gravel trail still left me feeling a bit worked over, but my feet were fine again by the next day.

The older models of Five-Fingers shoes (including the KSO model that I wear) have practically no tread or padding in the sole. In response to customer feedback, newer models incorporate some tread which also provides a little more damping out of the running surface roughness. Since I haven’t had an opportunity to try running in the new models, I can’t comment except to say that, now that I am well-adapted to running with the older thinner soles, I don’t feel any particular desire to have more protection under my feet than what I’ve got now. From a marketing point of view and the usual sort of instant gratification that many customers will want, I’m sure that a bit more sole will be a good thing; for more experienced minimalist runners like me, it doesn’t seem that more sole has any compelling attractions.

I also noted an unexpected pattern to the toughening of the pads on the balls of my feet. There is a transverse arch across the ball of the foot, and I, at least, expected that not much would happen in the middle of the arch (behind the second toe), thinking that the primary stress would be on the outsides of the arch. In actuality, the reverse happened. The most toughening occurred precisely in the middle of the arch, and there even tends to be some slight callous development there! Apparently, the transverse arch flattens completely on impact and the middle experiences as much or more force than the outsides even though the initial contact and maximum sole wear points are on the outside.

Traction
As I just noted, Vibram has recently introduced newer models that include more familiar looking shoe bottoms that have some lugs that provide both more padding and maybe more traction. After 1200 miles of running on varied surfaces including concrete, asphalt, rubber, dirt, mud, sand, rock, turf, fields, etc., I can say that I have almost never felt at a loss for traction in the KSO model soles. These soles are smooth flat rubber with laser-cut zig-zag patterns that increase grip on smooth surfaces. The only surfaces that I have found difficult to deal with are those with thin slippery mud which are challenging in any footwear (though probably respond better to lug soles than smooth soles). Deeper mud and soft sand/ash present no difficulty—the toes work very well to provide good grip and traction. Wet surfaces are generally not a problem—the rubber grips well. I don’t recommend Five-Fingers shoes for snow and ice, but under such conditions you probably want more thermal protection anyway, never mind the traction issues.

Foot Protection
Minimalist shoes clearly provide less protection for the foot against all sorts of insults. You wouldn’t want to wear them anywhere where normal safety practice would dictate steel-toed safety shoes, for example. You won’t get much protection from ankle twists, kicking hard objects (rocks and roots), sharp objects, others stepping on your feet, etc. If you need arch support or ankle support, you won’t get it (though some people who have failed to get much relief from arch-related problems with all kind of expensive orthotics have found that going minimalist instead actually turns out to be more beneficial).

So what’s my track record after 1200 miles? Pretty good and getting better! Early on, I caught one little toe on a root and wrenched it badly enough that it hurt for a couple of weeks, but that’s probably the worst thing that’s happened. I’ve also kicked a handful of rocks and roots, especially running in poor light. I have to consciously work on lifting my feet more when I can’t see the trail surface very well. I’ve poked my feet into an assortment of sharp sticks now and then, enough to do some damage to the shoe uppers, but not enough to break skin. Not surprisingly, the more you run with minimal protection, the more you instinctively avoid problems. Just as I’ve found that my rate of falling (never very high) has gradually decreased over the years, my rate of minor foot trauma has declined to almost zero over the last several months.

One of my most annoying problems as a shod runner was toenail bruising. Long downhill runs where you are constantly jamming your toes against the front of your shoe cause the most trouble. Even with careful shoe sizing for plenty of toe room, careful toenail trimming, and various aids in the form of taping, toecaps, tubes, and the like, I usually found myself losing toenails due to such bruising a few times a year. Hilly ultra-marathons generally did the most damage. This was probably the single most important factor that drove me to try Vibram Five Fingers in the first place. In the last eight months I still lost one toenail, but it was the result of kicking several rocks in a row while running in the dark, so I’d have to argue that it was really my own fault. I just don’t have toenail jamming issues with Five Fingers footwear. You fit the shoes small. I wear at least a size 44 (European) in most running shoes, but only a size 42 in Five Fingers. Your feet don’t slide inside the shoe. The front of your foot between the toes hits fabric and prevents the toes from jamming into anything.

Socks
Five Fingers shoes are usually worn without socks, though they can also be worn with toe socks such as those sold by Injinji. I started out wearing socks more often than not, and especially for runs of more than about an hour and when the weather was warmer (my feet tend to sweat more in hot weather). As time has gone on, I wear socks less and less; I just don’t need them. I almost never wear them for runs of less than two hours now, and I’ve done a full (winter) 50K without socks. One key to running without socks is to remember that the shoes, in effect, become your socks. So just as you wouldn’t wear socks again after a long run without washing them, you need to wash your Five Fingers regularly. You also need to make sure that your feet are really clean before you stick them into your Five Fingers. I regularly use a pumice stone to remove all surface debris from my feet including any sticky dirt and grease. That keeps the inside of the Five Fingers much cleaner and minimizes accumulation of junk that can cause abrasion. I wash my Five Fingers after any long run, any muddy run, and any very dusty run, and at least once a week regardless. After my 50K run, I did have a couple of minor blisters that I hadn’t realized I’d gotten. They were on the inside side of both feet in the arch region at a seam. I’ll probably opt for socks on future 50K+ runs just to protect myself from this particular hazard.

Keeping Stuff Out
The KSO model is named for “keep stuff out.” It has elastic fabric over the top of the foot that fits snuggly. It works! I’ve never had to stop to take my KSOs off to remove debris. I can’t say the same of any other shoes I’ve ever run in. KSOs still don’t keep everything out, though. They don’t keep water out, and they don’t keep fine dust out. After running in dusty conditions, your feet will look like you have dirt socks on. But I’ve never had any trouble either from dust or from wet feet. Neither has caused any harmful chafing. I consider myself fortunate to have ended up with the KSO model; other runners I’ve talked to that have ended up with other models that don’t have fabric over the top of the foot do have problems keeping stuff out.

Durability
Shoe manufactures would like you to believe that you need to replace your running shoes every few months or every few hundred miles whichever comes first. I never really bought into that plan, running happily for many months and miles in nominally worn-out shoes. Nevertheless, I am still impressed by how few signs of wear my Five Fingers show after 8 months and 1200 miles. They should be good for many more miles to come. That’s not to say that they have been completely problem free. There have been a handful of holes and seams to repair particularly wear I’ve poked the fabric with sticks. These are easy repairs to make since the material is just a cloth fabric that is easily sewn. The soles are holding up well. There is visible wear, but since there are no lugs to wear off, the wear is spread over more surface area. I have not yet needed to add any material to the soles and may not need to over the life of the shoes. As yet, I still can’t tell what the ultimate end-of-life failure mode is likely to be.

The most serious design flaw from a durability point of view in the KSO model is the strap and the slot through which the strap passes on each side of the foot. The strap is made from a relatively thin nylon fabric, and the slot is reinforced with a hard plastic resin. The nylon rubs against the edge of the slot and wears through after a while. I have so far dealt with the wear by reinforcing each strap where it goes through the slot with some thin leather. If I ever have to actually replace the strap, I will try to find some heavier duty material to use. But if I were to change one thing in the design of the KSO Five Fingers, it would be the choice of materials for the straps and slots.

Another weak point in most running shoes is the insoles. These often wear out before the rest of the shoe and need to be replaced. However, with my careful cleaning habits (both my feet and the shoes), I see no signs of wear at all yet on the insoles of my KSOs. When I wash them, I am careful to clean the surface of the insoles of any accumulated dirt and grime. I’m sure this helps. In fact, I suspect that the combination of clean practices and the natural tendency of the KSOs to keep stuff out are the primary reasons for my good experience.

The newer models of Five Fingers intended for trail runners have switched to leather uppers. While I haven’t tried these out, I don’t presently view this as a positive change. I like my thin elastic uppers. They have proven to have adequate durability and are easily repaired when damaged, they breath easily to keep my feet cool, and they can be quickly washed and dried. I am skeptical that leather would perform as well.

—David

Bibliography
There is an ever increasing number of articles and blogs about barefoot running, Vibram Five Fingers and the like. A selected bibliography includes:
http://www.nature.com/nature/journal/v463/n7280/full/nature08723.html
http://www.runningandrambling.com/2010/02/vibram-fivefingers-kso-trek-review.html
http://www.runningandrambling.com/2010/01/invisible-shoe-huarache-review.html
http://www.runningandrambling.com/2010/02/barefoot-professor.html
http://www.runningandrambling.com/2010/01/declaration-of-dependence.html
http://www.runningandrambling.com/2010/01/brooks-ceo-jim-weber-on-barefoot.html
http://www.runningandrambling.com/2009/08/barefoot-revolution.html
http://www.sportsscientists.com/2010/01/running-barefoot-vs-shoes.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+blogspot%2FcJKs+%28The+Science+of+Sport%29
http://stevemagness.blogspot.com/2010/01/why-running-shoes-do-not-work-looking.html
http://stevemagness.blogspot.com/2010/01/first-big-study-on-barefoot-running-in.html
http://www.time.com/time/video/player/0,32068,62885933001_1955910,00.html
http://www.time.com/time/magazine/article/0,9171,1955580,00.html
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/09/02/BA1G19FFPH.DTL
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/10/05/DDG419E4P0.DTL
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/10/05/DDGB19VSQV.DTL
http://www.nytimes.com/2009/08/30/business/30shoe.html?_r=1&scp=1&sq=vibram&st=cse
http://well.blogs.nytimes.com/2009/09/01/have-you-run-barefoot/?scp=2&sq=vibram&st=cse http://well.blogs.nytimes.com/2009/10/05/the-roving-runner-goes-barefoot/?scp=9&sq=vibram&st=cse