Some people say that runners who seek out ultramarathons are crazy. They insist that it’s a form of masochism where mentally deficient athletes go to destroy their bodies. The physical toll of exerting oneself over 30, 50, 60, 100 miles at a time is enormous. Consider the energetic demands: a study on energy expenditure during the grueling Western States 100-mile Endurance Run in California (originally designed as a horse race over big mountains, occasional snow, rivers, hot valleys, etc.) found that the race required over…drumroll please…13,000 kCal!
Obviously, energetic demands are not the layman’s only deterrent from ultramarathons. A long-term monitoring project, known as the Ultrarunners Longitudinal TRAcking (ULTRA, but they’re reaching on that one) study, has been following approximately 3,000 volunteers for the past few years and found some interesting results. (The use of the prefix “ultra” gets some flak due to the notion that these runners are in some way above and beyond normal runners. I will use it because it is convenient.) Some basic findings are that injuries were common (about 77% of participants), especially stress fractures and knee problems, and silly young runners got the majority of the injuries. There were also many reasons why these ultrarunners ended up in the hospital after events, including dehydration, heat exhaustion, skin lesions, fractures, and concussions. So, why do it?
I would join the camp of people who insist that it is more about strategy, like a game of chess: figure out what your body really needs and what it thinks it needs, then coax it further with mental games. This is based on the theory that we unconsciously hold back during exercise to prevent fatigue and physical harm. Athletes are realizing more and more that with a calculated approach to figuring out what the body really needs and when you can keep it satisfied and draw the most potential from its obstinate frame.
Doctors have done a wonderful job finding out what endurance athletes really need. Volunteers have been stopping occasionally to donate some blood to science whilst casually jogging or biking for 24 hours at a time, allowing us to see in real time the measures our body takes to preserve itself. First of all, our metabolism goes through certain shifts in fuel sources during the prolonged exercise. The initial energy source is stored in our muscles as creatine phosphate. This gets broken down quite rapidly, acting as more of a jump starter than a battery. At the right pace, our bodies shift into aerobic metabolism where we require oxygen to break down carbohydrates like glucose and glycogen, our primary energy storage molecules. Without constant supplementation, we will deplete these stores in about two hours. This would be okay if we were world-class marathon runners. And if we were only talking about marathon distances.
Marathon world record holder William Kipsang at the Berlin Marathon.
No, not the fool in the fluorescent shirt. The other guy.
Studies show that around this time our fats start to kick in. These hold quite a bit of energy, but not as much as carbohydrates and they require us to slow down to much lower exercise intensities. However, they are extremely important for keeping blood glucose concentrations relatively stable. Then what? Of the major macromolecules, we’re still missing nucleotides (nope, ATP burns up lickety split) and…protein! Protein metabolism has actually been shown to offer only a small amount to our energy budget, partly because proteins are important to every other function and their loss affects us in a multitude of ways. (Immediate body mass loss is one of these losses, but over 100 miles, who wouldn’t want to be a bit lighter on their feet? I call that a win.) In fact, a reliance on protein breakdown puts recovering ultrarunners in a negative energy balance for several days following an event while a disappointed body cleans up the mess. Any decent endurance athlete understands that the only way to stave off this process is to take in the right combination of nutrients while on the move.
Exercise physiologists also point to other signals of bodily stress over the course of ultra-endurance events. As I mentioned before, the Western States race ranges from freezing temperatures to 100oF while runners contend with a combined elevation gain of approximately 17,000 feet. As if running 100 miles on flat ground wasn’t hard enough.
|(http://www.wser.org/course/maps/) Western States Endurance Race elevation profile. Meh. Looks like a lot of downhill to me...|
Now picture yourself sweating throughout this event. Depending on intensity and ambient conditions, the rate of sweating would be between 1 and 2.5 liters per hour. If this race takes you 24 hours (you actually get a special prize if you do in this race…a belt buckle) that means you’ve sweat between 24 and 60 liters. Losing this kind of fluid without replacement can lead to fatal dehydration, but misjudging the ratio of water to electrolytes (sodium, potassium, magnesium, etc.) can also lead to potentially fatal hyponatremia. This makes calculated rehydration a tricky, but vital, business over the race duration.
Other signs of the grueling physical effects include the inflammatory response. Skeletal muscle damage from the excessive weight-bearing muscle contraction does not go unnoticed in the body, and boy is there a lot of it. Creatine Kinase (CK) in blood plasma is the most direct measurement of muscle damage, and a recent study during a 24-hour race showed up to a 70-fold increase in CK activity in their participants. (Melodramatic people like to compare the amount of CK triggered by these endurance events to that spurred by a severe heart attack, though this is flawed since the heart contains its own specific subset of CK.) This kind of damage incurs quite an immune response. These participants doubled their white blood cell count, likely stimulated by the 30-fold increase in the inflammatory mediator interleukin-6 (IL-6). While IL-6 increased during the race and stabilized, one of its functions is to induce high-sensitivity C-reactive protein (hsCRP), which induces anti-inflammatory cytokines and recognizes damaged cells for removal. How much did hsCRP increase? Well, after showing up around marathon-distance, it increased exponentially to over 20 times its original amount by the end of the 24-hour race.
Even before reading this, many people would agree that ultrarunners are completely mental. In some respects, they’re right. We all experience mental fatigue. Consider your exhaustion after a long drive during which, physically, you’re really just sitting in one spot. The reality is that fatigue from mental exertion activates the anterior cingulate cortex (ACC) of your brain, which just so happens to also be related to the perception of effort during exercise, even enough to affect autonomic body systems—ones which we don’t consciously control—like respiration and heart rate. This means that both the physical and mental effort involved in endurance events (most people get mentally fatigued just trying to stay awake for 24 hours!) recruit brain signals that influence your decisions about whether to keep moving or not. This contradicts the previously held notion that fatigue sets in only when the muscles’ demands for oxygen and fuel can no longer be met. In reality, you unconsciously guard your body to ensure that when you reach that finish line you don't actually give 100%, keel over, and Rest In Peace.
RMT device. What’s wrong with a straw?
So, with an event like the Western States 100, why doesn’t our brain want us to stop earlier? Well, it does. But you want that post-race barbeque, beer, and belt buckle.This is where strategy becomes crucial. The numerous studies on physiological changes during endurance events provides a list of carefully calculated ins & outs to prevent dehydration, hyponatremia, renal failure, etc. and cope with the stress. However, the mind needs some tricking. A new hype is Respiratory Muscle Training (RMT), using a device which was supposed to increase oxygen capacity but didn’t really work that way. Instead, researchers found that the training reduced perception of effort during exercise without any significant physiological changes, suggesting that there may have been a desensitization of the brain’s feedback mechanism, thus prolonging high-intensity exercise.
Other studies have attempted to separate the sensations that alert the brain to physiological effort from the psychological effort required to fight back and drag on for another mile. They found that the brain’s dorsal posterior insula may be the receptor for the body’s afferent alerts, which then will be processed into the overwhelming sense of fatigue that we feel in the right anterior insula. Don’t worry: all of these parts of the brain will come together soon.
In practice, ultrarunners don’t care where the signals are, just that they’re there. They try mental workouts to strengthen their resistance to mental fatigue, all-nighters and sauna workouts to simulate race conditions, preparatory workouts on courses to improve their task familiarity, Zen practices for improved mind control, and, of course, the carefully calculated cocktails of fluids to keep the brain working smoothly. In general, training is the most reliable way to improve endurance. Just like the RMT (um…breathing practice) the brain will become accommodated to long, stressful workouts as it realizes “Hey, I didn’t die!” Beyond this training, we are pushing into the realm where the mind can also be tricked. In 2009, Chambers et al. showed that simply swishing some liquid with carbohydrates, sweet or not, and then spitting it out stimulated areas of the brain involved in the reward and regulation of physical activity, including both the insula and the anterior cingulate cortex that we saw earlier! Furthermore, they gave some athletes a placebo and others carbohydrates, and those swishing the carbohydrates (not even swallowing them) completed a timed course significantly faster than those with the placebo.
Take one look at the video below and you'll see that there's very little that endurance athletes want to stop for. This research makes the prospect of tricking the brain into allowing increasingly more hazardous endurance events a reality. For athletes who constantly want to push the fringes of what the body is capable of, that is an extremely exciting opportunity. After all, what possibilities open up without the brain's panicked signals to slow, be careful, or stop?
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Edwards, A. M. 2013. Respiratory muscle training extends exercise tolerance without concomitant change to peak oxygen uptake: Physiological, performance and perceptual responses derived from the same incremental exercise test: Respiratory muscle training efficacy. Respirology18:1022–1027.
Hoffman, M. D., and E. Krishnan. 2014. Health and exercise-related medical issues among 1,212 ultramarathon runners: baseline findings from the Ultrarunners Longitudinal TRAcking (ULTRA) study. PLoS ONE 9:e83867.
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Waskiewicz, Z., B. Klapcinska, E. Sadowska-Krepa, M. Czuba, K. Kempa, E. Kimsa, and D. Gerasimuk. 2012. Acute metabolic responses to a 24-h ultra-marathon race in male amateur runners. European Journal of Applied Physiology 112:1679–1688.