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November 17 - November 25, 2019
Messner and Habeler settled on a motto: “Everest by fair means”—or not at all.
training studies have found that increases in VO2max aren’t necessarily proportional to increases in race performance.
VO2max really is a pretty good predictor of performance.
the researchers suggested that being born at altitude and having very active childhoods ensured that the Kenyans were better equipped to maintain the brain’s oxygen supply: they had more blood vessels to the brain, with thicker walls that were harder to squeeze shut.
But in practice, assigning the blame to mind or muscles is an often hopeless and sometimes misleading task. After all, the brain is part of the body.
In other words, feelings and emotions and urges are as physiologically real as changes in core temperature or decreases in hydration, and are mediated by chemical signals.
For every 100 calories of food you eat, in others words, you might get 25 calories of useful work and 75 calories of heat. As wasteful as that sounds, it’s surprisingly similar to the efficiency of a typical internal combustion engine.
the body is like a car with no air-conditioning: you’ve got no way of actively cooling yourself, so the best you can do is get rid of excess heat as quickly as possible.
In very hot conditions, when the air temperature is comparable to or higher than your skin temperature, evaporation is the only effective cooling method you’ve got. And if it’s so humid that sweat starts dripping off you instead of evaporating, the clock is ticking as your core temperature starts to inch upward.
Studies during World War II, when Allied troops were preparing for combat in stifling jungle and desert environments, found that 60 to 90 minutes of moderate exercise per day in hot conditions would produce rapid physiological changes within a few days, with full acclimatization taking place within about two weeks.
this may help explain the long-standing tradition in some cultures of drinking a hot drink like tea during scorching summer afternoons. By triggering the temperature receptors in your stomach, the hot drink ramps up your sweating response without heating the rest of your body, which has the net effect of cooling you down.
a British study in 2012 showed that cyclists in a heat chamber went 4 percent faster when the thermometer was rigged to display a falsely low temperature (79 instead of 89 degrees Fahrenheit).
They noticed a surprising trend: marathon runners were shrinking at an alarming rate.22 In 1990, the average top-100 runner had clocked in at just over 5'8" and 131 pounds; by 2011, those numbers had dropped to under 5'7" and 124 pounds.
“motivational self-talk” specifically tailored to exercising in heat, which basically involved suppressing negative thoughts like “It’s so hot in here” or “I’m boiling,” and replacing them with motivational statements like
words, allows you to push beyond your usual temperature limits: “Even if you’re already fit, you can still improve your perception of heat and how you perform in it.”
There’s a long list of factors that nudge your heatstroke risk upward, but researchers at the U.S. Army Research Institute of Environmental Medicine, in a 2010 review, singled out three in particular: heavy, poorly ventilated clothing; preexisting illness; and the use of certain drugs such as amphetamines.
she had drunk as much as she could stomach during her run, causing the levels of sodium in her blood to become diluted (that’s what “hyponatremia,” sometimes referred to as “water intoxication,” means).
Dehydration is a greater concern in longer races, because you have more time to sweat; heatstroke, in contrast, is most common in shorter races.
Given that his sweat rate was three times higher than that, there was never any chance he would be able to limit his fluid loss to 2 percent: drinking more would simply leave fluid sloshing around in his stomach without increasing hydration.
The results are consistently the opposite of what you would expect: the fastest finishers tend to be the most dehydrated.
an estimated 85 percent of collapses take place shortly after crossing the finish line. This suggests that there is something about the act of stopping after prolonged exertion that triggers problems; if the cause was dehydration, you would expect to see more athletes crumpling to the pavement in the closing miles of the race rather than a few steps beyond the finish line.
The problem, many researchers now believe, is a loss of blood pressure caused by blood pooling in the legs after you stop running or cycling. During exercise, your heart directs vast quantities of blood to the oxygen-starved muscles in the legs.
The first step is to make a distinction between thirst, which is the feeling that you would like to take a drink, and dehydration, which is the state of having lost fluids relative to your normal levels.
while being thirsty virtually always indicates that you’re dehydrated, the concept of “voluntary dehydration” illustrates that, conversely, being dehydrated won’t always make you thirsty.
Mountains of data now demonstrate that being dehydrated and thirsty, even at a relatively mild level, will slow you down.
Instead of monitoring fluid levels, your body monitors “plasma osmolality,” which is the concentration of small particles like sodium and other electrolytes in your blood.
By adjusting the amount of salt in our sweat, we’re able to keep plasma osmolality stable even as we lose water—for a while, at least.
The result is that you can be “dehydrated,” at least in the sense that you’ve lost weight, without hurting your performance. What matters, instead, is how thirsty you are.
Avoiding thirst, rather than avoiding dehydration, seems to be the most important key to performance.
When it comes to quenching your thirst, perception—not just in your mouth, but in the cool flow of liquid down a parched throat—is, at least in part, reality.
In recent years, the debate about hydration has become increasingly polarized.
One final caveat is that our ability to tolerate temporary bouts of dehydration is, well, temporary.
And in the absence of evidence, it makes sense to err on the side of caution and minimize dehydration (not just thirst) during extremely prolonged bouts of exercise.
That’s the message Cheung hopes people will take from his study, and from the spate of recent research challenging hydration orthodoxy: not that you shouldn’t drink when you have the chance, but that you shouldn’t obsess about it when you don’t. “It’s one less psychological crutch,” he says, “to hold you back from a top performance.”
The LCHF debate, which has been roiling the weight-loss world since the early 2000s, had recently made the leap to endurance sport.
It’s not just how much fuel is in the tank, in other words. Endurance performance also depends on what types of fuel you have available, where it’s stored, and how quickly you can access it.
the fitter you are, for example, the greater the proportion of fat you burn at any given speed. (That’s simply because maintaining a given speed gets easier as you get fitter.
Eating a diet high in either fat or carbohydrate also tilts your preferred fuel mix in that direction.
“When first thrown wholly upon the diet of reindeer meat, it seems inadequate to properly nourish the system and there is an apparent weakness and inability to perform severe exertive, fatiguing journeys,”18 Schwatka noted in his diary. “But this soon passes away in the course of 2-3 weeks.”
In the Arctic, he had noted, the Inuit relished the fattiest parts of the animal, giving the leanest meat to the dogs.
Proving that you can survive on meat alone—as remarkable as that still seems—is different than proving it’s a superior diet, and in particular that it enhances endurance.
in exchange for their enhanced ability to burn fat, the cyclists seemed to have lost some of their ability to harness quick-burning carbohydrate for short sprints, resulting in “a severe restriction on the ability of subjects to do anaerobic work.”
high-fat diets don’t just ramp up fat burning; they actually throttle carbohydrate usage by decreasing the activity of a key enzyme called pyruvate dehydrogenase.
scientists have traditionally figured that 60 grams an hour (about 250 calories) is pretty much the maximum amount you can absorb during exercise. The rate-limiting step is the absorption of carbohydrate from the intestine into the bloodstream.
Researchers in Scandinavia have recently shown that glycogen stores in your muscles don’t just act as energy reservoirs; they also help individual muscle fibers contract efficiently.27 That means your muscles will weaken as you burn through your glycogen stores, sapping your strength long before you’re actually out of fuel.
The sweet taste of sugar, in other words, is not enough to trigger the benefits. Instead, the mouth appears to contain previously unknown (and as yet unidentified) sensors that relay the presence of carbohydrate directly to the brain.
In practice, these findings mean that the benefits of sports drinks and other mid-race carbohydrates for short bouts of exercise are irrelevant as long as you don’t start out with an empty stomach and depleted fuel stores. (Pro tip: you shouldn’t.)
And given the complementary strengths and weaknesses of the two options—carbohydrate as a fast fuel with limited storage capability, fat as an inexhaustible but rate-limited alternative, it makes sense to aim for what Louise Burke, of the Australian Institute of Sport, calls “metabolic flexibility,” by maximizing both fuel pathways.
