The Science of Running

These Hearts Were Made For Running; More Vitamins Aren’t Always Better; This is Your Brain on Overtraining

These hearts were made for running

Back in 2004, a pair of scientists made headlines – and f luffed the egos of runners everywhere – by proposing that humans were “born to run.” The demands of hunting and gathering on the African savannah millions of years ago left us with dozens of adaptations that make us better runners, from shorter toes to a specialized neck tendon that holds our heads steady even at full speed. Running, they argued, was what made us recognizably human. Yet, the hypothesis left open a lingering question: were our hearts also adapted to handle the strain of prolonged exercise?

To answer that question, Harvard Universit y evolut iona r y biolog ist Daniel Lieberman, one of the scientists who originally proposed the “born to run” hypothesis, teamed up with a cardiologist and an exercise physiologist. They compared 42 long-distance runners from the Harvard track team with a comparable group of linemen from the Harvard football team, as well as groups of sedentary adults, subsistence farmers from the Tarahumara tribe in Mexico, and chimpanzees and gorillas. The results, published in the Proceedings of the National Academy of Sciences, suggest that we’re not just born to run – we need to run.

The differences between humans and chimps were pretty clear in the cardiac ultrasound images. In general, hearts have to deal with two distinct t ypes of challenges: pressure and volume. During short, sharp bouts of resistance exercise, your blood pressure shoots up. It’s helpful to have a relatively small and round heart with thick walls to deal with these high pressures. And sure enough, the chimps, whose physical activity mainly involves short bouts of fighting and climbing, had small, round hearts with thick walls.

During long bouts of sustained aerobic exercise, in contrast , the heart ideally pumps large volumes of oxygen-rich blood to the muscles. For this task, you want a bigger, more elongated heart that can fit more blood in its chambers, with relatively thin walls that can f lex and contract easily. That’s what the humans in the study had, bolstering the claim that our hearts have evolved to handle the sustained moderate-intensity effort involved in hunting, gathering and subsistence farming. But not all the humans were the same: the runners and farmers had hearts that were better adapted to handling high volumes of blood, while the football players and sedentary controls had smaller, thicker hearts that were, in some respects, indistinguishable from chimpanzee hearts.

The subjects in the sedentary control group were still young and healthy, with normal blood pressure – a crucial detail in the study. Scientists previously assumed that inactive people develop thicker hearts and stiffer blood vessels as a result of chronic high blood pressure. However, the new results suggest that it may be the other way around: if you don’t get enough endurance exercise, your heart walls begin to thicken, which in turn starts a vicious cycle that results in high blood pressure and heart disease, one of the most common causes of death in the developed world. Bottom line: don’t skip today’s run.

More vitamins aren’t always better

There aren’t many supplements left with untarnished reputations. Huge clinical trials have failed to find benefits for once-common daily pills like vitamins Can dE. Among the last hold outs is vitamin D and of particular concern for people in sunstarved northern climes like Canada. Whether vitamin D supplements actually improve the health of otherwise healthy people remains highly controversial, but they haven’t been proven unhealthy, and many doctors still recommend taking them during the winter.

A recent jam a study from the University of Calgary’s McCaig Institute for Bone and Joint Health randomized 311 volunteers to receive a daily dose of either 400 IU (which is in keeping with the recommended daily amount), 4,000 IU or 10,000 IU to find out whether these mega-doses could boost bone health. But after three years, the two higher-dosed groups had significantly lower bone mineral density. Supplements, it turns out, are a lot like training: just because some is good, more isn’t necessarily better.

This is your brain on overtraining

Researchers in France made a big ask of the endurance athletes who signed up for one of their recent studies: they had to boost their weekly training by a whopping 40 per cent. After three weeks, the subjects were understandably exhausted and dead-legged. But there was also a more subtle change, which showed up during cognitive tests in a brain scanner. When faced with questions like, “Would you prefer $10 now or $50 in six months?” the exhausted athletes became more likely to opt for instant rewards over delayed gratification.

As the researchers reported recently in Biology Letters, the results suggest that mental and physical fatigue are more closely related than we might expect. The changes in what you might call “willpower” weren’t a result of acute exhaustion since an all-out 45-minute cycling time trial didn’t produce the same effects. Instead, the brain-scanning results showed that a region of the brain called the middle frontal gyrus, part of the brain’s self-control network, becomes harder to activate when you’re on the edge of overtraining.

France’s anti-doping agency funded the study to understand whether athletes might be more vulnerable to the promised instant gratification of doping when they’re exhausted or overtrained. After all, who among us hasn’t felt the lure of junk food and other quick fixes growing stronger while in the throes of heavy training. The new results suggest that it’s not just that you’re craving calories; your decisionmaking preferences are shifting with fatigue, and that may be a clue that it’s time to ease back and recover.