For endurance athletes, “hitting the wall” feels a lot like it sounds. You want to keep going, but your body just won’t let you.
It’s already known that this phenomenon stems in part from a drop in glucose levels, but researchers at the Salk Institute wanted to find out more: How do we move “the wall,” or delay the fatigue runners and other athletes experience? And what about people who can’t exercise — can they get the same health benefits as endurance athletes?
Led by Ronald Evans, a professor at the Gene Expression Lab at the Salk Institute, new research out in the journal Cell Metabolism found that endurance can be enhanced in ways other than training — with some molecular help.
Athletes hit the wall when their brains use up their supply of sugar, Evans explains. “The muscle can dually burn sugar and fat, and the muscle is greedy for all nutrients.” So as you train your body to run longer distances, you’re training it to lose less sugar, to delay the impact of the wall.
“Most people thought, ‘Oh, they’re training to burn more fat.’ But actually, you're training to use less sugar,” Evans says.
With training, your body chemistry changes, he says: “The changing of the ratio of sugar and fat involves hundreds of genes and their products. You might think of music, and getting the right bass and treble and the net volume involving hundred of little dials that turn genes up and down.”
Evans says he’s found a shortcut to these health benefits that could eventually prove useful, whether for runners or for people who are unable to be active.
“What we've shown is that it's possible to develop a small molecule — you might call it a pill— that is able to confer the benefits of fitness without training," he says. "And that has a number of benefits, and it acts through a series of pathways that normally get stimulated by natural exercise.”
His study tested mice on a treadmill. When given a dose of a chemical compound called GW1516, the mice increased the time it took them to hit the wall, from 160 to 270 minutes. Though the mice had no training to improve their endurance, they improved by about 70 percent.
“So the very surprising feature is that you get the benefits of training but without actually having had to exercise," Evans says. "And that leads to dramatic endurance, even though you have not been running or training every day to achieve that.”
Needless to say, countless experiments that work in mice do not work in humans. But the study does add hope that someday, a drug might bring the benefits of exercise to people who can't get moving themselves.