Runners, swimmers, and cyclists are familiar with the phenomenon of "hitting the wall" when the connection between brain and body feels like it's been lost: You know that you're still trying to move, but doing it feels more conceptual than physical. In Cell Metabolism, researchers show in mice the physiological basis for why this phenomenon occurs. Their research also found that training is not the only way to enhance endurance - it can also be achieved using a small molecule to stimulate a pathway that was already known to be activated by training.
"It turns out that 'hitting the wall' happens when your brain can no longer get enough glucose.