Q. Why do I sometimes get a second wind when exercising?
A. Many people find that exercise occasionally gets easier in the middle of a long session, but understanding why has been tricky. “I don’t know that anyone knows how to induce a second wind,” says Bruce Gladden, an exercise physiologist at Auburn University, adding that there’s not much evidence for a second wind based on physical measures taken when people are exercising.
But there are a few plausible explanations. Gladden says that the energy system we rely on for long bouts of exercise is the oxidative (or aerobic) system, which uses oxygen to provide energy. It takes several minutes for the oxidative capacity of this system to increase to meet the body’s energy demands, and Gladden says a second wind could correspond to reaching this balance.
Paul Thompson, a cardiologist at Hartford Hospital, speculates that a second wind could also come from blood vessels in muscles or bronchial tubes in the lungs that become more fully dilated over time, and therefore more efficient, based on studies showing that warm-up exercise makes hard exercise easier.
A recent study found that people’s perceived exertion — how hard they think they’re exercising — fluctuates even when they’re cycling at constant power. Natalia Balagué, an exercise physiologist at the University of Barcelona and one of the study’s authors, suggests that various bodily systems working together have periods when they stabilize and exercise feels easier; a second wind may be one of these times.