Sprint Interval Training Affects Men And Women Differently

Sprint interval training, or short bursts of maximum effort interspersed with longer periods of active recovery, has been shown to improve insulin sensitivity, burn fat and improve endurance performance faster than moderate-pace exercise can.

While the benefits are spread out equally between men and women, men seem to have at least one advantage over women when it comes to this form of training: It creates significantly more muscle protein in men than it does women.

Researchers from the Department of Health and Exercise Science at Colorado State University, Fort Collins, found that while women experienced the same significant increase in aerobic performance as men, the training led to the creation of more muscle protein in men than women -- which, over time, could result in more lean muscle mass.

"What we found is that males were more responsive from a skeletal muscle standpoint than women" said Rebecca Scalzo, the primary author of the study. "This may be why men have more muscle mass than women do." In the past, researchers thought there must be differences in protein synthesis between men and women because of the differences in muscle mass between the sexes. However, no one had measured it before this study. Scalzo's findings also add to an emerging body of research about sprint interval training by exploring physiological differences between men and women.

However, that doesn't mean women should sit out when it comes to sprints, explained Scalzo. Both male and female participants increased their aerobic capacity, or the maximum amount of oxygen their bodies used during intense exercise, during the four-week sprint study.

"This doesn't mean women shouldn't be doing sprint interval training, because there are several benefits associated with it besides an increase in protein synthesis," said Scalzo. "But what our study really highlights is that there are sex differences in response to the training, and more studies need to be done on these responses."

Scalzo and her team asked 21 healthy young adults (11 male and 10 female) to come in for a baseline assessment of their aerobic capacity and muscle mass. She then instructed them to start drinking "heavy water," a special kind of water called deuterium oxide. They drank the heavy water for one week, and continued to drink it over the next three weeks as they completed a total of nine sprint interval training sessions.

The sessions were composed of 30-second sprints on a stationary bike, interspersed with 4 minutes of active recovery cycling at lower speeds. Each session ranged from four to eight sprint intervals. At the end of the training session, researchers biopsied participants' muscle mass, and the new proteins that were created during the experiment were marked with the deuterium oxide from their special water.

Past research has already shed more light on the differences between men and women when it comes to exercise. For instance, researchers at the Mayo Clinic in Rochester, Minn., found in 2014 that maximum heart rates are different between men and women, and therefore can't simply be calculated by subtracting age from 220, as was originally thought. And although both sexes' maximum heart rates decline with age, they do so at different rates, too.