Short high-intensity exercise may be as beneficial as longer moderate exercise

By Sally Robertson, B.Sc.Sep 20 2018

A new study has shown that performing high-intensity interval or sprinting exercise for a few minutes may be equally as beneficial as exercising at a moderate-intensity level for longer periods.

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The study, which has recently been published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, showed that short bursts of higher intensity exercise were just as effective at improving mitochondrial function as moderate-intensity exercise carried out for longer periods.

Previously, studies have shown that exercise generates more of the energy-producing mitochondria in our cells, as well as improving the function of mitochondria that are already present. This improved function can be beneficial to cells and decrease the risk of chronic disease, but whether or not the intensity of exercise affects this mitochondrial response has been unclear.

To investigate, the authors of the current study studied eight young adults who performed cycling workouts at different levels of intensity.

Moderate intensity was defined as 30 minutes of ongoing exercise at 50% peak effort; high-intensity as five four-minute sessions at 75% peak effort, with a one-minute rest period in-between each session and sprint cycling as four 30-second sessions at maximum effort with 4.5 minutes rest in-between.

Before and after each session, the researchers determined the amount of energy the participants used up during each session and compared mitochondrial changes in their thigh muscles.

They found that the concentration of hydrogen peroxide, which is a reactive oxygen species (ROS) molecule, changed in different parts of the mitochondria after exercise. While the presence of too much ROS can damage cells, this study found that the participants had levels of ROS that could potentially promote cellular processes that improve metabolic function rather than causing damage.

The team also found that fewer minutes of high-intensity exercise triggered similar mitochondrial responses as exercise performed at moderate-intensity for longer periods.

A total of only two minutes of sprint interval exercise was sufficient to elicit similar responses as 30 minutes of continuous moderate-intensity aerobic exercise"

"This suggests that exercise may be prescribed according to individual preferences while still generating similar signals known to confer beneficial metabolic adaptions. These findings have important implications for improving our understanding of how exercise can be used to enhance metabolic health in the general population.”