Study confirms differences in dominant- versus non-dominant-leg power output during exercise

Reviewed by James Ives, M.Psych. (Editor)Oct 24 2019

A new study confirms important differences in dominant- versus non-dominant-leg oxygen usage and power output during single-leg exercise. The study is published ahead of print in the American Journal of Physiology- Regulatory, Integrative and Comparative Physiology.

Single-leg exercise, such as cycling, may be a component of scientific studies that examine exercise capacity and other physiological changes that take place in the muscles during physical activity. Single-leg cycling may also play a role in physical, cardiac or respiratory rehabilitation in people who are recovering from injuries. In addition, "single-leg training might be a very useful tool in patients with conditions that prevent them from exercising at higher intensities during whole-body exercise, but who can still benefit from strong signals for adaptation within the active muscles," explained corresponding author Juan Murias, PhD, of the University of Calgary in Canada.

Previous research has shown that the dominant leg- the preferred side of the body for motor skills-;often generates more power than the non-dominant leg during double-leg exercise, such as riding a standard bicycle. However, even with this knowledge, there has been an assumption in the field of exercise physiology that both legs have a similar capacity for exercise before fatiguing. Murias' research team examined the physiological responses of both the dominant and non-dominant legs during sessions of single- and double-leg cycling.

A small group of healthy men performed single- and double-leg cycling incremental tests-;exercise intensity progressively increases until exhaustion-;and 30-minute constant-intensity trials. The single-leg trials were aided with a 15-pound counterweight attached to the opposite pedal. In single-leg cycling, the participant must actively flex and lift the exercised leg with each revolution. Counterweighting balances the exercised leg so it does not move in a different pattern than in double-leg cycling, reducing discomfort and fatigue. The research team then measured the power generated, oxygen usage and exercise capacity in both dominant and non-dominant legs.

During the single-leg incremental tests, the volunteers' dominant legs consistently worked at a higher level of VO2max, the ability to use oxygen during exercise and a marker of aerobic fitness. The dominant leg was also able to generate and sustain more power than the non-dominant leg during the constant-intensity trials. These findings could affect rehabilitation and training intervention programs that include single-leg exercise and "have important implications for the design of future studies using counterweighted single-leg cycling," the researchers wrote.