Single-leg cycling to maintain and improve function in healthy and clinical populations

Abstract

Exercise with reduced muscle mass facilitates greater muscle-specific adaptations than training with larger muscle mass. The smaller active muscle mass can demand a greater portion of cardiac output which allows muscle(s) to perform greater work and subsequently elicit robust physiological adaptations that improve health and fitness. One reduced active muscle mass exercise that can promote greater positive physiological adaptations is single-leg cycling (SLC). Specifically, SLC confines the cycling exercise to a smaller muscle mass resulting in greater limb specific blood flow (i.e., blood flow is no longer “shared” by both legs) which allows the individual to exercise at a greater limb specific intensity or for a longer duration. Numerous reports describing the use of SLC have established cardiovascular and/or metabolic benefits of this exercise modality for healthy adults, athletes, and individuals living with chronic diseases. SLC has served as a valuable research tool for understanding central and peripheral factors to phenomena such as oxygen uptake and exercise tolerance (i.e., V̇O2peak and V̇O2 slow component). Together, these examples highlight the breadth of applications of SLC to promote, maintain, and study health. Accordingly, the purpose of this review was to describe: 1) acute physiological responses to SLC, 2) long-term adaptations to SLC in populations ranging from endurance athletes to middle aged adults, to individuals living with chronic disease (COPD, heart failure, organ transplant), and 3) various methods utilized to safely perform SLC. A discussion is also included on clinical application and exercise prescription of SLC for the maintenance and/or improvement of health.

Counterweight mass influences single-leg cycling biomechanics

“…Given that a greater relative power output can be performed by cyclists during single-leg cycling, which provides a means to increase oxidative capacity of skeletal muscle [10], the limitations in transferability to a different task may be outweighed by the positive effects of the adaptations incurred. Lastly, the use of single-leg cycling in patient populations [4] is probably not diminished by the biomechanical differences between single-leg and double-leg cycling. For these applications, single-leg cycling is employed because it is more tolerable than double-leg cycling (e.g., for patients with COPD [11]) or because one leg is unable to train (e.g., for patients recovering from ACL surgery [13]).…”

“…Single-leg cycling is a common form of unilateral exercise that has been used frequently to study various aspects of human physiology [1][2][3][4]. As this mode of exercise allows legs to be exercised independently, it reduces the amount of active muscle mass during an exercise intervention by approximately half.…”