In another study on muscle, scientists aimed to challenge the widely held notion that external load—provided by lifting weights or performing body-weight movements, for example—is required to achieve hypertrophy.
Published in Physiology & Behavior (2016; 164, Part A, 345–52), this study compared external-load hypertrophy training and “no-load” muscular contractions. The 13 participants completed an elbow flexion exercise at 70% of one-repetition maximum with one arm. They also performed elbow flexion without load, contracting the muscle as much as possible throughout full range of motion using the other arm. Both protocols were repeated throughout 18 sessions.
Both the loaded and unloaded interventions resulted in similar improvements in hypertrophy. However, loaded training led to greater improvements in 1-RM and muscle endurance.
The authors stated, “Muscle growth can occur independent of the external load provided [that] sufficient tension is produced by the muscle; however, strength is proportional to the load being used and the modality of exercise being performed.”