Sex differences in thigh muscles characteristics: a systematic review

Objective: To determine differences between male and female subjects in the thigh muscles characteristics, separated into architectural (pennation, thickness, and/or fascicle length), mechanical (mass, strength, power, and/or stiffness), neuromuscular (activity) and fatigue aspects, in order to better understand the sex-related differences in the risk of muscle injuries. Methods: A systematic literature search on Pubmed was performed with different keywords: skeletal muscle AND sex characteristics AND muscle contraction, with the following limits: humans and adults (19–44 years old). Studies dealing with hamstring and quadriceps muscles, in physiological condition, and comparison between male and female healthy adult subjects were included. Studies dealing with other skeletal muscles, injuries or physiopathology situation were excluded. Thigh muscular architectural, mechanical, neuromuscular and fatigue characteristics have been analysed to determine differences between male and female subjects. Results: Seventeen studies were included, reporting significant sex-related differences for thigh muscles architecture and mechanical characteristics and muscle fatigue, and especially quadriceps, while for thigh muscles neuromuscular characteristics the results were not consensual, and few information was available regarding hamstring muscles. Conclusions: Sex-related differences in thigh muscles characteristics, and especially quadriceps, have been reported for mechanical characteristics and muscle fatigue, while for neuromuscular characteristics sex-related differences were found to be moderate. Although several macroscopic muscle characteristics have been reported to be different between male and female healthy adult subjects, it is difficult to conclude on its exact relationship with higher muscle injury rates reported in male athletes during international athletics championships.