Different morphology and function of hip extensor muscles between sprint runners and sprint cyclists

During a specific task, the whole-body motion favors those with muscles suited for its execution; in addition, it leads to adaptations in muscle morphology and function of muscles. Thus, the well suited and/or adapted muscles are particularly crucial for enhancing performance in each competitive sport. Here, we compared muscle morphology, strength, and EMG activity during isometric maximal voluntary contraction (MVC) at multiple hip angles in runners and cyclists with similar sagittal motion (but different ranges of motion) during competition. Ten sprint track runners and ten sprint track cyclists performed the MVC test of hip extension, and magnetic resonance images of the buttocks and thighs were acquired. Maximum hip extension torque and surface electromyography (EMG) signals from the gluteus maximus (GM) biceps femoris long head (BFlh) and semitendinosus (ST) muscles were assessed during the MVC test at six hip flexion angles (45°, 60°, 75°, 90°, 105°, and 120°). Muscle volumes were determined using magnetic resonance images. Cyclists had a significantly higher MVC torque normalized by the muscle volume than that observed in runners at a hip flexion angle of 120°. At hip flexion angles of 105° and 120°, the normalized root mean square of the EMG signal in cyclists was significantly higher than in runners. Torque-angle relationship in hip extension differed between runners and cyclists, with cyclists generating greater extension torque by increasing GM muscle EMG activity in the flexed position. This may differ in the neuromuscular adaptation to and/or suitability for specific tasks of hip extensor morphology and function in runners and cyclists.