The adductor magnus (AM) is the third largest muscles, and also monoarticular muscle in the lower limb. The purpose of this study was to compare the AM with the gluteus maximus (GM) and the hamstrings (semimembranosus SM, semitendinosus ST, and long head of the biceps femoris BF) in terms of how these muscles generate extension torque during antigravity movement and to assess whether or not the AM plays a role as a primary antigravity muscle.

Ten healthy young men took part in this study, approved by the ethics committee. Squatting activities were selected for an anti-gravity movement. Each subject performed unloaded squats maintaining the trunk as upright as possible with either the hips in neutral rotation or the feet shoulder width apart, or letting the trunk flex naturally with either the hips in neutral rotation or the feet shoulder width apart. Kinematic data were taken with a motion capture system (VICON) and floor reactions were recorded with force plates (Kistler). We determined muscle torques by optimization calculation. The skeletal model used was SIMM.

In task1 and task2, lacking trunk flexion, GM and AM exerted much greater hip extension torques than did hamstirngs. In task3 and task4, with the trunk naturally flexed, SM and BF were much more contributory, whereas ST exhibited relatively little torque in either task.

Given that the antigravity function of the AM is more like that of the GM than of the hamstrings, the AM might more appropriately be considered a primary antigravity muscle than an ancillary one.