Asymmetry of force generation and neuromuscular activity during multi-joint isometric exercise

Abstract

The purposes of the present study were (a) to determine whether a self-reported dominant leg was consistent with a dominant leg of force generation by using the isometric mid-thigh pull (IMTP) tests and (b) identify the features of bilateral IMTP (IMTP_Bi) and unilateral IMTP (IMTP_Uni) in terms of detecting strength imbalance of athletes. Fifteen male collegiate athletes performed IMTP_Uni and IMTP_Bi. The ground reaction force and surface electromyography were sampled with 1000Hz to assess force generation and neuromuscular activities in the gluteus maximus (G_max), gluteus medius (G_med), semitendinosus (ST), biceps femoris (BF), rectus femoris (RF) and vastus lateralis (VL) during IMTP. Legs were separated into dominant and non-dominant leg categories in accordance with two types of definitions including self-reported dominance of kicking leg and dominance of force generation in IMTP. In force generation and neuromuscular activity of IMTP_Bi and IMTP_Uni, there was no significant difference between self-reported dominant and non-dominant leg. However, results for a self-reported dominant leg were not consistent with results for dominant leg determined by force generation. In addition, the dominant leg of force generation exerted significantly larger PF than non-dominant leg, and the magnitude of asymmetry in IMTP_Bi was significantly larger than that of IMTP_Uni. Moreover, in IMTP_Bi, the neuromuscular activity of the VL of the dominant leg of force generation was significantly larger than that of the non-dominant leg. Therefore, it was suggested the necessity to distinguish the two types of IMTP tests because of the possibility that the strength imbalances detected by IMTP_Bi and IMTP_Uni would have different connotations.