Force generation and neuromuscular activity in multi-joint isometric exercises: comparison between unilateral and bilateral stance

抄録

The purpose of the present study was to look at lower extremity force generation and neuromuscular activation by comparing isometric mid-thigh pull in the unilateral stance (IMTP_Uni) and bilateral stance (IMTP_Bi), and identifying the characteristics of IMTP_Uni. Fifteen male collegiate athletes (age: 20.60 ± 1.50 years, height: 1.74 ± 0.05 m, mass: 69.04 ± 4.23 kg) performed IMTP_Uni and IMTP_Bi as multi-joint isometric exercise. Ground reaction force (GRF) was measured to assess force generation during IMTP. Surface electromyography (EMG) was used to measure neuromuscular activation in the gluteus maximus (G_max), gluteus medius (G_med), semitendinosus, biceps femoris (BF), rectus femoris (RF) and vastus lateralis (VL), which were represented as average rectified values (ARVs). The EMG of the muscles during IMTP_Uni was normalized by IMTP_Bi to compare relative change among muscles. The co-contraction index (CI) during IMTP_Uni was also calculated by using normalized EMG. As a result, IMTP_Bi was significantly higher in BF than IMTP_Uni. However, in IMTP_Uni, although only one leg contributed to produce force, GRF of IMTP_Uni reached 80% of neuromuscular activity relative to IMTP_Bi. While the neuromuscular activation of G_max, G_med, BF, RF and VL was significantly higher proportionately in IMTP_Uni compared to IMTP_Bi, neuromuscular activation was even greater in G_max and G_med. The co-contraction index (CI) was increased in IMTP_Uni. The features of neuromuscular activation during IMTP_Uni were similar to the single leg squat and step-up exercise examined in previous studies due to the necessity to support the body with a single leg.