Effects of knee flexion angles in supine bridge exercise on trunk and pelvic muscle activity

This study investigated the activity of surface electromyography (sEMG) on trunk and pelvic muscles during supine bridge exercise (SBE) with different knee flexion angles. Twenty-five physically active males participated in this study. Subjects received maximum voluntary isometric contraction (MVIC) tests followed by four SBEs with different knee flexion angles (40 degrees, 60 degrees, 90 degrees and 120 degrees) in random. sEMG activities of rectus abdominis (RA), erector spinae (ER), gluteus medius (GMed), superior gluteus maximus (SGMax), inferior gluteus maximus (IGMax), biceps femoris (BF) long head, and the ratio of SGMax/BF and IGMax/BF on the dominant side were measured. Non-clinical magnitude-based inference was performed to compare the effect. The results indicated a substantial change of muscle activity, especially between SBE with 40 degrees and 120 degrees knee flexion. With respect to ER and BF, moderate effect (-0.70 +/- 0.17) and extremely large effect (-4.78 +/- 0.51) were recorded, whereas very large effect for SGMax/BF (2.68 +/- 0.23) and IGMax/BF (2.95 +/- 0.26) was observed, respectively. Both ER and BF worked better with smaller knee flexion angles (40 degrees > 60 degrees > 90 degrees > 120 degrees), while SGMax and IGMax were more favourable to SBE with large knee flexion angles (90 degrees = 120 degrees > 60 degrees > 40 degrees).