Effects of knee flexion angles in supine bridge exercise on trunk and pelvic muscle activity.
Level 2 - randomized trial
Randomized crossover physiological trial
PubMed 32567954 · doi:10.1080/15438627.2020.1777552
What was done
Twenty-five physically active males performed maximum voluntary isometric contraction tests followed by supine bridge exercises at four randomized knee flexion angles (40°, 60°, 90°, and 120°). Surface electromyography (sEMG) was recorded on the dominant side for the rectus abdominis, erector spinae, gluteus medius, superior gluteus maximus, inferior gluteus maximus, and biceps femoris long head. Muscle activation ratios (superior gluteus maximus/biceps femoris and inferior gluteus maximus/biceps femoris) were calculated and compared using magnitude-based inference.
What was found
Muscle activation patterns varied significantly across knee angles, with the largest differences observed between 40° and 120°: - Erector spinae and biceps femoris activation decreased as knee flexion angle increased (40° > 60° > 90° > 120°), showing a moderate effect (-0.70 ± 0.17) for erector spinae and an extremely large effect (-4.78 ± 0.51) for biceps femoris when comparing 120° to 40°. - Superior and inferior gluteus maximus activation favored larger knee flexion angles (90° = 120° > 60° > 40°). - Ratios of gluteus to hamstring activity increased markedly at 120° versus 40°, with effect sizes of 2.68 ± 0.23 for superior gluteus maximus/biceps femoris and 2.95 ± 0.26 for inferior gluteus maximus/biceps femoris.
Why it matters
Performing supine bridges at 90° or 120° of knee flexion optimizes gluteus maximus recruitment while minimizing hamstring and erector spinae dominance, offering practical positioning guidance for rehabilitation and strength protocols.
Limits
The study was small (n = 25) and included only healthy, active young males, limiting generalizability to females, clinical rehabilitation cohorts, or older adults. Surface electromyography measures muscle electrical activation rather than direct force output, and long-term training adaptations were not assessed.
Cited by
- context During a hip thrust, placing the feet too close shifts the sensation to a stretch in the rectus femoris rather than glute activation.