Comparison of Muscle Activity in Three Single-Joint, Hip Extension Exercises in Resistance-Trained Women.
Level 2 - randomized trial
Individual randomized crossover trial measuring acute electromyographic responses
PubMed 33948095 · doi:10.52082/jssm.2021.181
What was done
Fifteen resistance-trained females performed three repetitions with a 6-repetition maximum (6-RM) load across three hip extension exercises in a randomized and counterbalanced order: the Romanian deadlift, the 45-degree Roman chair back extension, and the seated machine back extension. Electromyographic activity was measured in the gluteus maximus, biceps femoris, and erector spinae across the entire movement as well as during its lower and upper phases.
What was found
The Romanian deadlift and Roman chair back extension produced greater gluteus maximus activation than the seated machine back extension (94% to 140% higher, p < 0.01). For the biceps femoris, the Roman chair elicited 71% to 174% higher activation compared to both the Romanian deadlift and seated machine, while the Romanian deadlift elicited 61% greater activation than the seated machine (p < 0.01). The Roman chair produced greater activation in the upper movement phase for both the gluteus maximus and biceps femoris compared to the other exercises. Erector spinae activation did not differ between the three exercises (p = 1.00).
Why it matters
This study clarifies muscle recruitment differences among common hip extension movements, demonstrating that the Roman chair and Romanian deadlift stimulate the gluteus maximus substantially more than seated machine back extensions while offering distinct hamstring activation patterns.
Limits
The study had a small sample size (n = 15) and included only resistance-trained women, limiting generalizability to men or untrained populations. Surface electromyography measures acute neuromuscular activation rather than long-term strength or hypertrophy outcomes, and absolute loads and kinematic parameters were not reported in the abstract.
Cited by
- context Rounding the back during a 45-degree hyperextension reduces erector spinae involvement, shifting the load primarily to the gluteal muscles for hip extension.