Mixed
Performing leg extension exercises with a reduced hip flexion angle (approx. 40°) produces significantly greater hypertrophy in the rectus femoris compared to a standard upright hip angle (90°), while having no differential effect on the vastus lateralis.
If your goal is to maximize growth in the rectus femoris (the muscle in the middle of your thigh), adjust your leg extension machine to lean back slightly (approx. 40 degrees of hip flexion) rather than sitting fully upright. This position likely places the rectus femoris at a more optimal length for growth. Note that this change does not appear to affect the vastus lateralis (outer thigh) growth, so both positions are valid for general quad development.
Results indicated a greater hypertrophic response in the rectus femoris for the 40° condition... Therefore, both conditions could be viable options for increasing quadriceps femoris hypertrophy. However, when training for maximizing rectus femoris hypertrophy among untrained men, we suggest training with a reduced hip flexion in the leg extension exercise.
Why this rating
High-quality within-subject design with strong Bayesian evidence (BF > 100) for the rectus femoris difference, though the sample size (n=22) is modest.
Source
The effects of hip flexion angle on quadriceps femoris muscle hypertrophy in the leg extension exercise
Stian Larsen et al. · Journal of Sports Sciences · 2024
DOI 10.1080/02640414.2024.2444713
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