If you're a guy new to lifting and want your front thigh muscle to grow as much as possible, doing leg extensions with your hip more bent (40°) is probably better than keeping it straighter (90°).
Scientific Claim
For untrained men aiming to maximize rectus femoris growth, training the leg extension exercise with reduced hip flexion (40°) is a more effective strategy than 90° hip flexion.
Original Statement
“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.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
probability
Can suggest probability/likelihood
Assessment Explanation
The recommendation uses 'suggest' and is grounded in strong Bayesian evidence (BF > 100). The language is appropriately probabilistic given the small sample and lack of blinding, despite the RCT design supporting causal inference.
Evidence from Studies
Supporting (1)
The effects of hip flexion angle on quadriceps femoris muscle hypertrophy in the leg extension exercise
The study found that bending the hip only 40 degrees during leg extensions made the front thigh muscle (rectus femoris) grow more than bending it 90 degrees — so if you want to build that muscle faster, use a less bent hip position.