For the outer thigh muscle (vastus lateralis), bending your hip to 40 or 90 degrees during leg extensions doesn’t seem to make a difference in how much the muscle grows in guys who haven’t lifted before.

Scientific Claim

There is no meaningful difference in hypertrophy of the vastus lateralis muscle between 40° and 90° hip flexion during leg extension exercises in untrained men over 10 weeks.

Original Statement

“strong' evidence supporting no difference in hypertrophic response for the vastus lateralis (BF = 0.07)”

From study:The effects of hip flexion angle on quadriceps femoris muscle hypertrophy 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 abstract uses 'strong' Bayesian evidence for no difference, which is appropriately interpreted as probabilistic. The within-subject RCT design supports causal inference, but verb strength is moderated due to small sample size.

Evidence from Studies

Supporting (1)

The effects of hip flexion angle on quadriceps femoris muscle hypertrophy in the leg extension exercise

Randomized Controlled Trial

Human

2025 Jan

The study found that bending your hip to 40° or 90° during leg extensions doesn’t make a meaningful difference in how much the big outer thigh muscle (vastus lateralis) grows — so both positions work just as well for that muscle.

Contradicting (0)

No contradicting evidence found

Source Study

The effects of hip flexion angle on quadriceps femoris muscle hypertrophy in the leg extension exercise

Score: 54

DOI: 10.1080/02640414.2024.2444713

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