If you're a woman new to lifting and do leg extensions twice a week for two months, your front thigh muscle (rectus femoris) will grow more all along its length than if you did squats.
Scientific Claim
In untrained young women, 8 weeks of twice-weekly leg extension training causes greater hypertrophy of the rectus femoris at proximal (+11.4%), middle (+12.3%), and distal (+17.5%) sites compared to back squats, which produce minimal changes at these locations.
Original Statement
“The LE experienced greater increases in the 3 RF sites (proximal: +11.4% vs. +2.0%; middle: +12.3% vs. +5.7%; distal: 17.5% vs. +7.9%; all p < 0.001).”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
definitive
Can make definitive causal claims
Assessment Explanation
The RCT design, controlled volume, and significant p-values (<0.001) across all three RF sites support definitive causal language. The claim is limited to the studied population and muscle.
Evidence from Studies
Supporting (1)
The study found that leg extensions made the front thigh muscle grow much more than squats did in women who were new to lifting, exactly as the claim says.
Technical explanation
The study directly supports the claim by showing that in untrained young women, 8 weeks of twice-weekly leg extension training resulted in significantly greater hypertrophy of the rectus femoris at all three sites (proximal: +11.4% vs. +2.0%; middle: +12.3% vs. +5.7%; distal: +17.5% vs. +7.9%) compared to back squats, with all differences being statistically significant (p < 0.001). The back squat group showed minimal changes in rectus femoris size, consistent with the claim that it produces 'minimal changes.' The study’s methodology—randomized design, controlled training volume (3 sets of 8–12 RM, 2x/week), and precise ultrasound measurements at proximal, middle, and distal sites—aligns perfectly with the claim’s parameters. The conclusion explicitly states that leg extensions induce greater rectus femoris hypertrophy than back squats, confirming the claim’s accuracy.