Squats make the lower part of your outer thigh bigger, while leg extensions make your front thigh muscle bigger — your muscles grow in different spots depending on how you train them.
Scientific Claim
In untrained young women, the distal region of the vastus lateralis is more responsive to back squat training than to leg extension training, while the rectus femoris is more responsive to leg extensions, indicating muscle region-specific adaptations based on exercise mechanics.
Original Statement
“The LE experienced greater increases in the 3 RF sites... Conversely, the SQ showed greater increases in VL at the distal site (+18.2% vs. +11.2%; 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 study’s precise regional measurements and significant p-values support definitive causal claims about site-specific hypertrophy. No overgeneralization beyond the measured sites occurred.
Evidence from Studies
Supporting (1)
This study found that squats make the lower part of the outer thigh muscle grow more, while leg extensions make the front thigh muscle grow more—showing that different exercises target different parts of the muscles.
Technical explanation
The study directly supports the claim by demonstrating muscle region-specific adaptations: leg extensions produced significantly greater hypertrophy in the rectus femoris across all three sites (proximal, middle, distal), while back squats induced significantly greater hypertrophy in the distal vastus lateralis (18.2% vs. 11.2%, p < 0.001). These findings align with the claim that exercise mechanics drive differential adaptations—leg extensions, being a knee-extension-dominant isolation movement, preferentially stimulate the rectus femoris, while back squats, involving hip and knee extension with greater mechanical demand on the distal quadriceps, preferentially activate the distal vastus lateralis. The study controlled for training volume, frequency, and participant population (untrained young women), strengthening internal validity. Strength data further corroborate exercise-specific adaptation, with greater squat strength gains in the SQ group. No contradictory findings were observed.