Which leg exercise you choose matters: leg extensions grow the front thigh muscle more, squats grow the lower outer thigh more and make you stronger at squats—but both help you get stronger at leg extensions.

Scientific Claim

Exercise selection—specifically back squat versus leg extension—significantly influences regional muscle hypertrophy and strength adaptations in untrained young women over an 8-week period, with leg extensions favoring rectus femoris growth and back squats favoring distal vastus lateralis growth and squat-specific strength gains.

Original Statement

“Based on our results, the leg extension induce greater rectus femoris hypertrophy, while the back squat promotes greater vastus lateralis hypertrophy, particularly at the distal site. The back squat training seems to be more effective for increasing squat strength, but both exercises are likely similarly effective for increasing leg extension strength.”

From study:Comparison of Muscle Hypertrophy and Strength Adaptations Induced by Back Squat and Leg Extension Resistance Exercises.

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 definitive language ('induce', 'promotes', 'more effective'), but given the lack of blinding confirmation, probabilistic language ('likely', 'seems to') is more appropriate under conservative EBM standards.

More Accurate Statement

“Exercise selection—specifically back squat versus leg extension—likely significantly influences regional muscle hypertrophy and strength adaptations in untrained young women over an 8-week period, with leg extensions likely favoring rectus femoris growth and back squats likely favoring distal vastus lateralis growth and squat-specific strength gains.”

Evidence from Studies

Supporting (1)

Comparison of Muscle Hypertrophy and Strength Adaptations Induced by Back Squat and Leg Extension Resistance Exercises.

Randomized Controlled Trial

Human

2025 Dec 12

This study found that doing leg extensions makes the front thigh muscle (rectus femoris) grow more, while doing squats makes the lower part of the outer thigh muscle (vastus lateralis) grow more and makes you stronger at squats specifically.

Contradicting (0)

No contradicting evidence found

Source Study

Comparison of Muscle Hypertrophy and Strength Adaptations Induced by Back Squat and Leg Extension Resistance Exercises.

Score: 48

DOI: 10.1519/JSC.0000000000005338

Similar Assertions

Doing leg extensions makes the front thigh muscle grow more evenly along its length than doing squats, which don’t stimulate that muscle as much.

89%

Squats make the lower part of the outer thigh muscle grow more than leg extensions do, probably because squats involve more hip and knee movement together.

80%

Even if you only do squats, you still get almost as strong at leg extensions as someone who only does leg extensions—so squats aren’t useless for that movement.

78%

Squats build your thigh muscles (quads and inner thighs) more than hip thrusts do, because squats involve more knee and hip movement that engages those muscles more.

76%

If you want to get stronger at squats, doing squats is way better than doing leg extensions—but if you want to get stronger at leg extensions, both exercises work about the same.

76%