Squats and leg extensions produced different muscle and strength gains
In untrained young women, leg extensions produced greater growth at measured rectus femoris sites, while Smith machine squats favored one vastus lateralis site and squat strength.
Based on the published abstract. The full paper may contain additional methods, results and limitations.
The 30-second takeaway
The exercises produced different patterns of adaptation. Leg extensions led to greater thickness increases at each measured rectus femoris site, while squats led to a greater increase at the distal vastus lateralis site and greater squat strength gains. Leg extension strength gains did not differ significantly between groups, which does not prove equivalence.
This abstract-based account covers a short trial in untrained young women using a Smith machine squat. It cannot establish how these patterns extend to experienced lifters, other populations or longer training periods.
What researchers found
Change in distal vastus lateralis thickness
Smith machine squat versus leg extension after 8 weeks; reported percentage changes, p < 0.001.
Location mattered
Researchers measured thickness at several locations within the named thigh muscles, rather than treating the entire thigh as a single outcome. That makes the findings specific to the muscle and measurement site.
Strength depended on the test
Strength testing also used both exercises. Squat training produced the larger gain in the squat test, while the leg extension test did not clearly favor either training group in the reported comparison.
The original publication
Comparison of Muscle Hypertrophy and Strength Adaptations Induced by Back Squat and Leg Extension Resistance Exercises.
Kassiano W, Costa B, Kunevaliki G et al.
J Strength Cond Res · 2026
- PubMed ID
- 41379528
- Record checked
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