Whether you do squats or leg extensions for two months, you’ll get about equally stronger at doing leg extensions — the exercise you don’t do doesn’t hurt your progress on it.
Scientific Claim
In untrained young women, 8 weeks of twice-weekly back squat or leg extension training produces similar increases in leg extension 3RM strength (+19.8% vs. +23.4%, p = 0.824), indicating that both exercises are equally effective for improving this specific strength outcome.
Original Statement
“No between-group difference was observed in 3RM-LE increases (SQ = +19.8% vs. LE = +23.4%; p = 0.824).”
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 with precise strength testing and non-significant p-value (p = 0.824) supports definitive language that both exercises are equally effective for this outcome.
Evidence from Studies
Supporting (1)
Both exercises made women stronger at leg extensions by about the same amount, even though one is a squat and the other is a leg extension machine—so for improving leg extension strength, they work just as well.
Technical explanation
The study directly supports the claim by showing that both back squat and leg extension training produced statistically similar increases in leg extension 3RM strength (+19.8% vs. +23.4%, p = 0.824), indicating no significant difference between the two exercises for this specific outcome. Although the back squat group showed greater gains in squat strength and different muscle hypertrophy patterns (e.g., greater vastus lateralis growth), the leg extension strength improvement was comparable between groups. The study’s design—randomized, controlled, with identical training frequency and volume—ensures valid comparison. The authors explicitly conclude that 'both exercises are likely similarly effective for increasing leg extension strength,' directly aligning with the claim. The p-value of 0.824 confirms the null hypothesis of no difference, reinforcing equivalence in this specific adaptation.