New lifters get stronger at leg extensions by doing squats, but experienced lifters need to do leg extensions to get better at them.
Scientific Claim
In untrained individuals, compound movements can improve performance on isolation movements due to enhanced neuromuscular coordination, overriding the specificity principle; however, in trained individuals, strength gains are highly movement-specific.
Original Statement
“Squats were more effective than leg extensions to build leg extension strength. This finding was also observed in a previous study on leg presses. However, both of these studies were in untrained individuals. It's possible that in untrained individuals the overall benefits for strength development of doing a compound exercise, which is better coordination and letting the brain and the motor cortex learn, teach it how to control your movements better is more effective than the specificity principle, because in trained lifters the specificity principle usually holds.”
Context Details
Domain
exercise
Population
human
Subject
compound exercises (e.g., squats)
Action
improve performance on
Target
isolation movements (e.g., leg extensions) in untrained individuals
Intervention Details
Evidence from Studies
Supporting (2)
The study found that when beginners train one hamstring exercise, they get stronger at a different hamstring exercise too — even if their muscles don’t grow much. This means their brains and nerves got better at coordinating the movement, not just their muscles getting bigger — which supports the idea that beginners can improve across exercises without training them directly.
Comparison of Muscle Hypertrophy and Strength Adaptations Induced by Back Squat and Leg Extension Resistance Exercises.
People who only did squats got just as strong at leg extensions as people who only did leg extensions — meaning squats helped with the isolation move too, even though they weren’t training it directly. This supports the idea that compound moves can boost isolation move performance in beginners.