Why leg strength doesn’t change with body position
The role of agonist and antagonist muscles in explaining isometric knee extension torque variation with hip joint angle
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
This study checks if lying down makes your legs stronger than sitting when pushing straight out. Even though one key thigh muscle is stretched more when lying down, people don’t push harder. The reason seems to be that the brain doesn’t fully turn on the muscle in that position.
Surprising Findings
Despite the rectus femoris being lengthened in the supine position—where it should produce more force—maximal voluntary torque did not increase.
This contradicts the expected length-tension relationship in muscle physiology, which predicts higher force at longer muscle lengths on the ascending limb of the curve.
Practical Takeaways
When assessing muscle strength clinically or in training, consider that body position may influence neural drive, not just muscle mechanics.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
This study checks if lying down makes your legs stronger than sitting when pushing straight out. Even though one key thigh muscle is stretched more when lying down, people don’t push harder. The reason seems to be that the brain doesn’t fully turn on the muscle in that position.
Surprising Findings
Despite the rectus femoris being lengthened in the supine position—where it should produce more force—maximal voluntary torque did not increase.
This contradicts the expected length-tension relationship in muscle physiology, which predicts higher force at longer muscle lengths on the ascending limb of the curve.
Practical Takeaways
When assessing muscle strength clinically or in training, consider that body position may influence neural drive, not just muscle mechanics.
Publication
Journal
European Journal of Applied Physiology
Year
2017
Authors
T. Bampouras, N. Reeves, V. Baltzopoulos, C. Maganaris
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Claims (5)
When healthy guys lie on their back, their thigh muscles can push harder than when they're sitting — probably because the position stretches one key muscle and lets it work better.
When healthy guys push with their legs, they're just as strong sitting or lying down—even though one position stretches the muscle more. That means muscle strength isn’t just about how stretched the muscle is.
When guys sit down and squeeze their quads as hard as they can, their hamstrings resist more than when they're lying flat — probably because the hips are bent.
When lying down, your leg muscles don't get stronger even if one key muscle gets longer — and that's mostly because your brain isn't fully turning on those muscles, not because opposing muscles are getting in the way.
Leaning back during leg extensions might make your front thigh muscle work harder and grow more because it stretches the muscle more during the move.