How muscles turn on when pushing hard
Quadriceps EMG/force relationship in knee extension and leg press.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Vastus lateralis EMG increases linearly with force, while other quadriceps muscles do not, despite all being part of the same muscle group.
Most people assume all quadriceps muscles activate in a similar, proportional way as effort increases. This shows they don’t — recruitment is uneven, which challenges assumptions about muscle symmetry.
Practical Takeaways
Use vastus lateralis EMG as a more reliable indicator of force output during isometric leg exercises at 90 degrees.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Vastus lateralis EMG increases linearly with force, while other quadriceps muscles do not, despite all being part of the same muscle group.
Most people assume all quadriceps muscles activate in a similar, proportional way as effort increases. This shows they don’t — recruitment is uneven, which challenges assumptions about muscle symmetry.
Practical Takeaways
Use vastus lateralis EMG as a more reliable indicator of force output during isometric leg exercises at 90 degrees.
Publication
Journal
Medicine and science in sports and exercise
Year
2000
Authors
Björn A. Alkner, P. Tesch, H. Berg
Related Content
Claims (4)
Even though leg extensions only move one joint, they might work your front thigh muscles better than squats or leg presses because they really target one specific muscle in the quad.
When healthy guys push with their legs at a 90-degree bend, their quad muscles don’t fire in a straight line with how hard they push — the muscle activity changes unevenly as they push harder from 20% to 100% effort.
When healthy guys push with their legs, the electrical activity in one specific thigh muscle (vastus lateralis) goes up steadily with how hard they push — unlike two other thigh muscles — so it might be a better way to measure how much force their whole quad is producing.
When men push with their legs using different exercises but at the same knee angle, their thigh muscles turn on in a similar way, even though one exercise uses more joints than the other.