Hamstring-to-quadriceps activation ratio during lower-limb strengthening exercises

Area of Science:

• Biomechanics
• Exercise Physiology
• Sports Science

Background:

• Strength training often overemphasizes quadriceps activation over hamstring activation.
• This imbalance can lead to detrimental knee joint instability and potential injury.

Purpose of the Study:

• To analyze the hamstring-to-quadriceps (H:Q) surface electromyography (sEMG) activation ratio.
• To evaluate the lateral to medial hamstring activation ratio (LH:MH) across various strength exercises.
• To identify exercises that promote balanced hamstring and quadriceps engagement.

Main Methods:

• Surface electromyography (sEMG) was used to measure muscle activation.
• Key exercises analyzed included parallel squat, Romanian deadlift, hip thrust, lying leg curl, and seated knee extension.
• H:Q EMG and LH:MH ratios were calculated during concentric and eccentric phases.

Main Results:

• The lying leg curl demonstrated the highest H:Q EMG ratio during both concentric and eccentric phases.
• Romanian deadlift and hip thrust also showed relatively high H:Q EMG ratios.
• The parallel squat exhibited a greater LH:MH ratio compared to the Romanian deadlift and hip thrust.

Conclusions:

• The lying leg curl is optimal for increasing hamstring activation and the H:Q EMG ratio.
• This exercise also provides a more homogenous LH:MH, suggesting balanced hamstring activation.
• The lying leg curl is recommended for rehabilitation and training to enhance knee muscle balance.