Sex Difference in Lower-limb Electromyography and Kinematics when Using Resistance Bands during a Barbell Back Squat

Area of Science:

• Biomechanics
• Exercise Physiology
• Sports Science

Background:

• Barbell back squats (BBS) are a fundamental strength exercise.
• Resistance bands can alter biomechanics during squats.
• Understanding sex-based differences in muscle activation and knee displacement is crucial for training.

Purpose of the Study:

• To compare muscle activity (gluteus medius, gluteus maximus, biceps femoris, vastus lateralis, vastus medialis, erector spinae) and medial knee displacement (MKD) during BBS with varying resistance band stiffness.
• To investigate sex-based differences in these parameters.

Main Methods:

• 23 resistance-trained individuals (11 female) performed BBS at 85% 1RM with three resistance bands (red, black, gold).
• Muscle activity was measured via electromyography (EMG).
• Lower-limb kinematics and MKD were tracked using motion capture.

Main Results:

• The gold resistance band (highest stiffness) significantly increased MKD (p < 0.01).
• Males exhibited less MKD than females across all band conditions (p = 0.04).
• Males showed greater vastus lateralis activity with black and gold bands (p = 0.03); gluteus medius activation increased with the gold band (p < 0.01).
• Vastus medialis activity decreased with the gold band (p < 0.01). Biceps femoris and erector spinae activity remained unchanged.

Conclusions:

• Heavier resistance bands increase medial knee displacement during BBS.
• Females demonstrate greater MKD than males, potentially indicating a biomechanical disadvantage.
• Resistance bands alter lower-limb muscle activation patterns, with sex-specific responses observed.