Stance width and bar load effects on leg muscle activity during the parallel squat

Area of Science:

• Biomechanics
• Exercise Physiology
• Sports Science

Background:

• Foot stance variations are commonly used in parallel squats to target specific muscle groups.
• Understanding muscle activation patterns is crucial for optimizing training and injury prevention.

Purpose of the Study:

• To compare the electromyographic (EMG) activity of six hip and knee muscles during parallel squats.
• To investigate the effects of different stances (narrow, shoulder width, wide) and external loads (60% and 75% 1RM) on muscle activation.

Main Methods:

• Surface EMG data were collected from nine male lifters for rectus femoris, vastus medialis, vastus lateralis, adductor longus, gluteus maximus, and biceps femoris.
• Subjects performed squats with varying stances and loads, with repetition time controlled.
• A repeated measures ANOVA was used to analyze integrated EMG values across different phases, loads, and stances.

Main Results:

• Quadriceps muscles (rectus femoris, vastus medialis, vastus lateralis) showed significant load-dependent activation only.
• Adductor longus and gluteus maximus activity varied with stance and phase of the squat, and load.
• Biceps femoris activity was most pronounced during the ascent phase of the squat.

Conclusions:

• Varying foot stance width in parallel squats does not lead to isolation of the quadriceps muscles.
• Stance width significantly influences muscle activation in the medial thigh (adductor longus) and buttocks (gluteus maximus).
• External load is a primary factor affecting quadriceps activation during parallel squats.