Inter-subject variability in muscle synergies during squatting movements

Area of Science:

• Biomechanics
• Motor Control
• Human Movement Analysis

Background:

• Muscle synergies are fundamental to human movement.
• Understanding individual variability in muscle synergies is crucial for optimizing motor control strategies.
• The squat exercise is a common functional movement with complex muscle activation patterns.

Purpose of the Study:

• To investigate inter-subject variability in muscle synergies during the squat exercise.
• To identify distinct types of muscle synergies and their prevalence across individuals.
• To explore the coexistence of universal and individualized motor control strategies in squats.

Main Methods:

• Non-negative matrix factorization (NMF) was used to extract muscle synergies from electromyography data.
• K-means clustering and discriminant analysis were employed to categorize muscle synergies.
• Sixteen healthy adults performed standardized squats to assess muscle activation patterns.

Main Results:

• An average of 3.3 muscle synergies were identified per squat.
• Six distinct types of muscle synergies were observed across the participants.
• One universal synergy, involving trunk, hip, and knee extensors, was present in all subjects.
• Other synergies showed mutual exclusivity, indicating individual selection of motor strategies.

Conclusions:

• Significant inter-subject variability exists in muscle synergies during squats.
• Human motor control during squats involves both universal and individualized muscle synergy patterns.
• Findings provide a basis for personalized squat training and rehabilitation informed by neuromechanical principles.