Kinematic and EMG activities during front and back squat variations in maximum loads

Area of Science:

• Biomechanics
• Exercise Physiology
• Sports Science

Background:

• Squat variations are fundamental resistance exercises.
• Understanding muscle activation and joint kinematics is crucial for optimizing training and injury prevention.
• Maximal loading in squats presents unique biomechanical demands.

Purpose of the Study:

• To compare muscle activity and joint kinematics between front and back squats under maximal loading conditions.
• To identify differences in vastus medialis, semitendinosus, and trunk lean between the two squat variations.
• To provide insights into exercise selection for specific training goals and injury mitigation.

Main Methods:

• Electromyography (EMG) measured muscle activity of key lower body and trunk muscles.
• Two-dimensional kinematic analysis captured knee and hip joint movements.
• Twelve participants performed maximal loading front and back squats.
• Paired sample t-tests were used for statistical comparisons.

Main Results:

• Vastus medialis EMG was significantly higher during front squats (ascending phase and whole movement).
• Semitendinosus EMG was significantly higher during back squats (ascending phase).
• Back squats demonstrated significantly greater trunk lean compared to front squats, with no difference in knee kinematics.

Conclusions:

• Front squats may be superior for targeting knee extensor development due to higher vastus medialis activation.
• The reduced trunk lean in front squats might offer a protective effect against lumbar injuries during maximal loading.
• Exercise selection should consider specific goals, such as knee extensor emphasis or lumbar spine protection.