Motion and Muscle Activity Are Affected by Instability Location During a Squat Exercise

Area of Science:

• Biomechanics
• Exercise Physiology
• Sports Science

Background:

• Instability devices are popular for squat training, but most create bottom-up perturbations.
• The effects of top-down instability during squats are not well understood.
• The Attitube, a water-filled cylinder, can induce top-down instability.

Purpose of the Study:

• To investigate the effects of instability location (top-down, bottom-up, stable) on squat kinematics and muscle activation.
• To compare the biomechanical and neuromuscular responses to different squat instability conditions.

Main Methods:

• Ten male participants performed squats under three conditions: stable, bottom-up (BOSU ball), and top-down (Attitube).
• Kinematics were tracked using 75 markers on the body and equipment.
• Electromyography (EMG) was recorded from 12 bilateral muscles.

Main Results:

• Top-down instability (Attitube) led to reduced trunk flexion and erector spinae activation, alongside increased abdominal oblique activation.
• Bottom-up instability (BOSU ball) increased ankle eversion, knee flexion, and activation of gastrocnemius, biceps femoris, and quadriceps.
• Instability location significantly altered trunk and lower extremity motion and muscle activation patterns.

Conclusions:

• The location of instability during squats critically influences biomechanical and neuromuscular adaptations.
• Findings offer insights for rehabilitation, technique learning, and specialized training protocols.
• Further research can explore the practical applications of targeted instability in squat exercises.