Effect of stretching on hamstring muscle compliance

Area of Science:

• Biomechanics
• Musculoskeletal Physiology
• Sports Medicine

Background:

• Hamstring flexibility is crucial for athletic performance and injury prevention.
• Understanding the impact of stretching on muscle properties is essential for optimizing training protocols.

Purpose of the Study:

• To investigate the direct and indirect effects of a 4-week passive stretching program on hamstring muscle compliance.
• To assess changes in passive range of motion, muscle thickness, and strength following stretching.

Main Methods:

• A 4-week passive stretching protocol was applied to one leg of 12 healthy men, with the contralateral leg serving as a control.
• Instrumental straight leg raise, surface electromyography, computerized muscle tonometry, ultrasound, and dynamometry were used to assess outcomes.
• Measurements included stretching force, muscle activity, muscle compliance, biceps femoris thickness, and knee flexion strength.

Main Results:

• Stretched legs showed a significant 17-degree increase in straight leg raise and a 19 N increase in mean stretching force (p<0.001).
• Improved flexibility correlated with increased biceps femoris muscle thickness (r=0.74).
• No significant changes were observed in muscle compliance, muscle activity via surface electromyography, or maximal knee flexion strength.

Conclusions:

• Four weeks of passive hamstring stretching effectively improves passive straight leg raise range without negatively impacting muscle compliance.
• The study indicates that improvements in flexibility can occur while maintaining muscle viscoelastic properties and strength.