Can apparent increases in muscle extensibility with regular stretch be explained by changes in tolerance to stretch?

Area of Science:

• Sports Medicine
• Rehabilitation Science
• Biomechanics

Background:

• Limited hamstring muscle extensibility can affect athletic performance and increase injury risk.
• Distinguishing between actual muscle extensibility and stretch tolerance is crucial for evaluating stretching interventions.

Purpose of the Study:

• To investigate if an intensive stretching program enhances hamstring muscle extensibility or improves tolerance to stretch discomfort.
• To differentiate between changes in muscle extensibility and stretch tolerance following a four-week intervention.

Main Methods:

• A within-subjects design was employed with 20 healthy individuals.
• One leg received a four-week intensive stretch program (20 minutes/weekday); the other served as a control.
• Hamstring muscle extensibility and stretch tolerance were measured via hip flexion angles at standardized torque.

Main Results:

• The stretching intervention did not significantly increase hamstring muscle extensibility (mean change: -1 degree hip flexion).
• Subjects demonstrated a significant increase in tolerance to uncomfortable stretch sensations (mean change: 8 degrees hip flexion).

Conclusions:

• A four-week intensive stretching program can enhance stretch tolerance without a corresponding increase in muscle extensibility.
• Clinical assessments of stretching interventions should differentiate between objective measures of extensibility and subjective measures of tolerance.