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Relaxation of Skeletal Muscles

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
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Exercise and Muscle Performance

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Muscle Stimulation Frequency

Muscle Stimulation Frequency

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Wave summation
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Somatic Spinal Reflexes

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Related Experiment Video

Updated: Jun 22, 2026

Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity

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Published on: June 12, 2019

Regular stretch does not increase muscle extensibility: a randomized controlled trial.

M Ben¹, L A Harvey

¹Rehabilitation Studies Unit, Northern Clinical School, Faculty of Medicine, University of Sydney, Sydney, Australia.

Scandinavian Journal of Medicine & Science in Sports

|June 6, 2009

Summary

Regular stretching for six weeks did not enhance hamstring muscle extensibility in healthy individuals. However, it did improve stretch tolerance, leading to a greater range of motion without actual muscle flexibility gains.

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Published on: July 5, 2017

Area of Science:

Sports Medicine
Physiotherapy
Biomechanics

Background:

Muscle extensibility is crucial for athletic performance and injury prevention.
The optimal duration and frequency of stretching for improving muscle extensibility remain debated.
Distinguishing between actual muscle extensibility and stretch tolerance is important for effective training.

Purpose of the Study:

To investigate the effect of a 6-week regular stretching program on hamstring muscle extensibility.
To differentiate between changes in muscle extensibility and stretch tolerance following a stretching intervention.

Main Methods:

A randomized controlled trial involving 60 healthy participants.
An experimental group performed 30-minute supervised hamstring stretches 5 times/week for 6 weeks.
Passive hip flexion during a straight leg raise was measured using a standardized device and stretch torque.

Main Results:

No significant increase in passive hip flexion was observed when measured with a standardized stretch torque (mean difference: -1°, 95% CI: -3° to 2°).
A significant increase in passive hip flexion occurred when measured without a standardized stretch torque (mean difference: 10°, 95% CI: 6° to 14°).
The findings suggest improved stretch tolerance rather than increased muscle extensibility.

Conclusions:

Six weeks of sustained, intensive stretching does not increase hamstring muscle extensibility in healthy individuals.
The observed increase in range of motion is attributed to enhanced stretch tolerance, not a change in the muscle's intrinsic flexibility.
Clinical implications suggest focusing on stretch tolerance may be key for improving joint range of motion in specific populations.