Intermittent stretch reduces force and central drive more than continuous stretch

Area of Science:

• Neuromuscular Physiology
• Exercise Science
• Sports Medicine

Background:

• Understanding the factors contributing to force loss after stretching is crucial for optimizing training and rehabilitation protocols.
• Acute stretching can induce reductions in muscle force, with potential contributions from both central (neuromuscular) and peripheral (muscular) mechanisms.

Purpose of the Study:

• To investigate and compare the effects of acute continuous stretching (CS) versus intermittent stretching (IS) on plantarflexor force production.
• To differentiate the roles of central and peripheral factors in the force decrement induced by different stretching protocols.

Main Methods:

• Eighteen healthy men underwent three conditions: continuous stretch (CS), intermittent stretch (IS), and a control.
• Measurements included isometric plantarflexor peak torque (Tpeak), voluntary activation (%VA), EMG amplitude (EMG:M), V-wave, and excitation-contraction coupling efficiency.
• Near-infrared spectroscopy monitored gastrocnemius medialis oxygenation during stretching.

Main Results:

• Intermittent stretching (IS) resulted in a greater decrease in peak torque (-23.8%) compared to continuous stretching (CS) (-14.3%).
• IS led to significant reductions in voluntary activation (%VA) and EMG amplitude (EMG:M), indicating a greater central drive impairment.
• Force loss after both stretching types was correlated with reductions in central motor output measures.

Conclusions:

• Intermittent stretching appears to induce greater acute force loss than continuous stretching in healthy individuals.
• The enhanced force reduction following IS is strongly linked to a depression in central neural drive to the muscle.
• These findings suggest that the pattern of stretching influences neuromuscular control and subsequent force capacity.