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Altered reflex sensitivity after repeated and prolonged passive muscle stretching
J Avela1, H Kyröläinen, P V Komi
1Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, FIN-40100 Jyväskylä, Finland. Avela@maila.jyu.fi
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 8, 1999
Summary
Repeated passive stretching (RPS) significantly impairs muscle function and reduces reflex sensitivity, particularly in the triceps surae. This suggests RPS may decrease large-diameter afferent activity, impacting muscle spindle sensitivity.
Area of Science:
- Neuromuscular Physiology
- Skeletal Muscle Biology
- Biomedical Engineering
Background:
- Repeated passive stretching (RPS) is common in physical therapy and sports.
- Understanding the immediate effects of RPS on neuromuscular function is crucial for optimizing training and rehabilitation protocols.
- Previous research has explored acute stretching effects, but the impact on reflex sensitivity requires further elucidation.
Purpose of the Study:
- To investigate the immediate effects of prolonged and repeated passive stretching (RPS) on the reflex sensitivity of the triceps surae muscle.
- To quantify changes in muscle function parameters following RPS.
- To explore the underlying mechanisms responsible for altered reflex sensitivity.
Main Methods:
- Subjects underwent prolonged and repeated passive stretching of the triceps surae muscle.
- Muscle function was assessed via maximal voluntary contraction (MVC) and electromyographic (EMG) activity.
- Reflex sensitivity was evaluated using stretch reflex and Hoffmann reflex (H-reflex) measurements.
- Serum creatine kinase (CK) levels were monitored.
Main Results:
- Significant reductions were observed in MVC (23.2%), gastrocnemius and soleus EMG activity (19.9% and 16.5%), and soleus EMG zero crossing rate (12.2%).
- Stretch reflex peak-to-peak amplitude decreased by 84.8%, and the H-reflex to maximal compound action potential ratio decreased by 43.8%.
- A significant reduction in stretch-resisting force was noted (P < 0.01), while serum CK remained unchanged.
Conclusions:
- RPS leads to immediate and substantial impairments in triceps surae muscle function and reflex sensitivity.
- The findings suggest that RPS activates a mechanism reducing short-latency reflex sensitivity, likely due to decreased large-diameter afferent activity and reduced muscle spindle sensitivity.
- These results have implications for the application of stretching in clinical and athletic settings.