Article

Present literature and clinical practice provide strong support for
the use of aerobic exercise in reducing pain and improving function for
individuals with chronic musculoskeletal pain syndromes. However, the molecular
basis for the positive actions of exercise remains poorly understood. Recent
studies suggest that neurotrophin-3 (NT-3) may act in an analgesic fashion in
various pain states. OBJECTIVE: The purpose of the present study was to examine
the effects of moderate-intensity aerobic exercise on pain-like behavior and NT-3
in an animal model of widespread pain. DESIGN: This was a repeated-measures,
observational cross-sectional study. METHODS: Forty female mice were injected
with either normal (pH 7.2; n=20) or acidic (pH 4.0; n=20) saline in the
gastrocnemius muscle to induce widespread hyperalgesia and exercised for 3 weeks.
Cutaneous (von Frey monofilament) and muscular (forceps compression) mechanical
sensitivity were assessed. Neurotrophin-3 was quantified in 2 hind-limb skeletal
muscles for both messenger RNA (mRNA) and protein levels after exercise training.
Data were analyzed with 2-factor analysis of variance for repeated measures
(group x time). RESULTS: Moderate-intensity aerobic exercise reduced cutaneous
and deep tissue hyperalgesia induced by acidic saline and stimulated NT-3
synthesis in skeletal muscle. The increase in NT-3 was more pronounced at the
protein level compared with mRNA expression. In addition, the increase in NT-3
protein was significant in the gastrocnemius muscle but not in the soleus muscle,
suggesting that exercise can preferentially target NT-3 synthesis in specific
muscle types. LIMITATIONS: Results are limited to animal models and cannot be
generalized to chronic pain syndromes in humans. CONCLUSIONS: This is the first
study demonstrating the effect of exercise on deep tissue mechanical hyperalgesia
in a rodent model of pain and providing a possible molecular basis for exercise
training in reducing muscular pain.

Langue : ANGLAIS