Low-intensity resistance training promotes a reduction of mechanical hyperalgesia and increase of muscle strength in rats submitted to the diffused chronic muscle pain model

BACKGROUND AND OBJECTIVES: Fibromyalgia syndrome (FMS) is characterized by different factors, such as chronic diffuse muscle pain (CDMP), fatigue and psycho-emotional changes. Among the animal models that mimic FMS, the acid saline model is consolidated in the development and maintenance of CDMP. Resistance training (RT) has been an effective method for reducing pain in FMS. Thus, the aim of the present study was to evaluate the effects of resistance training on nociceptive and motor responses in an animal model of chronic diffuse muscular pain. METHODS: Twenty-four male Wistar rats were allocated into four groups: resistance training, RT control, amitriptyline (AMITRIP) and AMITRIP control; all treatment protocols lasted 4 weeks. CDMP was induced in all mice. Then, the animals were treated with low-intensity RT (40% 1 maximum repetition) and AMITRIP (10 mg/kg/day). The mechanical paw withdrawal threshold, locomotor activity and muscle strength were evaluated. RESULTS: Animals treated with both RT and AMITRIP showed an increase in the mechanical paw withdrawal threshold (p<0.05) compared to their controls, suggesting a reduction in mechanical hyperalgesia. There was no improvement in locomotor activity in all groups (p>0.05). Animals with CDMP that underwent RT showed an increase in hindlimb muscle strength (p<0.0001) compared to the RT control group. CONCLUSION: Low-intensity resistance training resulted in antihyperalgesic effects and improved muscle strength in animals submitted to the CDMP model.