MRI EVALUATION OF HEAT AND STRETCH AS TREATMENTS FOR MUSCLE DAMAGE AFTER ECCENTRIC EXERCISE

Abstract

Delayed muscle soreness (DMS) is the sensation of pain and/or discomfort experienced 24 - 48 hours after eccentric exercise (ECC). Magnetic resonance imaging (MRI) studies have shown that muscles subjected to ECC exercise exhibit an increase in T2 relaxation time post-exercise that parallels the development of pain and damage associated with DMS. Post-exercise static stretching and/or the application of superficial heat have been suggested as a method to alleviate DMS. PURPOSE: To examine the effects of topical heat and/or static stretch treatments on T2 relaxation time, muscle swelling, isometric strength, and pain following ECC exercise. METHODS: Thirty two untrained male subjects performed intense ECC knee extension exercise, followed by two weeks of treatment (heat, stretch, heat plus stretch) or no treatment (control, n = 8/group). Isometric strength testing, pain ratings, and T2-weighted images (TR/TE = 1500/30,60) of the thigh were performed before and at 2, 3, 4, 8, and 15 d. RESULTS: ECC exercise produced muscle damage in all groups as evidenced by the large increase in T2 and muscle swelling, and from the decrease in isometric strength in the first few days after the exercise. Independent of treatment, pain ratings and muscle swelling recovered to baseline by 15 d, although isometric strength remained lower (77 ± 4 vs. 95 ± 3 kg pre-exercise, mean ± SE) and T2 values higher (32.2 ± 0.8 vs. 28.6 ± 0.2 ms). T2, swelling, pain and the deficit in strength on day 15 were not different between the treatment groups. CONCLUSION: The similar time course and magnitude of the T2 changes and pain ratings in the days following ECC exercise demonstrates that therapeutic application of superficial heat and/or static stretching did not enhance the recovery of damaged muscle nor did it alleviate the soreness. (Supported by a gift from Proctor and Gamble)