E-14T Free Communication/Poster Skeletal Muscle Injury
Cooling has been suggested to cause a decrease in cell metabolism and consequently allow the uninjured cells to survive the period of hypoxia, a reduction in the edema formation, and a relief in muscle soreness. However, these effects remain controversial.
To estimate the effects of cooling skeletal muscle after exercise using 31P MR Specroscopy and MR Imaging.
Male subjects (mean age ± SD, 23.8 ± 2.3 yr) were assigned to the normal (N=7) or the cooling group (N=7). Both groups performed the ankle plantar flexion exercise including eccentric contractions (12 repetitions, 5 sets). 15-min cold water immersion was administered to the subjects□f legs in the cooling group after exercise and initial post-exercise measurements. Intracellular pH was calculated from 31P-spectra of the medial gastrocnemius before, immediately, 30, 60 min, 24, 48, 96, and 168 h after exercise. T2-weighted images were obtained to calculate T2 relaxation times (T2) of the medial gastrocnemius before, 24, 48, 96, and 168 h after exercise. The muscle soreness level of the calf was also assessed at the same time as 31 P-spectra measurements.
Only control group showed significantly increased T2 from rest at 48 h post-exercise (p < 0.05). Intracellular pH significantly decreased immediately after exercise in both groups (p < 0.05). After that, the cooling group showed a significantly higher pH than the value at rest or the control group at 60 min post-exercise (p < 0.05). The soreness level significantly elevated immediately and at 24–48 h after exercise in both groups (p < 0.05).
Many studies reported that eccentric exercise resulted in delayed T2 elevation that would partly reflect the ultrastructual muscle damage accompanied by increased intramuscular water. Thus, this study may suggest that the cooling prevented the delayed edema and decreased the extent of muscle damage resulting from exercise. In addition, the cooling appears to have a positive effect on intracellular pH after exercise. Supported by the University of Tsukuba Research Project Grant.