Urinary 3-methylhistidine excretion increases with repeated weight training exercise.

This investigation examines the effect of progressive resistance weight training exercise on urinary 3-methylhistidine (3-MH) excretions in untrained subjects. For 19 consecutive days, 11 males were fed a weight maintenance, lactovegetarian diet which contained the Recommended Dietary Allowance (0.8g.kg-1.d-1) for protein. No exercise was performed for the first 7 d of the study. Subjects were strength tested on day 8 and performed upper and lower body weight training exercises from days 9-19. Complete, 24-h urine collections were obtained from each subject on a daily basis. Samples were assayed for creatinine and 3-MH. Stable baseline 3-MH values were present during the pre-exercise control period. Significant increases in 3-MH occurred by study day 11, which was the third day of weight training exercise. This was true regardless of whether the data were expressed by daily excretions (microM.d-1; P less than 0.01), per unit of body weight (microM.kg-1.d-1; P less than 0.005), or per unit of creatinine excretion (microM.g Creat-1.d-1; P less than 0.001). Since urinary 3-MH is an index of actin and myosin catabolism, these data support the hypothesis that the rate of skeletal muscle degradation is increased during strength building exercises.