In this study we tested the effect of zinc (Zn) on muscle function in humans. After receiving 12 mg Zn/day for 17 days. 8 male subjects received 0.3 mg Zn/day tor either 33 or 41 days. Subjects were divided into two groups for repletion. Group A subjects received overnight infusions of 66 mg Zn on Days 1 and 10 and then were fed 12 mg Zn/day for another 16 days. Group B subjects were fed 12 mg Zn/day for 3 weeks. Peak force and total work capacity of the knee and shoulder extensor and flexor muscle groups were assessed using an isokinetic dynamometer at baseline, at two points during depletion, and at repletion. Plasma Zn declined significantly during depletion and remained below baseline levels after repletion. The peak force of the muscle groups tesied was not affected by acute Zn depletion: however, total work capacity for the knee extensor muscles and shoulder extensor and flexor muscles declined significantly. The data suggest that acute Zn depletion alters the total work capacity of skeletal muscle.
M.D. Van Loan. J.R. Turnlund, and J.C. King are with USDA, ARS, Western Human Nutrition Research Center, San Francisco, CA 94129. B. Sutherland and J.C. King are with the University of California, Department of Nutritional Sciences, Berkeley, C A 94720. N.M. Lowe is with the University of Liverpool, Department of Medicine, Liverpool, L69 3BX. Direct correspondence to Marta Van Loan, USDA/ARS/WHNRC, P.O. Box 29997, Presidio of San Francisco, CA 94129.