The effect of supplementation with a cysteine donor on muscular performance. Lands, L. C., Md, Phd_, V. L. Grey, Phd_ and A. A. Smountas, Bsc. *Division of Respiratory Medicine, _ Department of Pediatrics, _ Department of Biochemistry, McGill University Health Centre-Montreal Children's Hospital, Montreal, Quebec, Canada.
APStracts 6:0274A, 1999.
Oxidative stress contributes to muscular fatigue. Glutathione (GSH) is the major intracellular antioxidant, whose biosynthesis is dependent upon cysteine availability. We hypothesized that supplementation with a whey-based cysteine donor (Immunocal (HMS90)) designed to augment intracellular GSH, would enhance performance. Twenty healthy young adults (10 m) were studied pre- and 3 months post-supplementation with either Immunocal (20 gm/day) or casein placebo. Muscular performance was assessed by whole leg isokinetic cycle testing, measuring Peak Power and 30-sec Work Capacity. Lymphocyte GSH was used as a marker of tissue GSH. There were no baseline differences (age, ht, wt, % ideal wt, Peak Power, 30-sec Work Capacity). Follow -up data on 18 subjects (9 Immunocal, 9 placebo) were analyzed. Both Peak Power (mean(se: 13(3.5%, p<0.02) and 30-sec Work Capacity (13(3.7%, p<0.03) increased significantly in the Immunocal group, with no change (2( 9.0 and 1( 9.3%) in the placebo group. Lymphocyte GSH also increased significantly in the Immunocal group (35.5(11.04%, p<0.02) with no change in the placebo group (-0.9(9.6%). This is the first study to demonstrate that prolonged supplementation with a product designed to augment antioxidant defenses resulted in improved volitional performance. 

Received 28 October 1998; accepted in final form 7 June 1999.
APS Manuscript Number A979-8.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 25 June 1999