Effect of supplementation with a cysteine donor on muscular performance

"Follow-up data on 18 subjects (9 Immunocal, 9 placebo) were analyzed. Both peak power [13 ± 3.5 (SE) %,P < 0.02] and 30-s 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."

Source: https://www.physiology.org/doi/full/10.1152/jappl.1999.87.4.1381