NAC Impacts Muscle Fatigue and Aerobic Capacity

N-acetyl cysteine (NAC) affects muscle fatigue, oxygenation and oxidative stress after exercise, a recent study reports. NAC is a derivative of the amino acid cysteine and is the precursor of the potent antioxidant glutathione in the body.

Twenty-nine sedentary men were supplemented with 1,200 mg of NAC or placebo for 7 days. At the beginning of the study and again after the 7 days of supplementation, the men were evaluated using graded exercise treadmill tests. The subjects were assessed for fatigue index of the quadriceps muscle (muscle in the thigh), and VO2 max, which is a measurement of the maximal capacity of the body to transport and utilize oxygen during exercise and is used to assess physical fitness.

Blood tests were measured before and 20 minutes after exercise to evaluate total antioxidant capacity; lactate, which is a by-product of cellular energy production without oxygen; creatine kinase, a measurement of muscle break-down; and tumor necrosis factor (TNF)-alpha, which is a pro-inflammatory chemical mediator.

At the beginning of the study, exercise resulted in lower total antioxidant capacity and increased levels of lactate, creatine kinase, and TNF-alpha. Evaluation of exercise after 7 days of NAC supplementation showed that total antioxidant capacity (TAC) and lactate levels did not change significantly, but TAC decreased and lactate increased in the control group. The study also found that NAC supplementation resulted in beneficial effects on muscle fatigue and VO2 max.

The researchers concluded that NAC supplementation had beneficial effects on muscle fatigue and VO2 max, maintained total antioxidant capacity, and controlled lactate production with exercise.

Reference:

Leelarungrayub D, Khansuwan R, Pothongsunun P, Klaphajone J. N-Acetylcysteine Supplementation Controls Total Antioxidant Capacity, Creatine Kinase, Lactate, and Tumor Necrotic Factor-Alpha against Oxidative Stress Induced by Graded Exercise in Sedentary Men. Oxid Med Cell Longev. 2011;2011:329643. Published Online Ahead of Print.