From Ergo Log
N-Acetylcysteine is a strong antioxidant, and athletes take it to protect their muscles from the negative effects of extreme exertion, such as soreness and inflammation. But it also inhibits their muscle recovery, sports scientists at the Democritus University of Thrace in Greece discovered.
The peptide glutathione helps enzymes in muscle cells to carry out their protective functions. If you take N-acetylcysteine, your cells use this amino acid as a precursor for glutathione.
N-Acetylcysteine is a strong antioxidant, and athletes take it to protect their muscles from the negative effects of extreme exertion, such as soreness and inflammation. But it also inhibits their muscle recovery, sports scientists at the Democritus University of Thrace in Greece discovered. The more glutathione your muscle cells contain, the worse the transcription factor NF-kB works. As a result, post-workout supplementation using N-acetylcysteine can weaken inflammatory reactions initiated by immune cells clearing up damaged muscle cells.
Is that performance enhancing or not? This is the question the researchers posed. To answer it they did an experiment with 10 recreational sportsmen, who did two extreme quadriceps training sessions: they performed 20 sets of 15 reps on a leg extension machine.
On one occasion the men took 20 mg N-acetylcysteine per kg bodyweight after their workout every day for eight days. The subjects' dose was divided over three daily intakes. On the other occasion the men were given a placebo.
During the eight days after the training session the supplementation boosted the concentration of glutathione in the muscles and reduced the concentration of TBARS – an indicator of free radical activity.
Sounds good, but in the days after the workout, the torque [strength] recovery was less good when the subjects had taken N-acetylcysteine. On the other hand, N-acetylcysteine did reduce muscle soreness [DOMS].
N-Acetylcysteine reduced the secretion of inflammatory proteins such as CRP, interleukin 1-beta [below left] and interleukin-6. In addition, N-acetylcysteine also reduced the activity of anabolic signalling molecules such as Akt, mTOR [below right] and MyoD in the muscle cells.
"Our results corroborate those of previous studies suggesting that heavy use of antioxidants may have an adverse effect on muscle performance and recovery, probably by altering signaling pathways mediating muscle inflammation and recovery and potentially mitochondrial biogenesis and subsequent energy metabolism", the researchers write.
Perhaps athletes who are training to enhance their performance level should be given pro-oxidants instead of antioxidants.
Am J Clin Nutr. 2013 Jul;98(1):233-45.