Acute Effect of Oral N-Acetylcysteine Supplementation on Fatigue Effect and Isometric Force Production in Physically Active People

The main objective of this study was to assess the ergogenic effect of N-acetylcysteine (NAC) on myotendinous isometric force production in physically active people after being subjected to a fatigue protocol. Twenty-three physically active people were randomly divided into the following two groups: NAC (n = 12; age = 26.8 ± 4.5 years, height = 173.1 ± 7.2 cm, and weight = 75.5 ± 7.5 kg), who received 2400 mg oral NAC, and control (n = 11; age = 23.4 ± 5.8 years, height = 175.9 ± 4.5 cm, and weight = 72.3 ± 9.9 kg), who received a placebo, for eight days. The isometric force production was assessed pre- and post-NAC supplementation during a maximal voluntary contraction test (MVC) and also during a fatigue protocol composed of seven sets of ten maximal isometric contraction repetitions of 5 s, with 5 s of rest between repetitions and 20 s between sets. No differences were observed between the groups in the force production values at any moment, and no side effects were found after NAC supplementation. After supplementation, a significant decrease in force was observed in both groups, but this significant loss of force started one set later in the NAC group compared to the control group (4th set vs. 5th set), which could be an ergogenic effect of the treatment. Therefore, oral daily supplementation with 2400 mg of NAC for eight days, could delay the decrease in force production during an isometric exercise protocol and without adverse side effects.