The Effect of N‐acetylcysteine on Peripheral Hemodynamics and Fatigue during Exercise

Abstract

We hypothesized that oral N‐acetylcysteine (NAC) would lead to higher exercising arm blood flow and a delayed onset of peripheral fatigue. Thus far, three healthy men have completed constant power handgrip exercise tests at 80% peak power to exhaustion. Subjects orally consumed either placebo (PLA) or NAC (70mg/kg) 60 min before exercise. Brachial artery blood flow (BABF) was measured via Doppler ultrasound and flexor digitorum superficialis oxygenation characteristics were measured via near infrared spectroscopy. Peripheral and central fatigue were assessed via potentiated doublet twitch force (Qtw), MVC, and voluntary activation (%VA). The mean time to exhaustion was similar (p=0.83) with NAC (368.8±37.5s) and PLA (353.9±90.9s). Mean resting BABF was similar (p=0.68) with NAC (92.7±12.0mL/min) and PLA (112.3±37.2mL/min). Mean peak exercising BABF was similar (p=0.77) between NAC (550.5±73.1mL/min) and PLA (527.5±94.3mL/min). Mean deoxy‐[Hb+Mb] was not different between NAC and PLA from rest to exercise (p=0.63). Mean total‐[Hb+Mb] was similar (p=0.08) between NAC and PLA at rest (NAC: 101.6±2.2 µM; PLA: 90.8±1.8 µM) and during exercise. % change in MVC from pre to post exercise was not different (p=0.18) between NAC (‐43.9±16.6%) and PLA (‐32.5±13.2%). % change from pre to post exercise in Qtw was similar (p=0.29) with NAC (‐34.6±20.4%) and with PLA (24.8±18.6%). Change (%) from pre to post exercise in %VA was less (p=0.019) with NAC (‐8.0±8.9%) than PLA (‐13.8±9.0%). These preliminary data suggest NAC does not affect exercising BA blood flow, but may increase microvascular hematocrit at rest and during exercise. Also, NAC may reduce central fatigue during exercise.