Oral digoxin effects on exercise performance, K regulation and skeletal muscle Na ,K -ATPase in healthy humans.

We investigated whether digoxin lowered muscle Na ,K -ATPase (NKA), impaired muscle performance and exacerbated exercise K disturbances. Ten healthy adults ingested digoxin (0.25 mg; DIG) or placebo (CON) for 14 days and performed quadriceps strength and fatiguability, finger flexion (FF, 105% , 3 × 1 min, fourth bout to fatigue) and leg cycling (LC, 10 min at 33% and 67% , 90% to fatigue) trials using a double-blind, crossover, randomised, counter-balanced design.

N-acetylcysteine attenuates the decline in muscle Na+,K+-pump activity and delays fatigue during prolonged exercise in humans.

Reactive oxygen species (ROS) have been linked with both depressed Na(+),K(+)-pump activity and skeletal muscle fatigue. This study investigated N-acetylcysteine (NAC) effects on muscle Na(+),K(+)-pump activity and potassium (K(+)) regulation during prolonged, submaximal endurance exercise. Eight well-trained subjects participated in a double-blind, randomised, crossover design, receiving either NAC or saline (CON) intravenous infusion at 125 mg kg(-1) h(-1) for 15 min, then 25 mg kg(-1) h(-1) for 20 min prior to and throughout exercise.

Alkalosis increases muscle K+ release, but lowers plasma [K+] and delays fatigue during dynamic forearm exercise.

Alkalosis enhances human exercise performance, and reduces K+ loss in contracting rat muscle. We investigated alkalosis effects on K+ regulation, ionic regulation and fatigue during intense exercise in nine untrained volunteers. Concentric finger flexions were conducted at 75% peak work rate (3 W) until fatigue, under alkalosis (Alk, NaHCO3, 0.

Effects of intravenous N-acetylcysteine infusion on time to fatigue and potassium regulation during prolonged cycling exercise.

The production of reactive oxygen species in skeletal muscle is linked with muscle fatigue. This study investigated whether the antioxidant compound N-acetylcysteine (NAC) augments time to fatigue during prolonged, submaximal cycling exercise. Seven men completed a double-blind, crossover study, receiving NAC or placebo before and during cycling exercise, comprising 45 min at 70% of peak oxygen consumption (Vo2 peak) and then to fatigue at 90% Vo2 peak.