Acute L-arginine supplementation has no effect on cardiovascular or thermoregulatory responses to rest, exercise, and recovery in the heat

Purpose To investigate the effect of acute L-arginine (L-ARG) supplementation on cardiovascular and thermoregulatory responses to rest, exercise, and recovery in the heat. Methods Eight healthy men (age 27 +/- 6 years; stature 176 +/- 6 cm; body mass 76 +/- 4 kg; maximal power output 237 +/- 39 W) participated in a double-blind, crossover study, attending the laboratory for two experimental trials. On each occasion, participants consumed 500 ml of a blackcurrant-flavoured cordial beverage 30 min before completing a 90 min experiment in the heat (35 degrees C and 50 % rh). The experiment consisted of 30 min of seated rest, followed by 30 min submaximal cycling (60 % maximal power output) and 30 min passive seated recovery. On one visit the drink contained 10 g of dissolved L-ARG while on the other visit it did not. Results L-ARG supplementation increased plasma L-ARG concentrations (peak + 223 +/- 80 % after 60 min of the 90 min experiment); however, supplementation had no effect on rectal temperature, mean skin temperature, heart rate, arterial pressure, forearm skin vascular conductance, oxygen consumption or sweat loss at rest, during exercise, or during recovery in the heat (p > 0.05). Conclusion Acute ingestion of 10 g L-ARG supplementation failed to elicit any changes in the cardiovascular or thermoregulatory responses to active or passive heat exposure in young, healthy males.