Effects of a single low-dose acetaminophen on body temperature and running performance in the heat: a pilot project.

PURPOSE To examine the effects of a single low-dose (500 mg) acetaminophen on body temperature and running performance in the heat (30 °C). METHODS This is a randomized, cross-over pilot study performed in a climatic chamber at the Department of Sport Science of the University of Innsbruck. Seven male sport students (age, 25.9 ± 2.3 years; VO2max, 67.3 ± 7.1 mL/min/kg) participated in the study. Each participant performed two prolonged exercise tests at a constant intensity on a treadmill at a temperature of 30 °C at an individual intensity corresponding to 70 % VO2max. Two hours before exercising participants were randomly assigned to receive acetaminophen (500 mg) or placebo and performed the same test 2 weeks later with reverse pre-treatment. RESULTS After 20 min of running in the heat core temperature increase was less under acetaminophen (P = 0.004) and heart rates were higher (P = 0.02) compared to placebo. At the end of exercise neither running time nor body temperature nor ratings of perceived exertion differed between groups. CONCLUSION Although the increase in core temperature was slightly reduced by acetaminophen after 20 minutes of running in the heat running performance remained unaffected after pre-treatment with a single low-dose of acetaminophen.