An acute naproxen dose does not affect core temperature or Interleukin-6 during cycling in a hot environment.

Non-steroidal anti-inflammatory drugs' anti-pyretic and anti-inflammatory effects has led some individuals to theorize these medications may blunt core body temperature (Tc) increases during exercise. We utilized a double-blind, randomized, and counterbalanced cross-over design to examine the effects of a 24-h naproxen dose (3-220 ​mg naproxen pills) and placebo (0 ​mg naproxen) on Tc and plasma interleukin-6 (IL-6) concentrations during cycling in a hot or ambient environment. Participants ( n  ​= ​11; 6 male, 5 female; age ​= ​27.8 ​± ​6.5 years, weight ​= ​79.1 ​± ​17.9 ​kg, height ​= ​177 ​± ​9.5 ​cm) completed 4 conditions: 1) placebo and ambient (Control); 2) placebo and heat (Heat); 3) naproxen and ambient (Npx); and 4) naproxen and heat (NpxHeat). Dependent measures were taken before, during, and immediately after 90 ​min of cycling and then 3 ​h after cycling. Overall, Tc significantly increased pre- (37.1 ​± ​0.4 ​°C) to post-cycling (38.2 ​± ​0.3 ​°C, F _1.7,67.3  ​= ​150.5, p  ​< ​0.001) and decreased during rest (37.0 ​± ​0.3 ​°C, F _2.0,81.5  ​= ​201.6, p  ​< ​0.001). Rate of change or maximum Tc were not significantly different between conditions. IL-6 increased pre- (0.54 ​± ​0.06 ​pg/ml) to post-exercise (2.46 ​± ​0.28 ​pg/ml, p  ​< ​0.001) and remained significantly higher than pre-at 3 ​h post- (1.17 ​± ​0.14 ​pg/ml, 95% CI  ​= ​-1.01 to -0.23, p  ​= ​0.001). No significant IL-6 differences occurred between conditions. A 24-h, over-the-counter naproxen dose did not significantly affect Tc or IL-6 among males and females cycling in hot or ambient environments.
Competing Interests: Portions of the study were supported by funding from the American College of Sports Medicine Foundation and the National Athletic Trainers’ Association Research and Education Foundation. The agencies had no role in the study design, data collection or analysis, or the writing and submitting for publication. The authors have no other conflict of interests to disclose.
(© 2021 The Authors.)