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 degrees C) to post-cycling (38.2 +/- 0.3 degrees C, F-1.7,F-67.3 = 150.5, p < 0.001) and decreased during rest (37.0 +/- 0.3 degrees C, F-2.0,F-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.