Effects of a 24-h naproxen dose on hydration and electrolyte measures during moderate-intensity cycling in the heat
Dawn M. Emerson,
Toni M. Torres-McGehee,
J. Mark Davis,
Stephen C.L. Chen,
J. Larry Durstine,
Craig E. Pfeifer,
Charles C. Emerson,
Justin V. Stone,
Joseph D. Bivona
Affiliations
Dawn M. Emerson
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA; Present address: University of Kansas, Lawrence, KS 66045, USA
Toni M. Torres-McGehee
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA
J. Mark Davis
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA
Stephen C.L. Chen
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA; Present address: Bob Jones University, Greenville, SC 29614, USA
J. Larry Durstine
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA
Craig E. Pfeifer
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA; Present address: Lander University, Greenwood, SC 29649, USA
Charles C. Emerson
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA; Present address: University of Missouri-Kansas City, Kansas City, MO 64110, USA
Justin V. Stone
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA
Joseph D. Bivona
Department of Exercise Science, Public Health Research Center, University of South Carolina, 921 Assembly Street, Columbia, SC 29208, USA
Few controlled laboratory studies have examined the negative effects non-steroidal anti-inflammatory drugs can have on fluid–electrolyte balance during exercise. Our objective was to determine whether a 24-h naproxen dose negatively affected hydration and electrolyte measures before, during, and 3 h after 90 min of cycling in a hot or ambient environment. Using a double blind, randomized and counterbalanced cross-over design, 11 volunteers (six male, five female) completed four trials, with conditions as follows: (1) placebo and ambient, (2) placebo and heat, (3) naproxen and ambient, and (4) naproxen and heat. We found no statistically significant differences among experimental conditions for any dependent measures. Though not statistically significant, mean fluid volume was higher and urine volume was lower during naproxen trials compared with placebos. Mean aggregate plasma sodium was <135 mmol/L at all time points and did not significantly change over time. Overall plasma potassium significantly increased pre- (3.9 ± 0.4) to post-exercise (4.2 ± 0.4 mmol/L, p = 0.02). In conclusion, an acute naproxen dose did not significantly alter hydration–electrolyte balance. The trend for naproxen to increase fluid volume and decrease urine volume suggests the start of fluid retention, which should concern individuals at risk for hyponatremia or with pre-existing cardiovascular conditions.
