The Lab: “Electrolyte Losses in Urine and Sweat In Collegiate Football Players During Pre-Season Training Camp”

ABSTRACT

Electrolyte losses through urine and sweat are potentially detrimental to athlete performance.  Electrolyte loss may be influenced by practice in hot, humid environments.

PURPOSE:  To determine local sweat rates (LSR) and Na+ losses from urine and sweat during the 2 week, pre-season training camp in collegiate football players.

METHODS: Urine and sweat was collected before and after practices on 46 football players (20y, range 18-22y; BSA=2.34±0.24m2). Sweat was acquired using a dermal gauze patches on the lower back, centrifuged and LSR (g/cm2·hr) calculated by the change in gauze weight corrected for total patch surface area.  Ion-selective electrodes determined electrolyte concentrations for urine and sweat. Total electrolyte loss from sweat was estimated by adjusting for LSR. Environmental wet bulb globe temperature (WBGT) and humidity were taken at the start and end of practice.

RESULTS: A total of 164 urine and 179 sweat samples were collected.  Mean WBGT was 25.5±4.2°C (16.9–31.9°C).  Pre-practice urine indicators were urine specific gravity (USG; 1.021±0.006), color (3.4±1.6) and Na+ (133.0±61.4mmol/L).  USG (P=0.004) and color (P<0.001) increased and Na+ content decreased post-practice.  As training camp progressed, color (P<0.001) and Na+ (P<0.05) increased and USG tended to increase (P=0.13). Mean LSR was 0.38±0.22g/cm2·hr (range 0.02–1.26g/cm2·hr) and electrolyte losses were 42.1±20.5mmol/L (8.2–107.2mmol/L) for Na+. WBGT and body surface area (BSA) were positively correlated with LSR (P<0.001 both). Sweat Na+ losses increased with an increase in LSR (P<0.001). After adjusting for WBGT, a trend for acclimatization was observed for an increase in LSR (P=0.07).

DISCUSSION: Larger players had greater sweat and sweat Na+ losses. Sodium losses in urine and sweat were highly variable. The rise in sweat Na+ appears to be counteracted by a change in kidney function, as urine Na+ decreased as USG increased.  Supported by the Robert and Patricia Hines Endowment in Kinesiology

RESEARCHERS

NP. Lemoine, Jr.,1 AB. Simoneaux,1 MC. Scott,1 KS. Early,1 S. Mullenix,2 J. Marucci,2 A. Barker,2 TS. Church,3 RR. Castle,1 NM. Johannsen,1,2;  1School of Kinesiology and 2Dept. of Athletics, Louisiana State University and 3Pennington Biomedical Research Center, Baton Rouge, LA

REFERENCE

Lemoine Jr, N.P.,  Simoneaux AB, Scott MC, Early KS, Mullenix S, Marucci J, Barker A, Church TS, Castle RR, Johannsen NM. 2016. Electrolyte Losses in Urine and Sweat in Collegiate Football Players During Pre-season Training Camp: 3748 Board# 187 June 4, 930 AM-1100 AM. Medicine & Science in Sports & Exercise, 48(5S), p.1047.