The Lab: “Fluid Balance and Electrolyte Losses in Collegiate Female Soccer Players”

ABSTRACT

PURPOSE: To determine the fluid balance, electrolyte content, and sweat rate (SR) during 14 days of field practice in collegiate female soccer players.

METHODS: 18 female soccer players (age=19.2±1.0y, weight=68.3±9.3kg, ±SD) participated in this study; 3 forward (F), 7 midfielders (Mid), 5 Defenders (D), and 3 Goalkeepers (G). Body weight was measured and urine was collected before and after practice to examine fluid balance and urine color (UC), specific gravity (USG), and electrolytes. Water and carbohydrate (CHO) bottles were weighted throughout practice for fluid intake. Sweat was collected using cotton gauze covered by a waterproof dermal patch on the lower back and used to estimate SR (g/cm2·hr) by the change in cotton weight adjusted for patch surface area and electrolyte composition. Total fluid loss was calculated from fluid balance and fluid intake. Wet bulb globe temperature (WBGT) was measured before and after practice. The Zephyr Bioharness was used to measure the average (AHR) and maximal heart rates (MHR) in 11 players.

RESULTS: Mean WBGT was 64.0±8.7C and fluid balance was -0.4±0.4kg (-0.6%±0.6%). SR was 0.122±0.062g/cm2·hr. Mid (n=7) had poorer fluid balance (-0.4±0.4kg, -0.7±0.6%) and higher SR (0.131±0.060g/cm2·hr). F (n=3) had greater sweat Na+ loss (53.3 ± 22.7mmol/L) compared to Mid (45.0±18.0mmol/L), D (46.3±15.4mmol/L), G (21.4±7.1mmol/L) (P<0.001). Players who drank water only (n=4) had higher SR (0.131±0.065 g/cm2∙hr) than those who drank water and CHO beverages (n=14) (0.119 ±0.061 g/cm2∙hr). Greater fluid intake was associated with higher SR (r=0.37, P<0.001), and higher SR was related to higher sweat Na+ loss (r=0.17, P=0.015). Higher SR was also associated with higher AHR (r=0.40, P<0.001).

DISCUSSION: Midfielders should drink more fluids during practice because of higher weight loss and SR possibly due to higher exertion levels. Forward should replace more Na+ due to more Na+ loss.

RESEARCHERS

H Wang1, BM Theall2, NP Lemoine Jr.2, A Lowe2, KS Early3, TS Church3, R Castle3, S Mullenix3, J Marucci3, NM Johannsen1, School of Kinesiology1 and Athletics Department2, Louisiana State University, Baton Rouge, LA; Columbus State University3, Columbus, GA.

REFERENCE

Wang H, Theall BM, Lemoine NP Jr, Lowe A, Castle RR, Mullenix S, Marucci J, Church TS, Early KS, Johannsen NM.  Hydration study in collegiate female soccer players in pre-season training.  Poster at SEACSM, 2017