The effect of heat stress on hydration status and renal biomarkers in NCAA d1 female soccer players in south Texas

Recent research suggests that recurrent heat-associated hypohydration and strenuous physical exertion may be associated with the development of acute and potentially chronic renal dysfunction. South Texas pre-season conditions in which collegiate soccer is performed in August, may warrant concerns for promoting acute kidney injury (AKI). PURPOSE: The purpose of this study is to investigate hydration status and renal biomarkers in NCAA Division I female soccer players in South Texas. METHODS: (Mean±SEM; n=21; age: 19.3±0.25 y; ht: 169.6±1.3 cm; wt: 68.4±2.4 kg; LBM: 45.9±1.1 kg). Each subject participated in baseline and ending body composition measures via DXA (iDXA, Lunar Prodigy; GE Healthcare, Madison, WI), and provided 14-urine samples throughout the preseason for the analysis of Urine Specific Gravity (USG), Urine Color Analysis (UCA), Cystatin-C (uCys-C), and Creatinine (uCr). Urine samples were collected at start of preseason (PRE-PS), fitness testing days (FT1, FT2), regular practices (MidW1, MidW2, POST-PS) and exhibition games (PRE-BU, POST-BU,12HR-BU, 24HR-BU, PRE-UT, POST-UT, 12HR-UT, 24HR-UT). Heat index (37.4± 0.8) was assessed at practice sessions and exhibition matches (Kestrel 5000 environmental meter; Kestrel Meters, Boothwyn, PA). RESULTS: UCA and USG showed an effect of time (p <0.0001) between days with PRE-BU and PRE-UT values being lower compared to multiple days. A difference in USG (p = 0.0009) was found comparing PRE-BU (1.012  0.001) vs POST-BU (1.018  0.001) and PRE-UT (1.010  0.001) vs POST-UT (1.021  0.001) (p = 0.00001). uCr showed an effect of time (p <0.0001) between days with PRE-BU and PRE-UT being lower than multiple days. Significant increases in uCys-C were present at 12H-BU, 24H-BU, MidW1, PRE-UT, POSTUT, and 12H-UT (p= ≤ 0.0001). CONCLUSION: Our findings suggest that subjects arrived at exhibition games (BU, UT) in a euhydrated state with hypohydration occurring 12-hours post- exhibition game, prior to fitness assessments (FT1, FT2), and regular morning practice (MidW1). Values of uCr increased above normative post-exhibition game and may be an indicator of exercise-induced muscular injury. Concentrations of uCys-C remained elevated following 12HBU and did not return to normative values until 12H-UT. Our results indicate that NCAA D1 female soccer players in South Texas are at increased risk of both hypohydration and potential renal injury.