The fluid and electrolyte balance of New Zealand European and Maori/Pacific Island athletes: An observational study

Observational research on professional athletes from the USA suggests differences may exist in sweat sodium loss based on ethnic differences. The New Zealand (NZ) sporting population is mainly of European or Maori/Pacific Island origin. Therefore, this study aimed to describe the fluid-electrolyte balance of athletes by ethnicity. A total of 20 Maori/Pacific Islanders (MP; body mass 100.97 +/- 13.05 kg) and 29 NZ European (NZE; body mass 89.11 +/- 11.56 kg) elite male athletes were recruited. Sweat rates were determined by body mass change during a 1-h spin cycle exercise session, during which fluid intakes and heart rate were recorded. Sweat samples were analysed for sodium concentration. Mean +/- SD sweat sodium concentrations were 73.4 +/- 27.2 mmolL(-1) and 55.5 +/- 26.8 mmolL(-1) for the MP and NZE groups, respectively (p = 0.070). Sweat rate was 0.93 +/- 0.26 Lh(-1) for the MP group and 0.89 +/- 0.33 Lh(-1) for the NZE group (p = 0.357). Fluid intake was 1.05 +/- 0.48 L and 0.93 +/- 0.49 L for MP and NZE, respectively (p = 0.395). Half of the MP group gained weight during the exercise session compared to 37% of the NZE group. Pre-exercise urine specific gravity was significantly lower amongst the NZE group (1.016 +/- 0.009 g mL(-1)) than the MP group (1.024 +/- 0.008 g mL(-1)) p = 0.001. There was no significant difference in heart rate between the groups, p = 0.082. Hydration practices of athletes in NZ may differ by ethnicity, and this may highlight the need for more targeted education by ethnicity.