Hydration status and drinking behaviours of elite Kenyan endurance runners during intense training prior to competition

Previous studies of elite Kenyan endurance runners (Onywera et al. Int J Sport Nutr ExercMetab 14: 709–719, 2004; Fudge et al. Br J Nutr: In Press) reported low daily fluid intake, mainly water (mean ± SD) (1.1± 0.3;0.9± 0.5 L-d−1, respectively) and tea (1.2 ± 0.3; 0.9 ± 0.3 L-d−1, respectively). Those athletes did not consume liquids before or during training and infrequently consumed modest amounts of liquids after training, an intake that is substantially less than the current ACSM recommendations (Convertino et al. MedSci Sports Exerc 28: i-vii, 1996). PURPOSE: To assess hydration status and monitor drinking behaviors of elite Kenyan endurance runners during an intense training period. METHODS: Fourteen elite Kenyan endurance runners based at a high altitude training camp in the Rift Valley (altitude: 2400 m a.s.l.; daytime ambient temperature: 8 – 24°C; humidity: 31 – 100%) were recruited to participate 1 wk prior to the Kenyan national trials for the 2005 World Championships. Hydration status was monitored over a 5 d period by measuring body mass (BM), urine osmolality, total body water (TBW), and daily fluid intake. Dietary sodium (Na) intake was estimated using a 5 day nutritional diary with biochemical analysis, whilst [Na] was determined in urine and sweat. Core temperature was monitored continuously during all training sessions. RESULTS: Fluid intake was low (total: 2.4 ± 0.8 L-d−1; water: 0.7 ± 0.6 L-d−1; tea: 1.2 ± 0.4 L-d1) and consistent with previous observations. There was a significant BM loss during the morning (0.7± 0.3 kg;p ≥ 0.01), interval (0.7 ± 0.2 kg;p ≥ 0.01) and afternoon (0.7 ± 0.4 kg; p <0.001) training sessions; corresponding to 1.3 ± 0.5, 1.3 ± 0.4, and 1.3 ± 0.7% BM loss, respectively. Pre training BM in the morning was not significantly different from the evening pre training BM (56.2 ± 4.1 kg vs. 56.3 ± 4.1 kg; p = 0.42). Mean TBW (31.9 ± 3.0 L) was well maintained throughout the five days (p = 0.96). There was no significant difference between the osmolality of the morning urine sample and the evening sample (522 ± 117 vs. 505 ± 98 mOsmol-kg1; p = 0.69). Mean Na intake was not significantly different to Na loss in sweat and urine (3015 ± 718 mg-d−1 vs. 3162 ± 1210 mg-d−1, respectively; p = 0.70). No athlete showed signs or symptoms of heat stress with mean core temperatures of 37.6 ± 0.6°C during all training sessions. CONCLUSIONS: Elite Kenyan endurance runners training intensely remain well hydrated despite less than recommended fluid intake. These results support the principle of ad libitum fluid intake during intense training.