Hydration Status And Sweat Electrolyte Loss In Adolescent Judokas Training In Hot And Humid Conditions

Abstract

Acute and chronic hypohydration are a common problem among athletes training in a hot and humid environment. There are few data available on fluid and electrolyte loss, and hydration patterns of adolescent athletes who compete in sports that divide competitors into weight classes. PURPOSE To determine the hydration status of heat acclimatized adolescent judo athletes before, immediately after, and 24 hours after a training session in a hot and humid environment and to document sweat related electrolyte loss. METHODS Twenty five adolescent judo athletes (x age=14.5 ± 1.3) participated in this study. Urinary indices of hydration status, such as volume, color, and specific gravity (SG) were measured before (PRE), after (POST), and 24 hours after (24H) a training session (duration = 103.0 ± 2.4 min) in a non-air conditioned gymnasium (29.5 °C and 77.7 % RH; WBGT=27.2 °C). Acute changes in body mass were used to determine total fluid loss and dehydration level. A sweat sample was collected with an absorbent patch attached to the skin to measure sweat electrolyte loss. RESULTS During the training session subjects lost 0.9 ± 0.1 kg corresponding to 1.6 ± 0.1 % of the pre-training body weight. Sweat rate was 0.65 ± 0.1 L/h with a sodium concentration of 43.5 ± 4.8 mmol/L, corresponding to a total sodium loss of 1.1 ± 0.2 g. Fluid intake (224.4 ± 43.0 mL) replaced only 21% of the sweat loss (1,080 ± 90.2 mL). Urine color (PRE= 4.9 ± 0.2; POST= 5.6 ± 0.1; 24H= 5.1 ± 0.2), and SG (PRE=1.026 ± 0.001; POST= 1.029 ± 0.001; 24H= 1.027 ± 0.001 g/ml) indicated a significant level of dehydration before, immediately after and 24 hours after the training session (P <0.05, POST vs PRE). After training, 48% of the urine samples had a SG ≥1.030 g/ml. The majority (80%) of the subjects presented one or more symptoms of dehydration during training such as: thirst, dizziness, headache, fatigue and cramps. Thirst and headache persisted during the night and the next day for most of the subjects who reported these symptoms. CONCLUSIONS Adolescent judo athletes training in hot and humid conditions arrive to practice with a fluid deficit, do not drink enough to replenish sweat losses during the training session, experience symptoms of dehydration, and are still hypohydrated when they return to the next training session. This state of chronic hypohydration may compromise the athletes' performance and health. Frequent fluid breaks should be provided and young athletes should be advised to observe their urine color as an index of hydration status.