Article Title



Joseph I. Robillard, J.D. Adams, Evan C. Johnson, Costas N. Bardis, LynnDee G. Summers, Ainsley Huffman, Thomas Vidal, Mikell L. Hammer & Stavros A. Kavouras, FACSM

Human Performance Laboratory, Department of Health, Human Performance, and Recreation, University of Arkansas, Fayetteville, Arkansas

While there are a number of studies identifying a high percentage of athletes who start exercise in a hypohydrated state, there is limited data concerning hydration levels in swimming. PURPOSE: The purpose of this study was to identify the hydration status of adolescent swimmers during a typical day of training. METHODS: Forty-six adolescent swimmers (26 males; age: 12.8±2.3 y; weight: 50.6±13.4 kg) participated in the study. Hydration status was assessed in first morning urine samples as well as immediately before and after practice. Hypohydration was classified by urine osmolality (UOsm >700 mmol/kg). Thirst perception was measured using a visual analog scale (VAS). RESULTS: 67% of the swimmers were hypohydrated based on their morning urine sample (USG: 1.021±0.007; UOsm: 788±252 mmol/kg). Pre-practice urine samples revealed that 78% of athletes were hypohydrated (USG: 1.021±0.008; UOsm: 828±304 mmol/kg). Swimmers consumed ad libitum fluid volume of 472±219 ml and acquired sweat losses of 394±268 ml over 120 minutes of practice resulting in a mild decrease in their body weight of -0.3±0.6%. Thirst perception did not change significantly from pre- (45.5±26.1 mm) to post-practice (55.4±32.5 mm). Post-practice hydration markers indicated that subjects improved their hydration state even while losing body water (USG: 1.018±0.011; UOsm: 630±390 mmol/kg). CONCLUSION: We conclude that the prevalence of hypohydration among adolescent swimmers is high, as indicated by elevated USG and urine osmolality values both in the morning and prior to practice. Post-swimming urinary markers could be misleading when trying to assess hydration state. Possibly water immersion increases diuresis, by attenuating vasopressin secretion via central volume receptors loading due to the hydrostatic pressure.

This document is currently not available here.