The Effects Of Handling And Analysis Techniques Used In The Measurement Of Sweat Sodium Concentration

Christine E. Dziedzic; Megan L. Ross; Chris Barnes; Gary Slater; Louise M. Burke

doi:10.1249/01.MSS.0000401359.95707.a7

RESULTS: At the end of REC, the most effective percentage of rehydration occurred when the CE drink was consumed (CE vs. LT vs. DW: 77.4 ± 6.0 vs. 53.7 ± 6.5 vs. 45.5 ± 4.4 %, p < 0.05). The CE drink also caused the least diuretic effect among the beverages (CE vs. LT vs. DW: 638 ± 71 vs. 921 ± 89 vs. 915 ± 58 ml, p < 0.05) and produced the greatest restoration of plasma volume (CE vs. LT vs. DW: 11.2 ± 2.0 vs.-3.1 ± 1.8 vs. 0.2 ± 2.1, %, p < 0.05). CONCLUSIONS: The results of this study suggest that CE drinks are more effective than DW or LT in restoring fluid balance during short-term REC following exercise-induced dehydration. Coconut water (CW) is often referred to as " nature's sports drink " because of its high electrolyte (primarily potassium) content. However, the efficacy of CW in maintaining hydration or performance during exercise has not been investigated. PURPOSE: To compare the effects of CW (Amacoco; 5.6% carbohydrate, 48 mM K, 6 mM Na, 4 mM Ca, 3 mM Mg, 37 mM Cl), electrolyte water (EW; 45 mM K, 8 mM Na, 5 mM Ca, 3 mM Mg, 37 mM Cl), and water placebo (P) on performance. METHODS: Seventeen endurance-trained men (21-45 y) completed a 90-min steady state run (preload, 65% VO2max) followed by a 10K time trial in a warm environment (28°C). During preload, subjects drank a volume of CW, EW, or P (randomized, double-blind) to replace 80% of sweat losses. Venous blood samples were taken at baseline and at 30-min intervals during the 2-h preload run. [Hct] and [Hb] were measured in whole blood to determine percent change in plasma volume. Blood serum was analyzed for osmolality and electrolyte concentrations. Nude body weight was measured before and after exercise to assess fluid balance. RESULTS: There were no differences in 10K finish times among trials (2621 ± 383, 2629 ± 408, and 2622 ± 373 sec in CW, EW, and P trials respectively). In addition, the change in plasma volume (-9.6 ± 8.1,-9.3 ± 5.4, and-9.6 ± 5.2% in CW, EW, and P trials respectively) and change in body mass (-0.6 ± 0.4,-0.6 ± 0.5, and-0.5 ± 0.4% in CW, EW, and P trials respectively) were not different among trials. Post-preload serum osmolality (293 ± 6 vs. 299 ± 4 and 297 ± 6 mOsmol/kg), [K] (5.1 ± 0.4 vs. 5.9 ± 0.5 and 5.8 ± 0.4 mM), [Cl] (98 ± 2 vs. 100 ± 2 and 100 ± 2 mM), and [Mg] (1.86 ± 0.13 vs. 2.05 ± 0.12 and 1.95 ± 0.16 mg/dl) were significantly lower in the P vs. CW and EW trials. In addition, post-preload serum [Ca] was lower in P (9.7 ± 0.4) vs. CW (10.0 ± 0.4) and serum [Na] was lower in P (143 ± 3) and EW (143 ± 2) compared with CW (145 ± 3). (All values are means ± SD). CONCLUSIONS: Coconut water is not superior to water for maintaining performance in endurance-trained runners. Sweat loss can exceed 2.6 L·h¹ during exercise. A greater than 2% loss of body weight during activity can lead to decreased aerobic ability, decreased mental performance, muscle cramps, and fatigue due to the decrease in blood volume. In order to maintain appropriate blood volumes and electrolytes, staying hydrated during training is essential to athlete's performance. PURPOSE: The purpose of this study was to determine if water delivery method influenced intake of water amongst female athletes. METHODS: Water consumption in female athletes (n=34) from various sports were observed. The conditions of self-served water from a standard 3L jug, individual water bottles, and labeled individual bottles were applied randomly. Each of the three conditions was implemented four times. Measurements of the water amount were taken prior to practice to obtain an initial amount and then measured after practice. A 2x3 factorial ANOVA with repeated measures was used to analyze the data. RESULTS: A significant interaction was found for sport by water distribution (p<0.05). Volleyball players drank significantly more water (743.53±72.84 ml) from the jug than the soccer players (283.53±72.83). For the other two conditions labeled individual bottles and non-labeled individual bottles, no significant differences were found among sport. Finally, for soccer, players drank significantly less from the jug than the labeled and unlabeled water bottle conditions. For volleyball, there were no significant differences among the volume of water drank across the three conditions. CONCLUSION: Based on the present study, water consumption amongst female collegiate athletes was influenced by sport played and delivery method of water. Coaches need to be cognizant of the methods by which water is administered in order to encourage hydration among the athletes for their respective sports. (No relationships reported) The development of individualized hydration plans requires protocols to accurately assess fluid and sodium balance during exercise. While sweat sodium concentration and losses are most precisely measured by whole-body washdown techniques, the regional absorbent patch method provides a practical approach for field testing. Common laboratory-based techniques used to analyse sodium concentration of sweat samples include ion-selective electrode (ISE) and flame photometry. In addition, a desktop device assessing sweat conductivity may be appropriate for 'on the spot' analysis. The effects of differing handling protocols and analysis techniques on measurements of sweat sodium concentrations have not previously been examined. PURPOSE: To determine the effects of freezing and thawing sweat samples prior to analysis and of using different analytical techniques to measure sodium concentrations of sweat samples. METHODS: The regional absorbent patch method was used to collect sweat samples from the forearm during a standardized exercise protocol undertaken by 12 trained cyclists on four occasions. We undertook immediate single measure analysis of sodium concentration by ISE (Hitachi Model 911) and selected 30 samples covering a range of concentrations for further analysis. Three aliquots from each sample were frozen (-80°C) for re-analysis 4-12 weeks later using ISE (FISE), flame photometry (FFP) (Corning Model 410C) and sweat conductivity (FCON) (SweatChek 3120). RESULTS: Immediate analysis by ISE resulted in a mean sweat sodium concentration of 58 ± 19 mmol/L (range: 17-97 mmol/L). Re-analysis of stored samples by ISE produced a mean of 54 ± 18 mmol/L (range: 22-89 mmol/L). A mean of 66 ± 22 mmol/L (range: 23-109 mmol/L) and 62 ± 19 mmol/L (range: 25-97 mmol/L)

The Effects Of Handling And Analysis Techniques Used In The Measurement Of Sweat Sodium Concentration

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