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theses

Hydration status has been shown to have effects on athletic performance. Maintaining proper levels of hydration is paramount for athletes. Recommendations regarding fluid and electrolyte replenishment are primarily based on sweat loss data obtained in males. The purpose of this study was to monitor hydration markers and plasma electrolytes over the course of the competitive season and evaluate whether there are chronic changes in plasma electrolytes as a function of “high” vs “low” electrolyte concentration sweat in high-level female athletes. Methods: Division I female athletes (n= 42, weight= 64.27± 6.69 kg, %BF= 24.09± 5.72 %, VO2max= 47.3± 5.36 ml/kg/min, VJ= 54.79± 7.35 cm, VT=78.54± 3.75 %VO2max) participated in blood draws every four weeks starting at preseason (T1) and continuing until 24 hours after the last game (T2, T3, T4, T5). During a practice session lasting approximately 2 hrs, regional sweat collections were made from the forearm, chest, and navel using sweat patches. Urine specific gravity (USG), Blood urea nitrogen and Creatinine ratio (BUN/Cr), blood glucose (GLU) were assessed as well as sweat and plasma, sodium (Na+), potassium (K+), chloride (Cl-), calcium (Ca2+), and magnesium (Mg2+) concentrations were determined. Plasma osmolality (Posm) was calculated as Posm = 1.90 [Na+ + K+] + Glucose + BUN + 5.0. RESULTS: Soccer and field hockey were analyzed separately due to the amount of time points for hydration markers but were combined for sweat [electrolyte] analysis. There was a significant increase in Posm (ΔPosm= 4.0 ± 1.3 mOsm/kg H2O, P<0.05) from T1 to T4 and from T4 to T5 (ΔPosm= 2.7 ± 1.3 mOsm/kg H2O, P<0.05). USG significantly increased from 1.012 ± .002 at T1 to 1.018 ± .002 at T2 and continued to increase to 1.021 ± .001 at T3, where it plateaued and remained significant through T5 (P<0.05) for soccer. Field hockey had a significant increase in Posm (ΔPosm= 2.3 ± 0.95 mOsm/kg H2O, P<0.05) from T1 to T3 and from T3 to T4 (ΔPosm= 3.5 ± 0.90 mOsm/kg H2O, P<0.05). USG significantly increased from 1.011 ± .008 at T1 to 1.016 ± .007 at T2 (P<0.05) and peaked at 1.017 ± .006 at T3 and plateaued at T4. Plasma electrolytes changed throughout the season for both teams but remained within normal ranges. There were significant differences in sweat electrolyte content that occurred as a function of patch site (p<.05). The greatest [K+], [Ca2+], and [Mg2+] were found at the forearm ([K+] = 6.65 ± 1.84 mM; [Ca2+] = 1.18 ± 0.53 mg/dL; [Mg2+] = 0.36 ± 0.19 mg/dL). The largest [Na+] and [Cl-] were produced at the navel (67.02 ± 20.25 mM and 56.74 ± 20.40 mM, respectively). [Electrolyte] across sites were summed to represent the total loss of each individual electrolyte. Individuals were classified as “high” or “low” concentration sweaters for each measure after calculating z-scores, using 0 as the split point. There were no differences between groups for any plasma [electrolyte] over the season (p>.05). CONCLUSIONS: The increases seen in Posm and USG for soccer show that these athletes are in a chronic state of hypohydration. While field hockey saw similar changes, they did not meet a level of 1.020 for USG. Regional variations in sweat [electrolyte] were observed in female athletes. However acute sweat composition does not appear to effect plasma values across an athletic season. These results may suggest that these athletes adequately chronically replenish any electrolytes lost. The increases in Posm and USG may suggest that diet and fluid intake play important roles in hydration and replenishing electrolytes.

ETD_8648

M.S.

Includes bibliographical references

by Anthony N. Poyssick

doi:10.7282/T3G73HZR

ETD graduate

The author owns the copyright to this work.