Hydration testing in collegiate wrestlers undergoing hypertonic dehydration
ABSTRACT Because dehydration (DEH) violates assumptions used in the assessment of body composition, hydration testing has become an integral part of minimal weight (MW) assessment.
To determine the accuracy of hydration tests for the detection and quantification of hypertonic DEH.
Twenty-five male collegiate wrestlers (mean +/- SD, age: 20.0 +/- 1.4 yr, height: 175.0 +/- 7.1 cm, body mass: 81.7 +/- 15.3 kg) had their hydration assessed under well-controlled conditions of euhydration (EUH) and DEH. The DEH phase occurred on the same day as EUH, after subjects acutely dehydrated 2-6% of body weight through fluid/food restriction and exercise in a hot environment.
All hydration tests except plasma potassium significantly increased from EUH to DEH, and meaningful cutoff values could be established for most tests. Cutoff values for urine tests were 586 mOsm.L(-1) for osmolality and 71 mEq.L(-1) for potassium. Plasma cutoff values were 293 mOsm.L(-1) for osmolality, 140 mEq.L(-1) for sodium, 103 mEq.L(-1) for chloride, and 3.5 pg.mL(-1) for arginine vasopressin. For ratio tests, a urine:plasma osmolality of 2.06 and an extracellular:intracellular water of 0.533 measured by the bioelectrical impedance spectroscopy were cutoff values. For urine specific gravity, a cutoff value of 1.020 g.mL(-1) had a sensitivity and specificity of 96% each for the automated harmonic oscillation technique and 87% and 91% (respectively) for the dipstick technique. Protein (by dipstick) was detected in 5% of subjects in EUH, and 100% of subjects in DEH. Correlations between hydration tests and dehydration were only low to moderate.
This study supports a specific gravity cutoff of 1.020 g.mL(-1) for the identification of hypertonic DEH. Future research should test the cutoff values established in this study and explore the relationship between DEH and urine protein.
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ABSTRACT: It is well known that proper dietary intake (DI), hydration status (HS) and body composition (BC) may affect athletes health and performance. However, less is known about DI, HS and BC of elite canoe athletes during different periods of competition preparation. The purpose was to assess DI, HS and changes in BC of elite canoeist during 3 training periods (TP) of competition preparation. 5 female (F, 26±3 yrs, 173±4 cm; 66.9±3.6 kg) and 10 male (M, 25±4 yrs, 186±8 cm, 89.1±8.3 kg) canoeist of the German national team completed 6 measurement setups within 3 TPs. Each TP consisted of different training volumes, intensities and exercise tasks. Measurements were conducted at the beginning and at the end of each TP. Energy (E), carbohydrate (CHO), protein (PROT) and fat intake were investigated using a 3d-dietary record. HS was assessed by urine specific gravity (USG, dehydration cut-off ≥1.020) of 3 urine samples per measurement day. To evaluate body fatness, skinfold thickness was measured in the outset of TP1 and at the end of TP2/3. Statistical analysis by descriptive statistic (mean ± SD), Friedman-Test and one-way ANOVA for repeated measurements. Mean E intake was less than recommendations (details in table). TP E [kcal] PROT [g] FAT [g] CHO [g] USG BF [%] F 1 3246±361 116±17 113±18 410±54 1.022±0.008 11.4±2.5 2 3062±317 110±25 111±11 377±65 1.020±0.007 9.3±1.2 3 3074±126 104±22 112±12 387±65 1.017±0.012 8.7±0.7 M 1 4394±985 197±40 160±43 508±126 1.021±0.008 17.4±2.5 2 4181±1251 200±74 163±46 446±178 1.020±0.008 14.3±2.4 3 4169±955 197±62 181±50 446±189 1.021±0.009 14.0±2.3 No significant difference in DI for M and F between the TPs. USG differed significant during TP1 for M (p<0.05), but not in F. Differences of USG between the 3 TPs were not significant for M and F. A decrease of BF was measured for M (p<0.05) and F (p<0.05). Many athletes (73%) began the morning training session in a dehydrated state. However, USG changes during the day for M were observed and suggest an adaptation of fluid intake to exercise fluid demands. E intake was lower than recommended for elite endurance athletes, which might be ascribed to effects of under-reporting. In the course of the competition season, body fat slightly decreased, which might be due to higher exercise loads. Nutritional guidance is required to better DI to exercise demands of these athletes.International Sports & Exercise Nutrition Conference 2013, Newcastle upon Tyne; 12/2013
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ABSTRACT: The objective of the study was to investigate the hydration status and fluid balance of elite European youth soccer players during three consecutive training sessions. Fourteen males (age 16.9 ± 0.8 years, height 1.79 ± 0.06 m, body mass (BM) 70.6 ± 5.0 kg) had their hydration status assessed from first morning urine samples (baseline) and pre- and post-training using urine specific gravity (USG) measures, and their fluid balance calculated from pre- to post-training BM change, corrected for fluid intake and urine output. Most participants were hypohydrated upon waking (USG >1.020; 77% on days 1 and 3, and 62% on day 2). There was no significant difference between first morning and pre-training USG (p = 0.11) and no influence of training session (p = 0.34) or time (pre- vs. post-training; p = 0.16) on USG. Significant BM loss occurred in sessions 1-3 (0.69 ± 0.22, 0.42 ± 0.25, and 0.38 ± 0.30 kg respectively, p < 0.05). Mean fluid intake in sessions 1-3 was 425 ± 185, 355 ± 161, and 247 ± 157 ml, respectively (p < 0.05). Participants replaced on average 71.3 ± 64.1% (range 0-363.6%) of fluid losses across the three sessions. Body mass loss, fluid intake, and USG measures showed large inter-individual variation. Elite young European soccer players likely wake and present for training hypohydrated, when a USG threshold of 1.020 is applied. When training in a cool environment with ad libitum access to fluid, replacing ~71% of sweat losses results in minimal hypohydration (<1% BM). Consumption of fluid ad libitum throughout training appears to prevent excessive (≥2% BM) dehydration, as advised by current fluid intake guidelines. Current fluid intake guidelines appear applicable for elite European youth soccer players training in a cool environment. Key PointsThe paper demonstrates a notable inter-participant variation in first morning, pre- and post-training hydration status and fluid balance of elite young European soccer players.On average, elite young European soccer players are hypohydrated upon waking and remain hypohydrated before and after training.Elite young European soccer players display varied fluid intake volumes during training, but on average do not consume sufficient fluid to offset fluid losses.Consecutive training sessions do not significantly impair hydration status, suggesting that elite young European soccer players consume sufficient fluid between training to maintain a stable hydration status and prevent excessive (≥2% body mass) dehydrationCurrent fluid intake guidelines appear applicable to this population when training in a cool environment.Journal of sports science & medicine 12/2014; · 0.90 Impact Factor
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ABSTRACT: The aim of this study was to assess the hypothesis that water intake will accelerate cardiac vagal reactivation after a single session of upper-body resistance exercise. 13 healthy men (26.5±5.9 years) with previous experience in resistance training were enrolled. In visits 1 and 2, participants performed the one-repetition maximum (1RM) test and retest with the bench press exercise. The sessions 3 and 4 were performed randomly, while participants consumed 500 ml (experimental visit) or 50 ml (control visit) of water immediately after 3 sets of maximum repetitions at 80% of 1RM. Cardiac vagal activity was represented by cardiac vagal index (CVI) measured before, immediately after and 30 min post-exercise. Additionally, heart rate and blood pressure were measured. The results show that CVI was higher 30 min post-exercise when 500 ml of water was ingested compared to 50 ml (1.39±0.07 vs. 1.23±0.07; p=0.02) (mean±SEM). Heart rate and blood pressure values were similar in both trials. We conclude that water intake accelerates post-resistance exercise cardiac vagal reactivation. These findings suggest that hydration after resistance exercise might be beneficial for cardiovascular safety in healthy subjects.International Journal of Sports Medicine 11/2014; 36(03). DOI:10.1055/s-0034-1389971 · 2.37 Impact Factor