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Heat Cramps during Tennis: A Case Report

Michael F. Bergeron

A 17-year-old, nationally ranked, male tennis player (AH) had been experiencing heat cramps during tennis match play. His medical history and previous physical exams were unremarkable, and his in-office blood chemistry profiles were normal. On-court evaluation and an analysis of a 3-day dietary record revealed that AH's sweat rate was extensive (2.5 L · hr−1) and that his potential daily on-court sweat sodium losses (89.8 mmol · hr of play') could readily exceed his average daily intake of sodium (87.0-174.0 mmol · day−1). The combined effects of excessive and repeated fluid and sodium losses likely predisposed AH to heat cramps during play. AH was ultimately able to eliminate heat cramps during competition and training by increasing his daily dietary intake of sodium.

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Characterizing Hydration Practices in Healthy Young Recreationally Active Adults—Is There Utility in First Morning Urine Sampling?

Colleen X. Muñoz and Michael F. Bergeron

First morning urine (FMU) assessment would be a practical and convenient solution for clinically acceptable detection of underhydration prior to competition/training, and for the general public. Thus, we thus sought to determine the diagnostic accuracy of FMU as a valid indicator of recent (previous 24 hr, 5 days average) hydration practices. For 5 consecutive days and one final morning, 67 healthy women (n = 38) and men (n = 29; age: 20 [1] years, body mass index: 25.9 [5.5]) completed 24-hr diet logs for total water intake (from beverages and foods, absolute and relative to body mass), 24-hr urine and FMU collection (last morning only) for osmolality (Osm), specific gravity (SG), and color (Col), and morning blood sampling for plasma osmolality and copeptin. Correlations determined significance and relationship strength among FMU and all other variables. Area under the receiver operating characteristic curves, sensitivity, specificity, and positive likelihood ratios were employed using previously reported values to indicate underhydration (total water intake < 30 ml/kg, osmolality > 500, and >800 mOsm/kg, specific gravity > 1.017, and copeptin > 6.93 pmol/L). FMU_Osm and FMU_SG were significantly correlated (p < .05) to all variables except the previous 5-day plasma osmolality. FMU_Col was only significantly correlated with other color time intervals and total water intake per gram. FMU_Osm held greatest utility (area under the receiver operating characteristic curve, sensitivity, and specificity >80%) overall, with the best outcome being FMU_Osm indicating a previous 24-hr osmolality threshold of 500 mOsm/kg (FMU_Osm criterion >710 mOsm/kg and positive likelihood ratio = 5.9). With less effort and cost restriction, FMU is a viable metric to assess underhydration.

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Fluid-Electrolyte Balance Associated with Tennis Match Play in a Hot Environment

Michael F. Bergeron, Carl M. Maresh, Lawrence E. Armstrong, Joseph F. Signorile, John W. Castellani, Robert W. Kenefick, Kent E. LaGasse, and Deborah A. Riebe

Twenty (12 male and 8 female) tennis players from two Division I university tennis teams performed three days of round-robin tournament play (i.e., two singles tennis matches followed by one doubles match per day) in a hot environment (32.2 ± 1.5   C ° and 53.9 ± 2.4% rh at 1200 hr), so that fluid-electrolyte balance could be evaluated. During singles play, body weight percentage changes were minimal and were similar for males and females (males -1.3 ± 0.8%, females -0.7 ± 0.8%). Estimated daily losses (mmol · day 1 ) of sweat sodium (Na+) and potassium (K+) (males, Na + 158.7, K + 31.3; females, Na + 86.5, K + 18.9) were met by the players' daily dietary intakes (mmol · day 1 ) of these electrolytes (males, Na + 279.1 ± 109.4, K + 173.5 ± 57.7; females, Na + 178.9 ± 68.9, K + 116.1 ± 37.5). Daily plasma volume and electrolyte (Na+, K + ) levels were generally conserved, although, plasma [Na+] was lower (p < .05) on the morning of Day 4. This study indicated that these athletes generally maintained overall fluid-electrolyte balance, in response to playing multiple tennis matches on 3 successive days in a hot environment, without the occurrence of heat illness.

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Dietary Supplementation and Improved Anaerobic Performance

Carl M. Maresh, Lawrence E. Armstrong, Jay R. Hoffman, Daniel R. Hannon, Catherine L. V. Gabaree, Michael F. Bergeron, Michael J. Whittlesey, and Michael R. Deschenes

In the present study, the effects of an increased daily dose of a dietary supplement (ATP-E, 0.2 g · kg 1 · day 1 ) on Wingate test performance were examined in 12 men (21 ± 1.6 years) prior to and following 14 days of supplement and placebo ingestion. A double-blind and counterbalanced design was used. Results revealed higher (p < .007) preexercise blood ATP (95.4 ± 10.5 μmol · dl 1 ) for the entire group following 14 days of ATP-E ingestion compared to placebo measures (87.6 ± 10.9 μmol · dl 1 ). Mean power (667 ± 73 W) was higher (p < .008) after 14 days of ATP-E ingestion versus placebo (619 ± 67 W). Peak plasma lactate was lower (p < .07) after 14 days of ATP-E ingestion (14.9 ± 2.8 mmol · L 1 ) compared to placebo (16.3 ± 1.6 mmol · L 1 ). These data suggested that the improvement in 30-s Wingate test performance in this group may be related to the increased dose of ATP-E.

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Urinary Indices of Hydration Status

Lawrence E. Armstrong, Carl M. Maresh, John W. Castellani, Michael F. Bergeron, Robert W. Kenefick, Kent E. LaGasse, and Deborah Riebe

Athletes and researchers could benefit from a simple and universally accepted technique to determine whether humans are well-hydrated, euhydrated, or hypohydrated. Two laboratory studies (A, B) and one field study (C) were conducted to determine if urine color ( U col ) indicates hydration status accurately and to clarify the interchangeability of U col , urine osmolality ( U osm ), and urine specific gravity ( U sg ) in research. U col , U osm , and U sg were not significantly correlated with plasma osmolality, plasma sodium, or hemato-crit. This suggested that these hematologic measurements are not as sensitive to mild hypohydration (between days) as the selected urinary indices are. When the data from A, B, and C were combined, U col was strongly correlated with U hg and U„sm. It was concluded that (a) U col may be used in athletic/industrial settings or field studies, where close estimates of U sg or U osm are acceptable, but should not be utilized in laboratories where greater precision and accuracy are required, and (b) U osm and U sg may be used interchangeably to determine hydration status.