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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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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 (Ucol) indicates hydration status accurately and to clarify the interchangeability of Ucol, urine osmolality (Uosm), and urine specific gravity (Usg) in research. Ucol, Uosm, and Usg 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, Ucol was strongly correlated with Uhg and U„sm. It was concluded that (a) Ucol may be used in athletic/industrial settings or field studies, where close estimates of Usg or Uosm are acceptable, but should not be utilized in laboratories where greater precision and accuracy are required, and (b) Uosm and Usg may be used interchangeably to determine hydration status.

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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 · kg1 · day1) 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 · dl1) for the entire group following 14 days of ATP-E ingestion compared to placebo measures (87.6 ± 10.9 μmol · dl1). 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 · L1) compared to placebo (16.3 ± 1.6 mmol · L1). 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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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 · day1) 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 · day1) 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.