title: Fluid balance and sodium losses during indoor tennis match play.
abstract: This study assessed fluid balance, sodium losses, and effort intensity during indoor tennis match play (17 ± 2 °C, 42% ± 9% relative humidity) over a mean match duration of 68.1 ± 12.8 min in 16 male tennis players. Ad libitum fluid intake was recorded throughout the match. Sweat loss from change in nude body mass; sweat electrolyte content from patches applied to the forearm, calf, and thigh, and back of each player; and electrolyte balance derived from sweat, urine, and daily food-intake analysis were measured. Effort intensity was assessed from on-court heart rate compared with data obtained during a maximal treadmill test. Sweat rate (M ± SD) was 1.1 ± 0.4 L/hr, and fluid-ingestion rate was 1.0 ± 0.6 L/hr (replacing 93% ± 47% of fluid lost), resulting in only a small mean loss in body mass of 0.15% ± 0.74%. Large interindividual variabilities in sweat rate (range 0.3-2.0 L/hr) and fluid intake (range 0.31-2.52 L/hr) were noted. Whole-body sweat sodium concentration was 38 ± 12 mmol/L, and total sodium losses during match play were 1.1 ± 0.4 g (range 0.5-1.8 g). Daily sodium intake was 2.8 ± 1.1 g. Indoor match play largely consisted of low-intensity exercise below ventilatory threshold (mean match heart rate was 138 ± 24 beats/min). This study shows that in moderate indoor temperature conditions players ingest sufficient fluid to replace sweat losses. However, the wide range in data obtained highlights the need for individualized fluid-replacement guidance.
authors.affiliation: School of Sport, University of Stirling, Stirling, Scotland.
authors.forename: Matthew J E
authors.initials: MJ
authors.lastname: Lott
authors.forename: Stuart D R
authors.initials: SD
authors.lastname: Galloway
mesh_terms: D000293:Adolescent; D000328:Adult; D001835:Body Weight; D003681:Dehydration; D004326:Drinking; D004573:Electrolytes / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D006813:Humidity; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D012964:Sodium / Q000008:administration & dosage / Q000378:metabolism*; D013542:Sweat / Q000378:metabolism*; D013546:Sweating / Q000502:physiology; D013696:Temperature; D013715:Tennis / Q000502:physiology*; D014882:Water-Electrolyte Balance; D055815:Young Adult
chemical_list: D004573:Electrolytes; D012964:Sodium