Fluid and electrolyte balance during indoor tennis match play

Abstract

Fluid intake, electrolyte balance, and effort intensity during one best of three set indoor singles tennis match (17 ± 2°C, 42 ± 9% humidity) was measured in 16 male University tennis players. Sweat samples were collected through application of an absorbent sweat patch to the forearm, calf, thigh and back of each player. Effort intensity was measured through comparisons of on-court heart rates to data obtained from a maximal treadmill test.

The mean sweat loss was 1219 ± 417 ml, mean fluid intake was 1087 ± 625 ml (players replaced on average 89% of fluid lost), mean whole body sweat rate was 0.72 ± 0.26 l/h and no significant body mass loss was observed from pre to post match. However, a large inter-individual variability existed (range 0.43 - 1.28 l/h). 15 out of 16 players chose to consume water during their match; and these fluid intake choices were sufficient to on the whole maintain plasma sodium levels. Two players provided pre-match urine samples above 900 mOsmol/kg while another four provided samples approaching this level, indicating some players were hypohydrated prior to match play. The mean sweat sodium concentration was 41 ± 15 mmol/l suggesting lower heat acclimation statuses than in players competing at warmer environments, and total sodium losses during match play were 1.12 ± 0.45 g (range 0.46 – 1.93 g). Again, large individual variations existed. On average, dietary and on-court electrolyte intake exceeded electrolyte loss during match play by a considerable margin, but in some player’s there was not a great difference. Muscle cramping could occur if players fail to adequately replace both fluid and electrolyte losses that occur during match play, even in a comfortable indoor environment. Finally, indoor match play largely consisted of moderate intensity exercise, below ventilatory threshold, with a smaller high intensity contribution.

This study showed that in cool ambient conditions, sweat rates reached 1.28 l/h, and players ingested sufficient fluid to replace 89 ± 47% of sweat losses, suggesting that contrary to footballers, runners, and in some other sports, fluid replacement is easier to achieve in tennis due to the regular breaks in match play.