The fluid replacement needs of young tennis players : implications for tennis coaches.

[摘要] This study aimed to assess selected physiological, osmoregulatory andthermoregulatory responses to tennis play in children, Twenty-four youngmale tennis players (X age; 13.3+ 1.31 years) were stndied while playing for90 min under warm environmental conditions (WBGT index= 13-19). Adlibitum consumption of pure water was permitted.Questionnaires were used in order to elicit information regarding the healthstatus, degree of aeelimatizationnnd pre-match trait and state anxiety of thesubjects. The physiological variables assessed. included pre- and post-matchrectal temperature (T), heart rate (HR) and oxygen consumption (02)during the match. The biochemical observations included pre- and postmatchblood glucose, haematoerit (Ret), haemoglobin (lIb), plasma electrolyte(Na, Cl', K+, Mg++) and total plasma protein (TPP) concentrations.The findings )q~ed that the young tennis players investigated in this studyexperienced, ~de!'ate levels of pre-competitive trait and state amdety. Theestimated nie.m exercise intensity of 50-55% of VOzmax for a duration of 90min resulted. in a Tre increase of 0.73 •C. Mean percentage dehydration was0.MO+O.25. Plasma volume (PV) changes were insignificant and werepositively related to TPP changes. Mean plasma. Na and CI- concentrationsincreased by 0.88 mmol.r and 2.2 mmol.r:' respectively. The subjects' meanH... response (145 bpm) of a subset or the sample(n=13) and estimated VOz(21.38 ml.kg-l.min-~ represented a 55% of the age adjusted HRmax reserveand approximately a 50-55% of V02 max respectively. The time spent withinthe target heart rate range (60-85% HR. max reserve) comprised only 33% ofthe match duration. Mean energy expenditure was estimated to be 1772 KJdUl'ing the 90 min period.Itwas calculated that in order to prevent harmful levels of dehydration underwarm environmental conditions and at an exercise intensity of tennis play ofapproximately 55% of the age adjusted HR max reserve or 50-55% of V02max, consumption of 4.44-6.81 mI.Kg-1.br-1 or 200-360 ml.hr of water isrecommended in young tennis players possessing a body mass of 45-53 Kg.The precise quantity was concluded to be a function of the mass and exerciseintensity of the subjects and the environmental heat stress index during play.

[发布机构] University of the Witwatersrand