5.5. Proyecto educativo
5.5.2. Modalidades u orientaciones elegidas por las escuelas
D.Brown and E.M.Winter
De Montfort University Bedford, Bedford, UK
1 Introduction
It is well established that dehydration can reduce the endurance performance capabilities of sportspeople. For instance, Saltin and Costill (1988) reported that fluid losses in excess of 5 % of body mass can decrease exercise capabilities by about 30 %. Even at low levels (1.8 %) of dehydration exercise performance time may be reduced (Walsh et al., 1994). Armstrong et al. (1985) demonstrated that diuretic-induced water loss equivalent to approximately 2 % body mass increased the time to run simulated 1500–10,000 m races by 3–7 %. It has also been demonstrated that progressive dehydration by 2.7 % body mass can cause a 20 % increase in errors in tennis performance (Burke and Ekblom, 1982).
Squash is a sport which presents a considerable challenge to the body’s
thermoregulatory systems which incorporate mechanisms for fluid balance. Still air within a squash court means that the facility for convective and evaporative cooling is limited. Furthermore while a player can generate air movement on court by moving quickly, this action in itself is thermogenic.
Fluid losses in squash of 1.8 l.h-1 (van Rensburg et al., 1982) and sweating rates
in excess of 1.9 l.h-1, corresponding to a 2 % loss in body mass (Hansen and
Brotherhood, 1988), have been reported for top club players and competition level players respectively, while Noakes et al. (1982) found body fluid losses of 2 l for 90 min of match-play. Reilly (1990) stated that skill performance in sport may be affected after loss of body water equivalent to 4 % of body mass, and stressed the importance of rehydration for squash players who sweat liberally during play.
There is a dearth of information about fluid losses in elite male squash players. These players have matches which last from 40 to 90 min, although in exceptional circumstances they may be up to 2–3 hours in duration. Clearly this taxes the endurance capabilities of players and makes it harder for them to maintain skill, so it is important that they minimise dehydration. However, fluid losses in
international competition are not well documented so the purpose of this study was to investigate fluid losses during international standard match-play in squash.
Science and Racket Sports II, edited by A.Lees, I.Maynard, M.Hughes and T.Reilly. Published in 1998 by E & FN Spon, 11 New Fetter Lane, London EC4P 4EE, UK. ISBN: 0 419 23030 0
Fluid loss during match-play in squash 57 2 Methods
Fluid losses were assessed in 8 matches at the squash World Cup team event in Malaysia which was held in May and June 1996. Three male members of the England national squad provided written informed consent and were recruited to the study. Fluid loss was estimated from reductions in body mass. Body mass was recorded prior to the warm up, and within 5 minutes of the match ending after the players had been towelled dry. Match time was taken as the total time between the measurements pre-and post-match. Body mass was measured to the nearest 100 g using portable electronic scales (EKS Model 6010, North Finchley, London, UK). The electronic scales were calibrated prior to and on return from the competition using laboratory based beam balance scales (Herbert and Sons, Edmonton, UK). The volume of fluid ingested by the players during the matches was measured using portable electronic food scales (EKS Model 1002, North Finchley, London, UK), where 1 g was assumed to be equivalent to 1 ml of fluid. Players were permitted to drink water ad libitum throughout each match.
The observed reductions in body mass (kg) combined with the fluid consumed (ml) during each match were used to calculate actual body mass loss (kg). Using match time, actual body mass loss was expressed as a rate of fluid loss (l.h-1). It
was assumed that virtually all the reductions in body mass represented fluid lost as sweat, where 1 kg of body mass loss corresponded to 1 litre of sweat. Dry bulb temperature (°C) and humidity (%) were measured on the squash court using a combined digital thermometer and hygrometer (A.T.P. Instrumentation Ltd Model HT-23, Ashby-de-la-Zouch, Leics, UK).
The relationship between match time (min) and rate of fluid loss (l.h-1) was
investigated using a Pearson’s product moment correlation coefficient. The data set consisted of 8 matches: 3 matches each from two players and 2 matches from the third player. Statistical significance was set at P<0.05.
3 Results and Discussion
Table 1 displays the range of data for each subject and summarises the eight matches assessed. Court temperature and humidity for the matches (n=8) were 25.1 ± 1.3 °C and 64 ± 6 % (mean ± SD) respectively.
The rates of fluid loss in this study of 2.37±0.45 l.h-1 (mean±SD) are higher than
those previously reported for squash (Noakes et al., 1982; van Rensburg et al., 1982; Hansen and Brotherhood., 1988). Although some of the reductions in body mass are attributable to substrate utilisation and respiratory fluid loss, the majority are the result of fluid lost as sweat. Approximate losses of body mass attributable to substrate utilisation would be 0.1-0.2 kg.h-1, which would account for only 4–8
58 Brown and Winter
The mean reduction in recorded body mass of 1.28 kg indicates that the players were incurring a mean fluid deficit of 1.28 l. Fluid deficit differed from zero (P < 0.01) which indicated that more fluid was lost through sweat than was ingested during the matches. Using match time, fluid deficit can be expressed as a rate of approximately 1.5 l.h-1 ((1.28 l÷51 min)×60=1.51 l.h-1).
There was a positive relationship between match time and rate of fluid loss (r=0.75, P < 0.05). Lower calculated rates of fluid loss in the shorter matches are probably not explained by a delay in activation of sweating mechanisms because sweating started during the warm up, not after the matches began. It is reasonable to assume that the longer matches were physically more demanding, resulting in higher rates of fluid loss. In addition there was a significant positive correlation between match time and fluid deficit (r=0.85, P<0.05), indicating that larger fluid deficits were incurred as the match times increased. During prolonged matches players will go for longer periods of time without drinking as they can only drink in between games. This results in a discrepancy between the rate at which a player is losing fluid through sweat and the rate at which they are able to consume fluid. Generally the longer the match time the greater this discrepancy will be, which explains the increased fluid deficit observed in the longer matches.
This is the first report of fluid losses assessed during international tournament matchplay in squash. The results guide pre-, intra- and post-match hydration strategies used by elite male squash players during international competition. Pre- match hydration ensures that players do not start play already dehydrated. The short time allowed between games (90 s maximum), combined with the discomfort of large amounts of fluid in the gut, means that it is simply impractical to expect a player to consume much more than 1 litre of fluid an hour during play.
Realistically players will consume at most about 200–250 ml between games. Such drinking could be considered to be a “damage limitation exercise” which
minimises fluid deficits incurred during matches.
For matches lasting an hour, fluid deficits will be approximately 1.5 litres, and so considerable attention must be given to the rehydration means that players employ. The mean rate of fluid loss in this study of 2.37 l.h-1 provides a useful
guideline to players, coaches and practitioners.
Table 1. Range of individual and summary data (raw and adjusted) for the matches (n) played
Fluid loss during match-play in squash 59 It should be noted that there is both inter- and intra-individual variability in the data. This is perhaps not surprising as the rates of fluid loss will depend on the duration and intensity of the matches, and could also be influenced by court
conditions (temperature and humidity) and individual variation in sweating response. 4 Conclusions
The results demonstrate the demanding nature of international standard squash and provide guidelines which can be used to inform hydration strategies for elite male players. These strategies need to accommodate fluid losses which approximate to 2.5 l.h-1, dependent on the intensity of play.
5 References
Armstrong, L.E., Costill, D.L. and Fink, W.J. (1985) Influence of diuretic-induced dehydration on competitive running performance. Medicine and Science in Sports and
Exercise, 17, 456–461.
Burke, E.R. and Ekblom, B. (1982) Influence of fluid ingestion and dehydration on precision and endurance performance in tennis. Athletics Trainer, Winter, 275–277. Hansen, R.D. and Brotherhood, J.R. (1988) Prevention of heat-induced illness in squash
players. Medical Journal of Australia, 148, 100.
Noakes, T.D., Cowling, J.R., Gevers, W. and van Niekerk, J.P, (1982) The metabolic response to squash including the influence of pre-exercise carbohydrate ingestion.
South African Medical Journal, 62, 721–723.
Reilly, T. (1990) The racquet sports, in Physiology of Sports (eds T.Reilly, N.Secher, P.Snell and C.Williams), E. and F.N.Spon, London, pp.337–369.
Saltin, B. and Costill, D.L. (1988) Fluid and electrolyte balance during prolonged exercise, in Exercise, Nutrition and Metabolism (eds E.Horton and R.Terjung), Macmillan, New York, pp. 150–158.
van Rensburg, J.P., van der Linde, A., Ackermann, P.C., Keilblock, A.J. and Strydom, N.B. (1982) Physiological profile of squash players. South African Journal for Research in
Sport, Physical Education and Recreation, 5, 25–56.
Walsh, R.M., Noakes, T.D., Hawley, J.A. and Dennis, S.C. (1994) Impaired high intensity cycling performance time at low levels of dehydration. International Journal of
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