Body weight changes and voluntary fluid intakes of beach volleyball players during an official tournament

The aim of this study was to calculate sweat rates (measured by weight changes), voluntary fluid intakes, and fluid balance of beach volleyball players during a tournament. Data was collected during the 3 days of the tournament for male players (n=47) age M=26.17 (S.D.=5.12) years old. Participants were weighed before the warm up and they reweighed immediately after the game. The differences in body weight were calculated in grams. The voluntary fluid intake of players during the game was also recorded by observers, whose inter and intra reliability were evaluated (inter r=.89 and intra reliability r=.93). Fifty matches took place with a M=42.2min duration per match. A wide individual variation appeared in fluid intake and sweat loss. The calculated average sweat rate, fluid intake rate and fluid balance of players during each match were M=1440ml, M=731ml and M=-0.8%, respectively. Air temperature ranged from 26 degrees to 38 degrees C (M=33.58 degrees C, S.D.=2.8) and humidity from 42% to 75% (M=56.04%, S.D.=8.7) and both were measured in each day of tournament, at the beginning and at the end of each game. Although players' dehydration (-0.8%) was of mild level, it was more or less the same as it was reported in other team sports studies. ANOVA did not prove differences between elite and non-elite athletes in sweat loss and fluid intake (p>.01). Sweat rate was associated only with humidity (r=.99, p<.01) and with fluid intake (r=.315, p<.05). The athletes should be aware of the great significance of fluids and to intake greater quantities in order to prevent weight loss and at the same time loss of vital elements that would cause their performance to decline.     

The bone response to non-weight-bearing exercise is sport-, site-, and sex-specific.

OBJECTIVE: To examine whether skeletal adaptations to chronic non-weight-bearing exercise depend on the type of aquatic exercise (swimming or water polo) as well as on sex (men or women). DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional study at the Laboratory of Nutrition and Clinical Dietetics, Department of Nutrition and Dietetics, Harokopio University, Athens, Greece. A total of 43 water polo players, 26 swimmers, and 30 sedentary individuals, aged 17 to 34 years, were recruited (52 men, 47 women). MAIN OUTCOME MEASURES: Bone mineral content (BMC) and areal bone mineral density (aBMD) of the total body and of various subregions. RESULTS:: Compared with controls, swimmers had lower leg and total aBMD (P < 0.05), whereas water polo players had lower leg but higher arm and trunk aBMD (all P < 0.05). Swimmers and water polo athletes differed at the arms (men only), trunk, and total body (all higher in water polo players, at P < 0.05). Bone adaptations to water polo playing were unaffected by sex. Female swimmers, but not male swimmers, had 13% higher arm BMC than controls (P < 0.05), whereas male swimmers, but not female swimmers, had 12% lower leg BMC than controls (P < 0.05). CONCLUSIONS: Athletes participating in long-term water polo playing and swimming have substantially different total and regional aBMD. The effect is not mediated by sex in water polo players; however, sex may mediate the differences between swimmers and controls. Whether the observed differences between athlete groups and sexes arise from different bone adaptations to activity or from other factors cannot be answered by the current data. CLINICAL RELEVANCE: Water polo playing may be preferable over swimming for maintaining bone health; both types of aquatic exercise at the elite level of participation, however, have unfavorable effects on the lower limb bones.     

C-reactive protein serum concentrations in well-trained athletes

Previously it had been shown that there is a sharp increase in C-reactive protein (CRP) serum concentration during the first few days after severe exercise. To evaluate the effect of physical training on the CRP levels, a sensitive enzyme immunoassay was developed and used to assess the basal CRP concentrations in 356 male and 103 female athletes, who trained at least 4 times per week in various disciplines, in 45 male and 40 female untrained controls, and in 35 elderly coronary patients. In male athletes the lowest CRP values were found in swimmers (median: 102 ng/ml, n = 59), which were significantly lower (P less than 0.001) than those of male controls (median: 502 ng/ml, n = 45). The CRP concentrations in rowers (median: 260 ng/ml, n = 108) were also significantly lower (P less than 0.01) than in the control group. CRP levels in middle- and long-distance runners (median: 315 ng/ml, n = 53), racing cyclists (median: 620 ng/ml, n = 111), and soccer players (median: 660 ng/ml, n = 25) did not differ significantly from those of the controls. In female athletes the lowest CRP concentrations were also found in swimmers (median: 110 ng/ml, n = 49), which were significantly lower (P less than 0.001) than those of the female controls (median: 396 ng/ml, n = 40). Female middle- and long-distance runners (n = 36) and female rowers (n = 18) had median CRP values of 250 and 285 ng/ml, respectively. This results suggest that training induces a suppressive effect upon CRP, responsible for the low serum levels in athletes (particularly swimmers) when compared to controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

The sweating response of elite professional soccer players to training in the heat

Sweat rate and sweat composition vary extensively between individuals, and quantification of these losses has a role to play in the individualisation of a hydration strategy to optimise training and competitive performance. Data were collected from 26 male professional football (soccer) players during one 90 min pre-season training session. This was the 2nd training session of the day, carried out between 19.30 and 21.00 h when the mean +/- SD environment was 32 +/- 3 degrees C, 20 +/- 5 %rh and WBGT 22 +/- 2 degrees C. Training consisted of interval running and 6-a-side games during which the average heart rate was 136 +/- 7 bpm with a maximum rate of 178 +/- 7 bpm (n = 19). Before and after training all players were weighed nude. During training all players had free access to sports drinks (Gatorade) and mineral water (Solan de Cabras). All drink bottles were weighed before and after training. Players were instructed to drink only from their own bottles and not to spit out any drink. No player urinated during the training session. Sweat was collected by patches from the chest, arm, back, and thigh of a subgroup of 7 players. These remained in place for the first 15 - 30 min of the training session, and sweat was analysed for sodium (Na (+)) and potassium (K (+)) concentration. Body mass loss was 1.23 +/- 0.50 kg (ranging from 0.50 to 2.55 kg), equivalent to dehydration of 1.59 +/- 0.61 % of pre-training body mass. The sweat volume lost was 2193 +/- 365 ml (1672 to 3138 ml), but only 972 +/- 335 ml (239 to 1724 ml) of fluid was consumed. 45 +/- 16 % of the sweat volume loss was replaced, but this ranged from 9 % to 73 %. The Na (+) concentration of the subgroup's sweat was 30.2 +/- 18.8 mmol/l (15.5 to 66.3 mmol/l) and Na (+) losses averaged 67 +/- 37 mmol (26 to 129 mmol). The K (+) concentration of the sweat was 3.58 +/- 0.56 mmol/l (2.96 to 4.50 mmol/l) and K (+) losses averaged 8 +/- 2 mmol (5 to 12 mmol). The drinking employed by these players meant that only 23 +/- 21 % of the sweat Na (+) losses were replaced: This ranged from replacing virtually none (when water was the only drink) to replacing 62 % when the sports drink was consumed. These elite soccer players did not drink sufficient volume to replace their sweat loss. This, however, is in accord with data in the literature from other levels of soccer players and athletes in other events. These measurements allow for an individualisation of the club's hydration strategy.     

Elite Kenyan endurance runners are hydrated day-to-day with ad libitum fluid intake

Previous studies of elite Kenyan endurance runners reported that athletes did not consume liquids before or during training and infrequently consumed modest amounts of liquids after training that contributed to low daily fluid intake. PURPOSE: To assess hydration status of elite Kenyan endurance runners during an important training period. METHODS: Hydration status was monitored in fourteen elite Kenyan endurance runners over a 5-d training period 1 wk prior to the Kenyan national trials for the 2005 IAAF Athletics World Championships by measuring body mass, urine osmolality, total body water, and daily fluid intake. Dietary sodium (Na) intake was estimated using a 5-d nutritional diary and biochemical analysis, whilst [Na] was determined in urine and sweat. Intestinal temperature was monitored continuously during training sessions. RESULTS: Daily fluid intake was consistent with previous observations. There was a significant body mass loss during the morning, interval, and afternoon training sessions (P < 0.05). Nevertheless, mean total body water and pretraining body mass were well maintained day-to-day throughout the 5-d recording period (P = 0.194 and P = 0.302, respectively). Furthermore, there was no significant difference between the osmolality of the morning urine sample and the evening sample (P = 0.685). Mean Na intake was not significantly different to Na loss in sweat and urine (P = 0.975). No athlete showed signs or symptoms of heat strain at any time. CONCLUSIONS: These results demonstrate that elite Kenyan endurance runners remain well hydrated day-to-day with an ad libitum fluid intake; a pattern and volume of fluid intake that is consistent with previous observations of elite Kenyan endurance runners.     

Comparing sports injuries in men and women.

OBJECTIVE: To compare the pattern of injury between men and women in seven collegiate sports to determine if gender-specific factors exist which could be modified to reduce the risk of injury to female athletes. DESIGN: Retrospective cohort study of injury reports compiled by certified athletic trainers between Fall 1980 and Spring 1995. SETTING: An NCAA division III College. PARTICIPANTS: Eighteen to 22 year-old male and female college athletes competing in seven like sports (basketball, cross-country running, soccer, swimming, tennis, track and water polo) at the intercollegiate level, playing similar number of contests and using the same facilities. MAIN OUTCOME MEASURES: Analyses of injury patterns, classified by sport and anatomic location, for men and women in seven like sports. RESULTS: A total of 3,767 participants were included in the study, with 1874 sports-related injuries reported among the men and women's teams. Of these injuries, 856 (45.7%) were sustained by female and 1018 (54.3%) by male athletes. Overall, no statistically significant gender difference was found for injuries per 100 participant-years (52.5 for female athlete versus 47.7 for males). A statistically significant gender difference in injury incidence (p < 0.001) was seen for two sports: swimming and water polo. Female swimmers reported more back/neck, shoulder, hip, knee and foot injuries: and female water polo players reported more shoulder injuries. When evaluating all sports concurrently, female athletes reported a higher rate of hip, lower-leg and shoulder injuries, while male athletes reported a higher rate of thigh injuries. CONCLUSION: Except for some minor gender differences in total injuries for two sports and several differences in total injuries by anatomic location, our data suggest very little difference in the pattern of injury between men and women competing in comparable sports. The increased rate of shoulder injury among female swimmers probably resulted from the more rigorous training philosophy of their coach. Thus, no gender-specific recommendations can be suggested for decreasing the incidence of injury to female athletes competing in these sports.     

Echocardiographic data in hungarian top-level water polo players

PURPOSE: Water polo is a sport involving extremely intense exercise training that might be expected to result in major cardiac adaptations. The purpose of our study was to evaluate cardiac size, determine VO(2max) of top-level water polo players, and compare the findings with those of other top-level athletes. METHODS: Treadmill VO(2max) and 2D guided M-mode and Doppler echocardiographic data were obtained on players (N = 15) of the Olympic champion (Sydney 2000) Hungarian team and compared with data of Hungarian sedentary subjects (N = 19), and top-level endurance (N = 16) and power athletes (N = 15). RESULTS: Aerobic power of the water polo players was significantly lower (57.8 +/- 12.3 mL.min(-1).kg(-1)) than that of endurance athletes (70.9 +/- 8.9), higher than sedentary controls (49.7 +/- 4.3), and not different from that of power athletes (50.5 +/- 6.0). Body size related mean left ventricular wall thickness (LVWT/BSA(0.5)) was the highest in the water polo players (16.8 +/- 1.5 vs 15.9 +/- 1.1 in endurance, 14.5 +/- 1.0 in the power athletes, and 12.8 +/- 0.6 mm.m in nonathletes). Left ventricular muscle mass (LVMM/BSA(1.5)) was higher in the water polo players (115 +/- 22 g.m) than in power athletes (86 +/- 12) or nonathletes (74 +/- 9) and similar to that of endurance athletes (112 +/- 15). Resting heart rate was lower in the water polo players (55.1 +/- 9.7 beats.m(-1)) and endurance athletes (59.3 +/- 10.6) than in power athletes (66.0 +/- 16.1) or in sedentary subjects (72.9 +/- 10.9). CONCLUSIONS: Results indicate that high-level water polo results in marked cardiac hypertrophy that involves predominantly an increase of wall thickness, and in a VO(2max) lower than that of endurance athletes but similar to those of basketball and soccer players.     

Sweat iron loss of male and female runners during exercise

Male (n = 9) and female (n = 8) collegiate cross-country runners were studied during a training session to determine the amount of iron lost in the sweat. Sweat samples were collected from the arm using polyethylene bags. Total sweat loss was determined by weighing subjects before and after the runs. Average time of sweat collection was 42 min for males and 39 min for females. Sweat rate for the males (717.5 +/- 145.9 g/m2/h) was significantly greater than for the females (460.1 +/- 142.9 g/m2/h); however, the sweat rate per km was not significantly different. Females had a significantly greater sweat iron concentration (0.417 +/- 0.024 mg/l) than males (0.179 +/- 0.011 mg/l). Rate of sweat iron loss was not significantly different for females (0.276 +/- 0.140 mg/h) and males (0.21 +/- 0.13 mg/h). Sweat iron concentration was inversely related with sweat rate (r = -0.64). Our data suggest that although males lose more total sweat than females, the higher sweat iron concentration of females leads to similar rates of iron loss. For female runners, sweat iron loss coupled with a low dietary iron intake may result in a negative iron balance.     

Dietary intakes of age-group swimmers.

The purposes of this study were to collect information regarding the dietary habits of male and female age-group swimmers and report the energy consumptions of these athletes in relation to their daily training demands. Twenty competitive swimmers, who were training 6000 m per day 6 days a week, recorded all fluid and food consumed during a 4-day period. Dietary analysis revealed that 11 swimmers (55%) had calcium intakes below recommended dietary allowances (RDA), while 13 (65%) had iron intakes lower than RDA. Despite identical training loads and body mass, male swimmers had significantly greater (P = 0.004) daily mean (s.d.) energy consumption (3072(732) kcal, 12.9(3.1) MJ) than females (2130(544) kcal, 8.9(2.3) MJ) and were maintaining energy balance. Although the contribution of carbohydrate to total daily energy intake was the same for male (55%) and female swimmers (56%), the females ingested significantly less (P = 0.011) carbohydrate (292(87) g) than the males (404(88) g) and could be considered deficient in dietary carbohydrate with respect to their daily training demands.     

Hyponatraemic encephalopathy despite a modest rate of fluid intake during a 109 km cycle race

Methods: Men and women cyclists were weighed before and after the race. All subjects were interviewed and their water bottles measured to quantify fluid ingestion. A blood sample was drawn after the race for the measurement of serum Na⁺ concentration. Results: From the full set of data (n = 196), one athlete was found to have hyponatraemic encephalopathy (serum [Na⁺] 129 mmol/l). She was studied subsequently in the laboratory for measurement of sweat [Na⁺] and sweat rate. Conclusions: Despite a modest rate of fluid intake (735 ml/h) and minimal predicted sweat Na⁺ losses, this female athlete developed hyponatraemic encephalopathy. The rate of fluid intake is well below the rate currently prescribed as optimum. Drinking to thirst and not to a set hourly rate would appear to be the more appropriate behaviour.     

Effects of three different water temperatures on dehydration in competitive swimmers

Aims

The purpose of this study was to evaluate the effects of three different water temperatures on physiological responses (dehydration, sweat rate, urine output, rectal temperature and plasma electrolytes) of competitive athletes during a “simulated” race of 5 km in an indoor swimming pool.

Methods

Nine male competitive master swimmers swam 5 km with the water at temperatures of 23, 27 and 32 ?C. Immediately before (Pre) and after (Post) each trial, samples of blood and urine were collected, body weight was recorded and rectal temperature was measured. The dehydration percentage and sweat rate were the highest at 32 ?C and the lowest at 23 ?C (23 ?C: −0.9 ± 0.5; 27 ?C: −1.3 ± 0.6; 32 ?C: −2.2 ± 0.7% and 23 ?C: 0.48 ± 0.28; 27 ?C: 0.76 ± 0.36; 32 ?C: 1.25 ± 0.37 l/h). The Post urine volume output was not significantly different in the three trials (23 ?C: 122.6 ± 62.4; 27 ?C: 78.2 ± 24.9; 32 ?C 81.4 ± 37.0 mL). The 27 and 32 ?C water increased the rectal temperature (Pre: 37.0 ± 0.3; Post: 37.9 ± 0.5 ?C–Pre: 36.9 ± 0.4; Post: 38.0 ± 0.4 ?C, respectively).

Results

This study shows that dehydration, sweat rate and body temperatures simultaneously increase with the rise of water temperature during the shortest open water swimming event distance (5 km) performed at race intensity.     

运动员在热环境训练时的营养与代谢

运动员在热环境训练时大量排汗能引起体内微量元素的丢失以及HCT和Hb水平增加,血糖下降,尿液浓缩等生理反应。文章指出适当补充含糖5%的多种低渗电解质饮料,可使上述现象得到缓解。     

Fluid and electrolyte balance in ultra-endurance sport

It is well known that fluid and electrolyte balance are critical to optimal exercise performance and, moreover, health maintenance. Most research conducted on extreme sporting endeavour (>3 hours) is based on case studies and studies involving small numbers of individuals. Ultra-endurance sportsmen and women typically do not meet their fluid needs during exercise. However, successful athletes exercising over several consecutive days come close to meeting fluid needs. It is important to try to account for all factors influencing bodyweight changes, in addition to fluid loss, and all sources of water input. Increasing ambient temperature and humidity can increase the rate of sweating by up to approximately 1 L/h. Depending on individual variation, exercise type and particularly intensity, sweat rates can vary from extremely low values to more than 3 L/h. Over-hydration, although not frequently observed, can also present problems, as can inappropriate fluid composition. Over-hydrating or meeting fluid needs during very long-lasting exercise in the heat with low or negligible sodium intake can result in reduced performance and, not infrequently, hyponatraemia. Thus, with large rates of fluid ingestion, even measured just to meet fluid needs, sodium intake is vital and an increased beverage concentration [30 to 50 mmol/L (1.7 to 2.9 g NaCl/L) may be beneficial. If insufficient fluids are taken during exercise, sodium is necessary in the recovery period to reduce the urinary output and increase the rate of restoration of fluid balance. Carbohydrate inclusion in a beverage can affect the net rate of water assimilation and is also important to supplement endogenous reserves as a substrate for exercising muscles during ultra-endurance activity. To enhance water absorption, glucose and/or glucose-containing carbohydrates (e.g. sucrose, maltose) at concentrations of 3 to 5% weight/volume are recommended. Carbohydrate concentrations above this may be advantageous in terms of glucose oxidation and maintaining exercise intensity, but will be of no added advantage and, if hyperosmotic, will actually reduce the net rate of water absorption. The rate of fluid loss may exceed the capacity of the gastrointestinal tract to assimilate fluids. Gastric emptying, in particular, may be below the rate of fluid loss, and therefore, individual tolerance may dictate the maximum rate of fluid intake. There is large individual variation in gastric emptying rate and tolerance to larger volumes. Training to drink during exercise is recommended and may enhance tolerance.     

Comparison of lung volume in Greek swimmers, land based athletes, and sedentary controls using allometric scaling.

OBJECTIVE: To compare lung volumes in a large cross sectional sample of Greek swimmers, land based athletes, and sedentary controls by means of allometric scaling. METHODS: Four hundred and fifty nine asymptomatic Greek children and young adults (age 10-21 years), including 159 swimmers, 130 land based athletes, and 170 sedentary controls, performed forced expiratory manoeuvres into a portable spirometer. Measurements included forced vital capacity, forced expiratory volume in one second (FEV1.0), and peak expiratory flow. Body mass and stature were also measured using standardised anthropometric techniques. RESULTS: Logarithmic transformations showed that in FEV1.0 was highly related to in stature in males and females (r = 0.93 and 0.86 respectively, P < 0.001) and were used to determine the exponent in an allometric equation which also included age and age. Resulting power functions, FEV1.0/stature, were 0.64 (0.18) litres/m2.69 and 0.33 (0.24) litres/m2.32 for males and females respectively (mean (SE)). The male and female swimming groups had larger FEV1.0 than both land based athletes and sedentary controls (one way analysis of variance, P < 0.001). In addition, male national standard swimmers (n = 38) had superior FEV1.0 in comparison with male non-national standard swimmers (n = 24; t test, P < 0.05). However, when years of swimming training was controlled for by analysis of covariance, the difference in FEV1.0 between the two groups was no longer evident. CONCLUSIONS: Swimmers have superior FEV1.0 independent of stature and age in comparison with both land based athletes and sedentary controls. In addition, male national standard swimmers have superior FEV1.0 independent of stature and age in comparison with male non-national standard swimmers. When years of training is controlled for, the difference in FEV1.0 between the two groups is no longer evident. This suggests that the years of swimming training and/or the earlier age at which training begins may have a significant influence on subsequent FEV1.0 and swimming performance. However, because of the cross sectional nature of this study, the results do not exclude genetic endowment as a major determinant of the superior lung volume observed in swimmers.     

补水补盐联合辅助降温对热应激反应的影响

 目的 探讨训练前补水补盐联合训练中辅助降温措施对热应激反应的影响。方法 参加研究男性士兵62人,兵龄1~2年,训练科目为5 km及10 km跑步,户外跑步环境热指数40~42,随机分为实验组和对照组,实验组跑前30 min饮用60 mmol/L氯化钠溶液500 ml。跑步中辅助降温:实验组跑步中每间隔400 m给予用海绵块吸取20 ℃水浇头1次及20 ℃水全身喷雾降温3 s,对照组给予跑前30 min饮纯净水500 ml,跑步中无降温措施。对比5 km跑步实验组(n=20),对照组(n=21)以及10 km跑步实验组(n=10),对照组(n=11)生理应力指数(PSI)、出汗量、钠丢失量。结果 实验组与对照组比较,PSI、出汗量差异显著,有统计学意义(P<0.05)。5 km跑步与10 km跑步PSI比较差异显著,有统计学意义(P<0.05);而最快心率比较无统计学意义(P>0.05)。结论 训练前预补水补盐加训练中辅助降温可减小热应激反应,并减小脱水量,从而有预防热射病作用。     

Fluid tolerance while running: effect of repeated trials

This study assessed tolerance to fluid ingestion with repeated sessions of drinking while running. Runners (n = 7; age 22 +/- 2 yr; V O (2max) = 54.4 +/- 7.1 ml/kg/min) performed six 90-min runs (65 % V O (2max); separated by 7 - 11 days). During run 1, subjects drank a glucose-electrolyte solution AD LIBITUM for 1 min every 10 min. During runs 2 - 6, subjects drank a volume of the solution every 10 min equal to their sweat production over 10 min during run 1. Stomach comfort (1 - 4 scale) and gastrointestinal symptoms were also assessed every 10 min. Gastric emptying rate was determined in runs 2 and 6. Subjects consumed more (p < 0.05) fluid during runs 2 - 6 (mean +/- SD; 1247 +/- 162 ml), than during run 1 (508 +/- 476 ml). Stomach comfort improved (p < 0.05) on runs 5 and 6 (1.7 +/- 0.5 mean ranks) compared to run 2 (2.3 +/- 0.5 mean ranks). Gastric emptying rate was not different between runs 2 and 6 (12.0 +/- 1.9 ml/min vs. 12.3 +/- 2.3 ml/min, respectively). These results indicate repeated sessions of drinking at a rate matching sweat rate improves stomach comfort, however, gastric emptying rate does not change under such conditions.     

Balance ability and athletic performance

The relationship between balance ability and sport injury risk has been established in many cases, but the relationship between balance ability and athletic performance is less clear. This review compares the balance ability of athletes from different sports, determines if there is a difference in balance ability of athletes at different levels of competition within the same sport, determines the relationship of balance ability with performance measures and examines the influence of balance training on sport performance or motor skills. Based on the available data from cross-sectional studies, gymnasts tended to have the best balance ability, followed by soccer players, swimmers, active control subjects and then basketball players. Surprisingly, no studies were found that compared the balance ability of rifle shooters with other athletes. There were some sports, such as rifle shooting, soccer and golf, where elite athletes were found to have superior balance ability compared with their less proficient counterparts, but this was not found to be the case for alpine skiing, surfing and judo. Balance ability was shown to be significantly related to rifle shooting accuracy, archery shooting accuracy, ice hockey maximum skating speed and simulated luge start speed, but not for baseball pitching accuracy or snowboarding ranking points. Prospective studies have shown that the addition of a balance training component to the activities of recreationally active subjects or physical education students has resulted in improvements in vertical jump, agility, shuttle run and downhill slalom skiing. A proposed mechanism for the enhancement in motor skills from balance training is an increase in the rate of force development. There are limited data on the influence of balance training on motor skills of elite athletes. When the effectiveness of balance training was compared with resistance training, it was found that resistance training produced superior performance results for jump height and sprint time. Balance ability was related to competition level for some sports, with the more proficient athletes displaying greater balance ability. There were significant relationships between balance ability and a number of performance measures. Evidence from prospective studies supports the notion that balance training can be a worthwhile adjunct to the usual training of non-elite athletes to enhance certain motor skills, but not in place of other conditioning such as resistance training. More research is required to determine the influence of balance training on the motor skills of elite athletes.     

Water and electrolyte requirements for exercise.

Exercise performance can be compromised by a body water deficit, particularly when exercise is performed in hot climates. It is recommended that individuals begin exercise when adequately hydrated. This can be facilitated by drinking 400 mL to 600 mL of fluid 2 hours before beginning exercise and drinking sufficient fluid during exercise to prevent dehydration from exceeding 2% body weight. A practical recommendation is to drink small amounts of fluid (150-300 mL) every 15 to 20 minutes of exercise, varying the volume depending on sweating rate. Core temperature, heart rate, and perceived effort remain lowest when fluid replacement comes closest to matching the rate of sweat loss. During exercise lasting less than 90 minutes, water alone is sufficient for fluid replacement. During prolonged exercise lasting longer than 90 minutes, commercially available carbohydrate electrolyte beverages should be considered to provide an exogenous carbohydrate source to sustain carbohydrate oxidation and endurance performance. Electrolyte supplementation is generally not necessary because dietary intake is adequate to offset electrolytes lost in sweat and urine; however, during initial days of hot-weather training or when meals are not calorically adequate, supplemental salt intake may be indicated to sustain sodium balance.     

A multistage shuttle swim test to assess aerobic fitness in competitive water polo players

A 10m multistage shuttle swim test (MSST) was designed for the assessment of aerobic fitness of competitive water polo players. Test-retest reliability was determined using a sample of 22 female and 22 male trained water polo players. An intraclass correlation coefficient of 0.99 (p>0.05) was calculated between the two test scores. The technical error of measurement for the test was 2.3 shuttles or 5.0%. The validity of the test was determined using a sample of 13 female and 12 male water polo players. A validation correlation coefficient of 0.88 resulted between the number of shuttles completed during the MSST and VO2max [litres/body surface area/ minute (l x BSA-1 x min-1)] measured during an incremental tethered swim test to exhaustion. A stepwise multiple regression revealed that VO2max (l x BSA-1 x min-1) accounted for approximately 78% of the MSST variance. It was concluded that the 10m multistage shuttle swim test is a reliable and valid field test of aerobic fitness for use with trained water polo players.     

Energy balance in weight stable athletes with and without menstrual disorders

The energy balance and nutritional adequacy was assessed in a group of runners with irregular menstrual function (IR, n = 10) and in a comparable group of runners with normal menstrual function (R, n = 10). Based on computerized records of 3 days food intake, the mean content of energy and macronutrients were estimated. Excess energy expenditure (EEE) during training hours was estimated using HF monitoring and individual HF/VO2 nomograms. For the rest of a daily 24 h cycle, estimated values for basal metabolic rate (BMR) and sedentary metabolic rate were applied. Daily training-related excess energy expenditure (2.1 +/- 0.3 vs 2.2 +/- 0.4) MJ (Mean +/- SEM) and total energy expenditure (TEE) (11.0 +/- 0.3 vs 11.2 +/- 0.4) MJ in R vs IR were not different in the two groups. Calculated daily energy intake (EI) was, however, significantly lower in IR (9.7 +/- 0.5 MJ) than in R (12.3 +/- 0.7 MJ), (P = 0.007). Calculated EI and TEE were in balance in R athletes. When the same calculations were applied on IR athletes, a moderate but statistically significant negative energy balance was found (-1.5 +/- 0.6 MJ, P = 0.03). The calculated energy deficit was supported by significantly lower levels of free thyroxine in IR athletes, and may indicate an adaptive lower BMR in IR athletes. Mean intakes of carbohydrates (7.0 g/kg in R and 5.7 g/kg in IR) and protein (1.71 g/kg in R and 1.49 g/kg in IR) were close to guidelines. Intakes were not significantly different in the two groups. The most important difference in macronutrient intake was found in dietary fat (1.70 g/kg in R and 1.04 g/kg in IR) that was significantly lower in the IR group than in the R group (P = 0.007). The weight stable IR and R athletes seemed to meet the recommended intake of carbohydrates, protein and fat in their diet fairly well. However, according to the present calculations, a small energy deficit was observed in IR athletes but not in R athletes. Compared with the intake of the R athletes, this energy deficit seems primarily to be related to a lower intake of dietary fat in IR athletes.