Percent Dehydration Research Articles

Two Percent Dehydration Impairs and Six Percent Carbohydrate Drink Improves Boys Basketball Skills

To determine the effects of exercise heat-induced two percent dehydration (DEH) and euhydration (EUH) with a six percent carbohydrate-electrolyte solution (CES) compared with placebo EUH (P EUH) on basketball skills in skilled young players. Fifteen 12- to 15-yr-old boys underwent three separate 2-h exercise heat exposures (double blind, random order): 2% DEH by limiting fluid intake during exercise in the heat and basketball skill drills, EUH (no net weight change) with a 6% CES, and EUH with a flavored water placebo (P EUH). After recovery, subjects performed an orchestrated sequence of continuous basketball drills designed to simulate a game (12-min quarters + a 10-min halftime). Performance measures and component drills inherent to basketball included various individual and combined shooting percentages (3-point, 15-foot, free-throw shots), sprint (suicides, court widths), lateral movement (zigzags, lane slides), and defensive drill (combining lateral and front-to-back movement) times. Compared with P EUH (53 +/- 11%), combined shooting percentage was impaired by 2% DEH (45 +/- 9%; P = 0.002) and improved by CES intake (60 +/- 8%; P = 0.003). Total sprint times showed a similar effect (83 +/- 10 vs 78 +/- 9 vs 76 +/- 9 s; DEH vs P EUH vs CES; P < 0.001 and P = 0.04, respectively). Total lateral movement times were impaired by 2% DEH (73 +/- 8 vs 68 +/- 8 s; P = 0.001). CES improved total defensive drill times compared with 2% DEH (77 +/- 10 vs 82 +/- 10; P = 0.006). Deterioration in basketball skill performance accompanies two percent dehydration in skilled 12- to 15-yr-old basketball players. Additionally, EUH with a 6% CES significantly improves shooting performance and on-court sprinting over EUH with water.

Determinants of Endurance Exercise Capacity in the Heat in Prepubertal Boys

The goal of this study was to identify factors which limit exercise endurance in hot ambient conditions in prepubertal boys. Eight healthy non-acclimatized, highly physically active prepubertal boys performed steady load cycling at approximately 65 % peak VO (2) to exhaustion in both cool (19.6 +/- 0.6 degrees C, 66.4 +/- 11.0 % relative humidity) and hot (31.0 +/- 0.3 degrees C, 56.9 +/- 2.0 % relative humidity) environmental conditions. Cardiac output, oxygen uptake, rectal temperature (T (re)), rating of perceived exertion (RPE), blood pressure, and calculated arterial venous oxygen difference were obtained serially in each testing session, and percent dehydration was calculated from body weight loss. Endurance time was significantly shorter in the hot condition (29.30 +/- 6.19 minutes versus 41.38 +/- 6.30 minutes in the cool room). No significant differences in circulatory markers or hydration status were observed either during testing or between cycling thermal conditions. Rate of rise of T (re) was greater during exercise in the heat, but no significant difference in T (re) between conditions was observed at exhaustion. Mean values of RPE were consistently greater during exercise in the heat, but these differences did not reach statistical significance. These findings support the concept that rises in core temperature and/or brain perception (RPE) rather than circulatory insufficiency may be the critical factors defining limits to exercise in the heat.

Effect of Three Different Drinks on Physical Variables in Male Athletes, During a Running Trial

Athletes consume different drinks during exercise; however, the effects of these drinks on physical variables have not been compared yet. PURPOSE: Determine the effects of different drinks on physical variables in male athletes. METHODS: In a double-blind, crossover randomized design, 13 runners (mean age = 25.54 ± 6.75 yrs old) completed three, one hour running trial on a treadmill under stressful conditions (mean temperature = 30 °C, mean relative humidity = 60%). Tests were performed on 3 separate (1 week apart) occasions. During the trials, subjects drank their desired amount of either 6% carbohydrate sports drink (SD), 11% carbohydrate energy drink (ED) or placebo beverage (PL) every 15 minutes. Variables were total distance, rating of perceived effort (RPE), palatability, sensation of fullness, gastrointestinal (GI) symptoms, percent dehydration and sweat rate. The study considered a co-variable, the total intake of each drink during the tests. Statistical analysis using SPSS 8.0 and SAS included descriptive statistics, analysis of variance, multi-analysis of co-variance and McNemar χ2 test. RESULTS: There was no significant difference involuntary mean intake during the trials (SD = 987.46 ± 299.00 ml; ED = 782.46 ± 274.30 ml; PL = 786.54 ± 212.36 ml) (p = .055). No difference in mean total distance was found between the drinks (SD = 11.72 ± 1.21 km; ED = 11.49 ± 1.26 km; PL = 11.38 ± 1.42 km) (p = .34). There was no difference in RPE or any other variable during the trials, including palatability (SD = 7.33 ± 0.82, ED 6.00 ± 1.88, PL = 5.81 ± 1.64) (p = .077). More subjects reported GI problems when drinking ED or PL (92%) compared to SD (62%). No significant association was found between the type of drink and GI symptoms during the tests (p = .131). CONCLUSIONS: Performance in one hour running trial under stressful conditions was the same when consuming any drink. Subjects perceived the same effort, palatability and sensation of fullness when drinking SD, ED or PL. No association between type of drink and GI problems was found, but a high percentage of subjects reported this problem (ED and PL = 92%; SD = 62%).

Blood Electrolyte, Plasma Volume And Body Weight Changes In Sodium Supplemented NFL Players During Preseason

Preseason training for teams in the National Football League (NFL) consists of consecutive weeks of two-a-day practices during the hottest months of the year. The large body surface area (BSA) of football (FB) players combined with wearing equipment which reduces dry heat dissipation results in high sweat, and therefore substantial sodium (Na+) losses. PURPOSE To Na+ supplement NFL FB players with a history of heat-related illness during the first week of two-a-day s and measure blood electrolytes and changes in plasma volume (PV) and body weight (BW). METHODS Six NFL veterans with mean playing time in the league = 5.3 ± 2.3 yr, (range = 3–8 yr) and age = 25.5 ± 2.6yr, height = 186.3 ± 5.5 cm, weight = 104 ± 17.6 kg and BSA = 2.28 ± 0.19 m2 participated in the study. Blood samples were taken from subjects for baseline (BL) measures upon arrival to camp and prior to the morning (AM) practice on Days 3, 5 and 9. Blood Na+, potassium (K+), calcium (Ca++) and pH were determined by ion-selective electrode and percent change in PV was calculated using hematocrit and hemoglobin. BW was recorded to the nearest 1/2 1b before and after practices. Percent dehydration (%Dehy) was calculated from the change in BW from BL measures. Players did physical testing on Day 1, practiced two times per day on Days 2, 3 and 4, and then alternated one or two practice sessions per day for Days 5 through 9. Players were supplemented at and between meals with oral electrolyte solutions containing higher Na+ concentrations than that of commercial sports drinks. All subjects received a minimum of 4330 mg of Na+ per day above normal dietary intake. Data were analyzed with repeated measures and one-way ANOVA. RESULTS Mean wet bulb globe temperatures for days 1 – 9 were 23.3°C for AM and 26.5°C for afternoon (PM) practices. Blood Na+ was not different on Day 3 (141.1±1.01mmol · l−1) or Day 5 (140.2 ± 0.97 mmol · l−1) compared to BL (141±1.5mmol · l−1) but was lower on Day 9 (138.9 ± 1.6 mmol · l-1) compared to BL and Day 3. No differences were found for blood K+, Ca++ or pH. PV increased 10% by Day 5. Pre and post-practice %Dehy from BL on days 2, 3, 4, 5, and 9 (16 measures including 2 practices on days 2, 3 and 4, and one practice on days 5 and 9) were not different. Pooled data from all days revealed that %Dehy post-AM practice was higher than BL, pre-AM and pre-PM practice, and %Dehy post-PM practice was higher than pre-AM and pre-PM practice, all p<0.01. CONCLUSIONS Blood Na+ levels did not decline during the first 5 days of preseason training in Na+ supplemented NFL players. BW was maintained through day 9. Na+ supplementation is useful in maintaining Na+and fluid balance in professional FB players during the first week of pre-season two-a-day training.

Core Temperatures In NFL Players

Heat stroke deaths in football (FB) players usually occur during the first 3 days of pre-season practices. Experimental studies show that maximal core temperatures (Tc max) decline in subjects in response to the physiological adaptations associated with acclimatization. Using ingestible sensors that allow accurate measurements of Tc during exercise, we recently recorded Tc in National Football League (NFL) players during pre-season practices and compared the Tc response of large interior linemen to those of smaller backs and receivers. However, we are not aware of field study comparing the Tc responses of the same NFL players during the first few days of pre-season practice versus practices on the 10th day. PURPOSE To measure Tc in professional FB players and compare the Tc max reached on the 2nd or 3rd day (day 2/3) of practice to those obtained on the 10th day. METHODS Eight NFL first or second team players, age = 26.1 ± 3.3 yr, height = 188.9 ± 5.9 cm, mass = 120.2 ± 24.4 kg, body surface area (BSA) = 2.45 ± 0.23 m2 and BSA/mass = 0.0197 ± 0.0014 m2 kg−1, representing the following positions; wide receiver, corner back, tight ends, linebacker, defensive and offensive linemen participated. Subjects ingested a temperature sensor at 11:00 PM prior to, or in the morning of the days of data collection during preseason training camp. Subjects' resting Tc were recorded in an air-conditioned area 1 h prior to and then approximately every 12 min during two h of practice in full football equipment. Tc was also measured during the afternoon practices with players dressed in a helmet, shorts and shell. Body weight was recorded before and after practices for determination of percent dehydration (%Dehy). ΔTc over time were analyzed using repeated measures ANOVA and differences in Tc max and %Dehy on days 2/3 versus day 10 were analyzed using correlated t-tests. RESULTS Wet bulb globe temperatures ranged from 23.7 to 29 °C on days 2/3, and 20.4 to 27.2 °C on day 10. A significant linear trend was found for Tc on days 2/3 and day 10, p<0.01. When the highest Tc recorded in each subject were compared, Tc max were higher on days 2/3 (39.1 ± 0.6 °C, range = 38.3 to 40.9 °C) compared to day 10 (38.3 ± 0.4 °C, range = 37.6 to 39.4 °C), p<0.001. There were no differences in %Dehy on days 2/3 (−1.26 ± 1.1%) versus day 10 (−1.25 ± 0.87). No correlations were found between the players' Tc max and %Dehy. CONCLUSIONS NFL players reached higher Tc during the first few days of preseason practices compared to day 10. The highest Tc in all FB was generally obtained during live scrimmaging. %Dehy on days 2 or 3 was not different from day 10 and was not associated with Tc max. Supported by a faculty development grant from West Chester University.

Core Temperatures In NFL Players

Heat stroke deaths in football (FB) players usually occur during the first 3 days of pre-season practices. Experimental studies show that maximal core temperatures (Tc max) decline in subjects in response to the physiological adaptations associated with acclimatization. Using ingestible sensors that allow accurate measurements of Tc during exercise, we recently recorded Tc in National Football League (NFL) players during pre-season practices and compared the Tc response of large interior linemen to those of smaller backs and receivers. However, we are not aware of field study comparing the Tc responses of the same NFL players during the first few days of pre-season practice versus practices on the 10th day. PURPOSE To measure Tc in professional FB players and compare the Tc max reached on the 2nd or 3rd day (day 2/3) of practice to those obtained on the 10th day. METHODS Eight NFL first or second team players, age = 26.1 ± 3.3 yr, height = 188.9 ± 5.9 cm, mass = 120.2 ± 24.4 kg, body surface area (BSA) = 2.45 ± 0.23 m2 and BSA/mass = 0.0197 ± 0.0014 m2 kg−1, representing the following positions; wide receiver, corner back, tight ends, linebacker, defensive and offensive linemen participated. Subjects ingested a temperature sensor at 11:00 PM prior to, or in the morning of the days of data collection during preseason training camp. Subjects' resting Tc were recorded in an air-conditioned area 1 h prior to and then approximately every 12 min during two h of practice in full football equipment. Tc was also measured during the afternoon practices with players dressed in a helmet, shorts and shell. Body weight was recorded before and after practices for determination of percent dehydration (%Dehy). ΔTc over time were analyzed using repeated measures ANOVA and differences in Tc max and %Dehy on days 2/3 versus day 10 were analyzed using correlated t-tests. RESULTS Wet bulb globe temperatures ranged from 23.7 to 29 °C on days 2/3, and 20.4 to 27.2 °C on day 10. A significant linear trend was found for Tc on days 2/3 and day 10, p<0.01. When the highest Tc recorded in each subject were compared, Tc max were higher on days 2/3 (39.1 ± 0.6 °C, range = 38.3 to 40.9 °C) compared to day 10 (38.3 ± 0.4 °C, range = 37.6 to 39.4 °C), p<0.001. There were no differences in %Dehy on days 2/3 (−1.26 ± 1.1%) versus day 10 (−1.25 ± 0.87). No correlations were found between the players' Tc max and %Dehy. CONCLUSIONS NFL players reached higher Tc during the first few days of preseason practices compared to day 10. The highest Tc in all FB was generally obtained during live scrimmaging. %Dehy on days 2 or 3 was not different from day 10 and was not associated with Tc max. Supported by a faculty development grant from West Chester University.

Rapid Cooling Of An NFL Defensive Linemen With A Core Temperature Of 40.9 2C During A Full Padded Practice

HISTORY The athlete is a 9 yr veteran defensive lineman in the National Football League (NFL) with age = 30 yr, height =182.9 cm and body fat = 24%. He arrived at pre-season training camp 2004 with mass = 149 kg, similar to his 2003 pre-season mass (147.7 kg). He gained 5.6 kg by the 5th morning, 3.76% above baseline (BL). His sweat rate was 1.7 l·hr-1 in 2003 with ambient temperature = 23.7 °C and 83% RH. In pre-season 2003 his mean percent dehydration (%Dehy) after practice was 0.87% ranging from 0.0 to 1.85% in 23 consecutive practices. During the first 3 days of the 2004 pre-season this player's core temperature (Te) was monitored using ingestible sensors (HQ, Inc.). On Day 1 of two-a-days, his Te was >39.5°C (103°F) at the end of a one h indoor morning (AM) practice. Wet bulb globe temperature (WBGT) was 24.4°C and he was dressed in a helmet, shorts and shell. He denied a history of heat associated illness. PHYSICAL EXAMINATION The subjects' Te was closely monitored during the afternoon (PM) full padded practice due to his elevated AM Te. While dressed in shorts and a Tee-shirt, his resting Te recorded in an air-conditioned area 45 min prior to PM practice was 37.8°C (100°F). His Te was monitored approximately every 8 min during PM practice and he was questioned frequently about heat-related symptoms. His Te steadily increased to 40°C (104°F) by 1 h and 30 min into practice and he denied symptoms other than he felt hot. When his Te increased to 40.6°C (105°F) he was removed from practice against his will. His equipment was removed and he was transported to the on-field medical tent. Mean WBGT assessed three times during practice was 28.3°C. DIFFERENTIAL DIAGNOSIS Malignant hyperthermia Exercise induced heat stroke Exercise associated hyperthermia (benign) TEST AND RESULTS Te monitoring (40.9°C which decreased with cooling) Cognitive testing (−) Visual assessment (+ mild visual disturbance) % Dehydration (0% from baseline) FINAL WORKING DIAGNOSIS Benign exercise associated hyperthermia. TREATMENT AND OUTCOMES The athlete was removed from practice and rapidly cooled with ice-water soaked vests, neck collars and caps. His Te increased from 40.6°C when removed from practice to 40.9°C (105.7°F) just prior to aggressive cooling. While Te was continuously monitored the ice-water vests, collars and caps were changed approximately every 45 – 90 sec. A total of 6 changes were used for this player. Tc decreased from 40.9°C to 38.7°C (101.7°F) within 10 min of cooling. He had no residual symptoms or subsequent heat-associated problems. His post-practice % Dehy was 1.36% from pre-practice but 0% from BL. The highest Te recorded in this athlete on the 10th day of pre-season was 39.4°C (103°F).

Adequacy of Fluid Ingestion in Adolescents and Adults during Moderate-Intensity Exercise

We compared ad libitum fluid consumption in adolescent (n = 15) and adult athletes (n = 34) exercising in similar environmental conditions (26.5°C, 27.3% relative humidity) and similar modes and intensities of exercise (80-85% of their age-predicted maximum heart rate). Throughout 1 hr of exercise, participants had access to sports bottles containing a sports drink (6% carbohydrate with electrolytes and identical flavoring). Sweat rate (SR) and percent dehydration were calculated from the change in body weight corrected for urine loss and fluid intake (FI). FI was significantly higher for the adults than for the adolescents. SR was also higher for the adults compared with that of the adolescents. Compared with adults, adolescents had significantly lower FI and SR, the combination of which allowed them to meet their fluid needs more closely during exercise. Minimal voluntary dehydration occurred in either group during exercise, possibly because of the nature of the exercise (noncompetitive) or the beverage characteristics (presence of sodium and sweetness) or availability of the beverage.

Effects of Exercise in the Heat on Thermoregulation of Japanese and Malaysian Males

The effect of low-intensity exercise in the heat on thermoregulation and certain biochemical changes in temperate and tropical subjects under poorly and well-hydrated states was examined. Two VO2max matched groups of subjects consisting of 8 Japanese (JS) and 8 Malaysians (MS) participated in this study under two conditions: poorly-hydrated (no water was given) and well-hydrated (3 mL x Kg(-1) body weight of water was provided at onset of exercise, and the 15th, 35th and 55th min of exercise). The experimental room in both countries was adjusted to a constant level (Ta: 31.6+/-0.03 degrees C, rh: 72.3+/-0.13%). Subjects spent an initial 10 min rest, 60 min of cycling at 40% VO2max and then 40 min recovery in the experimental room. Rectal temperatures (Tre) skin temperatures (Tsk), heart rate (HR), heat-activated sweat glands density (HASG), local sweat rate (M sw-back) and percent dehydration were recorded during the test. Blood samples were analysed for plasma glucose and lactate levels.The extent of dehydration was significantly higher in the combined groups of JS (1.43+/-0.08%) compared to MS (1.15+/-0.05%). During exercise M sw-back was significantly higher in JS compared to MS in the well-hydrated condition. The HASG was significantly more in JS compared to MS at rest and recovery. Tre was higher in MS during the test. Tsk was significantly higher starting at the 5th min of exercise until the end of the recovery period in MS compared to JS. In conclusion, tropical natives have lower M sw-back associated with higher Tsk and Tre during the rest, exercise and recovery periods. However, temperate natives have higher M sw-back and lower Tsk and Tre during experiments in a hot environment. This phenomenon occurs in both poorly-hydrated and well-hydrated states with low intensity exercise. The differences in M sw-back, Tsk and Tre are probably due to a setting of the core temperature at a higher level and enhancement of dry heat loss, which occurred during passive heat exposure.

Effects of Short-term Exercise in the Heat on Thermoregulation, Blood Parameters, Sweat Secretion and Sweat Composition of Tropic-dwelling Subjects

This study investigates the effects of a short-term aerobic training program in a hot environment on thermoregulation, blood parameters, sweat secretion and composition in tropic-dwellers who have been exposed to passive heat. Sixteen healthy Malaysian-Malay male volunteers underwent heat acclimation (HA) by exercising on a bicycle ergometer at 60% of VO2max for 60 min each day in a hot environment (Ta: 31.1+/-0.1 degrees C, rh: 70.0+/-4.4%) for 14 days. All parameters mentioned above were recorded on Day 1 and at the end of HA (Day 16). On these two days, subjects rested for 10 min, then cycled at 60% of VO2max for 60 min and rested again for 20 min (recovery) in an improvised heat chamber. Rectal temperature (Tre), mean skin temperature (Tsk) heart rate (HR), ratings of perceived exertion (RPE), thermal sensation (TS), local sweat rate and percent dehydration were recorded during the test. Sweat concentration was analysed for sodium [Na+]sweat and potassium. Blood samples were analysed for biochemical changes, electrolytes and hematologic indices. Urine samples were collected before and after each test and analysed for electrolytes.After the period of acclimation the percent dehydration during exercise significantly increased from 1.77+/-0.09% (Day 1) to 2.14+/-0.07% (Day 16). Resting levels of hemoglobin, hematocrit and red blood cells decreased significantly while [Na+]sweat increased significantly. For Tre and Tsk there were no differences at rest. Tre, HR, RPE, TS, plasma lactate concentration, hemoglobin and hematocrit at the 40th min of exercise were significantly lower after the period of acclimation but mean corpuscular hemoglobin and serum osmolality were significantly higher while no difference was seen in [Na+]sweat and Tsk. It can be concluded that tropic-dwelling subjects, although exposed to prolonged passive heat exposure, were not fully heat acclimatized. To achieve further HA, they should gradually expose themselves to exercise-heat stress in a hot environment.

Fluid Balance, Hydration Status, and Sweat Electrolyte Concentrations in NBA Basketball Players During Pre-Season Practice

1236 Very little is known about the effects of two-a-day training on the hydration of professional basketball players. PURPOSE: To determine fluid intake habits and hydration status of NBA players, we observed four players on two separate occasions spaced two weeks apart. METHODS: The first observation day was during a preseason two-a-day practice. A urine sample was collected prior to each practice to determine urine specific gravity (USG). Players were weighed before and after practice as were bottles containing their choice of beverage. Sweat loss, percent dehydration, and fluid intake were calculated from these measurements. Sweat patches were placed on the right forearm during each practice to obtain sweat samples and were analyzed to measure sodium and potassium concentrations (flame photometry). Additionally, skin fold measurements were obtained. The same measurements were taken two weeks later to detect any changes that may have occurred due to training and acclimation. RESULTS: Average height, weight and percent body fat were 193.0 cm, 101.4 kg, and 14%, respectively. Sweat rates were modest, with an average of 0.85 liters per hour. Dehydration ranged from 0–1.5% of body weight. The range for USG was1.011 – 1.035 g/ml. The majority of samples (56%) were above 1.030, indicating the players were hypohydrated prior to the start of practice. Sweat sodium and potassium concentrations were within the normal range for all players (44.2 – 86.6 mEq Na/L and 3.6 – 6.3 mEq K/L, respectively) on the first practice day. Sweat samples were obtained on two of the four players during the second visit two weeks later. While potassium concentration remained constant, sweat sodium concentration decreased markedly (56 and 44 mEq/L to 27 and 29 mEq/L). CONCLUSIONS: The NBA players appeared to be inadequately hydrated prior to the start of practice. Based on USG, even if players restored their initial, pre-practice morning body weight, the players were hypohyrated when they returned for the second session. This limited sample suggests players need to be more proactive with rehydration strategies.

Core Temperature in Professional Football Players during practice

0369 Heat related deaths have been documented in football players at all levels of competition. Ingestible temperature sensors now allow accurate measurements of core temperature (Tc) in these athletes while they participate in football activity. Core temperatures of professional players in the National Football League (NFL) while they participate in football practice have never been reported. PURPOSE: To measure the rise in Tc during practice in professional football players and compare the Tc of larger interior lineman (LM) to those of backs and receivers (BKS). METHODS: Eight LM, age = 26.5 ± 2 yr, height = 191.8 ± 4.5 cm, body weight (BW) = 134.8 ± 10.7 kg and body surface area (BSA) = 2.61 ± 0.12 m2 and six BKS (wide receivers, half backs, defensive backs, tight ends) age = 27 ± 4.2 yr, height = 185 ± 6.3 cm, BW = 95.6 ± 11.1 kg and BSA = 2.19 ± 0.16 m2 participated in the study. All players were NFL first or second team veterans. Subjects ingested a sensor at 11:00 PM prior to the day of data collection during pre-season training camp in July. Resting Tc were recorded in an air-conditioned area 1 h prior to the morning practice. Tc was then recorded in each player approximately every 15 min during two hours of football practice in full equipment. The practice consisted of three distinct periods including individual drills, 7 on 7 team and live scrimmage. Tc was also measured during the afternoon practice in shells. BW was recorded before and after practices for determination of percent dehydration. Changes in Tc over time were analyzed using repeated measures ANOVA and group differences in Tc and percent dehydration were analyzed using independent t-tests. RESULTS: The highest wet bulb temperatures were 22.8°C and 20.6°C during the morning and afternoon practices, respectively. Height (p < 0.05), BW (p < 0.0001) and BSA (p < 0.001) were all higher in LM compared to BKS. A significant linear trend was found for Tc in both groups, p < 0.0001. During the AM practice Tc rose from 37.07 ± 0.13 °C to 38.81 ± 0.48 °C in LM and 36.99 ± 0.09 °C to 38.36 ± 0.44 °C in BKS. When the highest two Tc recorded in each subject were compared, Tc were higher in LM (38.65 ± 0.48 °C, range = 37.47 to 39.29 °C) than BKS (38.44 ± 0.32 °C, range = 37.81 to 39.08 °C). As measured by change in BW during practice the LM were less dehydrated compared to BKS (−0.94 ± 0.6 % versus −1.3 ± 0.7 %), p < 0.05. CONCLUSIONS: NFL LM reached higher Tc during football practice compared to smaller BKS. The highest Tc in all subjects were generally obtained during live scrimmaging. Level of dehydration as measured by BW loss was not associated with Tc. LM had higher Tc but were less dehydrated compared to BKS. Supported by a faculty development grant from West Chester University.

Fluid Balance, Hydration Status, and Sweat Electrolyte Concentrations in NBA Basketball Players During Pre-Season Practice

1236 Very little is known about the effects of two-a-day training on the hydration of professional basketball players. PURPOSE: To determine fluid intake habits and hydration status of NBA players, we observed four players on two separate occasions spaced two weeks apart. METHODS: The first observation day was during a preseason two-a-day practice. A urine sample was collected prior to each practice to determine urine specific gravity (USG). Players were weighed before and after practice as were bottles containing their choice of beverage. Sweat loss, percent dehydration, and fluid intake were calculated from these measurements. Sweat patches were placed on the right forearm during each practice to obtain sweat samples and were analyzed to measure sodium and potassium concentrations (flame photometry). Additionally, skin fold measurements were obtained. The same measurements were taken two weeks later to detect any changes that may have occurred due to training and acclimation. RESULTS: Average height, weight and percent body fat were 193.0 cm, 101.4 kg, and 14%, respectively. Sweat rates were modest, with an average of 0.85 liters per hour. Dehydration ranged from 0–1.5% of body weight. The range for USG was1.011 – 1.035 g/ml. The majority of samples (56%) were above 1.030, indicating the players were hypohydrated prior to the start of practice. Sweat sodium and potassium concentrations were within the normal range for all players (44.2 – 86.6 mEq Na/L and 3.6 – 6.3 mEq K/L, respectively) on the first practice day. Sweat samples were obtained on two of the four players during the second visit two weeks later. While potassium concentration remained constant, sweat sodium concentration decreased markedly (56 and 44 mEq/L to 27 and 29 mEq/L). CONCLUSIONS: The NBA players appeared to be inadequately hydrated prior to the start of practice. Based on USG, even if players restored their initial, pre-practice morning body weight, the players were hypohyrated when they returned for the second session. This limited sample suggests players need to be more proactive with rehydration strategies.

THE EFFECTS OF DIURETICS ON RESTING METABOLIC RATE AND SUBSEQUENT SHIFTS IN RESPIRATORY EXCHANGE RATIOS

The purpose of this research was to determine the effect of diuretic-induced dehydration on resting metabolic rate (RMR) and respiratory exchange ratio (RER). It was hypothesized, based on a prior pilot study, that a loss of 3–5% body water would reduce RMR. Fourteen nonobese, apparently healthy, female volunteers were recruited to participate in the study (body fat 17.19 ± 1.65%, body weight 58.25 ± 5.93 kg, age 25.21 ± 3.36 yr). The study utilized a within subjects repeated measures design where each participant underwent a diuretic (D) treatment and a control (C) treatment. Participants spent two consecutive nights in the Human Performance Research Laboratory. Under the diuretic treatment, participants received a 1mg/kg dose of furosemide upon arrival the first night. Participants were fed a control diet and lights were turned out at 10:30pm both nights. RMR and RER were measured in a waking state between 5:45–6:30 am both mornings. Percent dehydration in D ranged from 1.77–4.39% with a mean of 3.09%. The average urine outputs and hematocrits were significantly higher for D (2677 ± 700ml, 45 ± .02%) than for C (1519 ± 723ml, 42 ± .02%). There were no significant differences in urine specific gravities for D and C. Mean energy expenditure (MEE) was significantly lower (p < 0.05, one-tailed) in D (1253 ± 145 kcals/day) than in C (1304 ± 130 kcals/day). RER was significantly higher (p < 0.05, one-tailed) in D (.98 ± .06) than in C (.94 ± .08). Diuretic use to promote weight loss could result in a lower RMR and diminshed fat metabolism.

Intestinal permeability in runners in the 1996 Chicago marathon.

Abdominal cramping, nausea, diarrhea, and GI bleeding are often reported in long-distance runners. This study set out to determine the effects of prolonged (2-4 hrs) exercise and NSAID ingestion on gastric and intestinal permeability during the first 5 hrs following the 1996 Chicago Marathon. Thirty-four healthy volunteers (20 M, 14 F; ages 30-50) completed the race and ingested the test solution (5 g sucrose, 5 g lactulose, 2 g rhamnose, in 40 ml water) within 10-15 min. The urinary excretion ratio of lactulose/rhamnose was used to assess small intestine permeability; sucrose excretion was used to evaluate gastric impairment. There were no significant differences for mean training mileage, postrace rectal temperature, and percent dehydration between runners who ingested NSAIDs and those who did not. In all, 75% of subjects reported aspirin or ibuprofen ingestion before or during the race. Runners who ingested ibuprofen had significant elevations in urinary lactulose excretion and lactulose/rhamnose ratio, whereas those who ingested aspirin or who did not ingest either NSAID had no significant differences in urinary excretion of lactulose, rhamnose, sucrose, or lactulose/rhamnose ratio compared to resting controls. Thirteen of the 26 NSAID users and 4 of the 8 non-users reported GI symptoms. It is concluded that (a) ibuprofen but not aspirin ingestion during prolonged exercise may increase gastrointestinal permeability and lead to GI symptoms, and (b) prolonged exercise alone can produce GI symptoms.

PALATABILITY AND VOLUNTARY INTAKE OF SPORTS BEVERAGES, DILUTED FRUIT JUICE, AND WATER DURING EXERCISE.

1616 We investigated the impact of beverage palatability on voluntary intake of diluted orange juice (DOJ) water (W), a homemade 6% CHO-electrolyte sports beverage (HCE), and a commercially available 6% CHO-electrolyte sports beverage (CCE). All of the beverages, except W, were orange in flavor. Fifty triathletes and runners (25 to 61 years) exercised for 75 min at 80-85% of age-predicted maximum heart rate. After 30 and 60 min of exercise, subjects were allowed one min of free access to a beverage and then completed a sensory questionnaire. The subjects completed four exercise sessions, each time receiving a different beverage to drink The exercise protocol was designed to mimic training or competitive situations in which limited periods of time are available in which to drink. Results indicated that CCE scored significantly higher in palatability than HCE, DOJ, and W after both 30 min and 60 min (p<0.05). There were no significant differences among HCE, DOJ, and W in overall palatability. Voluntary intake was significantly greater for CCE than HCE, DOJ, and W (p<0.05). Intake of HCE was greater than DOJ and W (p<0.05). Percent dehydration was significantly less for CCE than for HCE, DOJ, and W (p<0.05). Dehydration was significantly less for HCE and DOJ than for W (p<0.05). These findings suggest that the optimized flavor system of the commercial beverage contributed to enhanced palatability, increased fluid intake, and reduced dehydration.

BODY MASS CHANGES AND VOLUNTARY FLUID INTAKES OF ELITE LEVEL WATER POLO PLAYERS AND SWIMMERS

1258 Calculated sweat rates (measured by body mass changes) and voluntary fluid intakes were measured in elite level water polo players and swimmers during normal exercise sessions to determine the degree of fluid replacement of these athletes. Data were collected from training and competition sessions for male water polo players (n=23) and training sessions only for swimmers (n=20 females; n=21 males). Calculated sweat rates and fluid intake rates during training sessions for male water polo players were 287 ml/hr and 142 ml/hr, respectively, with rates of 786 ml/hr and 380 ml/hr during competition. During training sessions for male swimmers, calculated sweat rates and fluid intake rates were 138 ml/km and 155 ml/km, respectively; and for female swimmers, 107 ml/km and 95 ml/km. There was a wide individual variation in fluid intakes and sweat losses of both water polo players and swimmers. Mean percent dehydration and 95% CI for male and female swimmers were 0.11% (0.02-0.20) and 0.14% (0.07-0.21), respectively. For water polo players mean percent dehydration and 95% CI for training and competition sessions were 0.26% (0.19-0.34) and 0.35% (0.23-0.46), respectively. Dehydration incurred by athletes in this study was less than typically reported for "land-based" athletes. Errors inherent in the technique used in this study are acknowledged and may be significant in the calculation of reported sweat losses and levels of dehydration in aquatic athletes.

How valid are clinical signs of dehydration in infants?

Our objective was to determine the ability of several clinical signs of dehydration to distinguish among degrees of dehydration in infants with acute diarrhea. The design was a prospective cohort study in a pediatric referral hospital in Cairo, Egypt. Infant boys, 3-18 months old, with a history of acute diarrhea (5 or more watery stools per day for no more than 7 days) were eligible, except those with frank protein-energy malnutrition, serious nongastrointestinal illness, or being exclusively breast-fed. Several clinical signs of dehydration were assessed upon study entry. Subjects were then rehydrated with an oral rehydration solution and fed a standardized diet until diarrhea ceased (no watery or loose stools for 16 h). The main outcome measure was percent body weight gain at rehydration and at resolution of illness. Data from 135 subjects were available for analysis. Average (SD) rehydration phase duration was 5.2 (2.1) h, and average (SD) duration of illness was 54.5 (38) h. Multiple regression analysis selected prolonged skinfold, altered neurologic status, sunken eyes, and dry oral mucosa as the clinical signs that correlated best with percent dehydration (R2 for model 0.244, p < 0.001). Mean weight gain for the two assessment systems was 3.6-3.9% for mild, 4.9-5.3% for moderate, and 9.5-9.8% for severe dehydration. The most valid clinical signs of dehydration include prolonged skinfold, altered neurologic status, sunken eyes, and dry oral mucosa. Children with clinical signs of mild or moderate dehydration have fluid deficits on the order of 3 or 5% body weight, respectively.

The effects of glucose polymer beverage ingestion during prolonged outdoor exercise in the heat

The aim of this study was to examine the effect of ingestion of a glucose polymer drink on fluid and metabolic balance during a 30 km outdoor march in the heat (ambient temperature, 26-31 degrees C; relative humidity, 53-34%). The subjects were randomly assigned to one of three groups: 7.2% glucose polymer-electrolyte beverage (GP) (N = 16), flavored sweetened placebo drink (SP) (N = 15), and tap water (TW) (N = 18). The subjects in the three groups consumed similar volumes of fluid, and no differences were found in sweat rate and percent dehydration. Changes in plasma volume were smaller, though not statistically significant, for GP than for SP and TW (-2.8%, -5.4%, -9.4%, respectively). Changes in sodium concentrations and serum osmolality were similar in the three groups. Subjects consuming GP maintained during exercise a significantly higher (P less than 0.001) blood glucose concentration (range: 6.5-7.4 mmol.l-1) than the SP and TW groups. They were also found to have increased levels of serum insulin (29.3 +/- 18.5 mU.l-1) and no change in serum free fatty acids (0.52 +/- 0.19 mmol.l-1). In contrast, subjects ingesting SP or TW had significantly elevated (P less than 0.001) concentrations of free fatty acids (range: 1.35-1.74 mmol.l-1) compared with subjects consuming GP (0.35-0.52 mmol.l-1), with no significant change in blood glucose and serum insulin levels over the exercise period. We conclude that highly trained endurance athletes may maintain a higher blood glucose level by consuming GP during prolonged exercise in the heat without impairing fluid replacement.

Metabolic rate, not percent dehydration, predicts rectal temperature in marathon runners

This study was designed to determine the factors predicting the post-race rectal temperature in marathon runners. Post-race rectal temperatures of 30 recreational runners (maximum oxygen consumption (VO2max) = 58.3 +/- 5.9 ml O2.kg-1.min-1; mean +/- SD) who completed a 42.2 km marathon at 75.8% (+/- 9.3%) VO2max were measured and related to their levels of dehydration (percent mass loss), their running velocities (km.h-1), and their estimated absolute metabolic rates (1 O2.min-1) for different segments of the 42.2 km race. The influence of certain anthropometric variables was also determined. Percent mass loss during the race (2.5 +/- 1.4%), post-race rectal temperatures (38.9 +/- 0.6 degrees C), and rates of sweat loss (1.0 +/- 0.3 1.h-1) were low. There was no statistical relationship between percent mass loss and post-race rectal temperature. Post-race rectal temperatures were significantly related to the metabolic rates for the full 42.2 km and for the last 21.1 and 6 km of the race, and to the average running velocity for the last 6 km (P less than 0.05 and P less than 0.01). Average sweat rates were related to metabolic rates for 42.2 km and for the last 6 km of the race (P less than 0.05) but were unrelated to running velocity. We conclude that metabolic rate sustained during the latter section of the race, and not the level of dehydration, is the principal determinant of the post-race rectal temperature in marathon runners.