We Measured the dose-response effects of drink sodium content (treatments: 0 mmol/l, 18 mmol/l, 30 mmol/l, 40 mmol/l, and 60 mmol/l) on sensory perception and palatability in athletes at four time points: in a sedentary laboratory setting (non-exercise context), pre-exercise, and after 60 min and 120 min of aerobic-circuit exercise. Fifty-five triathletes and runners (30 males, 39.7 (8.0 S.D.) years; 25 females, 37.2 (9.2 S.D.) years) sip-tested chilled 6% carbohydrate drinks varying in sodium content during sedentary and pre-exercise conditions and had ad lib access to drinks during exercise conditions. There was a significant intensity discrimination among all sodium levels (p <= 0.001) except 0 mmol/l vs. 18 mmol/l, and 30 mmol/l vs. 40 mmol/l. There were no significant differences among time points for perceived salt intensity. However, overall drink acceptability and liking of saltiness of the 60 mmol/l drink was greater pre-exercise, after 60 min and after 120 min of exercise than during the sedentary condition. The environmental cues of the exercise context may be associated with an increase in palatability of the drink containing 60 mmol/l of sodium over the sedentary condition. Sensory measures provided better differentiation (were more sensitive to treatment effects) among salt concentrations than was fluid intake. Neither thirst nor sweat loss were related to drink palatability or liking of saltiness. Liking of saltiness but not thirst was related to fluid intake. There was a significant negative correlation between sodium ingested (mg/kg) and percent body mass loss. (C) 2009 Elsevier Ltd. Ail rights reserved.

U. S. football players with a history of heat cramps were evaluated for the effect of physical training, sodium intake, and loss of sweat sodium on whole blood sodium concentration (BNa). Athletes (n=14 males, 24+/-1 y) were recruited and studied based on medical history, age, and position. The reference group (R, n=8 without a cramping history) and cramp-prone group (C, n=6, history of whole-body cramps associated with extensive sweat loss during exercise in the heat) were measured for body mass and BNa (ISTAT) before and after team training of 2.2 h in hot conditions (WBGT=29-32 degrees C). Intake and loss of fluid and sodium were also measured to determine respective acute balance. In R, BNa was stable pre- to post-training (138.9+/-1.8 to 139.0+/-2.0 mmol/L) while it tended to decline in C (137.8+/-2.3 to 135.7+/-4.9 mmol/L), and three subjects in C had BNa values below 135 mmol/L (131.7+/-2.9 mmol/L). C consumed a greater percentage of total fluid as water (p<0.05). Mean sweat sodium concentration was (52.6+/-29.2 mmol/L for C and 38.3+/-18.3 mmol/L for R (p>0.05). Compared to R, C tended to experience a decline in BNa and greater acute sodium imbalance. These changes may place cramp-prone players at greater risks for developing acute sodium deficits during training.

The purpose of this study was to determine whether high-school football players showed risks of fluid deficits during two-a-day training (Part 1), and whether implementing a drinking strategy could acutely improve the markers of hydration (Part 2). In Part 1, pre-training urine specific gravity (USG) and pre- and post-training body weight were measured at the morning session for 5 consecutive days of two-a-day practices to monitor the hydration status of 13 varsity players. The mean pre-training body weight was consistently lower (mean decrease of 0.5 kg, p<0.05) following the first day of measurement. Pre-training USG values remained consistently high each day (range for daily means: 1.022+/-0.003 to 1.024+/-0.005). Part 2 consisted of assessing hydration status in 46 varsity and junior varsity players prior to morning training during two-a-day training before and following implementing a drinking strategy. In association with the strategy, mean body weight increased 0.5 kg (p<0.01) and mean USG decreased from 1.021 to 1.016 (p<0.01) following the drinking protocol. The slight decline in body weight and consistently high USG (Part 1) suggested that standard fluid replacement strategies were less than optimal for a majority of the players. Implementing a drinking strategy appeared to improve hydration status based on changes in body weight and USG (Part 2).

Recent claims have been made regarding the putative erosive effects of regularly ingesting low-pH beverages on the integrity of tooth enamel. The purpose of this study was to determine whether fluid consumption during exercise affects the body's defenses against enamel erosion: saliva flow and salivary pH. Males and females (n=50) exercised in the heat (26.7 degrees C, 40 % RH) for 75 min on four occasions. Within each session, subjects consumed ad-lib either water, a sports drink (Gatorade), diluted orange juice, or a homemade sports drink, with the latter three fluids all having low pH values (3.0 to 4.0). Prior to and following exercise, subjects performed a standard stimulated saliva collection procedure. Immediately following collection, saliva flow rate and pH were determined for each sample. Repeated-measures ANOVA were used to evaluate the data. Compared to pre-exercise salivary flow rates (2.6+/- 0.8 ml/min), the post-exercise rate was not different when consuming the sports drink (2.6+/- 0.9 ml/min), but decreased when water or the homemade sports drink was ingested (2.4+/- 0.9 ml/min; p<0.05). A time-by-drink interaction (p<0.05) revealed slight differences in saliva pH after exercise, depending on the beverage consumed; post-exercise saliva pH was highest for water (7.2+/- 0.2) and lowest for the homemade sports drink (7.1+/- 0.2), with the sports drink and diluted orange juice values falling in between. The results suggest that minimal changes occur in saliva pH and the rate of stimulated saliva flow with beverage consumption during exercise. Subsequent research is needed to determine whether maintenance of saliva production by drinking beverages during exercise influences the body's defenses against dental erosion via saliva production.

Gastric emptying (GE) of a sports drink is influenced by many factors, including ingested volume, beverage composition, and osmolality. Carbohydrate (CHO), a primary contributor to beverage osmolality, is a critical component in sports drinks. However, how beverage osmolality and different CHO types and concentrations influence GE is not fully resolved. PURPOSE To investigate the effect of CHO type, concentration, and beverage osmolality on GE in euhydrated subjects at rest. METHODS The GE of water (W), four glucose solutions (2, 4, 6, and 8% glucose: 2G, 4G, 6G, and 8G) and four sucrose solutions (2, 4, 6 and 8% sucrose: 2S, 4S, 6S, and 8S) were determined in eight healthy subjects using the modified George double-sampling technique. Subjects ingested a beverage (7 ml/kg BW) containing 25-ppm phenol red as quickly as possible (≤1.0 min) and subsequent gastric and blood samples were collected every 10 min for 40 and 50 minutes, respectively. Linear regression and an ANOVA with repeated measures were used for statistical analysis. RESULTS The gastric secretion volume was not significantly different among beverages across time. Gastric residual volume (GRV) was not different among 2S, 4S, 6S, 8S and water (p>0.05). 8G resulted in a greater GRV compared with W & 2G; W, 2G & 4G; and W, 2G, 4G & 6G at 20, 30, and 40 minutes, respectively. GRV from 6G was significantly higher than 2G at 30 min, but no other statistical differences were found among W, 2G, 4G, and 6G. Percent of gastric fluid emptied was significantly smaller for 8G than others at 20, 30, and 40 minutes. At the end of the experiment, 8G resulted in a significant greater GRV than others and 8S had a greater GVR than W. Gastric osmolality did not significantly change over time. Mean gastric osmolality positively correlated to mean GRV (r=0.93). CONCLUSIONS The data show that inhibition of GE is greater with glucose compared to sucrose solutions at concentrations between 2 and 8%. This difference may be due to the greater osmolality of the glucose solutions and to the inhibitory effect of intestinal glucose content on GE.

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.

0368 PURPOSE: To determine changes in core temperature during the first day of twoa-day football practices. In preliminary work, we showed that core temperature in college football players increased rapidly and remained high during a sustained (90 min) intense strength and conditioning pre-season workout. In this study, we tested eight players on their first day of two-a-day practice. METHODS: Sweat loss, fluid intake, and core temperature (Tc) were measured during morning and evening practices each lasting ∼2.2 h. Change in bodyweight, corrected for fluid intake and urine loss, was used to estimate gross sweat loss (GSL). Voluntary fluid intake (water and sports drinks) was measured by recording pre-and post-practice bottle weights. Without interfering with normal drills, Tc was measured ∼10 min intervals using ingestible temperature sensors (HTI Technologies). RESULTS: The average level of heat stress during practices was 24 ± 1.8° C WBGT. Total fluid consumed was 2.9 ± 1.1 L per session, and sweat rate was determined to be 1.8 ± 0.5 L per hour. Average GSL was 4.1 ± 1.1 L and resulted in a net 1.2 ± 1 kg weight loss (0.9 ± 0.7% dehydration). Mean Tc was 37.4 ± 0.3° C at baseline and increased to 38.5 ± 0.4° C by the end of practice. Change in Tc was 1.1 ± 0.4° C (range 0.4 – 1.9° C). CONCLUSIONS: Moderate environmental conditions, minimal dehydration, and varying intensity during two-aday practices resulted in an increased, but not excessive, stable core temperature. These data suggest the varying intensity of two-a-day practices (held during lower heat stress periods of the day) in combination with rest breaks, provides enough recovery time to prevent extreme increases in core temperature.

1668 BIS is designed to measure total body water (TBW) based on the body's resistance to a benign electrical current. PURPOSE: This study was designed to determine whether BIS could detect changes in the hydration status of athletes after exerciseinduced dehydration. METHODS: 12 endurance trained males (ages 19–50 y, mean height 180.9 ± 8.4 cm, mean weight 80.7 ± 9.3 kg) exercised for 90 min at 70–75 % of maximum heart rate (room temperature, 30 ° C; 44% humidity). Subjects were instructed to consume 500 mL of water the evening before and 1000 mL on test day to ensure adequate hydration. Upon entering the lab, subjects provided a urine sample and a nude body weight. Subjects reclined for 10 min, after which BIS was measured. Subjects exercised to induce dehydration of about 2% of initial weight. To estimate electrolyte losses, sweat was collected using sweat patch methodology and analyzed for sodium and potassium concentrations. Two more BIS measurements were taken 20 min post-exercise (hypohydrated state), once using the subject's reduced weight and once using the pre-exercise body weight. RESULTS: Subjects appeared to have entered the laboratory well hydrated as indicated by their mean urine specific gravity of 1.008 ± 0.005 mg/dL. Mean body mass loss due to sweat was 1.76 ± 0.4 kg. The BIS-determined TBW was 50.1 ± 5.3 L pre-exercise. After dehydration, TBW did not change when the new lower weight was entered into the calculations (50.1 ± 5.6 L) (p>0.05) or when the pre-exercise weight was utilized (50.3 ± 4.8 L) (p>0.05). There was no relationship among sweat sodium and potassium losses and ECF and ICF changes respectively (r = −0.488, p>0.05), (r = 0.511, p>0.05). CONCLUSION: BIS appeared to provide reasonable estimates of TBW in the resting, euhydrated, postabsorptive male subject (62% of body weight). BIS was unable to accurately track changes in TBW shortly after exercise-induced dehyration.

0372 Dehydration can adversly affect athletic performance and capacity. In sports where multiple practice sessions and/or competitions occur, inadequate hydration can be a concern. In preliminary studies on high-school football players during two-a-day training, we observed chronically high values for urine specific gravity (≥1.02 g/mL in 60 to 80% of players) prior to the morning practice session. PURPOSE: The present study was designed to determine if simple drinking strategies could improve indicators of hydration status in the players. METHODS: Study participants were 46 male high school football players. Body weight (BW) and urine specific gravity (USG) were measured on two consecutive mornings prior to the morning practice of two-a-day sessions. After measurements on Day 1 were taken, participants were asked to consume 20 oz of fluid in the time after dinner but before bed, and 20 oz of fluid after waking but before practice. Differences in BW and USG were assessed using a paired t-test. RESULTS: Mean BW on Day 1 was 81.2 kg and on Day 2 81.7 kg. On Day 1 the mean USG was 1.021 g/mL and 1.016 g/mL on Day 2. There was a significant increase in body weight from Day 1 to Day 2 (p < 0.01) and a significant decrease in USG from Day 1 to Day 2 (p < 0.01). CONCLUSION: A simple drinking strategy was beneficial in improving markers of hydration in a group of high school football players during two-a-day practices. Further research needs to be done to see if improvement in these measures translates into better performance.

This study investigated whether different beverage carbohydrate concentration and osmolality would provoke gastrointestinal (GI) discomfort during intermittent, high-intensity exercise. Thirty-six adult and adolescent athletes were tested on separate days in a double-blind, randomized trial of 6% and 8% carbohydrate-electrolytes (CHO-E) beverages during four 12-min quarters (Q) of circuit training that included intermittent sprints, lateral hops, shuttle runs, and vertical jumps. GI discomfort and fatigue surveys were completed before the first Q and immediately after each Q. All ratings of GI discomfort were modest throughout the study. The cumulative index for GI discomfort, however, was greater for the 8% CHO-E beverage than for the 6% CHO-E beverage at Q3 and Q4 (P < 0.05). Averaging across all 4 quarters, the 8% CHO-E treatment produced significantly higher mean ratings of stomach upset and side ache. In conclusion, higher CHO concentration and osmolality in an ingested beverage provokes stomach upset and side ache.

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.

Fructose is absorbed slowly in the jejunum via a facilitated transport mechanism (GLUT5) and ingestion of significant amounts of fructose may potentially contribute to GI distress. PURPOSE To determine whether graded levels of GI distress in resting subjects are detectable by subjective survey in response to varying doses of ingested fructose. METHODS Ten subjects (7 men, 3 women) ingested 4 dosages of fructose (0, 25, 50, and 75 grams) at rest in a randomized order on 4 separate occasions following an overnight fast. Crystalline fructose was dissolved in water and chilled to 45°F. Total volume of all beverages was equal to 500 ml. Subjects completed surveys of GI distress prior to drinking (pre-drink), immediately after drinking (0-min) and at 60-minute intervals for 3 hours (60, 120, and 180-min). Study participants were not permitted to consume any food or fluid during the observation period. RESULTS A significant dose-response relationship was found between the various levels of fructose and symptoms related to GI distress (nausea, stomach upset, stomach bloating). Nausea scores (0 = No, 100 = Severe) were significantly higher across time (mean ± SD) with 75-g (14.6 ± 18.1) compared to 0 (3.0 ± 5.6), 25 (6.6 ± 12.8) and 50-g (8.1 ± 13.6). Additionally, 75-g (24.2 ± 21.8) scored significantly higher for ratings of stomach upset (0 = No, 100 = Severe) than 0 (4.7 ± 6.5), 25 (9.9 ± 15.2), and 50-g (12.3 ± 18.7) across time. CONCLUSION There appears to be a dose-dependent relationship between fructose and GI distress at rest. Subsequent research is needed to validate the survey using varying dosages of fructose during exercise.

PURPOSE This study compared sweat and electrolyte loss in Division I football players with a history of muscle cramping versus players who never cramped. METHODS We measured sweat loss, fluid intake, sweat sodium (swNa) and potassium (swK) in 10 players. Five players with a history of debilitating ‘full-body’ muscle cramps (C) during two-a-day practices were matched (by age, race, position and weight) to five players who never cramped (NC). Practices lasted 2.5 h in full gear. Change in bodyweight, corrected for fluid intake and urine loss, was used to estimate gross sweat loss (GSL). A forearm sweat patch was used to collect sweat to determine swNa and swK concentrations. Voluntary fluid intake (water and sports drinks) was measured by recording pre- and post-practice bottle weights. RESULTS Fluid intake was 2.6 ± 0.8 L in C and 2.8 ± 0.7 L in NC. GSL was higher in C (4.0 ± 1.1 L) than NC (3.5 ± 1.6L) (P < 0.05), resulting in significantly higher dehydration for C (1.3 ± 0.9%) versus NC (0.7 ± 1.2%) (P < 0.05). SwK was not different between groups, but swNa was significantly higher (P < 0.05) in C (55.0 ± 17 mEq/L) versus NC (25.9 ± 10.4 mEq/L). Summed across both sessions, mean total sodium loss was 5.2 ± 2.3 g (C) and 2.4 ± 1.7 g (NC) (P < 0.05). Intake of salty fluids on-field did not offset greater total body swNa losses in C versus NC who drank primarily water. Two studies using a 5-site sweat collection method earlier in the year with the same groups also showed higher swNa in C versus NC. CONCLUSION Crampers lost more total sodium, were more dehydrated, and had higher sweat rates than NC. Large acute sodium and fluid losses in the heat likely contribute to whole-body muscle cramping.

Being aware of sweat loss is critical to assessing need to drink during sport and physical exertion. In the absence of body weight measurements, introspective self-assessment of dehydration is required to determine need to drink. Factors other than actual dehydration (including mood) may be related to self-perception of sweat loss/dehydration. PURPOSE To explore the degree to which subjects in a realistic sport setting (18 holes of golf) accurately self-assess sweat loss/dehydration and to examine the relationship of these self-assessments to mood. METHODS Sixteen golfers (14 men, 2 women, 10.9 average handicap) played 18 holes of golf (ambient DB 32 +/− 1.5°C, RH 54.8 +/− 5.4%). Body wt, and mood surveys (Profile of Mood States,) were obtained before and after play. Perceived sweat loss and perceived fluid intake were obtained after play. Urine was collected and recorded during play. Subjects had unlimited access to chilled water and drove the course in golf carts. RESULTS Perceived sweat loss (1.2 L), for 18 holes of play, was significantly less than actual sweat loss (2.1 L, p < 0.05). The correlation between perceived sweat lost and actual sweat loss was low and non-significant (r=0.31), accounting for 10% of the variation. However, the correlations between perceived sweat loss and post-play POMS scales were significant (p < 0.05) for Tension-Anxiety, Depression-Dejection, Confusion-Bewilderment and Total Mood Disturbance (r = 0.58, 0.71, 0.69, 0.67 respectively). Conversely, the correlations between actual sweat loss and POMS scales were not significant, with the exception of actual sweat loss Vs Depression-Dejection (r = 0.50, P < 0.05). Perceived sweat loss was not related to % dehydration (r = −0.017, ns) or to amount consumed (r = 0.29, ns). The correlations between % dehydration and POMS were all low and not significant. CONCLUSION Self-perception of sweat loss may not be an accurate estimate of actual sweat loss or % dehydration. Self perceptions of sweat loss may be more related to other factors such as mood.

The purpose of this study was to assess responses of blood pressure (BP), heart rate (HR), and fluid retention (cumulative urine loss, UL) after ingestion of a standardized volume of a sports drink and an electrolyte supplement (ES) used to help athletes prone to cramping. Ten physically active, normotensive males were evaluated at rest during a routine workday under fasted but well-hydrated conditions (mean ± SEM for baseline urine SG was 1.018 ± 0.001 g/ml). Measurements of BP, HR, and urine volume were collected at baseline and at 30, 60, 120, and 180 minutes following one of five treatments: ingestion a 590 mL serving of placebo (P), sports drink (SD, 20 mEq Na+/L), sports drink plus caffeine (SDC, 20 mEq Na+/L plus 400 mg caffeine), sports drink plus ES (SDES, 75 mEq Na+/L) or no drink. Subjects returned to their desk jobs between measurement times. The results revealed no change in HR, systolic BP or diastolic BP during the three-hour period following the baseline measurement or among any treatments (repeated measures ANOVA, p > 0.05). Among the beverage comparisons, fluid retention was greatest for SDES (p < 0.05 vs. SDC, P). SD also produced greater fluid retention than did SDC (p < 0.05). Mean ± SEM (g) for cumulative urine volume following administration of the treatment were as follows: SDC, 552 ± 204; P, 488 ± 200; SD, 426 ± 189; SDES, 366 ± 171. Despite differences in fluid retention of as much as 186 mL, the fluid retained did not alter BP or HR responses at rest. The enhanced fluid retention consequent to acute use of the electrolyte supplement in a standard sports drink does not provoke changes in blood pressure under conditions where fluid and electrolyte losses are minimal (i.e., at rest in well-hydrated subjects).

Relatively few studies exist to characterize risk factors related to player safety, heat stress, and dehydration in professional football during on-field conditions. PURPOSE: Todescribesweatloss, dehydration, fluidintake, andsweatsodiumlossesduringon - fieldconditions. METHODS: We measured sweat loss and fluid intake in 16 NFL players and sweat sodium (s[Na+]) in a subset of the players (n = 13) during three practices in different US regions. Practices lasted about two hours during pre-season training camps. Change in bodyweight, corrected for fluid intake and urine loss, was used to estimate gross sweat loss. An arm-bag collection technique that excluded sweat from the hand was used to estimate whole-body s[Na+] values. Voluntary fluid intake (water and sports drinks) was measured by recording pre- and post-practice bottle weights. RESULTS: Conditions ranged from 12–31 °C WBGT. Practices were conducted in both partial and full gear. Gross sweat loss ranged from 1.3–5.2 liters per hour with s[Na+] ranging 513–2330 mg per liter (22–101 mEq/L). This resulted in total s[Na+] losses between 0.8–9.9 grams during the practices. Fluid intake ranged from 0.3–5.0 liters and resulted in replacing as little as 16% and as much as 120% of sweat losses. Average dehydration was 1.2 ± 1.0% of initial bodyweight. Players showed large interindividual variability in sweat loss, fluid intake and s[Na+]. CONCLUSION: The extent to which factors of environment, volume of work, or gear influenced fluid and total sodium loss could not be determined because training intensity and work volume were not standardized. Nonetheless, these data confirm that large fluid and sodium losses occur during pre-season practices. Often, little fluid is replaced. Long practices in full uniform and in hot, humid conditions appeared to increase the risk for larger sweat and sodium losses.

Adequate hydration is important for performance, health, and well-being during sport activity. However, athletes frequently do not consume sufficient amounts of fluids to meet sweat losses during exercise. The consequences of inadequate fluid consumption during training or competition can include decreased physical performance or heat injury. Being able to predict fluid loss would be useful in estimating the amount of fluid to drink during physical activity. PURPOSE: To derive a simple formula to predict fluid loss during exercise. METHODS: Fluid-loss data from the literature (14 studies) were analyzed relative to initial body weight (kg), exercise intensity, ambient temperature, percent relative humidity, and exercise type. Fluid loss was treated as the dependent variable. Body weight, exercise intensity, ambient temperature, humidity, and exercise type were treated as the independent variables in a multiple regression analysis with backward elimination. Subsequently, 13 subjects were evaluated in a repeated measures design for fluid loss during recreational exercise in which the above independent measurements were also obtained. The literature-based regression equation was applied to the observed dependent measures obtained during the recreational exercise. RESULTS: The multiple correlation for the literature data was 0.843 for the full model, and was 0.841 for a reduced model, which consisted of the temperature and exercise intensity terms. The correlation between the predicted fluid loss for the subjects engaged in the recreational exercise, (based on the application of the full model literature-equation) and the observed fluid loss was 0.722. Similarly, the correlation between the predicted fluid loss and the observed fluid loss, using the reduced literature-equation was 0.731. CONCLUSION: A simple literature-based multiple regression of readily available measures was able to account for 52% of the variability of observed fluid loss in recreational exercisers. Additional research is needed to refine the analysis within exercise type. Supported by the Gatorade Sports Science Institute.

Pre-exercise CHO feeding is known to induce a transient decline in blood glucose at the onset of exercise, although few studies have tried to determine if this decline is associated with changes in sensory perceptions of energy level or fatigue. PURPOSE: To determine the effects of ingesting a sports/energy bar before exercise on metabolic and sensory perception responses during exercise. METHODS: On three separate occasions five men (41 ± 3 yrs, 76.5 ± 5.5 kg, 178.8 ± 2.3 cm) and three women (37 ± 5 yrs, 65.9 ± 5.8 kg, 166.8 ± 5.9 cm) ran on a treadmill at 75% of maximal heart rate. One of three test products was consumed 30 min prior to exercise: 355 ml of an artificially sweet placebo (CON), energy bar 1 (EB1; 43g CHO, 4.7g fat, 6.5g protein) + 285 ml water, or energy bar 2 (EB2; 43g CHO, 2.0g fat, 10.0g protein) + 285 ml water. Total ingested volume was equal across treatments and energy bars were purposely matched for CHO, letting calories, fat and protein vary. Exercise was divided into three 15 min segments with five minutes of rest between segments. During rest, subjects completed sensory forms and were allowed to drink water ad libitum. Blood samples were drawn before and at 15 and 30 min after product ingestion. Blood samples were also drawn at the end of each 15 min exercise segment and indirect calorimetry was used to determine CHO oxidation during exercise. RESULTS: Blood glucose was stable throughout CON, ranging between 100–112 mg/dl. Glucose values for EB1 and EB2 were highest 30 min after ingestion (141 ± 5 and 131 ± 9 mg/dl, respectively), but dropped to 85 ± 10 and 76 ± 9 mg/dl after 15 min of exercise. Glucose returned to CON level for the remainder of exercise. Despite fluctuations in blood glucose, perception of energy level during EB1 and EB2 was not different from CON. As expected, CHO oxidation (g/min) rates after bar ingestion (2.28 ± 0.40) were higher (p < 0.05) than CON (2.01 ± 0.41). There were no GI complaints; however, subjects did report feeling less hungry during exercise after bar ingestion. Water intake was not different among treatments. CONCLUSION: Perception of energy level during short-term, moderately intense exercise is independent of blood glucose level and CHO oxidation rates.

Severe, debilitating muscle cramping is often associated with large fluid and sweat sodium losses. Our purpose was to determine whether or not sweat [Na+] and large fluid losses were associated in cramp-prone professional football players (N = 3). Players were referred for testing due to frequent cramping problems and were interviewed for history of severe muscle cramps in the lower extremities or whole body during pre-season preparation. Since pre-collegiate play, all players had experienced frequent, intense muscle cramps during explosive movements. Change in bodyweight and site-specific sweat patches were used to measure gross sweat loss and estimate mean whole-body sweat rate and sweat electrolyte values during one hour of cycle exercise (workload ≈ 150 W) in a warm environment (80°F, 50% RH) while wearing shorts.TableThese players showed large inter-individual variability in sweat rates and sweat [Na+]. Longer practices in full uniform and in hotter, more humid conditions than those of our one-hour study are likely to increase the risk for larger sweat and sodium losses and the potential for heat-related illness and cramping. While the association between muscle cramps and fluid/sodium losses has yet to be fully elucidated, these data do support that large fluid and sodium losses may be evidenced in players with a history of muscle cramps.