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Examined whether moderate overhydration would enhance the performance of otherwise euhydrated collegiate swimmers during two 183-meter time-trial swims held 3 days apart. Participants swam in alternate, randomized euhydrated, and overhydrated states. Results indicated that euhydration before an intense, short-duration swim was adequate for peak performance, and overhydration provided no performance advantage. (SM)

Presents recommendations from the National Athletic Trainers Association for optimizing the fluid replacement practices of athletes, explaining that dehydration can compromise athletic performance and increase the risk of exertional heat injury. Athletes must be educated about the risks of dehydration and overhydration. They must learn fluid replacement practices that optimize hydration status before, during, and after competition. (SM)

Ranalli, GF, DeMartini, JK, Casa, DJ, McDermott, BP, Armstrong, LE, and Maresh, CM. Effect of body cooling on subsequent aerobic and anaerobic exercise performance: a systematic review. J Strength Cond Res 24(12): 3488-3496, 2010--Body cooling has become common in athletics, with numerous studies looking at different cooling modalities and different types of exercise. A search of the literature revealed 14 studies that measured performance following cooling intervention and had acceptable protocols for exercise and performance measures. These studies were objectively analyzed with the Physiotherapy Evidence Database (PEDro) scale, and 13 of the studies were included in this review. These studies revealed that body cooling by various modalities had consistent and greater impact on aerobic exercise performance (mean increase in performance = 4.25%) compared to anaerobic (mean increase in performance = 0.66%). Different cooling modalities, and cooling during different points during an exercise protocol, had extremely varied results. In conclusion, body cooling seems to have a positive effect on aerobic performance, although the impact on anaerobic performance may vary and often does not provide the same positive effect. KEY WORDS hyperthermia, athletic performance, precooling

Highly trained cyclists may be hesitant to incorporate resistance training (RT) with their endurance training (ET) because of the mixed data regarding concurrent RT and ET (CT). The purpose of this review was to search the scientific body of literature for randomized controlled trials (RCTs) of CT on road cycling performance for highly trained cyclists. Key words (including cycling and strength training) were used to search relevant databases through September 2009 for literature related to CT. Randomized controlled trials were included if they scored [greater than or equal to] 5 on the Physiotherapy Evidence Database scale. Five studies met the inclusion criteria: highly trained road cyclists (>7 h*[wk.sup.-1] or > 150 km*[wk.sup.-1] with at least 6 months of training), outcome measure was cycling performance (time trial or time to exhaustion), and RT performed off-bike. Two of the 5 studies found no improvement in performance with CT, but these studies added RT on top of the athletes' existing ET. The 3 studies with improved cycling performance replaced a portion of the athletes' ET with RT, and 2 of the 3 studies included high-intensity explosive-type resistance exercises. Despite the limited research on CT for highly trained cyclists, it is likely that replacing a portion of a cyclist's ET with RT will result in improved time trial performance and maximal power. KEY WORDS endurance training, endurance athlete, time trial

J Strength Cond Res 24(1): 60-67, 2010--Physical activity of significant intensity and duration may cause varying degrees of skeletal muscle damage, but it is unclear whether mode of rehydration will attenuate muscle tissue disruption caused by exercise in the heat. To examine the effects of the mode of rehydration on markers of muscle damage (myoglobin and creatine kinase [CK]), 11 healthy active men (age = 23 [+ or -] 4 years, body mass = 80.9 [+ or -] 3.9 kg, height = 180.5 [+ or -] 5.4 cm) completed 4 experimental trials consisting of an exercise dehydration protocol (to -4% of baseline body mass), followed by a rehydration period (oral, intravenous [IV], oral and IV combined, and ad libitum), and finishing with an intense exercise challenge that included treadmill running and sprinting and a box lifting protocol. During rehydration, subjects returned to -2% of baseline body mass unless completing the ad libitum trial during which they consumed fluids as thirst dictated. Myoglobin (Mb) and CK were measured during euhydrated rest. Post-exercise blood was drawn at 1 and 24 hours post exercise challenge for Mb and CK, respectively. Urine was collected during euhydrated rest and 1-hour post exercise challenge for measurement of Mb clearance. Mb concentrations increased significantly from pre (1.06 [+ or -] 0.20, 0.88 [+ or -] 0.07, 1.15 [+ or -] 0.25 and 0.92 [+ or -] 0.06 nmol x [L.sup.-1]) to post (1.52 [+ or -] 0.28, 1.44 [+ or -] 0.11, 1.71 [+ or -] 0.45 and 1.58 [+ or -] 0.39) for IV, oral, oral and IV combined, and ad libitum, respectively, but were not significantly different among trials. Serum OK concentrations remained within the normal physiological range for all trials. Thus, despite previous research that clearly indicates the benefit of ingesting fluids during exercise to attenuate muscle damage, there were no significant differences between the modes of rehydration on circulating Mb and CK. KEY WORDS Key Words muscle damage, strenuous exercise, dehydration

The purpose of this study was to determine the influence of hydration status on pacing of trail runners in the heat (wet bulb globe temperature = 26.2 [+ or -] 1.8[degrees]C). A randomized, cross-over design was used and the participation occurred within a 2-week period. Seventeen competitive, well-trained distance runners (9 men, 8 women, age 27 [+ or -] 7 years, height 1 71 [+ or -] 9 cm, weight 64.2 [+ or -] 9.0 kg, body fat 14.6 [+ or -] 5.5%) completed the study. Subjects started maximum effort trials that were either hydrated (HYR) and dehydrated (DHR). Each trial subjects ran three 4-km loops with a 4-minute rest between loops. Significance was set at p [less than or equal to] 0.05. The DHR had a significantly greater body mass loss at the pre- and posttrial time points (-2.05 [+ or -] 1.25 and -4.3 [+ or -] 1.25%, respectively) vs. HYR (-0.79 [+ or -] 0.95 and -2.05 [+ or -] 1.09%, respectively). Subjects ran the 12 km faster (p < 0.001) in HYR (3,191 [+ or -] 366 seconds) vs. DHR (3,339 [+ or -] 450 seconds). Differences between fastest and slowest loops during HYR (54 [+ or -] 40 seconds) were significantly smaller than DHR (111 [+ or -] 93 seconds; p = 0.041). Additionally, loop times were slower for loop 1 (HYR 1,039 [+ or -] 116 seconds vs. DHR 1,071 [+ or -] 123 seconds; p = 0.028), loop 2 (HYR 1,066 [+ or -] 123 seconds vs. DHR 1,105 [+ or -] 148 seconds; p = 0.01) and loop 3 (HYR 1,081 [+ or -] 132 seconds vs. DHR 1,168 [+ or -] 189 seconds; p = 0.003) when dehydrated. Percent of the race completed by loop as calculated by finishing time was significantly different at loop 2 between HYR (33.6 [+ or -] 0.36%) and DHR (33.1 [+ or -] 0.35%, p = 0.002) and loop 3 (33.8 [+ or -] 0.75% vs. 34.9 [+ or -] 1.35%, respectively, p = 0.01). Total variation from the mean pace for the duration of the HYR compared to the DHR approached significance (p = 0.064). Average percent of variance approached significance between trials (p = 0.057). Differences between the fastest and slowest loops between trials demonstrated an increased ability for hydrated individuals to evenly pace themselves. While total variation from the mean pace was not significantly different, it could have practical applicability. These findings reveal that dehydration is associated with decreases in a runners' ability to evenly pace themselves during a competitive situation. KEY WORDS performance, dehydration, pace

Endurance athletes often ingest caffeine because of its reported ergogenic properties. Although there are a vast number of studies quantifying caffeine's effects, many research studies measure endurance performance using a time-to-exhaustion test (subjects exercise at a fixed intensity to volitional exhaustion). Time-to-exhaustion as a performance measure is not ideal because of the high degree of measurement variability between and within subjects. Also, we are unaware of any endurance sports in which individuals win by going a longer distance or for a longer amount of time than their competitors. Measuring performance with a time-trial test (set distance or time with best effort) has high reproducibility and is more applicable to sport. Therefore, the purpose of this review was to critically and objectively evaluate studies that have examined the effect of caffeine on time-trial endurance (>5 minutes) performance. A literature search revealed 21 studies with a total of 33 identifiable caffeine treatments that measured endurance performance with a time-trial component. Each study was objectively analyzed with the Physiotherapy Evidence Database (PEDro) scale. The mean PEDro rating was 9.3 out of 10, indicating a high quality of research in this topic area. The mean improvement in performance with caffeine ingestion was 3.2 [+ or -] 4.3%; however, this improvement was highly variable between studies (-0.3 to 17.3%). The high degree of variability may be dependent on a number of factors including ingestion timing, ingestion mode/vehicle, and subject habituation. Further research should seek to identify individual factors that mediate the large range of improvements observed with caffeine ingestion. In conclusion, caffeine ingestion can be an effective ergogenic aid for endurance athletes when taken before and/or during exercise in moderate quantities (3-6 mg x [kg.sup.-1] body mass). Abstaining from caffeine at least 7 days before use will give the greatest chance of optimizing the ergogenic effect. Key Words aerobic exercise, competition, ergogenic, racing, theopylline

Background: The purpose of this study was to investigate effects of heat acclimatization (HAz) followed by heat acclimation (HA), and intermittent heat training (IHT) on time-trial performance. Hypothesis: Time-trial performance will improve after HA and will further improve with twice a week of IHT. Study Design: Interventional study. Level of Evidence: Level 3. Methods: A total of 26 male athletes (mean ± SD; age, 35 ± 12 years; body mass, 72.8 ± 8.9 kg; peak oxygen consumption [VO2peak], 57.3 ± 6.7 mL·kg−1·min−1) completed five 4-km time trials (baseline, post-HAz, post-HA, post-IHT4, post-IHT8) in the heat (ambient temperature, 35.4°C ± 0.3°C; relative humidity, 46.7% ± 1.2%) on a motorized treadmill. After baseline time trial, participants performed HAz (109 ± 10 days) followed by post-HAz time trial. Then, participants completed 5 days of HA, which involved exercising to induce hyperthermia (38.50°C-39.75°C) for 60 minutes. Participants were then divided into 3 groups and completed IHT either twice per week (IHTMAX), once per week (IHTMIN), or not at all (IHTCON) over an 8-week period. The exercise used for the IHT matched the HA. Four-kilometer time trials were performed after 4 weeks (post-IHT4) and 8 weeks of IHT (post-IHT8). Results: Time trial was faster in post-HA (17.98 ± 2.51 minutes) compared with baseline (18.61 ± 3.06 minutes; P = 0.037) and post-HAz (18.66 ± 3.12 minutes; P = 0.023). Percentage change in time trial was faster in IHTMAX (−3.9% ± 5.2%) compared with IHTCON (11.5% ± 16.9%) (P = 0.020) and approached statistical significance with large effect (effect size = 0.96) compared with IHTMIN (1.6% ± 6.2%; P = 0.059) at post-IHT8. Additionally, IHTMAX (−2.2% ± 4.2%) was faster than IHTCON (3.6% ± 6.9%) (P = 0.05) at post-IHT4. Conclusion: These results indicate that HA after HAz induces additional improvement in time-trial performance. IHT twice per week shows improvement after 8 weeks, while once per week maintains performance for 8 weeks. No IHT results in a loss of adaptations after 4 weeks and even greater losses after 8 weeks. Clinical Relevance: HA after HAz improves time-trial performance, twice a week of IHT improves performance further, and once a week of IHT maintains performance for at least 8 weeks. [ABSTRACT FROM AUTHOR]

It is well established that resistance exercise can damage muscle tissue, but the combined effects of hypohydration and resistance exercise on muscle damage are unclear. Two common circulating markers of muscle damage, myoglobin (Mb) and creatine kinase (CK) may be attenuated by fluid ingestion post-exercise. The purpose of this study was to examine the combined effect of resistance exercise and hydration state on muscle damage. Seven healthy resistance-trained males (age = 23 [+ or -] 4 years; body mass = 87.8 [+ or -] 6.8 kg; body fat = 11.5 [+ or -] 5.2%) completed 3 identical resistance exercise bouts (6 sets of up to 10 repetitions of the back squat) in different hydration states: euhydrated (HYO), hypohydrated ~2.5% body mass (HY2.5), and hypohydrated ~5.0% body mass (HY5). Subjects achieved desired hydration states via controlled water deprivation, exercise-heat stress, and fluid intake. Both Mb and CK were measured during euhydrated rest (PRE). Mb was also measured immediately post-exercise, 1 hour (+1H) and 2 hours (+2H) post-exercise; CK was measured at 24 and 48 hours post-exercise. Body mass decreased 0.2 [+ or -] 0.4%, 2.4 [+ or -] 0.4%, and 4.8 [+ or -] 0.4% during HY0, HY2.5, and HY5, respectively. Mb concentrations increased significantly (effect size [greater than or equal to] 1, p < 0.05) from PRE (2.6 [+ or -] 1.1,3.5 [+ or -] 2.8, and 3.2 [+ or -] 1.6 nmol*[L.sup.-1]) to +1H (5.3 [+ or -] 3.4, 6.8 [+ or -] 3.2, and 7.6 [+ or -] 2.8 nmol*[L.sup.-1]), and +2H (5.5 [+ or -] 3.8, 6.2 [+ or -] 3.0, and 7.2 [+ or -] 3.0 nmol*[L.sup.-1]) for HY0, HY2.5, and HY5, respectively, but were not significantly different between trials. CK concentrations remained within the normal resting range at all time points. Thus, hypohydration did not enhance muscle damage following the resistance exercise challenge. Despite these results, athletes are encouraged to commence exercise in a euhydrated state to maximize endogenous hormonal, mechanical, and metabolic benefits. KEY WORDS hypohydration, exercise-induced damage, muscle protein

The ergogenic effects of caffeine on athletic performance have been shown in many studies, and its broad range of metabolic, hormonal, and physiologic effects has been recorded, as this review of the literature shows. However, few caffeine studies have been published to include cognitive and physiologic considerations for the athlete. The following practical recommendations consider the global effects of caffeine on the body: Lower doses can be as effective as higher doses during exercise performance without any negative coincidence; after a period of cessation, restarting caffeine intake at a low amount before performance can provide the same ergogenic effects as acute intake; caffeine can be taken gradually at low doses to avoid tolerance during the course of 3 or 4 days, just before intense training to sustain exercise intensity; and caffeine can improve cognitive aspects of performance, such as concentration, when an athlete has not slept well. Athletes and coaches also must consider how a person's body size, age, gender, previous use, level of tolerance, and the dose itself all influence the ergogenic effects of caffeine on sports performance. KEY WORDS ergogenic aid, athletic performance, cognitive, habituation

This investigation evaluated the effects of a nutritional supplement (the organic osmolyte betaine) in rehydration solutions, with and without carbohydrate and electrolytes. Ten male runners ((mean [+ or -] SD) age, 20 [+ or -] 2 years; weight, 70.6 [+ or -] 6.8 kg; maximal aerobic power, 63.5 [+ or -] 4.1 mL [O.sub.2]*[kg.sup.-1][min.sup.-1]) dehydrated to -2.7% of body weight. They next rehydrated to -1.4% of body weight by consuming 1 L fluid during each of four experiments (double-blind, randomized, cross-over design): flavored, non-caloric water (W); W + 5 g*[L.sup.-1] betaine (W+B); 6% carbohydrate-electrolyte fluid (C); or C + 5 g*[L.sup.-1] betaine (C+B). Subjects then performed prolonged treadmill running (75 minutes at 65%[Vo.sub.2]max) plus a performance sprint to volitional exhaustion (3.1-3.8 minutes at 84%[Vo.sub.2]max) in an environmental chamber (31.1[degrees]C, 88.0[degrees]F). Only W versus W+B and C versus C+B statistical comparisons were germane to the research questions. Observations indicated that rehydration with fluids containing betaine resulted in significant differences (p < 0.05) of plasma volume, oxygen consumption, plasma lactate concentration, and thermal sensation. The present experiments did not support the use of betaine to improve sprint duration, but nonsignificant trends occurred when betaine trials were compared with non-betaine trials (mean C+B > C by 32 seconds, +16%; mean W+B > W by 38 seconds, +21%). We interpret the increases of both aerobic and anaerobic metabolism (C+B > C) to mean that further investigation of betaine as a nutritional supplement, using other types of exercise, is warranted. KEY WORDS thirst, osmolality, plasma volume, plasma sodium, plasma lactate, oxygen consumption

This investigation evaluated the new National Collegiate Athletic Association model of heat acclimatization for football players using physiological, psychological, fluid balance, anthropometric, and nutritional variables. Eleven football players (20 [+ or -] 1 year, 1.88 [+ or -] 0.05 m, and 115.36 [+ or -] 18.85 kg) from a Division I football team were observed for the first 8 days of preseason practices. Measurements such as heart rate and gastrointestinal temperature ([T.sub.GI]) via telemetric sensor were taken before, 3 times during, and after practice daily. An average 1.39-kg (1.2%) decrease of body mass occurred from prepractice to postpractice (p < 0.01). Consistent with mild body mass losses, urinary indices of hydration status (i.e., color, specific gravity, and osmolality) indicated mild fluid deficits. A significant increase (p < 0.05) from pre- to postpractice was observed in urine color and urine specific gravity, but chronic hypohydration over the 8 days was not noted. The Environmental Symptoms Questionnaire (ESQ) postpractice score was significantly higher (p < 0.05) than the prepractice score was, but averages did not differ across practice days. There was no difference in postpractice [T.sub.GI] measurements across days (p < 0.05). Heart rate, [T.sub.GI], and ESQ measurements indicated that football players experienced gradual heat acclimatization and enhanced heat tolerance, despite progressive increases of exercise variables, clothing, and environmental stressors. Key Words. core body temperature, hydration, football uniform, surface area-to-mass ratio

Introduction: Exertional hyponatremia (EH) during prolonged exercise involves all avenues of fluid-electrolyte gain and loss. Although previous research implicates retention of excess fluid, EH may involve either loss, gain, or no change of body mass. Thus, the etiology, predisposing factors, and recommendations for prevention are vague--except for advice to avoid excessive drinking. Purpose: This retrospective field study presents case reports of two unacquainted recreational cyclists (LC, 31y and AM, 39 years) who began exercise with normal serum electrolytes but finished a summer 164-km ride (ambient, 34±5°C) with a serum [Na+] of 130 mmol/L. Methods: To clarify the etiology of EH, their pre- and post-exercise measurements were compared to a control group (CON) of 31 normonatremic cyclists (mean ± SD; 37±6 years; 141±3 mmol Na+/L). Results: Anthropomorphic characteristics, exercise time, and post-exercise ratings of thermal sensation, perceived exertion and muscle cramp were similar for LC, AM and CON. These two hyponatremic cyclists consumed a large and similar volume of fluid (191 and 189 ml/kg), experienced an 11 mmol/L decrease of serum [Na+], reported low thirst sensations; however, LC gained 3.1 kg (+4.3% of body mass) during 8.9 hr of exercise and AM maintained body mass (+0.1kg, +0.1%, 10.6h). In the entire cohort (n = 33), post-event serum [Na+] was strongly correlated with total fluid intake (R² = 0.45, p < .0001), and correlated moderately with dietary sodium intake (R²=0.28, p = .004) and body mass change (R² = 0.22, p = .02). Linear regression analyses predicted the threshold of EH onset (<135 mmol Na+/L) as 168 ml fluid/kg. Conclusions: The wide range of serum [Na+] changes (+6 to -11 mmol/L) led us to recommend an individualized rehydration plan to athletes because the interactions of factors were complex and idiosyncratic. [ABSTRACT FROM AUTHOR]

Both exercise and dietary protein intake affect whole-body protein turnover (WBPTO). Few studies have investigated the effect of aerobic exercise training on WBPTO [leucine rate of appearance (Ra), oxidation (Ox), and nonoxidative leucine disposal (NOLD)] in untrained individuals consuming a specified level of protein. This study examined the effect of aerobic exercise training on WBPTO in untrained men and women during a controlled diet intervention providing 0.88 g protein/(kg * d). After a 2-wk adaptation to the study diet, 7 subjects [3 men, 4 women; 76.1 [+ or -] 5.8 kg, 164.7 [+ or -] 4.4 cm, 30.7 [+ or -] 4.5% body fat, 39.1 [+ or -] 2.8 V[O.sub.2max] (maximal oxygen uptake) mL/(kg * min)] participated in 4 wk of aerobic exercise training (running and walking 4-5 times/wk at 65-85% maximal heart rate). WBPTO (determined via constant infusion of 1-[[sup.13]C] leucine), nitrogen balance, and body composition were determined at baseline and after 4 wk of training. Nitrogen balance (-1.0 [+ or -] 0.7 vs. 0.9 [+ or -] 1.1 g N/24 h, P = 0.03) improved with exercise training, whereas body mass and composition did not change. Leucine Ra did not change, Ox decreased [18 [+ or -] 2 to 15 [+ or -] 2 [micro]mol/(kg * h), P [less than or equal to] 0.001], and NOLD tended to increase [128 [+ or -] 18 to 151 [+ or -] 19 [micro]mol/(kg * h), P = 0.09] in response to training. These data indicate improved protein utilization in response to exercise training in weight-stable subjects. This study emphasizes the importance of dietary control, with specific regard to energy and protein intakes, in the characterization of protein utilization in response to an exercise intervention. KEY WORDS: * protein turnover * body composition * nitrogen balance

Although endogenous and exogenous steroid hormones affect numerous physiological processes, the interactions of reproductive hormones, chronic exercise training, and heat acclimation are unknown. This investigation evaluated the responses and adaptations of 36 inactive females [age 21 [+ or -] 3 (SD) yr] as they undertook a 7- to 8-wk program [heat acclimation and physical training (HAPT)] of indoor heat acclimation (90 min/day, 3 days/wk) and outdoor physical training (3 days/wk) while using either an oral estradiol-progestin contraceptive (ORAL, n = 15), a contraceptive injection of depot medroxyprogesterone acetate (DEPO, n = 7), or no contraceptive (EU-OV, n = 14: control). Standardized physical fitness and exercise-heat tolerance tests (36.5[degrees]C, 37% relative humidity), administered before and alter HAPT, demonstrated that the three subject groups successfully (P < 0.05) acclimated to heat (i.e., rectal temperature, heart rate) and improved muscular endurance (i.e., sit-ups, push-ups, 4.6-km run time) and body composition characteristics. The stress of HAPT did not disrupt the menstrual cycle length/phase characteristics, ovulation, or plasma hormone concentrations of EU-OV. No between-group differences (P > 0.05) existed for rectal and skin temperatures or metabolic, cardiorespiratory, muscular endurance, or body composition variables. A significant difference post-HAPT in the onset temperature of local sweating, ORAL (37.2 [+ or -] 0.4[degrees]C) vs. DEPO (37.7 [+ or -] 0.2[degrees]C), suggested that steroid hormones influenced this adaptation. In summary, virtually all adaptations of ORAL and DEPO were similar to EU-OV, suggesting that exogenous reproductive hormones neither enhanced nor impaired the ability of women to complete 7-8 wk of strenuous physical training and heat acclimation. estrogen; progesterone; estradiol; progestin; rectal temperature