International Journal of Sport Nutrition and Exercise Metabolism

Published by Human Kinetics
Online ISSN: 1543-2742
Print ISSN: 1526-484X
Publications
For some time, it has been appreciated that muscle mass is regulated locally as well as systemically. We have cloned the cDNA of two isoforms of IGF-1, which are derived from the IGF-1 gene by alternate splicing. The expression of one of these was only detectable after mechanical stimulation. For this reason, this has been called mechano growth factor (MGF). The MGF is not glycosylated, is smaller, and has a shorter half-life in the unbound state than the systemic liver type IGF-1. As the result of a reading frame shift the MGF peptide also has a different C terminal sequence and thus has different binding protein/receptor affinities. Another splice variant (muscle L.IGF-I) is expressed in muscle during rest but is also upregulated by exercise. The latter is similar to the systemic liver type IGF-1. The evidence suggests that MGF has a high potency for inducing local protein synthesis and preventing apoptosis and therefore has an important role in local tissue repair and remodeling. Our physiological experiments show that stretch and particularly stretch combined with electrical stimulation, rather than stimulation alone are important in inducing MGF expression. The mechanotransduction mechanism is believed to involve the muscle cytoskeleton. During aging, the production of growth hormone and IGF-1 by the liver declines markedly. The discovery of MGF and muscle IGF-1 provides a link between physical activity and gene expression. This underlines the need for the elderly to remain active as the locally produced growth factors supplement the circulating IGF-1 levels.
 
Athletes competing in ultra-endurance events are advised to meet energy requirements, to supply appropriate amounts of carbohydrates (CHO), and to be adequately hydrated before and during exercise. In practice, these recommendations may not be followed because of satiety, gastrointestinal discomfort, and fatigue. The purpose of the study was to assess energy balance, macronutrient intake and hydration status before and during a 1,230-km bike marathon. A group of 14 well-trained participants (VO2max: 63.2 ± 3.3 ml/kg/min) completed the marathon after 42:47 hours. Ad libitum food and fluid intake were monitored throughout the event. Energy expenditure (EE) was derived from power output and urine and blood markers were collected before the start, after 310, 618, 921 km, after the finish, and 12 hours after the finish. Energy intake (EI; 19,749 ± 4,502 kcal) was lower than EE (25,303 ± 2,436 kcal) in 12 of 14 athletes. EI and CHO intake (average: 57.1 ± 17.7 g/h) decreased significantly after km 618 (p<0.05). Participants ingested on average 392 ± 85 ml/h of fluid, but fluid intake decreased after km 618 (p<0.05). Hydration appeared suboptimal before the start (urine specific gravity: 1.022 ± 0.010 g/ml) but did not change significantly throughout the event. The results show that participants failed to maintain in energy balance and that CHO and fluid intake dropped below recommended values during the second half of the bike marathon. Individual strategies to overcome satiety and fatigue may be necessary to improve eating and drinking behavior during prolonged ultra-endurance exercise.
 
— The study design with the four different supplementations. 
Anthropometric Data
— The time differences to complete the 1,500 m between placebo and the three other interventions, + = faster time to complete the trial compared with placebo,— = slower time to complete the trial compared with placebo 
— The maximal blood lactate concentrations compared between the four different treatments. * p < .05; ** p < .01 
The aim of this study was to investigate whether caffeine and/or sodium citrate have an ergogenic effect on the 1500 m exercise performance in elite wheelchair athletes. A placebo-controlled, randomized, cross-over and double-blind study design was conducted with the four treatments placebo, caffeine, sodium citrate and the combination of caffeine and sodium citrate. Nine healthy, elite wheelchair racing athletes (median: [min; max] age: 28 y [23; 54]; height: 173 cm [165; 188]; weight: 62.9 kg [48.9; 68.4], category T53/54) completed the study. All athletes were national team members, including several Paralympic Games, World and European Championship medalists. The athletes performed a 1500 m time trial four times on a wheelchair training roller. Time to complete 1500 m, pH, bicarbonate and sodium concentration as well as lactate concentration were measured. The time to complete 1500 m was not significantly different between the four treatments (placebo: 170.6 s [141.7; 232.0]; caffeine: 179.5 s [134.8; 239.6]; sodium citrate: 178.3 s [136.4; 247.1]; combination: 177.6 s [136.1; 256.2]). However, pH and bicarbonate concentrations were significantly increased with sodium citrate ingestion compared to placebo. Moreover, maximal lactate concentrations were significantly higher in the caffeine and the combination treatment compared to placebo. The supplementation with sodium citrate and/or caffeine did not provide an ergogenic effect on the 1500 m exercise performance in wheelchair elite athletes.
 
The purpose of the present case study was threefold: (a) to estimate intake and expenditure of a dog driver (musher) while participating in the Iditarod, (b) to determine the hydration status of the musher at the completion of the event, and (c) to evaluate training related changes in aerobic capacity and body composition of a long-distance dog sled driver in preparation for and following completion of a 1049-mile (1692-km) sled dog race. Actual energy intake during the Iditarod Sled Dog Race was estimated at 8,921 kilojoules (kJ) per day. Nutrient intake expressed as percentage kJ of total energy (14%, 44% and 42% for protein, carbohydrates, and fat, respectively). Weight loss of .72 kg of body weight indicated an energy deficit of 1819 kJ per day during the race. Total energy needs per day were calculated to be 10,740 kJ/day. An increase in hematocrit and hemoglobin during the race may indicate dehydration during the event. There was an improvement in aerobic fitness during on-snow training as determined by ventilatory threshold and VO2peak data. Fat-free mass was maintained during training (46.4 kg), with a concomitant decrease in fat (2.4 kg). Fat-free mass was also maintained during the 12-day race.
 
Mean (± standard deviation) serum caffeine concentrations on days 6 and 11. * indicates signifi cantly different from the other 2 treatments ( P > 0.05) on day 11; C0, 0 mg caffeine · kg -1 · d -1 ; C3, 3 mg caffeine · kg -1 · d -1 ; C6, 6 mg caffeine · kg -1 · d -1 .  
This investigation determined if 3 levels of controlled caffeine consumption affected fluid-electrolyte balance and renal function differently. Healthy males (mean +/- standard deviation; age, 21.6 +/- 3.3 y) consumed 3 mg caffeine . kg(-1) . d(-1). on days 1 to 6 (equilibration phase). On days 7 to 11 (treatment phase), subjects consumed either 0 mg (C0; placebo; n= 20), 3 mg (C3; n = 20), or 6 mg (C6; n = 19) caffeine . kg(-1) . d(-1) in capsules, with no other dietary caffeine intake. The following variables were unaffected (P > 0.05) by different caffeine doses on days 1, 3, 6, 9, and 11 and were within normal clinical ranges: body mass, urine osmolality, urine specific gravity, urine color, 24-h urine volume, 24-h Na+ and K+ excretion, 24-h creatinine, blood urea nitrogen, serum Na+ and K+, serum osmolality, hematocrit, and total plasma protein. Therefore, C0, C3, and C6 exhibited no evidence of hypohydration. These findings question the widely accepted notion that caffeine consumption acts chronically as a diuretic.
 
— Correlation between mean scores of a participant for upper abdominal prob- lems during the runs and the participant’s reported history of upper abdominal problems ( r = .70) in Study 1. 
— Correlation between mean scores of a participant for lower abdominal prob- lems during the runs and the participant’s reported history of lower abdominal problems ( r = .46) in Study 1. 
Study 1: Reported Scores for Each Symptom With Both Glucose + Fructose Treatments
— Correlation between mean scores of a participant for upper abdominal prob- lems during the runs and the participant’s reported history of upper abdominal problems ( r = .89) in Study 2. 
— Correlation between mean scores of a participant for lower abdominal prob- lems during the runs and the participant’s reported history of lower abdominal problems ( r = .90) in Study 2. 
Two studies were conducted to investigate gastrointestinal (GI) tolerance of high carbohydrate (CHO) intakes during intense running. The first study investigated tolerance of a CHO gel delivering glucose plus fructose (GLU+FRC) at different rates. The second study investigated tolerance of high intakes of glucose (GLU) vs. GLU+FRC gel. Both studies used a randomized, 2-treatment, 2-period crossover design: Endurance-trained men and women (Study 1: 26 men, 8 women; 37 +/- 11 yr; 73 +/- 9 kg; 1.76 +/- 0.07 m. Study 2: 34 men, 14 women; 35 +/- 10 yr; 70 +/- 9 kg; 1.75 +/- 0.09 m) completed two 16-km outdoor-runs. In Study 1 gels were administered to provide 1.0 or 1.4 g CHO/min with ad libitum water intake every 3.2 km. In Study 2 GLU or GLU+FRC gels were given in a double-blind manner to provide 1.4 g CHO/min. In both studies a postexercise questionnaire assessed 17 symptoms on a 10-point scale (from 0 to 9). For all treatments, GI complaints were mainly scored at the low end of the scale. In Study 1 mean scores ranged from 0.00 +/- 0.00 to 1.12 +/- 1.90, and in Study 2, from 0.00 +/- 0.0 to 1.27 +/- 1.78. GI symptoms were grouped into upper abdominal, lower abdominal, and systemic problems. There were no significant treatment differences in these categories in either study. In conclusion, despite high CHO gel intake, and regardless of the blend (GLU vs. GLU+FRC), average scores for GI symptoms were at the low end of the scale, indicating predominantly good tolerance during a 16-km run. Nevertheless, some runners (~10-20%) experienced serious problems, and individualized feeding strategies might be required.
 
To determine whether 16 months of moderate-intensity exercise training changes resting metabolic rate (RMR) and substrate oxidation in overweight young adults. Participants were randomly assigned to nonexercise control (CON, 18 women, 15 men) or exercise (EX, 25 women, 16 men) groups. EX performed supervised and verified exercise 3-5 d/wk, 20-45 min/session, at 60-75% of heart-rate reserve. Body mass and composition, maximal oxygen consumption (VO2max), RMR, and resting substrate oxidation were assessed at baseline and after 9 and 16 months of training. EX men had significant decreases from baseline to 9 months in body mass (94.6+/-12.4 to 89.2+/-9.5 kg) and percent fat (28.3+/-4.6 to 24.5+/-3.9). CON women had significant increases in body mass (80.2+/-8.1 to 83.2+/-9.2 kg) from baseline to 16 months. VO2max increased significantly from baseline to 9 months in the EX men (3.67+/-0.62 to 4.34+/-0.58 L/min) and EX women (2.53+/-0.32 to 3.03+/-0.42 L/min). RMR increased from baseline to 9 months in EX women (1,583+/-221 to 1,692+/-230 kcal/d) and EX men (1,995+/-184 to 2,025+/-209 kcal/d). There were no significant differences within genders for either EX or CON in fat or carbohydrate oxidation. Fat oxidation was significantly higher for women than for men at 9 months in both CON and EX groups. Regular moderate-intensity exercise in healthy, previously sedentary overweight and obese adults increases RMR but does not alter resting substrate oxidation. Women tend to have higher RMR and greater fat oxidation, when expressed per kilogram fat-free mass, than men.
 
m ergometer time trial scores throughout the 16 wk investigation. 
Changes in (a) VO 2 peak and (b) resting metabolic rate (RMR) during the 16 wk body mass loss period. 
Average weekly training volume undertaken by volunteers during the 16 wk period of observation. "Other" primarily involved running, cycling, and other cross-training activities. 
Changes in (a) triiodothyronine (T 3 ), (b) cortisol, (c) insulin like growth factor-1 (IGF-1), (d) β-hydroxy butyrate (β-HB), and (e) pre-albumin (pre-ALB) concentrations throughout the 16 wk period of planned weight loss. 
To strengthen the depth of lightweight rowing talent, we sought to identify experienced heavyweight rowers who possessed physique traits that predisposed them to excellence as a lightweight. Identified athletes (n = 3) were monitored over 16 wk. Variables measured included performance, anthropometric indices, and selected biochemical and metabolic parameters. All athletes decreased their body mass (range 2.0 to 8.0 kg), with muscle mass accounting for a large proportion of this (31.7 to 84.6%). Two athletes were able to maintain their performance despite reductions in body mass. However, performance was compromised for the athlete who experienced the greatest weight loss. In summary, smaller heavyweight rowers can successfully make the transition into the lightweight category, being nationally competitive in their first season as a lightweight.
 
The purpose of this investigation was to determine the effect of ingested caffeine, sodium bicarbonate, and their combination on 2,000-m rowing performance, as well as on induced alkalosis (blood and urine pH and blood bicarbonate concentration [HCO3-]), blood lactate concentration ([La-]), gastrointestinal symptoms, and rating of perceived exertion (RPE). In a double-blind, crossover study, 8 well-trained rowers performed 2 baseline tests and 4 × 2,000-m rowing-ergometer tests after ingesting 6 mg/kg caffeine, 0.3 g/kg body mass (BM) sodium bicarbonate, both supplements combined, or a placebo. Capillary blood samples were collected at preingestion, pretest, and posttest time points. Pairwise comparisons were made between protocols, and differences were interpreted in relation to the likelihood of exceeding the smallest worthwhile-change thresholds for each variable. A likelihood of >75% was considered a substantial change. Caffeine supplementation elicited a substantial improvement in 2,000-m mean power, with mean (± SD) values of 354 ± 67 W vs. placebo with 346 ± 61 W. Pretest [HCO3-] reached 29.2 ± 2.9 mmol/L with caffeine + bicarbonate and 29.1 ± 1.9 mmol/L with bicarbonate. There were substantial increases in pretest [HCO3-] and pH and posttest urine pH after bicarbonate and caffeine + bicarbonate supplementation compared with placebo, but unclear performance effects. Rowers' performance in 2,000-m efforts can improve by ~2% with 6 mg/kg BM caffeine supplementation. When caffeine is combined with sodium bicarbonate, gastrointestinal symptoms may prevent performance enhancement, so further investigation of ingestion protocols that minimize side effects is required.
 
— 2,000-m rowing performance split times (s) before and after (A) beta-alanine and (B) placebo supplementation. 1 Sig- nificantly different from pretest ( p ≤ .05). a Moderate effect size ( d = 0.50–0.79) for difference between beta-alanine and placebo after supplementation. #Likely (75–95%) chance of benefit. *Likely (75–95%) chance of detriment. 
— 2,000-m rowing performance split average power outputs (W) before and after (A) beta-alanine and (B) placebo supplementation. 1 Significantly different from pretest ( p ≤ .05). a Moderate effect size ( ≥ .49) for difference between beta-alanine and placebo after supplementation. #Likely (75–95%) chance of benefit. 
Beta-alanine supplementation has been shown to improve exercise performance in short-term high-intensity efforts. However, whether supplementation with beta-alanine is ergogenic to actual sporting events remains unclear and should be investigated in field testing or race simulations. Purpose The aim of this study was to assess if beta-alanine supplementation could improve 2,000-m rowing-ergometer performance in well-trained male rowers. Methods Participants ( N = 16) completed duplicate trials (2 × before supplementation and 2 × after supplementation) of a 2,000-m rowing-ergometer race separated by 28 days of either beta-alanine ( n = 7; 80 mg · kg ⁻¹ BM · d ⁻¹ ) or placebo ( n = 9; glucose) supplementation. Results Beta-alanine group (pooled) race times improved by 2.9 ± 4.1 s and placebo group slowed by 1.2 ± 2.9 s, but these results were inconclusive for performance enhancement ( p = .055, ES = 0.20, smallest worthwhile change = 49% beneficial). Race split times and average power outputs only significantly improved with beta-alanine at the 750-m (time –0.7 s, p = .01, power +3.6%, p = .03) and 1,000-m (time –0.5 s, p = .01, power +2.9%, p = .02) distances. Blood La ⁻ and pH postrace values were not different between groups before or after supplementation. Conclusions Overall, 28 d of beta-alanine supplementation with 80 mg · kg ⁻¹ BM · d ⁻¹ (~7 g/d) did not conclusively improve 2,000-m rowing-ergometer performance in well-trained rowers.
 
Purpose To examine the effect of beta-alanine only and beta-alanine with sodium bicarbonate supplementation on 2,000-m rowing performance. Methods Twenty well-trained rowers (age 23 ± 4 y; height 1.85 ± 0.08 m; body mass 82.5 ± 8.9 kg) were assigned to either a placebo or beta-alanine (6.4 g·d ⁻¹ for 4 weeks) group. A 2,000-m rowing time trial (TT) was performed before supplementation (Baseline) and after 28 and 30 days of supplementation. The post supplementation trials involved supplementation with either maltodextrin or sodium bicarbonate in a double-blind, crossover design, creating four study conditions (placebo with maltodextrin; placebo with sodium bicarbonate; beta-alanine with maltodextrin; beta-alanine with sodium bicarbonate). Blood lactate, pH, bicarbonate, and base excess were measured pre-TT, immediately post-TT and at TT+5 min. Performance data were analyzed using magnitude based inferences. Results Beta-alanine supplementation was very likely to be beneficial to 2,000-m rowing performance (6.4 ± 8.1 s effect compared with placebo), with the effect of sodium bicarbonate having a likely benefit (3.2 ± 8.8 s). There was a small (1.1 ± 5.6 s) but possibly beneficial additional effect when combining chronic beta-alanine supplementation with acute sodium bicarbonate supplementation compared with chronic beta-alanine supplementation alone. Sodium bicarbonate ingestion led to increases in plasma pH, base excess, bicarbonate, and lactate concentrations. Conclusions Both chronic beta-alanine and acute sodium bicarbonate supplementation alone had positive effects on 2,000-m rowing performance. The addition of acute sodium bicarbonate to chronic beta-alanine supplementation may further enhance rowing performance.
 
Basic Characteristics of the Studied Groups (M ± SD) Group 
The aim of this study was to investigate the effect of plant superoxide dismutase extract (GliSODin) supplementation on the balance of oxidants and antioxidants in the serum and erythrocytes of competitive rowers. The double-blinded study included 19 members of the Polish rowing team who were participating in a preparatory camp. Subjects were randomly assigned to the supplemented group (n = 10), who received 2 capsules (500 mg) of GliSODin extract once daily for 6 weeks, or the placebo group (n = 9). At the beginning and end of the study, subjects performed a 2,000-m maximum-effort test on a rowing ergometer. Blood samples were taken from the antecubital vein before each exercise test, 1 min after completing the test, and after a 24-hr restitution period. The following redox parameters were assessed in erythrocytes: superoxide dismutase (SOD) activity, glutathione peroxidase activity, and concentrations of thiobarbituric-acid-reactive substances. In addition, creatine kinase activity and total antioxidant capacity were measured in plasma samples, lactate levels were determined in capillary blood samples, and C-reactive protein and lactate dehydrogenase concentrations were measured in serum. After supplementation, SOD activity was significantly higher (p = .0037) in the supplemented group than the placebo group, and C-reactive protein was significantly (p = .00001) lower in athletes receiving GliSODin than those in the placebo group. In conclusion, supplementation with an extract rich in SOD activity promoted antioxidant status and protected against increased inflammation in the serum of professional rowers but had no effect on oxidative damage induced by exhaustive exercise.
 
The purpose of this study was to investigate the effects of sodium bicarbonate (NaHCO(3)), caffeine, and their combination on repeated 200-m freestyle performance. Six elite male freestyle swimmers ingested NaHCO(3) (0.3 g/kg; B), caffeine (6.2 +/- 0.3 mg/kg; C), a combination of both (B+C), and placebo (P) on 4 separate occasions before completing 2 maximal 200-m freestyle time trials (TT1 and TT2) separated by 30 min. No significant differences (p = .06) were observed for performance in TT1 (B 2:03.01 +/- 0:03.68 min, C 2:02.42 +/- 0:03.17 min, B+C 2:01.69 +/- 0:03.19 min, P 2:03.77 +/- 0:03.21 min) or TT2 (B 2:02.62 +/- 0:04.16 min, C 2:03.90 +/- 0:03.58 min, B+C 2:01.70 +/- 0:02.84 min, P 2:04.22 +/- 0:03.75 min). The drop-off in performance time from TT1 to TT2, however, was significantly greater when C was ingested than with B (-1.5%, p = .002) or B+C (-1.2%, p = .024). This is likely because of the lower blood pH and slower recovery of blood HCO(3) post-TT1 after C ingestion. These findings suggest that the ergogenic benefit of taking C alone for repeated 200-m swimming performance appears limited. When combined with NaHCO(3), however, its negative impact on repeated maximal exercise performance is reversed.
 
Eight competitive oarswomen (age, 22 +/- 3 years; mass, 64.4 +/- 3.8 kg) performed three simulated 2,000-m time trials on a rowing ergometer. The trials, which were preceded by a 24-hour dietary and training control and 72 hours of caffeine abstinence, were conducted 1 hour after ingesting caffeine (6 or 9 mg á kg-1 body mass) or placebo. Plasma free fatty acid concentrations before exercise were higher with caffeine than placebo (0.67 +/- 0.34 vs. 0.72 +/- 0.36 vs. 0.30 +/- 0.10 mM for 6 and 9 mg á kg-1 caffeine and placebo, respectively; p <.05). Performance time improved 0.7% (95% confidence interval [CI] 0 to 1.5%) with 6 mg á kg-1 caffeine and 1. 3% (95% CI 0.5 to 2.0%) with 9 mg á kg-1 caffeine. The first 500 m of the 2,000 m was faster with the higher caffeine dose compared with placebo or the lower dose (1.53 +/- 0.52 vs.1.55 +/- 0.62 and 1. 56 +/- 0.43 min; p =.02). We concluded that caffeine produces a worthwhile enhancement of performance in a controlled laboratory setting, primarily by improving the first 500 m of a 2,000-m row.
 
Beta-alanine supplementation has been shown to improve exercise performance in short-term high-intensity efforts. However, whether supplementation with beta-alanine is ergogenic to actual sporting events remains unclear and should be investigated in field testing or race simulations. PURPOSE: The aim of this study was to assess if beta-alanine supplementation could improve 2000 m rowing ergometer performance in well-trained male rowers. METHODS: Participants (n=16) completed duplicate trials (2 x pre-supplementation and 2 x post-supplementation) of a 2000 m rowing ergometer race, separated by 28 days of either beta-alanine (n=7; 80 mg·kg-1BM·day-1) or placebo (n=9; glucose) supplementation. RESULTS: Beta-alanine group (pooled) race times improved by 2.9±4.1 s and placebo group slowed by 1.2±2.9 s, but these results were inconclusive for performance enhancement (p=0.055, ES=0.20, SWC=49% beneficial). Race split times and average power outputs only significantly improved with beta-alanine at the 750 m (time -0.7 s, p=0.01, power +3.6%, p=0.03) and 1000 m (time -0.5 s, p=0.01, power +2.9%, p=0.02) distances. Blood La- and pH values post-race were not different between groups before or after supplementation. CONCLUSIONS: Overall, 28 days of beta-alanine supplementation with 80 mg·kg-1BM·day-1 (~7 g·day-1) did not conclusively improve 2000 m rowing ergometer performance in well trained rowers.
 
This article describes the development, analysis, and implementation of the menu available to athletes and patrons in the main dining hall of the Athletes Village at the Sydney 2000 Olympic Games and the significant role of sports dietitians in this process. Menu design and development was informed by focus groups, literature reviews, and food-preference surveys of athletes. The final menu was also assessed by an expert panel of Australian sports dietitians. A custom-designed database (Foodweb) was developed to enable dietary analysis of food-production data and creation of point-of-choice nutrition labels. Dietitians assisted with quality assurance testing and training of catering staff. Athletes surveyed in the main dining hall (N=414) agreed that the menu contained sufficient variety and adequate meat, pasta/rice, vegetable/salad, fruit, and snack items. Sports dietitians played a significant role in ensuring that the menu met the needs of athletes from a range of differing cultural and sporting backgrounds. Dining-hall patrons provided positive feedback and few complaints about the overall dining experience. The information presented in this report can help future caterers and dietitians with the planning and provision of suitable food for athletic performance at an Olympic Games.
 
Purpose: To examine the effect of beta-alanine only and beta-alanine with sodium bicarbonate supplementation on 2,000-m rowing performance. Methods: Twenty well-trained rowers (age 23 ± 4 y; height 1.85 ± 0.08 m; body mass 82.5 ± 8.9 kg) were assigned to either a placebo or beta-alanine (6.4 g · d(-1) for 4 weeks) group. A 2,000-m rowing time trial (TT) was performed before supplementation (Baseline) and after 28 and 30 days of supplementation. The post supplementation trials involved supplementation with either maltodextrin or sodium bicarbonate in a double-blind, crossover design, creating four study conditions (placebo with maltodextrin; placebo with sodium bicarbonate; beta-alanine with maltodextrin; beta-alanine with sodium bicarbonate). Blood lactate, pH, bicarbonate, and base excess were measured pre-TT, immediately post-TT and at TT+5 min. Performance data were analyzed using magnitude based inferences. Results: Beta-alanine supplementation was very likely to be beneficial to 2,000-m rowing performance (6.4 ± 8.1 s effect compared with placebo), with the effect of sodium bicarbonate having a likely benefit (3.2 ± 8.8 s). There was a small (1.1 ± 5.6 s) but possibly beneficial additional effect when combining chronic beta-alanine supplementation with acute sodium bicarbonate supplementation compared with chronic beta-alanine supplementation alone. Sodium bicarbonate ingestion led to increases in plasma pH, base excess, bicarbonate, and lactate concentrations. Conclusions: Both chronic beta-alanine and acute sodium bicarbonate supplementation alone had positive effects on 2,000-m rowing performance. The addition of acute sodium bicarbonate to chronic beta-alanine supplementation may further enhance rowing performance.
 
This study assessed the knowledge, prevalence, and quantity of caffeine use by athletes competing at the 2005 Ironman Triathlon World Championships. Caffeine-related questionnaires were self-administered to 140 (105 male and 35 female, 40.3 +/- 10.7 y) athletes representing 16 countries. Fifty of these athletes further consented to immediate post-race blood samples for analysis of plasma caffeine and paraxanthine using high-performance liquid chromatography (HPLC). Seventy-two percent of 70 athletes correctly identified caffeine as being an unrestricted substance in triathlon. The majority of athletes [125 (89%)] were planning on using a caffeinated substance immediately prior to or throughout the race. Cola drinks (78%), caffeinated gels (42%), coffee (usually pre-race) (37%), energy drinks (13%), and NoDoz tablets (9%) were the most popular caffeinated choices. Mean +/- standard deviation (and range) post race plasma caffeine and paraxanthine levels were 22.3 +/- 20 micromol/L (1.7 to 98.4) and 9.4 +/- 6 micromol/L (1.8 to 28.9), respectively. Seven athletes (14%) finished with plasma caffeine levels > or = 40 micromol/L. Plasma values from elite athletes did not differ from age group competitors. Despite the prevalence of its consumption and the training experience of this athletic group, over one quarter of athletes remained either confused or uninformed about caffeine's legality. Levels of plasma caffeine taken immediately post race indicated that athletes typically finish with quantities of caffeine that have been shown to improve endurance performance (i.e., approximately 20 micromol/L or a dose of > or = 3 mg/kg body weight).
 
— Differences in doping knowledge. 
Competitive Sports Represented, n (%)
— Three highly ranked sources of information on antidoping regulation by (a) age and (b) gender. 
Athletes report frequent use of various dietary supplements (DSs). However, no study has examined DS use and antidoping knowledge in Korean Olympians. The objectives of this study were to obtain information about Korean Olympians' DS use during the training period for the Beijing 2008 Summer Olympic Games and immediately before their Olympic events, to obtain DS-intake reasons and DS providers, and to obtain information on athletes' doping education, knowledge, and educators. Korean Olympians completed 2 questionnaires 1 wk before the opening and within 1 wk after the closing of the Beijing 2008 Summer Olympic Games. Results showed that 79% of male and 82% of female Olympians take more than 1 DS during the training period and that vitamins and Oriental supplements are the 2 top-ranked DSs. Reasons for DS use were to improve recovery ability (66%) and muscle performance (22%), and sources of obtaining DSs were parents (36%) and coaches (35%). Furthermore, 79% of Korean Olympians reported receiving regular education on antidoping regulations from Olympic-sponsored education classes (64%) and coaches (15%). In conclusion, this study was the first to examine DS use and antidoping-related information in Korean Olympians. Because some herbal products contain substances banned by the World Anti-Doping Agency, athletes should be cautious in using mixed Oriental supplements.
 
The Vendée Globe is a solo round-the-world sailing race without stopovers or assistance, a physically demanding challenge for which appropriate nutrition should maintain energy balance and ensure optimum performance. This is an account of prerace nutritional preparation with a professional and experienced female racer and assessment of daily nutritional intake (NI) during the race using a multimethod approach. A daily energy intake (EI) of 15.1 MJ/day was recommended for the race and negotiated down by the racer to 12.7 MJ/day, with carbohydrate and fluid intake goals of 480 g/day and 3,020 ml/day, respectively. Throughout the 99-day voyage, daily NI was recorded using electronic food diaries and inventories piloted during training races. NI was assessed and a postrace interview and questionnaire were used to evaluate the intervention. Fat mass (FM) and fat-free mass (FFM) were assessed pre- (37 days) and postrace (11 days) using dual-energy X-ray absorptiometry, and body mass was measured before the racer stepped on the yacht and immediately postrace. Mean EI was 9.2 MJ/day (2.4-14.3 MJ/day), representing a negative energy balance of 3.5 MJ/day under the negotiated EI goal, evidenced by a 7.9-kg loss of body mass (FM -7.5 kg, FFM -0.4 kg) during the voyage, with consequent underconsumption of carbohydrate by ~130 g/day. According to the postrace yacht food inventory, self-reported EI was underreported by 7%. This intervention demonstrates the practicality of the NI approach and assessment, but the racer's nutrition strategy can be further improved to facilitate meeting more optimal NI goals for performance and health. It also shows that evaluation of NI is possible in this environment over prolonged periods, which can provide important information for optimizing nutritional strategies for ocean racing.
 
The aim of this study was to investigate the dietary regimens reported by athletes competing at a major international competition and report whether these were based on nutrient composition, religious beliefs, cultural eating style, food intolerance or avoidance of certain ingredients. A questionnaire was randomly distributed to 351 athletes in the main dining hall of the athletes' village over the three main meal periods during the Delhi 2010 Commonwealth Games (23rd Sept-14th Oct, 2010). The majority (n = 218, 62%) of athletes reported following one or more dietary regimens, with 50% (n = 174) following a diet based on the nutrient composition of the food. Significantly more athletes from weight category and aesthetic sports (28%, p = .005) and from power/sprint sports (41%, p = .004) followed low fat and high protein regimens respectively. Other specialized dietary regimens were followed by 33% of participants, with avoidance of red meat (13%), vegetarian (7%), Halal (6%), and low lactose regimens (5%) reported most frequently. Significantly more athletes from non-Western regions followed a vegetarian diet (p < .001), while more vegetarians reported avoiding additives (p = .013) and wheat (p ≤ .001). A Western style of eating was the most commonly reported cultural regimen (72% of total with 23% from non-Western regions). Those following a Western diet were significantly more likely to report following a regimen based on nutrient composition (p = .02). As a high proportion of athletes from differing countries and sports follow specialized dietary regimens, caterers and organizers should ensure that adequate nutrition support and food items are available at similar events.
 
The aim of this study was to investigate whether athletes' opinion of food provision in the main dining hall of the athletes' village at the Delhi 2010 Commonwealth Games varied according to cultural background, sport, stage of competition, and previous experience at similar events. A previously developed questionnaire was distributed over 3 meal periods to 351 athletes dining in the main dining hall during the course of the games (Sept. 23 to Oct. 4, 2010). Despite the challenges of food provision in a non-Western region, the availability of food and beverage items was rated highly. However, athletes from Western regions tended to rate food-provision qualities lower than athletes from non-Western regions. Most athletes found it easy to find items to meet their nutrition needs; however, requests for sports foods, snacks, and culturally specific items were received. Power/sprint athletes were more critical of the food provision, whereas athletes from aesthetic sports tended to rate it more highly. Athletes farther from competition gave higher ratings for taste, while athletes who had more experience in this type of environment also tended to be more critical of the food provision. Overall daily mean opinion scores for taste and menu variety decreased over the games period. The results of this study can help organizers and caterers ensure that appropriate food and beverage are provided for athletes at major competition events.
 
— Protocol timeline. Arrows indicate measurement time points. #1 = baseline (8–8:30 a.m.); #2 = preexercise (8:45–9:15); #3 = during exercise (9:15–9:55); #4 = postexer- cise (9:55–10:25); #5 = 2 hr postexercise (12–12:30 p.m.); #6 = 3 hr postexercise (12:45–1:15); #7 = 6 hr postexercise (4–430); #8 = recovery baseline (800–8:30 a.m. the next day). Exercise occurred from 9:15 to 9:55 a.m. Breakfast was a 29-kJ/kg meal, lunch was a 46-kJ/kg meal, and dinner was a 58-kJ/kg meal. 
— Total oxygen consumed (L) and average heart rate (beats/min) during the sessions of sprint-interval exercise (SIE) and continuous-endurance exercise (CEE). * p < .001. 
— Oxygen consumption before, during, and after treatments for control (CTRL), sprint-interval exercise (SIE), and continuous-endurance exercise (CEE). Unlike letters indicate within-time-point treatment differences ( p < .001). The table presents mean data for each time point. 
— Respiratory-exchange ratio before, during, and after treatments for control (CTRL), sprint-interval exercise (SIE), and continuous-endurance exercise (CEE). Unlike letters indicate within-time-point treatment differences ( p < .001). The table presents mean data for each time point. 
— (A) Total oxygen consumed over 8 hr for control (CTRL), sprint-interval exercise (SIE), and continuous-endurance exercise (CEE). (B) Total oxygen consumed over 24 hr for CTRL, SIE, and CEE. Unlike letters indicate time-point treatment dif- ferences ( p < .001). 
Six weeks (3 times/wk) of sprint-interval training (SIT) or continuous endurance training (CET) promote body-fat losses despite a substantially lower training volume with SIT. In an attempt to explain these findings, the authors quantified VO2 during and after (24 h) sprint-interval exercise (SIE; 2 min exercise) vs. continuous endurance exercise (CEE; 30 min exercise). VO2 was measured in male students (n = 8) 8 times over 24 hr under 3 treatments (SIE, CEE, and control [CTRL, no exercise]). Diet was controlled. VO2 was 150% greater (p < .01) during CEE vs. SIE (87.6 ± 13.1 vs. 35.1 ± 4.4 L O2; M ± SD). The observed small difference between average exercise heart rates with CEE (157 ± 10 beats/min) and SIE (149 ± 6 beats/min) approached significance (p = .06), as did the difference in peak heart rates during CEE (166 ± 10 beats/min) and SIE (173 ± 6 beats/min; p = .14). Total O2 consumed over 8 hr with CEE (263.3 ± 30.2 L) was greater (p < .01) than both SIE (224.2 ± 15.3 L; p < .001) and CTRL (163.5 ± 16.1 L; p < .001). Total O2 with SIE was also increased over CTRL (p < .001). At 24 hr, both exercise treatments were increased (p < .001) vs. CTRL (CEE = 500.2 ± 49.2; SIE = 498.0 ± 29.4; CTRL = 400.2 ± 44.6), but there was no difference between CEE and SIE (p = .99). Despite large differences in exercise VO2, the protracted effects of SIE result in a similar total VO2 over 24 hr vs. CEE, indicating that the significant body-fat losses observed previously with SIT are partially due to increases in metabolism postexercise.
 
Weight categorized athletes use a variety of techniques to induce rapid weight loss (RWL) in the days leading up to weigh in. This study examined the fluid and electrolyte balance responses to 24-hr fluid restriction (FR), energy restriction (ER) and fluid and energy restriction (F+ER) compared with a control trial (C), which are commonly used techniques to induce RWL in weight category sports. Twelve subjects (six male, six female) received adequate energy and water (C) intake, adequate energy and restricted water (~10% of C; FR) intake, restricted energy (~25% of C) and adequate water (ER) intake or restricted energy (~25% of C) and restricted (~10% of C) water intake (F+ER) in a randomized counterbalanced order. Subjects visited the laboratory at 0 hr, 12 hr, and 24 hr for blood and urine sample collection. Total body mass loss was 0.33% (C), 1.88% (FR), 1.97% (ER), and 2.44% (F+ER). Plasma volume was reduced at 24 hr during FR, ER, and F+ER, while serum osmolality was increased at 24 hr for FR and F+ER and was greater at 24 hr for FR compared with all other trials. Negative balances of sodium, potassium, and chloride developed during ER and F+ER but not during C and FR. These results demonstrate that 24 hr fluid and/ or energy restriction significantly reduces body mass and plasma volume, but has a disparate effect on serum osmolality, resulting in hypertonic hypohydration during FR and isotonic hypohydration during ER. These findings might be explained by the difference in electrolyte balance between the trials.
 
To compare dermal electrolyte loss between whole body and regional patch methods in women during 24-h. Dermal loss was collected in 6 healthy women mean age 27 +/- 4 years, while consuming 936 mg/d sodium, 1764 mg/d potassium, 696 mg/d calcium, and 152 mg/d magnesium. Twenty-four hour whole body dermal loss was collected using cotton suits by a washdown procedure. Twenty-four hour patch loss was collected from 8 patches placed on the legs, arms, and back. Dermal loss from whole body was 108 +/- 110 mg/d sodium, 133 +/- 87 mg/d potassium, 103 +/- 22 mg/d calcium, and 35 +/- 13 mg/d magnesium. Electrolyte content from the 8 patches was similar among sites and ranged from 1.01-1.41 mg/d sodium, 0.35-0.83 mg/d potassium, 1.0-1.45 mg/d calcium, and 0.43-0.49 mg/d magnesium. Projections from patches to whole body by the ratio of body surface area appear to overestimate actual whole body losses by 3.2X for sodium and calcium, 3.6X for magnesium, and 1.3X for potassium. Regional patch methods are more appropriate for relative comparisons than for accurately determining total daily dermal electrolyte losses.
 
a) Relationship between %BF 3C and %BF Siri for women (n = 110). (b) Analysis of individual residual %BF scores using the Siri (1961) equation for women. Mean difference (-0.26% BF) represented by solid horizontal line; upper and lower bounds (2.86% BF and-3.38% BF, respectively) for 95%-level agreement represented by dashed lines. %BF indicates percent body fat. 
Physical Characteristics of the Sample 
a) Relationship between %BF 3C and %BF Siri for men (n = 110). (b) Analysis of individual residual %BF scores using the Siri (1961) equation for men. Mean difference (-1.86% BF) represented by solid horizontal line; upper and lower bounds (1.68% BF and-5.40% BF, respectively) for 95%-level agreement represented by dashed lines. %BF indicates percent body fat. 
a) Relationship between %BF 3C and %BF DXA for women (n = 110). (b) Analysis of individual residual %BF scores of women for DXA. Mean difference (-1.60% BF) represented by solid horizontal line; upper and lower bounds (6.52% BF and-9.72% BF, respectively) for 95%-level agreement represented by dashed lines. %BF indicates percent body fat. 
a) Relationship between %BF 3C and %BF DXA for men (n = 110). (b) Analysis of individual residual %BF scores of men for DXA. Mean difference (-2.30% BF) represented by solid horizontal line; upper and lower bounds (5.26% BF and-9.86% BF, respectively) for 95%-level agreement represented by dashed lines. %BF indicates percent body fat. 
The authors used 3-component (3C) Db-mineral-model (Lohman, 1986) reference measures to cross-validate Siri's (1961) 2-component (2C) conversion formula and dual-energy X-ray absorptiometry (DXA) estimates of relative body fat (%BF) for physically active adults. Participants varied in age (18 to 59 y), body fatness, ethnicity (black, Hispanic, white), and physical activity level. The 3C Db-mineral model was used to obtain reference measures of % BF (%BF3C) for comparison with body-composition measures from DXA and hydrodensitometry. For men (n = 110) and women (n= 110), %BF3C (14.0 % BF and 24.4 % BF, respectively) was more accurately estimated by Siri's 2C formula (% FSiri; men, r = 0.97, SEE = 1.77 % BF; women, r = 0.98, SEE = 1.56 % BF) than by DXA (% FDXA; men, r = 0.86, SEE = 3.54 % BF; women, r =0.88, SEE = 3.73 % BF). The average %BFSiri (men, 15.8 % BF; women, 24.7 % BF) and % FDXA (men, 16.2 % BF; women, 26.0 %BF) differed significantly (P < 0.001) from %BF3C. Siri's 2C model estimated the average % BF3C in this sample more accurately than DXA did.
 
-TBARS response to vitamin C supplementation at 75% VO 2max for 30 min. TBARS, thiobarbituric acid reactive substances.
-Protein carbonyls response to vitamin C supplementation at VO 2max for 30 min. * = significant difference compared to rest for same treatment. A, B, C = significantly different compared other exercise treatments.
Characteristics of Subjects
Vitamin C supplementation (VC) (either 500 or 1000 mg/d for 2 wk) was compared to a placebo treatment (P) to ascertain if VC could influence oxidative stress. Twelve healthy males (25 +/- 1.4 y) were randomly assigned in a counter-balanced design with a 2-wk period between treatments. Data were analyzed using repeated measures ANOVA. Exercise intensity measures (VO(2), RER, RPE, HR, lactate) were similar across treatments. Resting blood oxidative-stress markers were unaffected by treatment. Exercise decreased total blood glutathione (TGSH) and reduced glutathione (GSH) and increased oxidized glutathione (GSSG) (P < 0.01) independent of treatment. Protein carbonyls (PC) increased 3.8 fold in the P (P < 0.01). VC attenuated the PC exercise response in a dose-dependent manner ( P < 0.01). Thiobarbituric acid reactive substances (TBARS) was not influenced by exercise (P = 0.68) or VC. These data suggest that VC supplementation can attenuate exercise-induced protein oxidation in a dose-dependent manner with no effect on lipid peroxidation and glutathione status.
 
Attenuation of exercise-induced interleukin-6 (IL-6) responses by carbohydrate (CHO) has been demonstrated in studies comparing controlled doses (> or = 0.9 g x kg(-1) x h(-1)) to placebo, but not in studies of voluntary intake. This study sought to determine if attenuation of the IL-6 response during a 32.2-km mountain trail race occurs for high compared to low ad libitum CHO intakes. IL-6, C-reactive protein (CRP), and creatine kinase activity (CK) were analyzed from blood samples collected 12 h pre-, 0, 4, and 24 h post-race. Subjects were grouped into low (n =14, 0.4 +/- 0.1 g x kg(-1) x h(-1)) and high (n =18, 0.8 +/- 0.2 g x kg(-1) x h(-1)) CHO intake groups. IL-6 0 h post-race (P < 0.05) was higher in the low (40.2 +/- 22.7 pg x mL(-1)) compared to the high CHO group (32.7 +/- 22.1 pg x mL(-1)). CRP and CK both increased post-race, but no differences were observed between groups. Attenuation of exercise-induced IL-6 is apparent across a range of CHO intakes.
 
The aims of this study were to assess the dietary intake and monitor self-reported recovery quality and clinical symptomology of a male ultra-endurance runner who completed a multiday ultra-endurance running challenge covering 4,254 km from North Scotland to the Moroccan Sahara desert over 78 consecutive days. Food and fluid intakes were recorded and analyzed through dietary analysis software. Body mass (BM) was determined before and after running each day, and before sleep. Clinical symptomology and perceived recovery quality were recorded each day. Whole blood hemoglobin and serum ferritin were determined before and after the challenge. Total daily energy (mean ± SD: 23.2 ± 3.2MJ·day-1) and macronutrient intake (182 ± 31g·day-1 protein, 842 ± 115g·day-1 carbohydrate, 159 ± 55 g·day-1 fat) met consensus nutritional guidelines for endurance performance. Total daily water intake through foods and fluids was 4.8 ± 2.0L·day-1. Water and carbohydrate intake rates during running were 239 ± 143ml·h-1 and 56 ± 19g·h-1, respectively. Immediately after running, carbohydrate and protein intakes were 1.3 ± 1.0g·kg BM-1 and 0.4 ± 0.2g·kg BM-1, respectively. Daily micronutrient intakes ranged from 109 to 662% of UK RNIs. Prerunning BM was generally maintained throughout. Overall exercise-induced BM loss averaged 0.8 ± 1.0%; although BM losses of ≥ 2% occurred in the latter stages, a reflection of the warmer climate. Varying degrees of self-reported perceived recovery quality and clinical symptomology occurred throughout the challenge. This case study highlights oscillations in dietary habits along 78 consecutive days of ultra-endurance running, dependent on changes in ambient conditions and course topography. Nevertheless, nutrition and hydration status were maintained throughout the challenge. Despite dietary iron intake above RNI and iron supplementation, this alone did not prevent deficiency symptoms.
 
To examine the effects of a 3-day high carbohydrate (H-CHO) and low carbohydrate (L-CHO) diet on 45 min of cycling exercise, 12 endurance-trained cyclists performed a 45-min cycling exercise at 82 +/- 2% VO2peak following an overnight fast, after a 6-day diet and exercise control. The 7-day protocol was repeated under 2 randomly assigned dietary trials H-CHO and L-CHO. On days 1-3, subjects consumed a mixed diet for both trials and for days 4-6 consumed isocaloric diets that contained either 600 g or 100 g of carbohydrates, for the H-CHO and the L-CHO trials, respectively. Muscle biopsy samples, taken from the vastus lateralis prior to the beginning of the 45-min cycling test, indicated that muscle glycogen levels were significantly higher (p < .05) for the H-CHO trial (104.5 +/- 9.4 mmol/kg wet wt) when compared to the L-CHO trial (72.2 +/- 5.6 mmol/kg wet wt). Heart rate, ratings of perceived exertion, oxygen uptake, and respiratory quotient during exercise were not significantly different between the 2 trials. Serum glucose during exercise for the H-CHO trial significantly increased (p < .05) from 4.5 +/- 0.1 mmol x L(-1) (pre) to 6.7 +/- 0.6 mmol x L(-1) (post), while no changes were found for the L-CHO trial. In addition, post-exercise serum glucose was significantly greater (p < .05) for the H-CHO trial when compared to the L-CHO trial (H-CHO, 6.7 +/- 0.6 mmol x L(-1); L-CHO, 5.2 +/- 0.2 mmol x L(-1)). No significant changes were observed in serum free fatty acid, triglycerides, or insulin concentration in either trial. The findings suggest that L-CHO had no major effect on 45-min cycling exercise that was not observed with H-CHO when the total energy intake was adequate.
 
The aim of this study was to ascertain whether a high carbohydrate diet in the days prior to movement patterns simulating a squash match would increase carbohydrate oxidation during the match, and alter physical performance. Nine New Zealand level squash players were recruited to complete a simulated squash match on two occasions: 1) following a 48 hr high-carbohydrate (11.1g·kg-1); and 2) following a calorie-matched low-carbohydrate (2.1 g·kg-1) diet. The interventions were assigned in a randomised, single-blind, cross-over design. The match simulation was designed to mimic a five-game match lasting approximately one hour. Performance was measured as time to complete each game. Expired respiratory gases and heart rate were continuously collected throughout the trial using a portable gas analysis system. Capillary blood glucose and lactate samples were obtained during a 90 second rest period between each game. Rating of perceived exertion was also recorded after each set. Respiratory exchange ratio was significantly higher during exercise following the high CHO diet (0.80 vs 0.76) p<0.001) and this was associated with significantly faster time to complete the games (2340 ± 189 s vs 2416 ± 128 s, p=0.036). Blood glucose and lactate concentrations were also significantly higher in the high carbohydrate condition (p = 0.038 and p=0.021 respectively). These results suggest that ingestion of a diet high in carbohydrate (>10 g/kg body weight) preceding simulated competitive squash produces increased rates of carbohydrate oxidation and maintains higher blood glucose concentrations. These metabolic effects were associated with improved physical performance.
 
— Schematic of trial events. B-fast = breakfast; NBM = nude body mass. Reprinted with permission from Oliver, Laing, Wilson, Bilzon, Walters, and Walsh (2007). 
— The effects of 48 hr of fluid restriction ( ■ ), energy restriction ( ∆ ), and fluid and energy restriction ( ◆ ) compared with control ( ) and a 30-min treadmill time trial (TT) on (A) circulating lymphocyte cell counts, (B) CD3 + cell counts, and (C) CD4 + cell counts ( × 10 9 /L), M ± SEM , N = 13. a Versus control. b Versus fluid restriction. *Versus 0 hr, p < .05. aa Versus control, bb versus fluid restriction, and **versus 0 hr, p < .01. 
The aim was to investigate the effects of 48 hr of fluid, energy, or combined fluid and energy restriction on circulating leukocyte and lymphocyte subset counts (CD3+, CD4+, and CD8+) and bacterially stimulated neutrophil degranulation at rest and after exercise. Thirteen healthy men (M +/- SEM age 21 +/- 1 yr) participated in 4 randomized 48-hr trials. During control (CON) participants received their estimated energy (2,903 +/- 17 kcal/day) and fluid (3,912 +/- 140 ml/day) requirements. During fluid restriction (FR) they received their energy requirements and 193 +/- 19 ml/day water to drink. During energy restriction (ER) they received their fluid requirements and 290 +/- 6 kcal/day. Fluid and energy restriction (F+ER) was a combination of FR and ER. After 48 hr, participants performed a 30-min treadmill time trial (TT) followed by rehydration (0-2 hr) and refeeding (2-6 hr). Circulating leukocyte and lymphocyte counts remained unchanged for CON and FR. Circulating leukocyte, lymphocyte, CD3+, and CD4+ counts decreased by ~20% in ER and ~30% in F+ER by 48 hr (p < .01), returning to within 0-hr values by 6 hr post-TT. Circulating neutrophil count and degranulation were unaltered by dietary restriction at rest and after TT. In conclusion, a 48-hr period of ER and F+ER, but not FR, decreased circulating leukocyte, lymphocyte, CD3+, and CD4+ counts but not neutrophil count or degranulation. Circulating leukocyte and lymphocyte counts normalized on refeeding. Finally, dietary restriction did not alter circulating leukocyte, lymphocyte, and neutrophil responses to 30 min of maximal exercise.
 
Beta-alanine supplementation has been shown to improve exercise performance in short-term, high-intensity efforts. Purpose The aim of this study was to assess if beta-alanine supplementation could improve 800 m track running performance in male recreational club runners ( n = 18). Methods Participants completed duplicate trials (2 presupplementation, 2 postsupplementation) of an 800 m race, separated by 28 days of either beta-alanine ( n = 9; 80 mg·kg ⁻¹ BM·day ⁻¹ ) or placebo ( n = 9) supplementation. Results Using ANCOVA (presupplementation times as covariate), postsupplementation race times were significantly faster following beta-alanine ( p = .02), with post- versus presupplementation race times being faster after beta-alanine (–3.64 ± 2.70 s, –2.46 ± 1.80%) but not placebo (–0.59 ± 2.54 s, –0.37 ± 1.62%). These improvements were supported by a moderate effect size ( d = 0.70) and a very likely (99%) benefit in the beta-alanine group after supplementation. Split times (ANCOVA) at 400 m were significantly faster ( p = .02) postsupplementation in the beta-alanine group, compared with placebo. This was supported by large effect sizes ( d = 1.05–1.19) and a very likely (99%) benefit at the 400 and 800 m splits when comparing pre- to postsupplementation with beta-alanine. In addition, the first and second halves of the race were faster post- compared with presupplementation following beta-alanine (1st half –1.22 ± 1.81 s, likely 78% chance of benefit; 2nd half –2.38 ± 2.31 s, d = 0.83, very likely 98% chance of benefit). No significant differences between groups or pre- and postsupplementation were observed for postrace blood lactate and pH. Conclusion Overall, 28 days of beta-alanine supplementation (80 mg·kg ⁻¹ BM·day ⁻¹ ) improved 800 m track performance in recreational club runners.
 
Beta-alanine supplementation has been shown to improve exercise performance in short-term, high-intensity efforts. PURPOSE: The aim of this study was to assess if beta-alanine supplementation could improve 800 m track running performance in male recreational club runners (n=18). METHODS: Participants completed duplicate trials (2 pre-supplementation, 2 post-supplementation) of an 800 m race, separated by 28 days of either beta-alanine (n=9; 80 mg·kg-1BM·day-1) or placebo (n=9) supplementation (single blind design). RESULTS: Using ANCOVA (pre-supplementation times as covariate), post-supplementation race times were significantly faster following beta-alanine (p=0.02), with post- versus pre-supplementation race times being faster after beta-alanine (-3.64±2.70 s, -2.46±1.80%), but not placebo (-0.59±2.54 s, -0.37±1.62%). These improvements were supported by a moderate effect size (d=0.70) and a 'very likely' (99%) benefit in the beta-alanine group after supplementation. Split times (ANCOVA) at 400 m were significantly faster (p=0.02) post-supplementation in the beta-alanine group, compared with placebo. This was supported by large effect sizes (d=1.05-1.19) and a 'very likely' (99%) benefit at the 400 and 800 m splits when comparing pre- to post-supplementation with beta-alanine. Additionally, the first and second halves of the race were faster post- compared to pre-supplementation following beta-alanine (1st half -1.22±1.81 s, 'likely' 78% chance of benefit; 2nd half -2.38±2.31 s, d=0.83, 'very likely' 98% chance of benefit). No significant differences between groups or pre- and post-supplementation were observed for post-race blood lactate and pH. CONCLUSION: Overall, 28 days of beta-alanine supplementation (80 mg·kg-1BM·day-1) improved 800 m track performance in recreational club runners.
 
The present study investigated the effect of ingested fluid composition on the experience of exercise-related transient abdominal pain (ETAP). Forty subjects, susceptible to ETAP, completed 4 treadmill exercise trials: a no-fluid trial and flavored water (FW, no carbohydrate, osmolality = 48 mosmol/L, pH = 3.3), sports drink (SD, freshly mixed Gatorade, 6% total carbohydrate, 295 mosmol/L, pH = 3.3), and reconstituted fruit juice (FJ, BERRI trade mark orange, 10.4 % total carbohydrate, 489 mosmol/L, pH= 3.2) trials. Measures of the experience of ETAP and gastrointestinal disturbances, particularly bloating, were quantified. The FJ was significantly (p =.01) more provocative of both ETAP and bloating than all other trials. There was no difference among the no-fluid, FW, and SD in the severity of ETAP experienced, although the difference between the no-fluid and SD approached significance at the.05 level (p =.056). There was a significant relationship between both the mean (r = 0.40, p =.01) and peak (r= 0.44, p=.01) levels of ETAP and bloating. When the level of bloating was controlled for, the FJ remained significantly (p =.01) more provocative of ETAP than the other conditions, with no difference between the FW and SD (p =.37). The results indicate that in order to avoid ETAP, susceptible individuals should refrain from consuming reconstituted fruit juices and beverages similarly high in carbohydrate content and osmolality, shortly before and during exercise. Further, the mechanism responsible for the heightened experience of ETAP in the FJ trial extends beyond a gastric mass explanation.
 
In order to study weight concerns and eating disorders in women tennis players, 107 women tennis players and 26 women's tennis coaches from colleges across the U.S. responded to questionnaires relating to weight concern, body image, and abnormal eating. When evaluating drawings of female figures, players and coaches both considered the ideal body shape to be smaller than the healthiest one. Most players had normal weight, eating habits, and self-esteem; however, they also exhibited noticeable concern about their weight and appearance. Coaches revealed only moderate knowledge of weight related issues, believed such knowledge to be important, recognized that most of their players were of normal weight, and revealed somewhat negative feelings about overweight people. Players and coaches shared a healthy attitude toward tennis. The results of this study do not imply that college women tennis players are at greater risk of eating disorders than other young women, nor that college coaches are encouraging abnormal eating behaviors
 
Changes in body composition and metabolism have been a central feature of HIV infection from the outset--initially, as the wasting syndrome and, more recently, as metabolic and body fat redistribution syndromes associated with antiretroviral (ARV) therapy. Here, advances in physiologic and biochemical understanding of these conditions are reviewed. First, the pathophysiology of wasting in HIV-1 infection is discussed, focusing on the failure of nutrients to increase lean tissue ("anabolic block") and the role of hypogonadism. Results of anabolic interventions, including recombinant growth hormone, testosterone, and progressive resistance exercise, are presented. Next, ARV-associated disorders are reviewed, including lipoatrophy and an hypothesized "mitochondrial toxicity." The possibility of establishing pathogenesis in vivo in humans, by direct measurement of mitochondrial DNA synthesis and adipocyte proliferation, is discussed. In summary, important advances have occurred toward the goal of explaining body composition and metabolic abnormalities associated with HIV disease.
 
Athletes have traditionally been evaluated for body composition by percent fat, percent muscle, and somatotype. Since the late 1980s, dual X-ray absorptiometry (DXA) has offered total and regional body composition of bone mineral content (BMC), lean tissue and fat, but studies involving athletes are rare (11) and have not included regional tissue distribution. In the present study, DXA was used to compare a total of 121 male subjects belonging to 9 different athletic groups and controls. ANOVA showed total tissue percent BMC, lean tissue, and fat were significantly different between the various athletic groups (p <.001). Regional differences in tissue distribution between different athletic groups affect BMC and lean tissue (p <.001), but not fat (p >.05). However, athletes of the leanest groups had different fat distribution to that of nonexercising controls (p <.01). It appears that fat distribution is nonspecific in its response to exercise, while lean and BMC distributions show highly specific adaptations to specific sports.
 
– Positioning protocol for dual-energy X-ray absorptiometry. 
— Calculations of sums of partial scans to estimate whole-body composition. 
— Comparison between scans for estimating (A) head derived from head scan or whole scan, (B) body derived from whole scan or body scan, (C) body derived from whole scan or the addition of right body from right scan and left body from left scan, and (D) body from body scan or the addition of right body from right scan and left body from left scan. 
Dual-energy X-ray absorptiometry (DXA) is becoming a popular tool to measure body composition, owing to its ease of operation and comprehensive analysis. However, some people, especially athletes, are taller and/or broader than the active scanning area of the DXA bed and must be scanned in sections. The aim of this study was to investigate the reliability of DXA measures of whole-body composition summed from 2 or 3 partial scans. Physically active young adults (15 women, 15 men) underwent 1 whole-body and 4 partial DXA scans in a single testing session under standardized conditions. The partial scanning areas were head, whole body from the bottom of the chin down, and right and left sides of the body. Body-composition estimates from whole body were compared with estimates from summed partial scans to simulate different techniques to accommodate tall and/or broad subjects relative to the whole-body scan. Magnitudes of differences in the estimates were assessed by standardization. In simulating tall subjects, summation of partial scans that included the head scan overestimated whole-body composition by ~3 kg of lean mass and ~1 kg of fat mass, with substantial technical error of measurement. In simulating broad subjects, summation of right and left body scans produced no substantial differences in body composition than those of the whole-body scan. Summing partial DXA scans provides accurate body-composition estimates for broad subjects, but other strategies are needed to accommodate tall subjects.
 
— Correlation between relative volume of fluid administered during glycerol- induced hyperhydration and the relative fluid retention provided by glycerol-induced hy- perhydration. N = 22 studies. 
— Difference in fluid retention between glycerol-induced-hyperhydration proto- cols using glycerol boluses or not. Results are M ± SEM . N = 22 studies. 
— Correlation between the elapsed time between end of ingestion of the fluid- glycerol load and the onset of exercise and the relative retention of fluid provided by the glycerol-induced hyperhydration. N = 17 studies. 
Glycerol-induced hyperhydration (GIH) has been shown to improve fluid retention and endurance performance compared with water-induced hyperhydration. The goal of this article is to report on what is known and unknown about how glycerol-containing hyperhydration solutions (GCHSs) are processed at the stomach and intestine level, propose strategies to improve the efficacy of GIH, and provide research questions for future studies. Through statistical analyses, it is demonstrated that the effectiveness of GCHSs in increasing fluid retention is maximized when fluid ingestion is in the upper range of what is normally administered by studies (~26 ml/kg body weight) and the duration of the protocol is no longer than the time it takes for the glycerol-fluid load to be totally or nearly completely integrated inside the body. The rate of gastric emptying and intestinal absorption of GCHSs is unknown. However, based on an analysis of indirect evidence obtained from human studies, it is proposed that most glycerol (~80 g) and fluid (~1,700 ml) ingested during a typical GIH protocol can be integrated inside the body within 60-90 min. Whether the stress associated with competition could alter these figures is unknown. Research in rats indicates that combining glycerol with glucose at a 3:1 ratio accelerates intestinal absorption of both glycerol and water, thereby potentially improving the efficacy of GIH. Human studies must be conducted to determine how GCHSs are processed by the gastrointestinal system and whether adding glucose to GCHSs could improve the technique's efficacy.
 
The small intestine acts as interface and regulator between the gut lumen and the rest of the body and controls the degree and rate of transport of amino acids coming from dietary protein via the portal vein to the liver and the systemic circulation. To measure protein absorption, kinetics multicatheter animal (pig) models in combination with amino acid tracer technology are available. Dietary factors influence the absorption rates from the lumen to the gut, metabolism of dietary component in the gut, and the release of amino acids to the portal circulation from digested protein. In a balanced-protein meal, the gut dietary amino acid utilization (30-50%) for gut protein synthesis will result in a labile protein pool in the gut that can be beneficial during the postabsorptive state. To enhance gut retention, amount and quality of protein and the presence of carbohydrate are major factors. Besides this the use of a slowly digestible protein or the presence of fiber in the meal can increase retention further. During the absorption of low-quality protein meals, fewer amino acids are utilized by the gut, resulting in higher amounts of amino acid release to the portal circulation. Malnutrition or starvation, protein depletion, deficiencies of specific nutrients, or illness such as sepsis all inhibit the growth and change protein turnover of the intestinal mucosa and therefore affect absorption kinetics. Therefore, the kind of protein meal that has the most optimal absorption kinetics (the most beneficial) for gut and for the rest of the body depends on these (patho)physiological circumstances. Despite the absence of different absorption kinetics between protein, peptides, and amino acids, they could be beneficial in specific circumstances.
 
The purpose of this study was to determine if lowering carbohydrate (CHO) concentration in a sport drink influences gastric emptying, intestinal absorption, or performance during cycle ergometry (85 min, 60% VO(2peak)). Five subjects (25 +/- 1 y, 61.5 +/- 2.1 mL . kg(-1) . min(-1) VO(2peak)) ingested a 3% CHO, 6% CHO, or a water placebo (WP) beverage during exercise. Gastric emptying was determined by repeated double sampling and intestinal absorption by segmental perfusion. Total solute absorption and plasma glucose was greater for 6% CHO; however, neither gastric emptying, intestinal water absorption, or 3-mi time trial performance (7:58 +/- 0:33 min, 8:13 +/- 0:25 min, and 8:25 +/- 0:29 min, respectively, for 6% CHO, 3% CHO, and WP) differed among solutions. These results indicate lowering the CHO concentration of a sport drink from 6% CHO does not enhance gastric emptying, intestinal water absorption, or time trial performance, but reduces CHO and total solute absorption.
 
Isotonic sports drinks are often consumed to offset the effects of dehydration and improve endurance performance, but hypotonic drinks may be more advantageous. The purpose of the study was to compare absorption and effects on performance of a commercially available hypotonic sports drink (Mizone Rapid: 3.9% carbohydrate [CHO], 218 mOsmol/kg) with those of an isotonic drink (PowerAde: 7.6% CHO, 281 mOsmol/ kg), a hypertonic drink (Gatorade: 6% CHO, 327 mOsmol/kg), and a noncaloric placebo (8 mOsmol/kg). In a crossover, 11 cyclists consumed each drink on separate days at 250 ml/15 min during a 2-hr preload ride at 55% peak power followed by an incremental test to exhaustion. Small to moderate increases in deuterium oxide enrichment in the preload were observed with Mizone Rapid relative to PowerAde, Gatorade, and placebo (differences of 88, 45, and 42 parts per million, respectively; 90% confidence limits ±28). Serum osmolality was moderately lower with Mizone Rapid than with PowerAde and Gatorade (-1.9, -2.4; mOsmol/L; ±1.2 mOsmol/L) but not clearly different vs. placebo. Plasma volume reduction was small to moderate with Mizone Rapid, PowerAde, and Gatorade relative to placebo (-1.9%, -2.5%, -2.9%; ± 2.5%). Gut comfort was highest with Mizone Rapid but clearly different (8.4% ± 4.8%) only vs PowerAde. Peak power was highest with Mizone Rapid (380 W) vs. placebo and other drinks (1.2-3.0%; 99% confidence limits ±4.7%), but differences were inconclusive with reference to the smallest important effect (~1.2%). The outcomes are consistent with fastest fluid absorption with the hypotonic sports drink. Further research should determine whether the effect has a meaningful impact on performance.
 
The purpose of this study is to summarize water, carbohydrate (CHO), and electrolyte absorption from carbohydrate-electrolyte (CHO-E) solutions based on all of the triple-lumen-perfusion studies in humans since the early 1960s. The current statistical analysis included 30 reports from which were obtained information on water absorption, CHO absorption, total solute absorption, CHO concentration, CHO type, osmolality, sodium concentration, and sodium absorption in the different gut segments during exercise and at rest. Mean differences were assessed using independent-samples t tests. Exploratory multiple-regression analyses were conducted to create prediction models for intestinal water absorption. The factors influencing water and solute absorption are carefully evaluated and extensively discussed. The authors suggest that in the human proximal small intestine, water absorption is related to both total solute and CHO absorption; osmolality exerts various impacts on water absorption in the different segments; the multiple types of CHO in the ingested CHO-E solutions play a critical role in stimulating CHO, sodium, total solute, and water absorption; CHO concentration is negatively related to water absorption; and exercise may result in greater water absorption than rest. A potential regression model for predicting water absorption is also proposed for future research and practical application. In conclusion, water absorption in the human small intestine is influenced by osmolality, solute absorption, and the anatomical structures of gut segments. Multiple types of CHO in a CHO-E solution facilitate water absorption by stimulating CHO and solute absorption and lowering osmolality in the intestinal lumen.
 
The purpose of this study was to determine the effects of exercise intensity on active and passive intestinal glucose absorption. Eight trained runners (age = 23 +/- 2 y; VO2max = 62.1 +/- 5.8 mL x kg(-1) x min(-1)) performed a 1 h resting experiment and three 1 h treadmill experiments at 30, 50, or 70% VO2max in a thermoneutral environment. Immediately prior to each experiment, euhydrated subjects ingested a solution containing two non-metabolizable glucose analogs, 3-O-methyl-D-glucose (3MG; actively absorbed; 5 g) and D-xylose (passively absorbed; 5 g). During the following 5 h, all urine was collected and the amount of 3MG and D-xylose in the urine was determined. Using repeated measures ANOVA, a significant (P < 0.05) reduction in urinary excretion of each carbohydrate was observed at 70% VO2max compared to the other intensities suggesting that both active and passive intestinal absorption of glucose may be reduced during prolonged running at this intensity.
 
Insulin resistance (IR) is a common pathophysiological feature of Type 2 diabetes. Although the mechanisms leading to IR are still elusive, evidence has shown that aerobic exercise can reverse this process. To investigate the effects of aerobic exercise on IR, the authors created an IR animal model by feeding C57BL/6 mice a high-fat diet for 8 wk. They then compared the effect of 6 wk of treadmill training (60 min/d) at 75% VO2max on mice in normal-diet (NE) and high-fat-diet (HE) groups with their sedentary control groups. Levels of skeletal-muscle AMPKα (AMP-activated protein kinase α), ACC (acetyl-CoA carboxylases), and CPT1 (carnitine palmitoyltransferase 1) mRNA and AMPKα, pAMPK-Thr172, ACC, pACC-Ser79, and CPT1 protein expressions were analyzed. In addition, fasting serum levels of insulin, triglyceride, and cholesterol were measured. The results demonstrate that 6 wk of exercise increased AMPKα mRNA expression by 11% and 25 % (p<.01) in the NE and HE groups, respectively, and AMPKα protein expression by 37.9% and 20.1% (p<.01) in NE and HE compared with their sedentary control. In addition, ACC mRNA and protein expressions declined, whereas CPT1 mRNA and protein expressions were elevated in both exercise groups compared with sedentary control groups. In addition, pAMPK-Thr172 and pACC-Ser79 expression increased significantly in the NE and HE groups compared with sedentary control groups. In conclusion, our results demonstrate that 6 wk of aerobic exercise can effectively ameliorate IR by increasing the expression of AMPKα and pAMPK-Thr172, thereby activating the key enzymes that facilitate lipid metabolism.
 
– Experimental session variables 
It has been shown that water intake (WI) improves post-exercise parasympathetic recovery after moderate-intensity exercise session. However, the potential cardiovascular benefit promoted by WI has not been investigated after high-intensity exercise. To assess the effects of WI on post-high-intensity parasympathetic recovery. Twelve recreationally active young men participated in the study (22 ± 1.4 years, 24.1 ± 1.6 kg.m-2). The experimental protocol consisted of two visits to the laboratory. Each visit consisted in the completion of a 30-min high-intensity [~80% of maximal heart rate (HR)] cycle ergometer aerobic session performing randomly the WI or control (CON, no water consumption) intervention at the end of the exercise. RR intervals (RRi) were continuously recorded by a heart rate monitor before, during and after the exercise. Differences in HR recovery [e.g., absolute heart rate decrement after 1 min of recovery (HRR60s) and time-constant of the first order exponential fitting curve of the HRR (HRRτ)] and in post-exercise vagal-related HRV indexes (rMSSD30s, rMSSD, pNN50, SD1 and HF) were calculated and compared for WI and CON. A similar HR recovery and an increased post-exercise HRV [SD1 = 9.4 ± 5.9 vs. 6.0 ± 3.9 ms, HF(ln) = 3.6 ± 1.4 vs. 2.4 ± 1.3 ms2, for WI and CON, respectively; p < 0.05] was observed in WI compared to CON. The results suggest that WI accelerates the post-exercise parasympathetic reactivation after high-intensity exercise. Such outcome reveals an important cardioprotective effect of WI.
 
There is a growing need to accurately assess exercise energy expenditure (EEE) in athletic populations that may be at risk for health disorders because of an imbalance between energy intake and energy expenditure. The Actiheart combines heart rate and uniaxial accelerometry to estimate energy expenditure above rest. The authors' purpose was to determine the utility of the Actiheart for predicting EEE in female adolescent runners (N = 39, age 15.7 ± 1.1 yr). EEE was measured by indirect calorimetry and predicted by the Actiheart during three 8-min stages of treadmill running at individualized velocities corresponding to each runner's training, including recovery, tempo, and 5-km-race pace. Repeated-measures ANOVA with Bonferroni post hoc comparisons across the 3 running stages indicated that the Actiheart was sensitive to changes in intensity (p < .01), but accelerometer output tended to plateau at race pace. Pairwise comparisons of the mean difference between Actiheart- and criterion-measured EEE yielded values of 0.0436, 0.0539, and 0.0753 kcal × kg-1 × min-1 during recovery, tempo, and race pace, respectively (p < .0001). Bland-Altman plots indicated that the Actiheart consistently underestimated EEE except in 1 runner's recovery bout. A linear mixed-model regression analysis with height as a covariate provided an improved EEE prediction model, with the overall standard error of the estimate for the 3 speeds reduced to 0.0101 kcal × kg-1 × min-1. Using the manufacturer's equation that combines heart rate and uniaxial motion, the Actiheart may have limited use in accurately assessing EEE, and therefore energy availability, in young, female competitive runners.
 
Top-cited authors
Louise Mary Burke
  • Australian Institute of Sport (AIS)
Luc J C van Loon
  • Maastricht University
Naomi M Cermak
  • Maastricht University
James P Morton
  • Liverpool John Moores University
Graeme Close
  • Liverpool John Moores University