Joint Position Statement: nutrition and athletic performance. American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada

Resistance training reduces whole-body protein turnover and improves net protein retention in untrained young males

It is thought that resistance exercise results in an increased need for dietary protein; however, data also exists to support the opposite conclusion. The purpose of this study was to determine the impact of resistance exercise training on protein metabolism in novices with the hypothesis that resistance training would reduce protein turnover and improve whole-body protein retention. Healthy males (n = 8, 22 +/- 1 y, BMI = 25.3 +/- 1.8 kg.m(-2)) participated in a progressive whole-body split routine resistance-training program 5d/week for 12 weeks. Before (PRE) and after (POST) the training, oral [15N]-glycine ingestion was used to assess nitrogen flux (Q), protein synthesis (PS), protein breakdown (PB), and net protein balance (NPB = PS-PB). Macronutrient intake was controlled over a 5d period PRE and POST, while estimates of protein turnover and urinary nitrogen balance (N(bal) = N(in) - urine N(out)) were conducted. Bench press and leg press increased 40% and 50%, respectively (p < 0.01). Fat- and bone-free mass (i.e., lean muscle mass) increased from PRE to POST (2.5 +/- 0.8 kg, p < 0.05). Significant PRE to POST decreases (p <0.05) occurred in Q (0.9 +/- 0.1 vs. 0.6 +/- 0.1 g N.kg(-1).d(-1)), PS (4.6 +/- 0.7 vs. 2.9 +/- 0.3 g.kg(-1).d(-1)), and PB (4.3 +/- 0.7 vs. 2.4 +/- 0.2 g.kg(-1).d(-1)). Significant training-induced increases in both NPB (PRE = 0.22 +/- 0.13 g.kg(-1).d(-1); POST = 0.54 +/- 0.08 g.kg(-1).d(-1)) and urinary nitrogen balance (PRE = 2.8 +/- 1.7 g N.d(-1); POST = 6.5 +/- 0.9 g N.d(-1)) were observed. A program of resistance training that induced significant muscle hypertrophy resulted in reductions of both whole-body PS and PB, but an improved NPB, which favoured the accretion of skeletal muscle protein. Urinary nitrogen balance increased after training. The reduction in PS and PB and a higher NPB in combination with an increased nitrogen balance after training suggest that dietary requirements for protein in novice resistance-trained athletes are not higher, but lower, after resistance training.

Carbohydrate supplementation during prolonged cycling exercise spares muscle glycogen but does not affect intramyocellular lipid use

Using contemporary stable-isotope methodology and fluorescence microscopy, we assessed the impact of carbohydrate supplementation on whole-body and fiber-type-specific intramyocellular triacylglycerol (IMTG) and glycogen use during prolonged endurance exercise. Ten endurance-trained male subjects were studied twice during 3 h of cycling at 63 +/- 4% of maximal O(2) uptake with either glucose ingestion (CHO trial; 0.7 g CHO kg(-1) h(-1)) or without (CON placebo trial; water only). Continuous infusions with [U-(13)C] palmitate and [6,6-(2)H(2)] glucose were applied to quantify plasma free fatty acids (FFA) and glucose oxidation rates and to estimate intramyocellular lipid and glycogen use. Before and after exercise, muscle biopsy samples were taken to quantify fiber-type-specific IMTG and glycogen content. Plasma glucose rate of appearance (R (a)) and carbohydrate oxidation rates were substantially greater in the CHO vs CON trial. Carbohydrate supplementation resulted in a lower muscle glycogen use during the first hour of exercise in the CHO vs CON trial, resulting in a 38 +/- 19 and 57 +/- 22% decreased utilization in type I and II muscle-fiber glycogen content, respectively. In the CHO trial, both plasma FFA R (a) and subsequent plasma FFA concentrations were lower, resulting in a 34 +/- 12% reduction in plasma FFA oxidation rates during exercise (P < 0.05). Carbohydrate intake did not augment IMTG utilization, as fluorescence microscopy revealed a 76 +/- 21 and 78 +/- 22% reduction in type I muscle-fiber lipid content in the CHO and CON trial, respectively. We conclude that carbohydrate supplementation during prolonged cycling exercise does not modulate IMTG use but spares muscle glycogen use during the initial stages of exercise in endurance-trained men.

Assessment of hydration status by urinary analysis of elite junior taekwon-do athletes in preparing for competition

The aim of this study was to assess over time the hydration status of taekwon-do athletes during a preparatory camp. Measures of urine osmolality, conductivity, specific gravity and colour were made on the first urine sample passed by the participants (n = 32) in the morning before breakfast. The urinary measurements were made on samples collected at the beginning of the camp, 5 days later and one day before competition. Body mass was also measured at the same instants. Body mass (mean +/- s) was essentially the same on each of the measurement days (62.6 +/- 12.2, 62.7 +/- 12.3 and 62.2 +/- 12.6 kg, respectively). Mean urine osmolality at the beginning of the camp was relatively high (998 +/- 171 mOsmol . kg-1), suggesting that a significant number of the athletes were already hypohydrated. However, no significant differences were detected in urine osmolality at the three time points during the study. There were no significant differences in any of the four methods of urine analysis during the study (P > 0.05). The average values for all samples were 989 +/- 205 mOsmol . kg-1 for osmolality, 25.5 +/- 6.7 mS . cm-1 for conductivity, 1.017 +/- 0.010 g . cm-3 for specific gravity and 4 +/- 1 arbitrary units for colour. Correlation analysis between the different methods suggested moderately good agreement (correlation coefficient = 0.5-0.7) between all four measurement techniques (P < 0.01). The coefficients of variation for these techniques were relatively low (CV = 11.8 - 35.0%). The results of this study suggest that some of the taekwon-do athletes were slightly hypohydrated in the morning on each of the test days, but there was no evidence to suggest that most of the athletes further restricted their fluid intake to make weight. In addition, it appears that each of the four methods used gave essentially the same estimate of hydration status of these athletes.

Effect of protein intake on strength, body composition and endocrine changes in strength/power athletes

Comparison of protein intakes on strength, body composition and hormonal changes were examined in 23 experienced collegiate strength/power athletes participating in a 12-week resistance training program. Subjects were stratified into three groups depending upon their daily consumption of protein; below recommended levels (BL; 1.0 - 1.4 g.kg-1.day-1; n = 8), recommended levels (RL; 1.6 - 1.8 g.kg-1.day-1; n = 7) and above recommended levels (AL; > 2.0 g.kg-1.day-1; n = 8). Subjects were assessed for strength [one-repetition maximum (1-RM) bench press and squat] and body composition. Resting blood samples were analyzed for total testosterone, cortisol, growth hormone, and insulin-like growth factor. No differences were seen in energy intake (3,171 +/- 577 kcal) between the groups, and the energy intake for all groups were also below the recommended levels for strength/power athletes. No significant changes were seen in body mass, lean body mass or fat mass in any group. Significant improvements in 1-RM bench press and 1-RM squat were seen in all three groups, however no differences between the groups were observed. Subjects in AL experienced a 22% and 42% greater change in Delta 1-RM squat and Delta 1-RM bench press than subjects in RL, however these differences were not significant. No significant changes were seen in any of the resting hormonal concentrations. The results of this study do not provide support for protein intakes greater than recommended levels in collegiate strength/power athletes for body composition improvements, or alterations in resting hormonal concentrations.

Diagnóstico do estado nutricional dos atletas da Equipe Olímpica Permanente de Levantamento de Peso do Comitê Olímpico Brasileiro (COB)

Objetivou-se neste estudo diagnosticar o estado nutricional da Equipe Olímpica Permanente de Levantamento de Peso do Comitê Olímpico Brasileiro (COB). A amostra foi composta por 24 atletas, na faixa etária entre 16 e 23 anos, sendo 12 do sexo masculino (19,7 ± 2,4 anos) e 12 do feminino (19,2 ± 1,8 ano). Realizou-se o seguinte procedimento para o diagnóstico do estado nutricional: análise da adequação da ingestão de energia e dos macronutrientes - carboidratos (CHO), lipídios (LIP) e proteínas (PRO) -, por meio dos métodos Recordatório de 24 horas e Questionário de Freqüência de Consumo Alimentar, além da caracterização do perfil antropométrico. Os resultados da avaliação dietética indicaram que a distribuição energética entre os macronutrientes encontra-se adequada sendo de 54 ± 6,8% (CHO); 28,5 ± 5,9% (LIP); e 14,5 ± 3,4% (PRO) para os homens e 56,3 ± 4,7% (CHO); 28,6 ± 4,6% (LIP); e 13,7 ± 2,4% (PRO) para a equipe feminina. Entretanto, quanto ao consumo energético total, 83% dos atletas estavam com ingestão energética abaixo dos valores recomendados, considerando o alto nível de atividade física, promovendo deficiência calórica diária. O percentual de gordura corporal dos atletas do sexo masculino (3,6 ± 0,7%) indicou que todos estavam abaixo do padrão de referência, enquanto 58% dos esportistas do sexo feminino apresentavam excesso de gordura (17,9 ± 5,8%). Tem-se, como conclusão, que, apesar de os desportistas avaliados terem realizado distribuição energética adequada entre os macronutrientes, esta ainda não foi suficiente para suprir as exigências energéticas da modalidade, necessitando assim de orientação nutricional.

Zinco no plasma e eritrócito de atletas profissionais de uma equipe feminina brasileira de voleibol

OBJETIVO: Avaliar o estado nutricional relativo ao zinco de 12 atletas profissionais do voleibol feminino. MÉTODOS: Determinou-se a concentração de zinco plasmático e eritrocitário por espectrofotometria de absorção atômica, e avaliou-se a ingestão dietética por meio de registro alimentar de três dias, de 12 atletas profissionais do sexo feminino, integrantes de uma equipe de voleibol de Curitiba, PR, na faixa etária de 18 a 24 anos, no ano de 2003. RESULTADOS: Todas as atletas apresentaram valores normais de zinco plasmático. Quanto ao zinco eritrocitário, 100,00% apresentaram valores abaixo da normalidade. Em relação à ingestão dietética de zinco, 83,33% apresentaram adequação. Decréscimos no conteúdo de zinco eritrocitário podem representar o efeito agudo de exercícios prolongados pela utilização enzimática da superóxido dismutase ou anidrase carbônica. CONCLUSÃO: O estado nutricional das atletas relativo ao zinco parece estar inadequado, pois, apesar dos valores normais para a concentração de zinco plasmático, a concentração eritrocitária esteve abaixo da faixa de normalidade para todas as atletas.

[Volume and electrolyte disturbances in endurance sport]

Long-lasting endurance exercise is associated with significant losses of fluid and sodium chloride, mainly due to sweat loss. To maintain endurance capacity and to avoid negative health consequences, endurance athletes should, therefore, drink fluids containing electrolytes during and after training or competition. In long-lasting endurance exercise it is recommended that athletes drink about 600-800 ml/h of fluid including adequate substitution of sodium. The excessive ingestion of fluid, however, brings about a danger of hyponatremia, which can be avoided by suitable measures. Body weight control is one of the parameters that should be carefully monitored before and after intensive endurance exercise.

Dietas vegetarianas e desempenho esportivo

As evidências atuais apontam benefícios da dieta vegetariana para a saúde humana. Contudo, a partir da adoção de práticas vegetarianas mais restritivas, confirmam-se os riscos à saúde. As dietas vegetarianas são caracterizadas pelo elevado consumo de carboidratos, fibras, magnésio, potássio, folato e antioxidantes, podendo apresentar deficiências em aminoácidos e ácidos graxos essenciais, cálcio, zinco, ferro e cobalamina. Pesquisas experimentais em humanos indicam que vegetarianos e não-vegetarianos apresentam capacidade aeróbica semelhante. Em relação ao desempenho em atividades de força e potência muscular, as pesquisas são escassas, mas as existentes não apontam diferenças significativas. Situações de risco cardiovascular têm sido confirmadas, devido ao provável quadro de hiperhomocisteinemia, em decorrência da baixa ingestão de cobalamina. As dietas vegetarianas são isentas de creatina, o que resulta em estoques musculares mais baixos nessa população. Possivelmente ocorrem alterações hormonais e metabólicas em resposta às dietas vegetarianas, como baixos níveis de testosterona e androstenediona. A função imune parece não ser prejudicada. Dessa forma, a prática de dietas vegetarianas apresenta-se compatível com a prática esportiva cotidiana, desde que bem planejada para evitar deficiências nutricionais.

Failure of Protein to Improve Time Trial Performance when Added to a Sports Drink

INTRODUCTION

Recent studies have reported that adding approximately 2% protein to a carbohydrate sports drink increased cycle endurance capacity compared with carbohydrate alone. However, the practical implications of these studies work are hampered by the following limitations: (a) the rate of carbohydrate ingestion was less than what is considered optimal for endurance performance, and (b) the performance test (exercise time to fatigue) did not mimic the way in which athletes typically compete (i.e., a race in which a fixed distance or set amount of work is performed as quickly as possible).

PURPOSE

We tested the hypothesis that adding 2% protein to a 6% carbohydrate drink (CHO-PRO) would improve 80-km cycling time trial performance, as compared with a 6% carbohydrate drink (CHO) and a nonenergetic sweetened placebo (PLAC).

METHODS

Ten trained male cyclists (24 +/- 2 yr; VO2peak = 63 +/- 2 mL.kg(-1).min(-1); mean +/- SE) performed an 80-km laboratory time trial (TT) on three occasions separated by 7 d. In a double-blind crossover manner, subjects ingested CHO-PRO, CHO, or PLAC at a rate of 250 mL every 15 min with no temporal, verbal, or physiological feedback.

RESULTS

Time to complete the TT was 4.4% lower (P < 0.002) during CHO (135 +/- 9 min) and CHO-PRO (135 +/- 9) compared with PLAC (141 +/- 10), with no difference between CHO and CHO-PRO (P = 0.92).

CONCLUSION

Ingesting 6% carbohydrate at a rate of 1 L.h(-1) (60 g.h(-1)) improved an 80-km TT performance in trained male cyclists. However, adding 2% protein to a 6% carbohydrate drink provided no additional performance benefit during a task that closely simulated the manner in which athletes typically compete.

Nutritional strategies for football: Counteracting heat, cold, high altitude, and jet lag

Environmental factors often influence the physical and mental performance of football players. Heat, cold, high altitude, and travel across time zones (i.e. leading to jet lag) act as stressors that alter normal physiological function, homeostasis, metabolism, and whole-body nutrient balance. Rather than accepting performance decrements as inevitable, well-informed coaches and players should plan strategies for training and competition that offset environmental challenges. Considering the strength of scientific evidence, this paper reviews recommendations regarding nutritional interventions that purportedly counterbalance dehydration, hyperthermia, hypothermia, hypoxia, acute or chronic substrate deficiencies, sleep loss, and desynchronization of internal biological clocks.

Substrate utilization during prolonged exercise with ingestion of 13C-glucose in acute hypobaric hypoxia (4,300 m)

Energy substrate oxidation was measured using indirect respiratory calorimetry combined with tracer technique in five healthy young male subjects, during a 80-min exercise period on ergocycle with ingestion of 140 g of (13)C-labelled glucose, in normoxia and acute hypobaric hypoxia (445 mmHg or 4,300 m), at the same relative [77% V(.-)((O)(2)(max))] and absolute workload (161+/-8 W, corresponding to 77 and 54% V(.-)((O)(2)(max)) in hypoxia and normoxia). The oxidation rate of exogenous glucose was not significantly different in the three experimental situations: 21.4+/-2.9, 20.2+/-1.2 and 17.2+/-0.6 g over the last 40 min of exercise at approximately 77 and approximately 54% V(.-)((O)(2)(max)) in normoxia and in hypoxia, respectively, providing 12.5+/-1.5, 16.8+/-1.1 and 14.9+/-1.1% of the energy yield, although ingestion of glucose during exercise resulted in a higher plasma glucose concentration in hypoxia than normoxia. The contribution of carbohydrate (CHO) oxidation to the energy yield was significantly higher in hypoxia (92.0+/-2.1%) than in normoxia for both a given absolute (75.3+/-5.2%) and relative workload (78.1+/-1.8%). This greater reliance on CHO oxidation in hypoxia was entirely due to the significantly larger contribution of endogenous glucose oxidation to the energy yield: 75.9+/-1.7% versus 66.6+/-3.3 and 55.2+/-3.7% in normoxia at the same relative and absolute workload.

Core temperature and hydration status during an Ironman triathlon

BACKGROUND

Numerous laboratory based studies have documented that aggressive hydration strategies (approximately 1-2 litres/h) are required to minimise a rise in core temperature and minimise the deleterious effects of hyperthermia on performance. However, field data on the relations between hydration level, core body temperature, and performance are rare.

OBJECTIVE

To measure core temperature (Tcore) in triathletes during a 226 km Ironman triathlon, and to compare Tcore with markers of hydration status after the event.

METHOD

Before and immediately after the 2004 Ironman Western Australia event (mean (SD) ambient temperature 23.3 (1.9) degrees C (range 19-26 degrees C) and 60 (14)% relative humidity (44-87%)) body mass, plasma concentrations of sodium ([Na+]), potassium ([K+]), and chloride ([Cl-]), and urine specific gravity were measured in 10 well trained triathletes. Tcore was measured intermittently during the event using an ingestible pill telemetry system, and heart rate was measured throughout.

RESULTS

Mean (SD) performance time in the Ironman triathlon was 611 (49) minutes; heart rate was 143 (9) beats/min (83 (6)% of maximum) and Tcore was 38.1 (0.3) degrees C. Body mass significantly declined during the race by 2.3 (1.2) kg (-3.0 (1.5)%; p < 0.05), whereas urine specific gravity significantly increased (1.011 (0.005) to 1.0170 (0.008) g/ml; p < 0.05) and plasma [Na+], [K+], and [Cl-] did not change. Changes in body mass were not related to finishing Tcore (r = -0.16), plasma [Na+] (r = 0.31), or urine specific gravity (r = -0.37).

CONCLUSION

In contrast with previous laboratory based studies examining the influence of hypohydration on performance, a body mass loss of up to 3% was found to be tolerated by well trained triathletes during an Ironman competition in warm conditions without any evidence of thermoregulatory failure.

Medication and supplement use by athletes

Athletes are affected in various ways by medications and supplements. Physicians caring for athletes need to be aware of medicines that athletes are taking and how they may interact with performance, exercise, environment, and other medicines. Athletes may attempt to gain a performance advantage with the use of a variety of dietary supplements and performance enhancers. Physicians must be knowledgeable of these so that athletes are properly educated about potential benefits and risks and physical effects. This article first reviews common medicines that athletes use and their potential efficacy and interactions with exercise and environment, then reviews dietary supplements and the data on their efficacy for performance enhancement. Finally, current and future doping issues are discussed.

Level of dietary protein impacts whole body protein turnover in trained males at rest

The current investigation examined the effect of variations in protein intake on Whole body protein turnover (WBPTO) at rest in endurance-trained males. Whole body protein turnover is influenced by both diet and exercise. Whether endurance athletes require more protein than the non-exerciser remains equivocal. Five male runners (21.3 +/- 0.3 years, 179 +/- 2 cm, 70.6 +/- 0.1 kg, 8.7% +/- 0.4% body fat, 70.6 +/- 0.1 VO(2)max) participated in a randomized, crossover design diet intervention where they consumed either a low-protein (LP; 0.8 g/kg), moderate-protein (MP; 1.8 g/kg), or high-protein (HP; 3.6 g/kg) diet for 3 weeks. Whole body protein turnover (Ra, leucine rate of appearance; NOLD, nonoxidative leucine disposal; and Ox, leucine oxidation), nitrogen balance, and substrate oxidation were assessed at rest following each dietary intervention period. The HP diet increased leucine Ra (indicator of protein breakdown; 136.7 +/- 9.3, 129.1 +/- 7.4, and 107.8 +/- 3.1 micromol/[kg . h] for HP, MP, and LP diets, respectively) and leucine Ox (31.0 +/- 3.6, 26.2 +/- 4.3, and 18.3 +/- 0.6 micromol/[kg . h] for HP, MP, and LP diets, respectively) compared with LP diet (P < .05). No differences were noted in nonoxidative leucine disposal (an indicator of protein synthesis) across diets. Nitrogen balance was greater for HP diet than for MP and LP diets (10.2 +/- 0.7, 1.8 +/- 0.6, and -0.3 +/- 0.5 for HP, MP, and LP diets, respectively). Protein oxidation increased with increasing protein intake (54% +/- 6%, 25% +/- 1%, and 14% +/- 2% for HP, MP, and LP diets, respectively). Findings from this study show that variations in protein intake can modulate WBPTO and that protein intake approximating the current recommended dietary allowance was not sufficient to achieve nitrogen balance in the endurance-trained males in this investigation. Our results suggest that a protein intake of 1.2 g/kg or 10% of total energy intake is needed to achieve a positive nitrogen balance. This is not a concern for most endurance athletes who routinely consume protein at or above this level.

Carbohydrate supplementation improves time-trial cycle performance during energy deficit at 4,300-m altitude

Carbohydrate supplementation (CHOS) typically improves prolonged time-trial (TT) performance at sea level (SL). This study determined whether CHOS also improves TT performance at high altitude (ALT; 4,300 M) despite increased hypoxemia and while in negative energy balance (∼1,250 kcal/day). Two groups of fasting, fitness-matched men performed a 720-kJ cycle TT at SL and while living at ALT on days 3 (ALT3) and 10 (ALT10). Eight men drank a 10% carbohydrate solution (0.175 g/kg body wt) and eight drank a placebo (PLA; double blind) at the start of and every 15 min of the TT. Blood glucose during each TT was higher ( P < 0.05) for CHOS than for PLA. At SL, TT duration (∼59 min) and watts (∼218 or ∼61% of peak watts; %SL Wpeak) were similar for both groups. At ALT, the TT was longer for both groups ( P < 0.01) but was shorter for CHOS than for PLA on ALT3 (means ± SE: 80 ± 7 vs. 105 ± 9 min; P < 0.01) and ALT10 (77 ± 7 vs. 90 ± 5 min; P < 0.01). At ALT, %SL Wpeak was reduced ( P < 0.01) with the reduction on ALT3 being larger for PLA (to 33 ± 3%) than for CHOS (to 43 ± 2%; P < 0.05). On ALT3, O2 saturation fell similarly from 84 ± 2% at rest to 73 ± 1% during the TT for both groups ( P < 0.05), and on ALT10 O2 saturation fell more ( P < 0.02) for CHOS (91 ± 1 to 76 ± 2%) than for PLA (90 ± 1 to 81 ± 1%). %SL Wpeak and O2 saturation were inversely related during the TT for both groups at ALT ( r ≥ −0.76; P ≤ 0.03). It was concluded that, despite hypoxemia exacerbated by exercise, CHOS greatly improved TT performance at ALT in which there was a negative energy balance.

Calcium Requirements for the Athlete

There is oftentimes a notion of "the more, the better" with regard to vitamin and mineral intake among individuals, and especially among athletes. Although adequate calcium intake is necessary to promote bone health and prevent osteoporosis, increased physical activity alone does not necessarily demand an increased intake of dietary calcium or other micronutrients. Athletes may lose calcium via sweat, in which case replenishment is advocated either via dietary intake of calcium-rich foods or a commercial calcium supplement. The important message to athletes is to consume a diet adequate in energy, protein, fat, vitamins, minerals, and fluids to support the physical demands and replenish the physiologic losses incurred with physical training.

Early identification and interventions for female athlete triad

The diagnosis of female athlete triad is based on three criteria: (a) disordered eating, (b) amenorrhea, and (c) osteopenia. Prevention involves increasing awareness of this problem in athletes, parents, and coaches. Routine and opportunistic screening for risk factors by health care providers will increase early detection in athletes. Appropriate evaluation and treatment will decrease the consequences of this disorder. Consequences include stress fractures, development of eating disorders, and lower peak bone mass resulting in increased risk of osteoporosis later in life. A primary care case manager who provides motivation and support along with a multidisciplinary approach to treatment is recommended. This approach includes nutritional, exercise, and psychological therapies and possibly supplements and medication for optimal results.

Exercise, nutrition and you: an off-campus course for grades 2-12

Since interest in science classes has declined recently and obesity, especially in youth, continues to increase, an exercise physiology-based course was taught in public parks to promote active-learning science and healthy living. The course emphasized and integrated exercise, nutrition, and health during a 3-h session. Following an introduction, five hands-on laboratory-based student modules were performed. Students performed respiratory, cardiovascular, temperature regulation, energy expenditure, oxygen uptake, and exercise modules. During most modules, the students made measurements at rest and during the performance of exercise at different intensities. The students were very involved and engaged in problem solving throughout the session. The program was given for 10 days to more than 500 students representing 18 classes from 10 different schools. Evaluations indicated that the program was a real-life science experience that gave the students a new understanding of how their bodies worked and the purpose of exercise. The students and teachers also experienced "school learning" put into action as the program fit well with their science curriculum.

Use of intramuscular triacylglycerol as a substrate source during exercise in humans

Fat and carbohydrate are the principal substrates that fuel aerobic ATP synthesis in skeletal muscle. Most endogenous fat is stored as triacylglycerol in subcutaneous and deep visceral adipose tissue. Smaller quantities of triacylglycerol are deposited as lipid droplets inside skeletal muscle fibers. The potential role of intramyocellular triacylglycerol (IMTG) as a substrate source during exercise in humans has recently regained much of its interest because of the proposed functional relationship between IMTG accumulation and the development of skeletal muscle insulin resistance. Exercise likely represents an effective means to prevent excess IMTG accretion by stimulating its rate of oxidation. However, there is much controversy on the actual contribution of the IMTG pool as a substrate source during exercise. The apparent discrepancy in the literature likely stems from methodological difficulties that have been associated with the methods used to estimate IMTG oxidation during exercise. However, recent studies using stable isotope methodology, 1H-magnetic resonance spectroscopy, and electron and/or immunofluorescence microscopy all support the contention that the IMTG pool can function as an important substrate source during exercise. Although more research is warranted, IMTG mobilization and/or oxidation during exercise seem to be largely determined by exercise intensity, exercise duration, macronutrient composition of the diet, training status, gender, and/or age. In addition, indirect evidence suggests that the capacity to mobilize and/or oxidize IMTG is substantially impaired in an obese and/or Type 2 diabetic state. As we now become aware that skeletal muscle has an enormous capacity to oxidize IMTG stores during exercise, more research is warranted to develop combined exercise, nutritional, and/or pharmacological interventions to effectively stimulate IMTG oxidation in sedentary, obese, and/or Type 2 diabetes patients.

Nutritional considerations for the older athlete

In this review article, nutritional considerations of the aging athlete are discussed. The focuses of the review include energy, carbohydrate, protein, selected vitamins and minerals, and fluids. Age-associated changes in body composition, resting energy expenditure, and volume and intensity of training, may decrease the need for dietary energy and the intakes of macro- and micronutrients and fluids. The older athlete should monitor nutrient intakes to insure adequacy, especially regarding carbohydrate to promote glucose storage and use as an energy source during exercise, and protein to promote strength-training-induced muscle hypertrophy. Emphasis should also be placed on the dietary intakes of certain micronutrients, as well as the potential need for supplementation of certain vitamins and minerals, including the vitamins B(2), B(6), B(12), D, E, and folate, and the minerals calcium and iron. Age-associated changes in thermoregulation and an increased susceptibility to dehydration underscore the critical importance to the older athlete of adequate fluid intake to sustain health and performance. Nutrition is a tool that the older athlete should use to enhance exercise performance and health.

Carbohydrate intake during exercise and performance

It is generally accepted that carbohydrate (CHO) feeding during exercise can improve endurance capacity (time to exhaustion) and exercise performance during prolonged exercise (>2 h). More recently, studies have also shown ergogenic effects of CHO feeding during shorter exercise of high intensity ( approximately 1 h at >75% of maximum oxygen consumption). During prolonged exercise the mechanism behind this performance improvement is likely to be related to maintenance of high rates of CHO oxidation and the prevention of hypoglycemia. Nevertheless, other mechanisms may play a role, depending on the type of exercise and the specific conditions. The mechanism for performance improvements during higher-intensity exercise is less clear, but there is some evidence that CHO can have central effects. In the past few years, studies have investigated ways to optimize CHO delivery and bioavailability. An analysis of all studies available shows that a single CHO ingested during exercise will be oxidized at rates up to about 1 g/min, even when large amounts of CHO are ingested. Combinations of CHO that use different intestinal transporters for absorption (e.g., glucose and fructose) have been shown to result in higher oxidation rates, and this seems to be a way to increase exogenous CHO oxidation rates by 20% to 50%. The search will continue for ways to further improve CHO delivery and to improve the oxidation efficiency resulting in less accumulation of CHO in the gastrointestinal tract and potentially decreasing gastrointestinal problems during prolonged exercise.

Anorexia athletica

In many sports, athletes with low body weight have a distinct advantage over their opponents; however, this advantage can easily turn into a noticeable disadvantage because low body weight may also be associated with health problems. The present review focuses on the problem of anorexia athletica, with its emphasis on leanness and thinness in female and male sports athletes. Athletes often restrict calories and/or overexercise to achieve or maintain low body and fat masses. There is a growing body of evidence that several metabolic and endocrine disturbances are the result of prolonged energy restriction. However, the long-term outcome of such sport-related disordered eating has not been thoroughly studied. Effective methods of treatment are scarce and similar to treatment of eating disorders. Scientific studies are needed that help establish alternative regulations for sports in which a low body weight is a primary advantage for performance.

Nutrient intake and performance during a mountain marathon: an observational study

In order to study nutrient intake of amateur runners during a mountain marathon, compliance with recommendations, and association with performance, an intake of 42 participants in a Swiss mountain marathon was assessed by direct observation. Data on demographics, dietary preparation and race experience were obtained by questionnaires. Anthropometrical measures were performed before and after the race. Mean hourly intakes (SD) of fluid, carbohydrate, energy and sodium were 545 (158) ml, 31 (14) g, 141 (63) kcal [or 590 (264) kJ], and 150 (203) mg respectively. A third of the runners drank 600 ml h(-1) or more, 52% consumed less than 30 g h(-1 )carbohydrates, 95% consumed less than 500 mg h(-1) sodium. Mean weight loss was 4 (1.5) kg; 30 runners (71%) lost over 3% body mass. Mean running time was 7 h 3 min (1 h 17 min). Most participants failed to meet nutritional recommendations. None were at risk of overhydration. Body composition and race experience were correlated with performance, but not nutrient intake. Because experienced runners are well trained, fitter, and know better their personal needs during such a race, it is difficult to disentangle these associations. As causal relationship cannot be proven with this cross-sectional design, non-compliance with intake recommendations requires additional experimental research on the impact of nutrient intake on field performance.

Physical activity: the health benefits outweigh the risks

PURPOSE OF REVIEW

This article will summarize the current findings on the effects of physical activity on human health and well-being.

RECENT FINDINGS

Physical activity is associated with enhanced health and reduced risk of all-cause mortality such as cardiovascular disease, hypertension, type 2 diabetes, obesity, osteoporosis, sarcopenia, cognitive disorders, and some forms of cancer. Nevertheless, the effects of exercise with respect to potential health consequences are complex. When untrained or previously sedentary persons undertake vigorous exertion suddenly, the undesired side effects of injuries, dehydration or cardiac arrest are amplified.

SUMMARY

It is reasonable to conclude that the risk exposure through physical activity is outweighed by its overall benefits, and health authorities strongly encourage participation in moderate intensity physical activity on a daily basis. In the future, the identification and characterization of particularly inactive sub-groups of the population may facilitate and optimize the planning of public health interventions.

Recommendations for treatment of hyponatraemia at endurance events

This review focuses on possible pathophysiology of exercise-associated hyponatraemia and its implication on evaluation and treatment of collapsed athletes during endurance events. Rehydration guidelines and field care have traditionally been based on the belief that endurance events create a state of significant fluid deficit in athletes, which must be corrected by liberal hydration. Beliefs in the necessity of liberal hydration may have contributed to cases of hyponatraemia. Assumptions that fluid loss accounts for the entire weight loss during exercise and that fluid ingestion is the only source of water gain during exercise may lead to an overestimation of the degree of volume depletion and the amount of fluid needed for replacement. Increasing evidence suggests that hyponatraemic athletes are fluid overloaded; ingestion of large amount of hypotonic fluid in combination with inappropriate or inadequate physiological responses leads to excessive retention of free fluid. Risk factors include hot weather, female sex, slower finishing time, and possibly the use of nonsteroidal anti-inflammatory medications. Symptoms of hyponatraemia can be subtle and can mimic those of other exercise-related illnesses, thereby complicating its diagnosis and leading to possible inappropriate treatment. Most athletes who collapse at the finish line experience exercise-associated collapse, a benign and transient form of postural hypotension that can be treated simply by continued ambulation after finishing or elevation of legs while in a supine position for those who cannot walk. Care providers should consider the use of intravenous hydration with normal saline carefully since it is not needed by most collapsed athletes and may worsen the condition of patients with unsuspected hyponatraemia. Historic information and clinical signs of volume depletion should be elicited prior to its use. Most hyponatraemic athletes will recover uneventfully with careful observation while awaiting spontaneous diuresis. Use of hypertonic saline should be reserved for patients with severe symptoms. Moderate consumption of carbohydrate-electrolyte solution during exercise may allow the maintenance of adequate hydration and the prevention of hyponatraemia.

Protein requirements for endurance athletes

Acute endurance exercise results in the oxidation of several amino acids. The total amount of amino acid oxidation during endurance exercise amounts to only 1-6% of the total energy cost of exercise. The branched chain amino acid, leucine, has been most often studied in relation to endurance exercise. Leucine is oxidized by the enzyme, branched-chain oxo-acid dehydrogenase (BCOAD). BCOAD is relatively inactive at rest ( approximately 4-7%) and is activated at the onset of exercise by dephosphorylation (to about 25%). After a period of endurance exercise training, the activation of BCOAD and amino acid oxidation are attenuated, however the total amount of BCOAD enzyme is up-regulated. A low energy and/or carbohydrate intake will increase amino acid oxidation and total protein requirements. With adequate energy and carbohydrate intake, low to moderate intensity endurance activity has little impact on dietary protein requirements and 1.0 gPRO/kg/d is sufficient. The only situation where dietary protein requirements exceed those for relatively sedentary individuals is in top sport athletes where the maximal requirement is approximately 1.6 gPRO/kg/d. Although most endurance athletes get enough protein to support any increased requirements, those with low energy or carbohydrate intakes may require nutritional advice to optimize dietary protein intake.

Protein requirements and supplementation in strength sports

Daily requirements for protein are set by the amount of amino acids that is irreversibly lost in a given day. Different agencies have set requirement levels for daily protein intakes for the general population; however, the question of whether strength-trained athletes require more protein than the general population is one that is difficult to answer. At a cellular level, an increased requirement for protein in strength-trained athletes might arise due to the extra protein required to support muscle protein accretion through elevated protein synthesis. Alternatively, an increased requirement for protein may come about in this group of athletes due to increased catabolic loss of amino acids associated with strength-training activities. A review of studies that have examined the protein requirements of strength-trained athletes, using nitrogen balance methodology, has shown a modest increase in requirements in this group. At the same time, several studies have shown that strength training, consistent with the anabolic stimulus for protein synthesis it provides, actually increases the efficiency of use of protein, which reduces dietary protein requirements. Various studies have shown that strength-trained athletes habitually consume protein intakes higher than required. A positive energy balance is required for anabolism, so a requirement for "extra" protein over and above normal values also appears not to be a critical issue for competitive athletes because most would have to be in positive energy balance to compete effectively. At present there is no evidence to suggest that supplements are required for optimal muscle growth or strength gain. Strength-trained athletes should consume protein consistent with general population guidelines, or 12% to 15% of energy from protein.

Carbohydrates and fat for training and recovery

An important goal of the athlete's everyday diet is to provide the muscle with substrates to fuel the training programme that will achieve optimal adaptation for performance enhancements. In reviewing the scientific literature on post-exercise glycogen storage since 1991, the following guidelines for the training diet are proposed. Athletes should aim to achieve carbohydrate intakes to meet the fuel requirements of their training programme and to optimize restoration of muscle glycogen stores between workouts. General recommendations can be provided, preferably in terms of grams of carbohydrate per kilogram of the athlete's body mass, but should be fine-tuned with individual consideration of total energy needs, specific training needs and feedback from training performance. It is valuable to choose nutrient-rich carbohydrate foods and to add other foods to recovery meals and snacks to provide a good source of protein and other nutrients. These nutrients may assist in other recovery processes and, in the case of protein, may promote additional glycogen recovery when carbohydrate intake is suboptimal or when frequent snacking is not possible. When the period between exercise sessions is < 8 h, the athlete should begin carbohydrate intake as soon as practical after the first workout to maximize the effective recovery time between sessions. There may be some advantages in meeting carbohydrate intake targets as a series of snacks during the early recovery phase, but during longer recovery periods (24 h) the athlete should organize the pattern and timing of carbohydrate-rich meals and snacks according to what is practical and comfortable for their individual situation. Carbohydrate-rich foods with a moderate to high glycaemic index provide a readily available source of carbohydrate for muscle glycogen synthesis, and should be the major carbohydrate choices in recovery meals. Although there is new interest in the recovery of intramuscular triglyceride stores between training sessions, there is no evidence that diets which are high in fat and restricted in carbohydrate enhance training.

Meat‐Adaptive Genes and the Evolution of Slower Aging in Humans

The chimpanzee life span is shorter than that of humans, which is consistent with a faster schedule of aging. We consider aspects of diet that may have selected for genes that allowed the evolution of longer human life spans with slower aging. Diet has changed remarkably during human evolution. All direct human ancestors are believed to have been largely herbivorous. Chimpanzees eat more meat than other great apes, but in captivity are sensitive to hypercholesterolemia and vascular disease. We argue that this dietary shift to increased regular consumption of fatty animal tissues in the course of hominid evolution was mediated by selection for "meat-adaptive" genes. This selection conferred resistance to disease risks associated with meat eating also increased life expectancy. One candidate gene is apolipoprotein E (apoE), with the E3 allele evolved in the genus Homo that reduces the risks for Alzheimer's and vascular disease, as well as influencing inflammation, infection, and neuronal growth. Other evolved genes mediate lipid metabolism and host defense. The timing of the evolution of apoE and other candidates for meat-adaptive genes is discussed in relation to key events in human evolution.

Popular sports supplements and ergogenic aids

This article reviews the evidence-based ergogenic potential and adverse effects of 14 of the most common products in use by recreational and elite athletes today. Both legal and prohibited products are discussed. This is an aggressively marketed and controversial area of sports medicine worldwide. It is therefore prudent for the clinician to be well versed in the more popular supplements and drugs reputed to be ergogenic in order to distinguish fact from fiction.Antioxidants, proteins and amino acids are essential components of diet, but additional oral supplementation does not increase endurance or strength. Caffeine is ergogenic in certain aerobic activities. Creatine is ergogenic in repetitive anaerobic cycling sprints but not running or swimming. Ephedrine and pseudoephedrine may be ergogenic but have detrimental cardiovascular effects. Erythropoietin is ergogenic but increases the risk of thromboembolic events. beta-Hydroxy-beta-methylbutyrate has ergogenic potential in untrained individuals, but studies are needed on trained individuals. Human growth hormone and insulin growth factor-I decrease body fat and may increase lean muscle mass when given subcutaneously. Pyruvate is not ergogenic. The androgenic precursors androstenedione and dehydroepiandrosterone have not been shown to increase any parameters of strength and have potentially significant adverse effects. Anabolic steroids increase protein synthesis and muscle mass but with many adverse effects, some irreversible. Supplement claims on labels of product content and efficacy can be inaccurate and misleading.

Creatine supplementation and athletic performance

Nutritional supplements and other ergogenic aids have gained widespread use among professional, amateur, recreational, and student athletes for their potential to enhance athletic performance and provide a competitive edge. Creatine monohydrate is one of the more commonly used and potentially beneficial supplements that currently is viewed to be safe. Supplementation with oral creatine augments skeletal muscle creatine concentrations in most individuals, which has been shown to promote gains in lean body mass when used in conjunction with resistance training, to enhance power and strength, and to improve performance in intense exercise, especially during repeated bouts. Young athletes, however, must be cautious about taking creatine because its effects on growth and development are unknown and long-term safety has not been established. Variability in research study designs and small sample sizes have left many questions unanswered regarding the safety and efficacy of chronic supplementation. This is an active area of clinical investigation and the results of ongoing and future research should guide the appropriate use of creatine to enhance athletic performance among athletes of all ages.

Methodology of dietary assessment in athletes: concepts and pitfalls

PURPOSE OF REVIEW

Evaluation of an athlete's diet is important in both clinical practice and research. The main purpose of this review is to provide health professionals with guidance regarding the special issues that are likely to be encountered when assessing the dietary intake of sportspersons.

RECENT FINDINGS

A number of methods may be used for the dietary assessment of individuals and/or groups of athletes, including retrospective (diet recall, food-frequency questionnaire, and diet history) and prospective (diet record, duplicate portion) techniques. A 3-4-day estimated diet record is the most widely used approach, but collection of single or multiple diet recalls is also common. Care must be taken, however, to ensure that days of diet monitoring accurately reflect usual food consumption during the period of interest. Under-reporting of habitual energy intake is widespread among athletes, and its magnitude should be carefully addressed when interpreting the results of dietary assessment. Other issues, specifically related to sportspersons, that are often neglected include adequacy of standard portion sizes, frequency of snacking, fluid intake, supplement use, weight-control practices, and seasonality of sport activities and food consumption.

SUMMARY

There are subtle methodological differences in the dietary assessment of athletes and non-athletes, which, when taken into consideration, may substantially increase the quality of intake data and optimise the outcome of dietary intervention.

Atividade física e gestação: saúde da gestante não atleta e crescimento fetal

São reconhecidos os benefícios da prática de atividade física sobre o ciclo vital, sem consenso quanto à gestação. Este artigo reviu considerações e efeitos da prática da atividade física durante a gestação sobre a saúde da gestante não-atleta e o feto. Foram utilizados os bancos de dados Medline e Pubmed referentes ao período 1992-2002. Dentre os benefícios, os artigos destacam: prevenção e redução de lombalgias, de dores das mãos e pés e estresse cardiovascular, fortalecimento da musculatura pélvica, redução de partos prematuros e cesáreas, maior flexibilidade e tolerância à dor, controle do ganho ponderal e elevação da auto-estima da gestante. No feto, observou-se aumento do peso ao nascer e melhoria da condição nutricional. Não se encontraram recomendações de necessidades nutricionais para a gestante não-atleta. Não existiu consenso quanto às necessidades nutricionais e o tipo de atividade física dessa gestante, sendo o exercício na água o mais indicado. Porém destacaram-se diversas contra-indicações da prática de exercícios na gestação. Concluiu-se que a atividade física, sendo regular, moderada e controlada desde o início da gestação, promove benefícios para a saúde materna e fetal.

Hydration testing of athletes

Dehydration not only reduces athletic performance, but also places athletes at risk of health problems and even death. For athletes, monitoring hydration has significant value in maximising performance during training and competition. It also offers medical personnel the opportunity to reduce health risks in situations where athletes engage in intentional weight loss. Simple non-invasive techniques, including weight monitoring and urine tests, can provide useful information. Bioimpedance methods tend to be easy to use and fairly inexpensive, but generally lack the precision and accuracy necessary for hydration monitoring. Blood tests appear to be the most accurate monitoring method, but are impractical because of cost and invasiveness. Although future research is needed to determine which hydration tests are the most accurate, we encourage sports teams to develop and implement hydration monitoring protocols based on the currently available methods. Medical personnel can use this information to maximise their team's athletic performance and minimise heat- and dehydration-related health risks to athletes.

Planning strategies for development of effective exercise and nutrition countermeasures for long-duration space flight

Exercise and nutrition represent primary countermeasures used during space flight to maintain or restore maximal aerobic capacity, musculoskeletal structure, and orthostatic function. However, no single exercise, dietary regimen, or combination of prescriptions has proven entirely effective in maintaining or restoring cardiovascular and musculoskeletal functions to preflight levels after prolonged space flight. As human space flight exposures increase in duration, identification, assessment, and development of various effective exercise- and nutrition-based protective procedures will become paramount. The application of adequate dietary intake in combination with effective exercise prescription will be based on identification of basic physiologic stimuli that maintain normal function in terrestrial gravity, and understanding how specific combinations of exercise characteristics (e.g., duration, frequency, intensity, and mode) can be combined with minimal nutritional requirements that mimic the stimuli normally produced by living in Earth's gravity environment. This can be accomplished only with greater emphasis of research on ground-based experiments targeted at understanding the interactions between caloric intake and expenditure during space flight. Future strategies for application of nutrition and exercise countermeasures for long-duration space missions must be directed to minimizing crew time and the impact on life-support resources.

Effect of different protocols of caffeine intake on metabolism and endurance performance

Competitive athletes completed two studies of 2-h steady-state (SS) cycling at 70% peak O(2) uptake followed by 7 kJ/kg time trial (TT) with carbohydrate (CHO) intake before (2 g/kg) and during (6% CHO drink) exercise. In Study A, 12 subjects received either 6 mg/kg caffeine 1 h preexercise (Precaf), 6 x 1 mg/kg caffeine every 20 min throughout SS (Durcaf), 2 x 5 ml/kg Coca-Cola between 100 and 120 min SS and during TT (Coke), or placebo. Improvements in TT were as follows: Precaf, 3.4% (0.2-6.5%, 95% confidence interval); Durcaf, 3.1% (-0.1-6.5%); and Coke, 3.1% (-0.2-6.2%). In Study B, eight subjects received 3 x 5 ml/kg of different cola drinks during the last 40 min of SS and TT: decaffeinated, 6% CHO (control); caffeinated, 6% CHO; decaffeinated, 11% CHO; and caffeinated, 11% CHO (Coke). Coke enhanced TT by 3.3% (0.8-5.9%), with all trials showing 2.2% TT enhancement (0.5-3.8%; P < 0.05) due to caffeine. Overall, 1) 6 mg/kg caffeine enhanced TT performance independent of timing of intake and 2) replacing sports drink with Coca-Cola during the latter stages of exercise was equally effective in enhancing endurance performance, primarily due to low intake of caffeine (approximately 1.5 mg/kg).

Effects of short-term fat adaptation on metabolism and performance of prolonged exercise

The concept of manipulating an individuals habitual diet before an exercise bout in an attempt to modify patterns of fuel substrate utilization and enhance subsequent exercise capacity is not new. Modern studies have focused on nutritional and training strategies aimed to optimize endogenous carbohydrate (CHO) stores while simultaneously maximizing the capacity for fat oxidation during continuous, submaximal (60-70% of maximal O(2) uptake [(.)VO(2max)] exercise. Such "nutritional periodization" typically encompasses 5-6 d of a high-fat diet (60-70% E) followed by 1-2 d of high-CHO intake (70-80% E; CHO restoration). Despite the brevity of the adaptation period, ingestion of a high-fat diet by endurance-trained athletes results in substantially higher rates of fat oxidation and concomitant muscle glycogen sparing during submaximal exercise compared with an isoenergetic high-CHO diet. Higher rates of fat oxidation during exercise persist even under conditions in which CHO availability is increased, either by having athletes consume a high-CHO meal before exercise and/or ingest glucose solutions during exercise. Yet, despite marked changes in the patterns of fuel utilization that favor fat oxidation, fat-adaptation/CHO restoration strategies do not provide clear benefits to the performance of prolonged endurance exercise.

What are the dietary protein requirements of physically active individuals? New evidence on the effects of exercise on protein utilization during post-exercise recovery

Exercise and physical activity increase energy expenditure up to 10-fold. This brief review will focus on the effect of exercise on protein requirements. Evidence has accumulated that amino acids are oxidized as substrates during prolonged submaximal exercise. In addition, studies have determined that both endurance and resistance training exercise increase skeletal muscle protein synthesis and breakdown in the post-exercise recovery period. Studies using nitrogen balance have further confirmed that protein requirements for individuals engaged in regular exercise are increased. The current recommended intakes of protein for strength and endurance athletes are 1.6 to 1.7 g/kg and 1.2 to 1.4 g/kg per day, respectively. Presently, most athletes consume an adequate amount of protein in their diet. The timing and nutritional content of the post-exercise meal, although often overlooked, are known to have synergistic effects on protein accretion after exercise. New evidence suggests that individuals engaging in strenuous activity consume a meal rich in amino acids and carbohydrate soon after the exercise bout or training session.

Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability

PURPOSE

Five days of a high-fat diet produce metabolic adaptations that increase the rate of fat oxidation during prolonged exercise. We investigated whether enhanced rates of fat oxidation during submaximal exercise after 5 d of a high-fat diet would persist in the face of increased carbohydrate (CHO) availability before and during exercise.

METHODS

Eight well-trained subjects consumed either a high-CHO (9.3 g x kg(-1) x d(-1) CHO, 1.1 g x kg(-1) x d(-1) fat; HCHO) or an isoenergetic high-fat diet (2.5 g x kg(-1) x d(-1) CHO, 4.3 g x kg(-1) x d(-1) fat; FAT-adapt) for 5 d followed by a high-CHO diet and rest on day 6. On day 7, performance testing (2 h steady-state (SS) cycling at 70% peak O(2) uptake [VO(2peak)] + time trial [TT]) of 7 kJ x kg(-1)) was undertaken after a CHO breakfast (CHO 2 g x kg(-1)) and intake of CHO during cycling (0.8 g x kg(-1) x h(-1)).

RESULTS

FAT-adapt reduced respiratory exchange ratio (RER) values before and during cycling at 70% VO(2peak); RER was restored by 1 d CHO and CHO intake during cycling (0.90 +/- 0.01, 0.80 +/- 0.01, 0.91 +/- 0.01, for days 1, 6, and 7, respectively). RER values were higher with HCHO (0.90 +/- 0.01, 0.88 +/- 0.01 (HCHO > FAT-adapt, P < 0.05), 0.95 +/- 0.01 (HCHO > FAT-adapt, P < 0.05)). On day 7, fat oxidation remained elevated (73 +/- 4 g vs 45 +/- 3 g, P < 0.05), whereas CHO oxidation was reduced (354 +/- 11 g vs 419 +/- 13 g, P < 0.05) throughout SS in FAT-adapt versus HCHO. TT performance was similar for both trials (25.53 +/- 0.67 min vs 25.45 +/- 0.96 min, NS).

CONCLUSION

Adaptations to a short-term high-fat diet persisted in the face of high CHO availability before and during exercise, but failed to confer a performance advantage during a TT lasting approximately 25 min undertaken after 2 h of submaximal cycling.