Sports dietitians Australia position statement : sports nutrition for the adolescent athlete

It is the position of Sports Dietitians Australia (SDA) that adolescent athletes have unique nutritional requirements as a consequence of undertaking daily training and competition in addition to the demands of growth and development. As such, SDA established an expert multidisciplinary panel to undertake an independent review of the relevant scientific evidence and consulted with its professional members to develop sports nutrition recommendations for active and competitive adolescent athletes. The position of SDA is that dietary education and recommendations for these adolescent athletes should reinforce eating for long term health. More specifically, the adolescent athlete should be encouraged to moderate eating patterns to reflect daily exercise demands and provide a regular spread of high quality carbohydrate and protein sources over the day, especially in the period immediately after training. SDA recommends that consideration also be given to the dietary calcium, Vitamin D and iron intake of adolescent athletes due to the elevated risk of deficiency of these nutrients. In order to maintain optimal hydration, adolescent athletes should have access to fluids that are clean, cool and supplied in sufficient quantities before, during and after participation in sport. Finally, it is the position of SDA that use of nutrient needs should be met by core foods rather than supplements, as the recommendation of dietary supplements to developing athletes over-emphasises their ability to manipulate performance in comparison to other training and dietary strategies.

Antioxidants in Athlete's Basic Nutrition: Considerations towards a Guideline for the Intake of Vitamin C and Vitamin E

Antioxidants in acute physical exercise and exercise training remain a hot topic in sport nutrition, exercise physiology and biology, in general (Jackson, 2008; Margaritis and Rousseau, 2008; Gomez-Cabrera et al., 2012; Nikolaidis et al., 2012). During the past few decades, antioxidants have received attention predominantly as a nutritional strategy for preventing or minimising detrimental effects of reactive oxygen and nitrogen species (RONS), which are generated during and after strenuous exercise (Jackson, 2008, 2009; Powers and Jackson, 2008). Antioxidant supplementation has become a common practice among athletes as a means to (theoretically) reduce oxidative stress, promote recovery and enhance performance (Peternelj and Coombes, 2011). However, until now, requirements of antioxidant micronutrients and antioxidant compounds for athletes training for and competing in different sport events, including marathon running, triathlon races or team sport events involving repeated sprinting, have not been determined sufficiently (Williams et al., 2006; Margaritis and Rousseau, 2008). Crucially, evidence has been emerging that higher dosages of antioxidants may not necessarily be beneficial in this context, but can also elicit detrimental effects by interfering with performance-enhancing (Gomez-Cabrera et al., 2008) and health-promoting training adaptations (Ristow et al., 2009). As originally postulated in a pioneering study on exercise-induced production of RONS by Davies et al. (1982) in the early 1980s, evidence has been increasing in recent years that RONS are not only damaging agents, but also act as signalling molecules for regulating muscle function (Reid, 2001; Jackson, 2008) and for initiating adaptive responses to exercise (Jackson, 2009; Powers et al., 2010). The recognition that antioxidants could, vice versa, interact with the signalling pathways underlying the responses to acute (and repeated) bouts of exercise has contributed important novel aspects to the continued discussion on antioxidant requirements for athletes. In view of the recent advances in this field, it is the aim of this report to examine the current knowledge of antioxidants, in particular of vitamins C and E, in the basic nutrition of athletes. While overviews on related topics including basic mechanisms of exercise-induced oxidative stress, redox biology, antioxidant defence systems and a summary of studies on antioxidant supplementation during exercise training are provided, this does not mean that this report is comprehensive. Several issues of the expanding and multidisciplinary field of antioxidants and exercise are covered elsewhere in this book and/or in the literature. Exemplarily, the reader is referred to reviews on oxidative stress (Konig et al., 2001; Vollaard et al., 2005; Knez et al., 2006; Powers and Jackson, 2008; Nikolaidis et al., 2012), redox-sensitive signalling and muscle function (Reid, 2001; Vollaard et al., 2005; Jackson, 2008; Ji, 2008; Powers and Jackson, 2008; Powers et al., 2010; Radak et al., 2013) and antioxidant supplementation (Williams et al., 2006; Peake et al., 2007; Peternelj and Coombes, 2011) in the context with exercise. Within the scope of the report, we rather aim to address the question regarding requirements of antioxidants, specifically vitamins C and E, during exercise training, draw conclusions and provide practical implications from the recent research.

Methods of body-mass reduction by combat sport athletes

The aim of this study was to investigate the methods adopted to reduce body mass (BM) in competitive athletes from the grappling (judo, jujitsu) and striking (karate and tae kwon do) combat sports in the state of Minas Gerais, Brazil. An exploratory methodology was employed through descriptive research, using a standardized questionnaire with objective questions self-administered to 580 athletes (25.0 +/- 3.7 yr, 74.5 +/- 9.7 kg, and 16.4% +/- 5.1% body fat). Regardless of the sport, 60% of the athletes reported using a method of rapid weight loss (RWL) through increased energy expenditure. Strikers tend to begin reducing BM during adolescence. Furthermore, 50% of the sample used saunas and plastic clothing, and only 26.1% received advice from a nutritionist. The authors conclude that a high percentage of athletes uses RWL methods. In addition, a high percentage of athletes uses unapproved or prohibited methods such as diuretics, saunas, and plastic clothing. The age at which combat sport athletes reduce BM for the first time is also worrying, especially among strikers.

The prevalence of vitamin supplementation in ultraendurance athletes

Ultraendurance exercise training places large energy demands on athletes and causes a high turnover of vitamins through sweat losses, metabolism, and the musculoskeletal repair process. Ultraendurance athletes may not consume sufficient quantities or quality of food in their diet to meet these needs. Consequently, they may use oral vitamin and mineral supplements to maintain their health and performance. We assessed the vitamin and mineral intake of ultraendurance athletes in their regular diet, in addition to oral vitamin and mineral supplements. Thirty-seven ultraendurance triathletes (24 men and 13 women) completed a 7-day nutrition diary including a questionnaire to determine nutrition adequacy and supplement intake. Compared with dietary reference intakes for the general population, both male and female triathletes met or exceeded all except for vitamin D. In addition, female athletes consumed slightly less than the recommended daily intake for folate and potassium; however, the difference was trivial. Over 60% of the athletes reported using vitamin supplements, of which vitamin C (97.5%), vitamin E (78.3%), and multivitamins (52.2%) were the most commonly used supplements. Almost half (47.8%) the athletes who used supplements did so to prevent or reduce cold symptoms. Only 1 athlete used supplements on formal medical advice. Vitamin C and E supplementation was common in ultraendurance triathletes, despite no evidence of dietary deficiency in these 2 vitamins.

Carbohydrate gel ingestion and immunoendocrine responses to cycling in temperate and hot conditions

PURPOSE: Heat stress might attenuate the effects of carbohydrate on immunoendocrine responses to exercise by increasing endogenous glucose production and reducing the rate of exogenous carbohydrate oxidation. The authors compared the efficacy of carbohydrate consumption on immune responses to exercise in temperate vs. hot conditions. METHODS: Ten male cyclists exercised on 2 separate occasions in temperate (18.1 +/- 0.4 degrees C, 58% +/- 8% relative humidity) and on another 2 occasions in hot conditions (32.2 +/- 0.7 degrees C, 55% +/- 2% relative humidity). On each occasion, the cyclists exercised in a fed state for 90 min at approximately 60% VO2max and then completed a 16.1-km time trial. Every 15 min during the first 90 min of exercise, they consumed 0.24 g/kg body mass of a carbohydrate or placebo gel. RESULTS: Neutrophil counts increased during exercise in all trials (p < .05) and were significantly lower (40%, p = .006) after the carbohydrate than after the placebo trial in 32 degrees C. The concentrations of serum interleukin (IL)-6, IL-8, and IL-10 and plasma granulocyte-colony-stimulating factor, myeloperoxidase, and calprotectin also increased during exercise in all trials but did not differ significantly between the carbohydrate and placebo trials. Plasma norepinephrine concentration increased during exercise in all trials and was significantly higher (50%, p = .01) after the carbohydrate vs. the placebo trial in 32 degrees C. CONCLUSION: Carbohydrate ingestion attenuated neutrophil counts during exercise in hot conditions, whereas it had no effect on any other immune variables in either temperate or hot conditions.

Variability in estimation of self-reported dietary intake data from elite athletes resulting from coding by different sports dietitians

A routine activity for a sports dietitian is to estimate energy and nutrient intake from an athlete's self-reported food intake. Decisions made by the dietitian when coding a food record are a source of variability in the data. The aim of the present study was to determine the variability in estimation of the daily energy and key nutrient intakes of elite athletes, when experienced coders analyzed the same food record using the same database and software package. Seven-day food records from a dietary survey of athletes in the 1996 Australian Olympic team were randomly selected to provide 13 sets of records, each set representing the self-reported food intake of an endurance, team, weight restricted, and sprint/power athlete. Each set was coded by 3-5 members of Sports Dietitians Australia, making a total of 52 athletes, 53 dietitians, and 1456 athlete-days of data. We estimated within- and between- athlete and dietitian variances for each dietary nutrient using mixed modeling, and we combined the variances to express variability as a coefficient of variation (typical variation as a percent of the mean). Variability in the mean of 7-day estimates of a nutrient was 2- to 3-fold less than that of a single day. The variability contributed by the coder was less than the true athlete variability for a 1-day record but was of similar magnitude for a 7-day record. The most variable nutrients (e.g., vitamin C, vitamin A, cholesterol) had approximately 3-fold more variability than least variable nutrients (e.g., energy, carbohydrate, magnesium). These athlete and coder variabilities need to be taken into account in dietary assessment of athletes for counseling and research.

Vitamin C : effects of exercise and requirements with training

Ascorbic acid or vitamin C is involved in a number of biochemical pathways that are important to exercise metabolism and the health of exercising individuals. This review reports the results of studies investigating the requirement for vitamin C with exercise on the basis of dietary vitamin C intakes, the response to supplementation and alterations in plasma, serum, and leukocyte ascorbic acid concentration following both acute exercise and regular training. The possible physiological significance of changes in ascorbic acid with exercise is also addressed. Exercise generally causes a transient increase in circulating ascorbic acid in the hours following exercise, but a decline below pre-exercise levels occurs in the days after prolonged exercise. These changes could be associated with increased exercise-induced oxidative stress. On the basis of alterations in the concentration of ascorbic acid within the blood, it remains unclear if regular exercise increases the metabolism of vitamin C. However, the similar dietary intakes and responses to supplementation between athletes and nonathletes suggest that regular exercise does not increase the requirement for vitamin C in athletes. Two novel hypotheses are put forward to explain recent findings of attenuated levels of cortisol postexercise following supplementation with high doses of vitamin C.

Interval training intensity affects energy intake compensation in obese men

Abstract PURPOSE: Compensatory responses may attenuate the effectiveness of exercise training in weight management. The aim of this study was to compare the effect of moderate- and high-intensity interval training on eating behavior compensation. METHODS: Using a crossover design, 10 overweight and obese men participated in 4-week moderate (MIIT) and high (HIIT) intensity interval training. MIIT consisted of 5-min cycling stages at ± 20% of mechanical work at 45%VO(2)peak, and HIIT consisted of alternate 30-s work at 90%VO(2)peak and 30-s rests, for 30 to 45 min. Assessments included a constant-load exercise test at 45%VO(2)peak for 45 min followed by 60-min recovery. Appetite sensations were measured during the exercise test using a Visual Analog Scale. Food preferences (liking and wanting) were assessed using a computer-based paradigm, and this paradigm uses 20 photographic food stimuli varying along two dimensions, fat (high or low) and taste (sweet or nonsweet). An ad libitum test meal was provided after the constant-load exercise test. RESULTS: Exercise-induced hunger and desire to eat decreased after HIIT, and the difference between MIIT and HIIT in desire to eat approached significance (p = .07). Exercise-induced liking for high-fat nonsweet food tended to increase after MIIT and decreased after HIIT (p = .09). Fat intake decreased by 16% after HIIT, and increased by 38% after MIIT, with the difference between MIIT and HIIT approaching significance (p = .07). CONCLUSIONS: This study provides evidence that energy intake compensation differs between MIIT and HIIT.

Body image and body composition: comparisons of young male elite soccer players and controls

[EN] The purpose of this study was to evaluate body composition and body image (perception and satisfaction) in a group of young elite soccer players and to compare the data with those of a control group (age and BMI matched). Participants were 56 volunteer males whose mean age and BMI were 19.6 (SD 1.3) years and 23.3 (SD 1.1) kg/m2, respectively. Results showed that soccer players have a higher lean mass and lower fat mass than controls. Moreover, body perception (difference between current and actual image) was more accurate in controls than in soccer players, and the results suggest a tendency for soccer players to aspire to have more muscle mass and body fat. Soccer players perceived an ideal image with significantly higher body-fat percentage than their current and actual images. There were no body-dissatisfaction differences between groups, however. Although the results are necessarily limited by the small sample size, the findings should be of interest to coaches of young elite soccer teams.

Influence of acute vitamin C and/or carbohydrate ingestion on hormonal, cytokine, and immune responses to prolonged exercise

Davison, G. and Gleeson, M. (2005). Influence of Acute Vitamin C and/or Carbohydrate Ingestion on Hormonal, Cytokine, and Immune Responses to Prolonged Exercise. International Journal of Sport Nutrition and Exercise Metabolism. 15(5), pp.465-479 RAE2008

Influence of a fed or fasted state on the s-IgA response to prolonged cycling in active men and women

This study investigated the effect of a fed or fasted state on the salivary immunoglobulin A (s-IgA) response to prolonged cycling. Using a randomized, crossover design, 16 active adults (8 men and 8 women) performed 2 hr of cycling on a stationary ergometer at 65% of maximal oxygen uptake on 1 occasion after an overnight fast (FAST) and on another occasion 2 hr after consuming a 2.2-MJ high-carbohydrate meal (FED). Timed, unstimulated whole saliva samples were collected immediately before ingestion of the meal, immediately preexercise, 5 min before cessation of exercise, immediately postexercise, and 1 hr postexercise. The samples were analyzed for s-IgA concentration, osmolality, and cortisol, and saliva flow rates were determined to calculate s-IgA secretion rate. Saliva flow rate decreased by 50% during exercise (p < .05), and s-IgA concentration increased by 42% (p < .05), but s-IgA secretion rate remained unchanged. There was a 37% reduction in s-IgA:osmolality postexercise (p < .05), and salivary cortisol increased by 68% (p < .05). There was no effect of FED vs. FAST on these salivary responses. The s-IgA concentration, secretion rate, and osmolality were found to be significantly lower in women than in men throughout the exercise protocol (p < .05); however, there was no difference between genders in saliva flow rate, s-IgA:osmolality ratio, or cortisol. These data demonstrate that a fed or fasted state 2 hr before exercise does not influence resting s-IgA or the response to prolonged cycling. Furthermore, these results show lower levels of s-IgA and osmolality in women than in men at rest.

La existencia de necesidades de información y comportamiento informativo en los entrenadores en deportes de combate

Este trabajo tiene como propósito esencial, realizar un acercamiento para detectar e identificar las necesidades de información y el comportamiento informativo de entrenadores en deportes de combate. Para ello se aplicó un cuestionario a instructores de aikido, boxeo, esgrima, judo, karate, kendo, lima lama, lucha y taekwondo seleccionados mediante un muestreo no probabilístico por causalidad. En general encontramos que los principales temas de interés entre los instructores son: los programas de entrenamiento, nutrición y dietas de entrenamiento. Por otra parte, los entrenadores son más propensos a utilizar su experiencia, internet y cursos para obtener información. En contraste se nota que la biblioteca y los libros son poco usados.

Déterminants des choix alimentaires d'athlètes adolescents en période de compétition

Cette étude s’insère dans une étude s’intitulant « Choix alimentaires d’adolescents canadiens et attitudes de leurs entraîneurs impliqués dans des activités sportives organisées ». Les objectifs étaient d’étudier chez des adolescents impliqués dans une compétition sportive provinciale où l’offre alimentaire est contrôlée 1) leur maîtrise des recommandations nutritionnelles 2) les facteurs individuels, comportementaux, socio-environnementaux influençant leurs choix alimentaires. Deux observateurs ont visité les différents sites alimentaires et de compétition pendant les Jeux du Québec de 2011 à Valleyfield. Les plateaux des athlètes ont été photographiés à table au moment des repas avec une caméra numérique et les commentaires oraux colligés par écrit. Au total, 173 photographies ont été analysées et comparées aux recommandations reconnues en nutrition sportive. Dans notre étude, les préférences alimentaires, l’offre alimentaire et la présence des coéquipiers sont les facteurs qui influencent le plus les choix alimentaires en compétition. Par contre, le sexe de l’athlète n’a pas influencé les choix alimentaires des athlètes observés. En pré-compétition, 85,4% des plateaux présentent une valeur énergétique supérieure aux recommandations et 66,3% d’entre eux ont une répartition en énergie inadéquate, peu importe le sexe. Un excès de lipides et de protéines au sein du repas précédant l’effort caractérise majoritairement les plateaux dont la répartition en énergie est non optimale (69,5%). Les recommandations en post-compétition (100%) et lors des jours de repos (95,8%) ont facilement été rencontrées. Il en est de même pour l’hydratation (99,4%). Le lait au chocolat est la boisson la plus populaire (59,5%). Les produits céréaliers (99,4%), le lait et substituts (87,3%), les légumes (85,7%), les viandes et substituts (83,2%), les aliments riches en sucres (79,8%), les fruits (70,5%) et les mets riches en gras (59,4%) sont particulièrement appréciés par les athlètes. Les commentaires recueillis font ressortir une vision dichotomique des aliments chez certains athlètes qui classifient les aliments en « bons » ou « mauvais ». Notre étude démontre que la présence d’une politique alimentaire permet de promouvoir des habitudes alimentaires saines et favorise la consommation d’aliments nutritifs lors d’une compétition sportive d’envergure. Cependant, de l’éducation en nutrition est toujours requise pour viser l’amélioration du comportement alimentaire avant l’effort.

Comparison of the Effects of Hydration with Water or Isotonic Solution on the Recovery of Cardiac Autonomic Modulation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Beta-alanine supplementation improves jumping power and affects severe-intensity performance in professional alpine skiers.

INTRODUCTION Supplementation with beta-alanine may have positive effects on severe-intensity, intermittent, and isometric strength-endurance performance. These could be advantageous for competitive alpine skiers, whose races last 45 to 150 s, require metabolic power above the aerobic maximum, and involve isometric muscle work. Further, beta-alanine supplementation affects the muscle force-frequency relationship, which could influence explosiveness. We explored the effects of beta-alanine on explosive jump performance, severe exercise energy metabolism, and severe-intensity ski-like performance. METHODS Nine male elite alpine skiers consumed 4.8 g/d beta-alanine or placebo for 5 weeks in a double-blind fashion. Before and after, they performed countermovement jumps (CMJ), a 90-s cycling bout at 110% VO2max (CLT), and a maximal 90-s box jump test (BJ90). RESULTS Beta-alanine improved maximal (+7 ± 3%, d = 0.9) and mean CMJ power (+7 ± 2%, d = 0.7), tended to reduce oxygen deficit (-3 ± 8%, p = .06) and lactate accumulation (-12 ± 31%) and enhance aerobic energy contribution (+1.3 ± 2.9%, p = .07) in the CLT, and improved performance in the last third of BJ90 (+7 ± 4%, p = .02). These effects were not observed with placebo. CONCLUSIONS Beta-alanine supplementation improved explosive and repeated jump performance in elite alpine skiers. Enhanced muscle contractility could possibly explain improved explosive and repeated jump performance. Increased aerobic energy production could possibly help explain repeated jump performance as well.