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Identification, evaluation and management of disordered eating (DE) is complex. DE exists along the spectrum from optimised nutrition through to clinical eating disorders (EDs). Individual athletes can move back and forth along the spectrum of eating behaviour at any point in time over their career and within different stages of a training cycle. Athletes are more likely to present with DE than a clinical ED. Overall, there is a higher prevalence of DE and EDs in athletes compared with non-athletes. Additionally, athletes participating in aesthetic, gravitational and weight-class sports are at higher risk of DE and EDs than those in sports without these characteristics. The evaluation and management of DE requires a cohesive team of professional practitioners consisting of, at minimum, a doctor, a sports dietitian and a psychologist, termed within this statement as the core multidisciplinary team. The Australian Institute of Sport and the National Eating Disorders Collaboration have collaborated to provide this position statement, containing guidelines for athletes, coaches, support staff, clinicians and sporting organisations. The guidelines support the prevention and early identification of DE, and promote timely intervention to optimise nutrition for performance in a safe, supported, purposeful and individualised manner. This position statement is a call to action to all involved in sport to be aware of poor self-image and poor body image among athletes. The practical recommendations should guide the clinical management of DE in high performance sport.

Researchers and practitioners in sports nutrition would greatly benefit from a rapid, portable, and non-invasive technique to measure muscle glycogen, both in the laboratory and field. This explains the interest in MuscleSound®, the first commercial system to use high-frequency ultrasound technology and image analysis from patented cloud-based software to estimate muscle glycogen content from the echogenicity of the ultrasound image. This technique is based largely on muscle water content, which is presumed to act as a proxy for glycogen. Despite the promise of early validation studies, newer studies from independent groups reported discrepant results, with MuscleSound® scores failing to correlate with the glycogen content of biopsy-derived mixed muscle samples or to show the expected changes in muscle glycogen associated with various diet and exercise strategies. The explanation of issues related to the site of assessment do not account for these discrepancies, and there are substantial problems with the premise that the ratio of glycogen to water in the muscle is constant. Although further studies investigating this technique are warranted, current evidence that MuscleSound® technology can provide valid and actionable information around muscle glycogen stores is at best equivocal.

Standardizing a dual x-ray absorptiometry (DXA) protocol is thought to provide a reliable measurement of body composition.We investigated the effects of manipulating muscle glycogen and creatine content independently and additively on DXA estimates of lean mass.Eighteen well-trained male cyclists undertook a parallel group application of creatine loading (n = 9) (20 g·d for 5 d loading; 3 g·d maintenance) or placebo (n = 9) with crossover application of glycogen loading (12 v 6 g·kg BM per day for 48 h) as part of a larger study involving a glycogen-depleting exercise protocol. Body composition, total body water, muscle glycogen and creatine content were assessed via DXA, bioelectrical impedance spectroscopy and standard biopsy techniques. Changes in the mean were assessed using the following effect-size scale:0.2 small,0.6, moderate,1.2 large and compared with the threshold for the smallest worthwhile effect of the treatment.Glycogen loading, both with and without creatine loading, resulted in substantial increases in estimates of lean body mass (mean ± SD; 3.0% ± 0.7% and 2.0% ± 0.9%) and leg lean mass (3.1% ± 1.8% and 2.6% ± 1.0%) respectively. A substantial decrease in leg lean mass was observed after the glycogen depleting condition (-1.4% ± 1.6%). Total body water showed substantial increases after glycogen loading (2.3% ± 2.3%), creatine loading (1.4% ± 1.9%) and the combined treatment (2.3% ± 1.1%).Changes in muscle metabolites and water content alter DXA estimates of lean mass during periods in which minimal change in muscle protein mass is likely. This information needs to be considered in interpreting the results of DXA-derived estimates of body composition in athletes.

Quantity and timing of protein ingestion are major factors regulating myofibrillar protein synthesis (MPS). However, the effect of specific ingestion patterns on MPS throughout a 12 h period is unknown. We determined how different distributions of protein feeding during 12 h recovery after resistance exercise affects anabolic responses in skeletal muscle. Twenty-four healthy trained males were assigned to three groups (n = 8/group) and undertook a bout of resistance exercise followed by ingestion of 80 g of whey protein throughout 12 h recovery in one of the following protocols: 8 × 10 g every 1.5 h (PULSE); 4 × 20 g every 3 h (intermediate: INT); or 2 × 40 g every 6 h (BOLUS). Muscle biopsies were obtained at rest and after 1, 4, 6, 7 and 12 h post exercise. Resting and post-exercise MPS (l-[ring-(13)C6] phenylalanine), and muscle mRNA abundance and cell signalling were assessed. All ingestion protocols increased MPS above rest throughout 1-12 h recovery (88-148%, P INT>PULSE hierarchy in magnitude of phosphorylation. MuRF-1 and SLC38A2 mRNA were differentially expressed with BOLUS. In conclusion, 20 g of whey protein consumed every 3 h was superior to either PULSE or BOLUS feeding patterns for stimulating MPS throughout the day. This study provides novel information on the effect of modulating the distribution of protein intake on anabolic responses in skeletal muscle and has the potential to maximize outcomes of resistance training for attaining peak muscle mass.

We determined the effects of “periodized nutrition” on skeletal muscle and whole body responses to a bout of prolonged exercise the following morning. Seven cyclists completed two trials receiving isoenergetic diets differing in the timing of ingestion: they consumed either 8 g/kg body mass (BM) of carbohydrate (CHO) before undertaking an evening session of high-intensity training (HIT) and slept without eating (FASTED), or consumed 4 g/kg BM of CHO before HIT, then 4 g/kg BM of CHO before sleeping (FED). The next morning subjects completed 2 h of cycling (120SS) while overnight fasted. Muscle biopsies were taken on day 1 (D1) before and 2 h after HIT and on day 2 (D2) pre-, post-, and 4 h after 120SS. Muscle [glycogen] was higher in FED at all times post-HIT ( P < 0.001). The cycling bouts increased PGC1α mRNA and PDK4 mRNA ( P < 0.01) in both trials, with PDK4 mRNA being elevated to a greater extent in FASTED ( P < 0.05). Resting phosphorylation of AMPKThr172, p38MAPKThr180/Tyr182, and p-ACCSer79 (D2) was greater in FASTED ( P < 0.05). Fat oxidation during 120SS was higher in FASTED ( P = 0.01), coinciding with increases in ACCSer79 and CPT1 as well as mRNA expression of CD36 and FABP3 ( P < 0.05). Methylation on the gene promoter for COX4I1 and FABP3 increased 4 h after 120SS in both trials, whereas methylation of the PPARδ promoter increased only in FASTED. We provide evidence for shifts in DNA methylation that correspond with inverse changes in transcription for metabolically adaptive genes, although delaying postexercise feeding failed to augment markers of mitochondrial biogenesis.

Background Hypohydration and hyperthermia are factors that may contribute to fatigue and impairment of endurance performance. The purpose of this study was to investigate the effectiveness of combining glycerol hyperhydration and an established precooling technique on cycling time trial performance in hot environmental conditions. Methods Twelve well-trained male cyclists performed three 46.4-km laboratory-based cycling trials that included two climbs, under hot and humid environmental conditions (33.3 ± 1.1°C; 50 ± 6% r.h.). Subjects were required to hyperhydrate with 25 g.kg-1 body mass (BM) of a 4°C beverage containing 6% carbohydrate (CON) 2.5 h prior to the time trial. On two occasions, subjects were also exposed to an established precooling technique (PC) 60 min prior to the time trial, involving 14 g.kg-1 BM ice slurry ingestion and applied iced towels over 30 min. During one PC trial, 1.2 g.kg-1 BM glycerol was added to the hyperhydration beverage in a double-blind fashion (PC+G). Statistics used in this study involve the combination of traditional probability statistics and a magnitude-based inference approach. Results Hyperhydration resulted in large reductions (−0.6 to −0.7°C) in rectal temperature. The addition of glycerol to this solution also lowered urine output (330 ml, 10%). Precooling induced further small (−0.3°C) to moderate (−0.4°C) reductions in rectal temperature with PC and PC+G treatments, respectively, when compared with CON (0.0°C, P Conclusions Despite increasing fluid intake and reducing core temperature, performance and thermoregulatory benefits of a hyperhydration strategy with and without the addition of glycerol, plus practical precooling, were not superior to hyperhydration alone. Further research is warranted to further refine preparation strategies for athletes competing in thermally stressful events to optimize health and maximize performance outcomes.

A–Z of nutritional supplements : dietary supplements, sports nutrition foods and ergogenic aids for health and performance—part 10

Purpose: To develop and investigate the efficacy of a new precooling strategy combining external and internal techniques on the performance of a cycling time trial (TT) in a hot and humid environment. Methods: Eleven well-trained male cyclists undertook three trials of a laboratory-based cycling TT simulating the course characteristics of the Beijing Olympic Games event in a controlled hot and humid environment (32°C-35°C at 50%-60% relative humidity). The trials, separated by 3-7 d, were undertaken in a randomized crossover design and consisted of the following: 1) CON-no treatment apart from the ad libitum consumption of cold water (4°C), 2) STD COOL-whole-body immersion in cold (10°C) water for 10 min followed by wearing a cooling jacket, or 3) NEW COOL-combination of consumption of 14 g of ice slurry ("slushie") per kilogram body mass made from a commercial sports drink while applying iced towels. Results: There was an observable effect on rectal temperature (Trec) before the commencement of the TT after both precooling techniques (STD COOL < NEW COOL < CON, P < 0.05), but pacing of the TT resulted in similar Trec, HR, and RPE throughout the cycling protocol in all trials. NEW COOL was associated with a 3.0% increase in power (~8 W) and a 1.3% improvement in performance time (~1:06 min) compared with the CON trial, with the true likely effects ranging from a trivial to a large benefit. The effect of the STD COOL trial compared with the CON trial was "unclear." Conclusions: This new precooling strategy represents a practical and effective technique that could be used by athletes in preparation for endurance events undertaken in hot and humid conditions

We determined the effects of varying daily carbohydrate intake by providing or withholding carbohydrate during daily training on endurance performance, whole body rates of substrate oxidation, and selected mitochondrial enzymes. Sixteen endurance-trained cyclists or triathletes were pair matched and randomly allocated to either a high-carbohydrate group (High group; n = 8) or an energy-matched low-carbohydrate group (Low group; n = 8) for 28 days. Immediately before study commencement and during the final 5 days, subjects undertook a 5-day test block in which they completed an exercise trial consisting of a 100 min of steady-state cycling (100SS) followed by a 7-kJ/kg time trial on two occasions separated by 72 h. In a counterbalanced design, subjects consumed either water (water trial) or a 10% glucose solution (glucose trial) throughout the exercise trial. A muscle biopsy was taken from the vastus lateralis muscle on day 1 of the first test block, and rates of substrate oxidation were determined throughout 100SS. Training induced a marked increase in maximal citrate synthase activity after the intervention in the High group (27 vs. 34 μmol·g−1·min−1, P < 0.001). Tracer-derived estimates of exogenous glucose oxidation during 100SS in the glucose trial increased from 54.6 to 63.6 g ( P < 0.01) in the High group with no change in the Low group. Cycling performance improved by ∼6% after training. We conclude that altering total daily carbohydrate intake by providing or withholding carbohydrate during daily training in trained athletes results in differences in selected metabolic adaptations to exercise, including the oxidation of exogenous carbohydrate. However, these metabolic changes do not alter the training-induced magnitude of increase in exercise performance.

When testing is undertaken to monitor an athlete’s progress toward competition goals or the effect of an intervention on athletic outcomes, sport scientists should aim to minimize extraneous variables that influence the reliability, sensitivity, or validity of performance measurement. Dietary preparation is known to influence metabolism and exercise performance. Few studies, however, systematically investigate the outcomes of protocols that acutely control or standardize dietary intake in the hours and days before a performance trial. This review discusses the nutrients and dietary components that should be standardized before performance testing and reviews current approaches to achieving this. The replication of habitual diet or dietary practices, using tools such as food diaries or dietary recalls to aid compliance and monitoring, is a common strategy, and the use of education aids to help athletes achieve dietary targets offers a similarly low burden on the researcher. However, examination of dietary intake from real-life examples of these protocols reveals large variability between and within participants. Providing participants with prepackaged diets reduces this variability but can increase the burden on participants, as well as the researcher. Until studies can better quantify the effect of different protocols of dietary standardization on performance testing, sport scientists can only use a crude cost–benefit analysis to choose the protocols they implement. At the least, study reports should provide a more comprehensive description of the dietary-standardization protocols used in the research and the effect of these on the dietary intake of participants during the period of interest.