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1.
Diet Quality of Elite Australian Athletes Evaluated Using the Athlete Diet Index.
Capling, L, Tam, R, Beck, KL, Slater, GJ, Flood, VM, O'Connor, HT, Gifford, JA
Nutrients. 2020;(1)
Abstract
While athletes' nutrient intakes have been widely reported, few studies have assessed the diet quality of athletes. This is the first study to evaluate the diet quality of athletes using the purpose-built Athlete Diet Index (ADI). A convenience sample of 165 elite athletes from Australian sporting institutions completed the ADI online, with subsequent automated results provided to their respective accredited sports dietitians (ASDs). At the completion of athlete participation, ASDs (n = 12) responded to a range of survey items using a Likert scale (i.e., 1 = strongly agree to 5 = strongly disagree) to determine the suitability of the ADI in practice. Differences in ADI scores for demographics and sport-specific variables were investigated using independent t-tests, analysis of variance (ANOVA) and Bonferroni multiple comparisons. Spearman's rank correlation was used to assess the association between total scores and demographics. The mean total ADI score was 91.4 ± 12.2 (range 53-117, out of a possible 125). While there was no difference in total scores based on demographics or sport-specific variables; team sport athletes scored higher than individual sport athletes (92.7 vs. 88.5, P < 0.05). Athletes training fewer hours (i.e., 0-11 h/week) scored higher on Dietary Habits sub-scores compared with athletes training more hours (> 12 h/week; P < 0.05), suggesting that athletes who train longer may be at risk of a compromised dietary pattern or less than optimal nutrition practices that support training. Most (75%) ASDs surveyed strongly agreed with the perceived utility of the ADI for screening athletes and identifying areas for nutrition support, confirming its suitability for use in practice.
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2.
Is an Energy Surplus Required to Maximize Skeletal Muscle Hypertrophy Associated With Resistance Training.
Slater, GJ, Dieter, BP, Marsh, DJ, Helms, ER, Shaw, G, Iraki, J
Frontiers in nutrition. 2019;:131
Abstract
Resistance training is commonly prescribed to enhance strength/power qualities and is achieved via improved neuromuscular recruitment, fiber type transition, and/ or skeletal muscle hypertrophy. The rate and amount of muscle hypertrophy associated with resistance training is influenced by a wide array of variables including the training program, plus training experience, gender, genetic predisposition, and nutritional status of the individual. Various dietary interventions have been proposed to influence muscle hypertrophy, including manipulation of protein intake, specific supplement prescription, and creation of an energy surplus. While recent research has provided significant insight into optimization of dietary protein intake and application of evidence based supplements, the specific energy surplus required to facilitate muscle hypertrophy is unknown. However, there is clear evidence of an anabolic stimulus possible from an energy surplus, even independent of resistance training. Common textbook recommendations are often based solely on the assumed energy stored within the tissue being assimilated. Unfortunately, such guidance likely fails to account for other energetically expensive processes associated with muscle hypertrophy, the acute metabolic adjustments that occur in response to an energy surplus, or individual nuances like training experience and energy status of the individual. Given the ambiguous nature of these calculations, it is not surprising to see broad ranging guidance on energy needs. These estimates have never been validated in a resistance training population to confirm the "sweet spot" for an energy surplus that facilitates optimal rates of muscle gain relative to fat mass. This review not only addresses the influence of an energy surplus on resistance training outcomes, but also explores other pertinent issues, including "how much should energy intake be increased," "where should this extra energy come from," and "when should this extra energy be consumed." Several gaps in the literature are identified, with the hope this will stimulate further research interest in this area. Having a broader appreciation of these issues will assist practitioners in the establishment of dietary strategies that facilitate resistance training adaptations while also addressing other important nutrition related issues such as optimization of fuelling and recovery goals. Practical issues like the management of satiety when attempting to increase energy intake are also addressed.
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3.
SPRINTING. . . Dietary Approaches to Optimize Training Adaptation and Performance.
Slater, GJ, Sygo, J, Jorgensen, M
International journal of sport nutrition and exercise metabolism. 2019;(2):85-94
Abstract
Although sprint athletes are assumed to primarily be interested in promoting muscle hypertrophy, it is the ability to generate explosive muscle power, optimization of power-to-weight ratio, and enhancement of anaerobic energy generation that are key outcomes of sprint training. This reflects the physique of track sprinters, being characterized as ecto-mesomorphs. Although there is little contemporary data on sprinters dietary habits, given their moderate energy requirements relative to body mass, a carbohydrate intake within the range of 3-6 g·kg-1·day-1 appears reasonable, while ensuring carbohydrate availability is optimized around training. Similarly, although protein needs may be twice general population recommendations, sprint athletes should consume meals containing ∼0.4 g/kg high biological value protein (i.e., easily digested, rich in essential amino acids) every 3-5 hr. Despite the short duration of competitions and relative long-recovery periods between races, nutrition still plays an important role in sprint performance. As energy expenditure moderates during competition, so too should intake of energy and macronutrients to prevent unwanted weight gain. Further adjustments in macronutrient intake may be warranted among athletes contemplating optimization of power-to-weight ratio through reductions in body fat prior to the competitive season. Other novel acute methods of weight loss have also been proposed to enhance power-to-weight ratio, but their implementation should only be considered under professional guidance. Given the metabolic demands of sprinting, a few supplements may be of benefit to athletes in training and/or competition. Their use in competition should be preceded with trialing in training to confirm tolerance and perceived ergogenic potential.
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4.
Chronic Ketogenic Low Carbohydrate High Fat Diet Has Minimal Effects on Acid-Base Status in Elite Athletes.
Carr, AJ, Sharma, AP, Ross, ML, Welvaert, M, Slater, GJ, Burke, LM
Nutrients. 2018;10(2)
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The low-fat, high-carbohydrate ketogenic diet has recently been applied to the context of elite athletes to observe potential impact on performance and metabolism during exercise and rest. The aim to this study was to assess the effect of a long-term ketogenic diet on the acid-base status in elite athletes, particularly investigating whether sustained diet change caused alterations in overall acid production. Twenty-one athletes were assigned to a high carbohydrate diet, low carbohydrate diet and periodised carbohydrate availability diet for three sustained weeks. Acid-base balance was measured via blood samples at baseline and post-intervention. The main finding of this study was that a sustained ketogenic diet had no influence of acid-base status. Based on these results, the authors conclude that long-term manipulation of macronutrient intake is unlikely to influence acid-base status in this population. It is also noted that elite athletes may have an increased buffering capacity compared with the general population, and that further research should be done in different participant populations.
Abstract
Although short (up to 3 days) exposure to major shifts in macronutrient intake appears to alter acid-base status, the effects of sustained (>1 week) interventions in elite athletes has not been determined. Using a non-randomized, parallel design, we examined the effect of adaptations to 21 days of a ketogenic low carbohydrate high fat (LCHF) or periodized carbohydrate (PCHO) diet on pre- and post-exercise blood pH, and concentrations of bicarbonate (HCO₃-) and lactate (La-) in comparison to a high carbohydrate (HCHO) control. Twenty-four (17 male and 7 female) elite-level race walkers completed 21 days of either LCHF (n = 9), PCHO (n = 7), or HCHO (n = 8) under controlled diet and training conditions. At baseline and post-intervention, blood pH, blood [HCO₃-], and blood [La-] were measured before and after a graded exercise test. Net endogenous acid production (NEAP) over the previous 48-72 h was also calculated from monitored dietary intake. LCHF was not associated with significant differences in blood pH, [HCO₃-], or [La-], compared with the HCHO diet pre- or post-exercise, despite a significantly higher NEAP (mEq·day-1) (95% CI = [10.44; 36.04]). Our results indicate that chronic dietary interventions are unlikely to influence acid-base status in elite athletes, which may be due to pre-existing training adaptations, such as an enhanced buffering capacity, or the actions of respiratory and renal pathways, which have a greater influence on regulation of acid-base status than nutritional intake.
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5.
Core Temperature Responses to Cold-Water Immersion Recovery: A Pooled-Data Analysis.
Stephens, JM, Sharpe, K, Gore, C, Miller, J, Slater, GJ, Versey, N, Peiffer, J, Duffield, R, Minett, GM, Crampton, D, et al
International journal of sports physiology and performance. 2018;(7):917-925
Abstract
PURPOSE To examine the effect of postexercise cold-water immersion (CWI) protocols, compared with control (CON), on the magnitude and time course of core temperature (Tc) responses. METHODS Pooled-data analyses were used to examine the Tc responses of 157 subjects from previous postexercise CWI trials in the authors' laboratories. CWI protocols varied with different combinations of temperature, duration, immersion depth, and mode (continuous vs intermittent). Tc was examined as a double difference (ΔΔTc), calculated as the change in Tc in CWI condition minus the corresponding change in CON. The effect of CWI on ΔΔTc was assessed using separate linear mixed models across 2 time components (component 1, immersion; component 2, postintervention). RESULTS Intermittent CWI resulted in a mean decrease in ΔΔTc that was 0.25°C (0.10°C) (estimate [SE]) greater than continuous CWI during the immersion component (P = .02). There was a significant effect of CWI temperature during the immersion component (P = .05), where reductions in water temperature of 1°C resulted in decreases in ΔΔTc of 0.03°C (0.01°C). Similarly, the effect of CWI duration was significant during the immersion component (P = .01), where every 1 min of immersion resulted in a decrease in ΔΔTc of 0.02°C (0.01°C). The peak difference in Tc between the CWI and CON interventions during the postimmersion component occurred at 60 min postintervention. CONCLUSIONS Variations in CWI mode, duration, and temperature may have a significant effect on the extent of change in Tc. Careful consideration should be given to determine the optimal amount of core cooling before deciding which combination of protocol factors to prescribe.
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6.
Cold-Water Immersion for Athletic Recovery: One Size Does Not Fit All.
Stephens, JM, Halson, S, Miller, J, Slater, GJ, Askew, CD
International journal of sports physiology and performance. 2017;(1):2-9
Abstract
The use of cold-water immersion (CWI) for postexercise recovery has become increasingly prevalent in recent years, but there is a dearth of strong scientific evidence to support the optimization of protocols for performance benefits. While the increase in practice and popularity of CWI has led to multiple studies and reviews in the area of water immersion, the research has predominantly focused on performance outcomes associated with postexercise CWI. Studies to date have generally shown positive results with enhanced recovery of performance. However, there are a small number of studies that have shown CWI to have either no effect or a detrimental effect on the recovery of performance. The rationale for such contradictory responses has received little attention but may be related to nuances associated with individuals that may need to be accounted for in optimizing prescription of protocols. To recommend optimal protocols to enhance athletic recovery, research must provide a greater understanding of the physiology underpinning performance change and the factors that may contribute to the varied responses currently observed. This review focuses specifically on why some of the current literature may show variability and disparity in the effectiveness of CWI for recovery of athletic performance by examining the body temperature and cardiovascular responses underpinning CWI and how they are related to performance benefits. This review also examines how individual characteristics (such as physique traits), differences in water-immersion protocol (depth, duration, temperature), and exercise type (endurance vs maximal) interact with these mechanisms.
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7.
The effect of a whey protein supplement dose on satiety and food intake in resistance training athletes.
MacKenzie-Shalders, KL, Byrne, NM, Slater, GJ, King, NA
Appetite. 2015;:178-84
Abstract
OBJECTIVE Many athletes perform resistance training and consume dietary protein as a strategy to promote anabolic adaptation. Due to its high satiety value, the regular addition of supplemented dietary protein could plausibly displace other key macronutrients such as carbohydrate in an athlete's diet. This effect will be influenced by the form and dose of protein. Therefore, this study assessed the impact of liquid whey protein dose manipulation on subjective sensations of appetite and food intake in a cohort of athletes. DESIGN Ten male athletes who performed both resistance and aerobic (endurance) training (21.2 ± 2.3 years; 181.7 ± 5.7 cm and 80.8 ± 6.1 kg) were recruited. In four counter-balanced testing sessions they consumed a manipulated whey protein supplement (20, 40, 60 or 80 g protein) 1 hour after a standardised breakfast. Subsequent energy intake was measured 3 hours after the protein supplement using an ad libitum test meal. Subjective appetite sensations were measured periodically during the test day using visual analogue scales. RESULTS All conditions resulted in a significant decrease in ratings of hunger (50-65%; P < 0.05) at the time of supplement consumption. However, there were no significant differences between the conditions at any time point for subjective appetite sensations or for energy consumed in the ad libitum meal: 4382 ± 1004, 4643 ± 982, 4514 ± 1112, 4177 ± 1494 kJ respectively. CONCLUSION Increasing whey protein supplement dose above 20 g did not result in a measurable increase in satiety or decrease in food intake. However, the inclusion of additional whey protein supplementation where not otherwise consumed could plausibly reduce dietary intake.
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8.
Variability of measurements of sweat sodium using the regional absorbent-patch method.
Dziedzic, CE, Ross, ML, Slater, GJ, Burke, LM
International journal of sports physiology and performance. 2014;(5):832-8
Abstract
CONTEXT There is interest in including recommendations for the replacement of the sodium lost in sweat in individualized hydration plans for athletes. PURPOSE Although the regional absorbent-patch method provides a practical approach to measuring sweat sodium losses in field conditions, there is a need to understand the variability of estimates associated with this technique. METHODS Sweat samples were collected from the forearms, chest, scapula, and thigh of 12 cyclists during 2 standardized cycling time trials in the heat and 2 in temperate conditions. Single measure analysis of sodium concentration was conducted immediately by ion-selective electrodes (ISE). A subset of 30 samples was frozen for reanalysis of sodium concentration using ISE, flame photometry (FP), and conductivity (SC). RESULTS Sweat samples collected in hot conditions produced higher sweat sodium concentrations than those from the temperate environment (P = .0032). A significant difference (P = .0048) in estimates of sweat sodium concentration was evident when calculated from the forearm average (mean ± 95% CL; 64 ± 12 mmol/L) compared with using a 4-site equation (70 ± 12 mmol/L). There was a high correlation between the values produced using different analytical techniques (r2 = .95), but mean values were different between treatments (frozen FP, frozen SC > immediate ISE > frozen ISE; P < .0001). CONCLUSION Whole-body sweat sodium concentration estimates differed depending on the number of sites included in the calculation. Environmental testing conditions should be considered in the interpretation of results. The impact of sample freezing and subsequent analytical technique was small but statistically significant. Nevertheless, when undertaken using a standardized protocol, the regional absorbent-patch method appears to be a relatively robust field test.
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9.
Pseudoephedrine and preexercise feeding: influence on performance.
Pritchard-Peschek, KR, Osborne, MA, Slater, GJ, Taaffe, DR, Jenkins, DG
Medicine and science in sports and exercise. 2013;(6):1152-7
Abstract
PURPOSE This study examined the influence of preexercise food intake on plasma pseudoephedrine (PSE) concentrations and subsequent high-intensity exercise. In addition, urinary PSE concentrations were measured under the same conditions and compared with the present threshold of the World Anti-Doping Agency (WADA). METHODS Ten highly trained male cyclists and triathletes (age = 30.6 ± 6.6 yr, body mass [BM] = 72.9 ± 5.1 kg, and V˙O2max = 64.8 ± 4.5 mL·kg·min; mean ± SD) undertook four cycling time trials (TT), each requiring the completion of a set amount of work (7 kJ·kg BM) in the shortest possible time. Participants were randomized into a fed or nonfed condition and orally ingested 2.8 mg·kg BM of PSE or a placebo (PLA) 90 min before exercise; in the fed trials, they consumed a meal providing 1.5 g·kg BM of CHO. Venous blood was sampled at 30, 50, and 70 min and pre-warm-up and postexercise for the analysis of plasma PSE and catecholamine concentrations, and urine was also collected for the analysis of PSE concentration. RESULTS Independent of the preexercise meal, 2.8 mg·kg BM of PSE did not significantly improve cycling TT performance. The fed trials resulted in lower plasma PSE concentrations at all time points compared with the nonfed trials. Both plasma epinephrine and blood lactate concentrations were higher in the PSE compared with the PLA trials, and preexercise and postexercise urinary PSE concentrations were significantly higher than the threshold (150 μg·mL) used by WADA to determine illicit PSE use. CONCLUSION Irrespective of the preexercise meal, cycling TT performance of approximately 30 min was not improved after PSE supplementation. Furthermore, 2.8 mg·kg BM of PSE taken 90 min before exercise, with or without food, resulted in urinary PSE concentrations exceeding the present WADA threshold.
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10.
Effects of exercise sessions on DXA measurements of body composition in active people.
Nana, A, Slater, GJ, Hopkins, WG, Burke, LM
Medicine and science in sports and exercise. 2013;(1):178-85
Abstract
PURPOSE Dual-energy x-ray absorptiometry (DXA) is rapidly becoming more accessible and popular as a technique to monitor body composition, especially in athletic populations. This study investigates the reliability of DXA in measuring body composition of active individuals, specifically to ascertain biological variability associated with two different types of exercise under free-living conditions in active individuals. METHODS Well-trained individuals (27 strength-trained male subjects, 14 female cyclists, and 14 male cyclists) underwent three whole-body DXA scans over a 1-d period: in the morning after an overnight fast, approximately 5 min later after repositioning on the scanning bed, and shortly after a self-chosen exercise session (resistance training or cycling). Subjects were allowed to consume food and fluid ad libitum before and during exercise as per their usual practices. Magnitude of typical (standard) errors of measurement and changes in the mean of DXA measures were assessed by standardization. RESULTS Exercise and its related practices of fluid and food intake are associated with changes in the mean estimates of total and regional body composition that range from trivial to small but substantial. An exercise session also increases the typical error of measurement of these characteristics by approximately 10%. CONCLUSION The easiest and most practical way to minimize the biological "noise" associated with undertaking a DXA scan is to have subjects fasted and rested before measurement. Until sufficient data on the smallest important effect are available, both biological and technical "noises" should be minimized so that any small but potentially "real" changes can be confidently detected.