Evidence suggests that increasing protein distribution may be desirable to promote muscle protein synthesis (MPS) in combination with resistance exercise. However, there is a threshold above which additional protein consumption has limited benefit for MPS and may promote protein loss due to increased oxidation. This study aimed to measure daily protein intake and protein distribution in a cohort of rugby players. Twenty-five developing elite rugby union athletes (20.5 ± 2.3 years, 100.2 ± 13.3 kg, 184.4 ± 7.4 cm) were assessed at the start and end of a rugby preseason. Using a 7-day food diary the reported daily protein intake was 2.2 ± 0.7 g·kg·day-1 which exceeds daily recommendations. The reported carbohydrate intake was 3.6 ± 1.3 g·kg·day-1 which may reflect a suboptimal intake or dietary underreporting. In general, the rugby athletes were regularly consuming more than 20 g of protein; 3.8 ± 0.9 times per day (68 ± 18% of eating occasions). In addition to documenting current dietary intakes, an excess protein estimation score was calculated to determine how frequently the rugby athletes consumed protein above a known effective dose with a margin of error. 2.0 ± 0.9 eating occasions contained protein in excess of doses (20 g) known to promote MPS. Therefore, it is currently unclear whether the consumption of regular large doses of protein will benefit rugby athletes via increasing protein distribution, or whether high protein intakes may have unintended effects including a reduction in carbohydrate and/or energy intake.
Kristen MacKenzie, Gary Slater, Neil King and Nuala Byrne
Ava Kerr, Gary Slater, Nuala Byrne and Janet Chaseling
The three-compartment (3-C) model of physique assessment (fat mass, fat-free mass, water) incorporates total body water (TBW) whereas the two-compartment model (2-C) assumes a TBW of 73.72%. Deuterium dilution (D2O) is the reference method for measuring TBW but is expensive and time consuming. Multifrequency bioelectrical impedance spectroscopy (BIS SFB7) estimates TBW instantaneously and claims high precision. Our aim was to compare SFB7 with D2O for estimating TBW in resistance trained males (BMI >25kg/m2). We included TBWBIS estimates in a 3-C model and contrasted this and the 2-C model against the reference 3-C model using TBWD2O. TBW of 29 males (32.4 ± 8.5 years; 183.4 ± 7.2 cm; 92.5 ± 9.9 kg; 27.5 ± 2.6 kg/m2) was measured using SFB7 and D2O. Body density was measured by BODPOD, with body composition calculated using the Siri equation. TBWBIS values were consistent with TBWD2O (SEE = 2.65L; TE = 2.6L) as were %BF values from the 3-C model (BODPOD + TBWBIS) with the 3-C reference model (SEE = 2.20%; TE = 2.20%). For subjects with TBW more than 1% from the assumed 73.72% (n = 16), %BF from the 2-C model differed significantly from the reference 3-C model (Slope 0.6888; Intercept 5.093). The BIS SFB7 measured TBW accurately compared with D2O. The 2C model with an assumed TBW of 73.72% introduces error in the estimation of body composition. We recommend TBW should be measured, either via the traditional D2O method or when resources are limited, with BIS, so that body composition estimates are enhanced. The BIS can be accurately used in 3C equations to better predict TBW and BF% in resistance trained males compared with a 2C model.
Adam J. Zemski, Elizabeth M. Broad and Gary J. Slater
Body composition in elite rugby union athletes is routinely assessed using surface anthropometry, which can be utilized to provide estimates of absolute body composition using regression equations. This study aims to assess the ability of available skinfold equations to estimate body composition in elite rugby union athletes who have unique physique traits and divergent ethnicity. The development of sport-specific and ethnicity-sensitive equations was also pursued. Forty-three male international Australian rugby union athletes of Caucasian and Polynesian descent underwent surface anthropometry and dual-energy X-ray absorptiometry (DXA) assessment. Body fat percent (BF%) was estimated using five previously developed equations and compared to DXA measures. Novel sport and ethnicity-sensitive prediction equations were developed using forward selection multiple regression analysis. Existing skinfold equations provided unsatisfactory estimates of BF% in elite rugby union athletes, with all equations demonstrating a 95% prediction interval in excess of 5%. The equations tended to underestimate BF% at low levels of adiposity, whilst overestimating BF% at higher levels of adiposity, regardless of ethnicity. The novel equations created explained a similar amount of variance to those previously developed (Caucasians 75%, Polynesians 90%). The use of skinfold equations, including the created equations, cannot be supported to estimate absolute body composition. Until a population-specific equation is established that can be validated to precisely estimate body composition, it is advocated to use a proven method, such as DXA, when absolute measures of lean and fat mass are desired, and raw anthropometry data routinely to derive an estimate of body composition change.
Geoff P. Lovell, John K. Parker and Gary J. Slater
Research in sports-science disciplines such as sport psychology has demonstrated that practitioners’ physical characteristics influence clients’ perceptions of their effectiveness, potentially mediating the efficacy of subsequent interventions. However, very little research has been directed toward this issue for sports dietitians (SDs), the health professionals whom athletes are likely to engage to assist with manipulation of traits of physique. Therefore, the purpose of this investigation was to determine whether SDs’ phenotype, specifically body-mass index (BMI), and type of dress influence potential clients’ preference to consult them for dietetic support and if this affects their perceived effectiveness.
One hundred volunteers (mean age 18.7 ± 0 .8 years) all participating in regular competitive sport, classified by gender (male, n = 55, or female, n = 45) and competitive standard (elite/subelite, n = 68, or club/recreational, n = 32) viewed slides representing four concurrently presented computer-generated images of the same female SD manipulated to represent different BMIs and dress types. Participants were asked to rank the SDs in order of their preference to work with them and, second, to rate their perceived effectiveness of each of the SDs.
Key findings included the observation of a significant BMI main effect F(6, 91) = 387.39, p < .001 (effect size .96), with participants’ ranking of preference and rating of perceived effectiveness of female SDs decreasing with increasing BMI.
SDs should consider their physical appearance when meeting with athletes, as this may affect their perceived efficacy.
Reid Reale, Gregory R. Cox, Gary Slater and Louise M. Burke
Combat-sport athletes acutely reduce body mass (BM) before weigh-in in an attempt to gain a size/strength advantage over smaller opponents. Few studies have investigated these practices among boxers and none have explored the impact of this practice on competitive success.
One hundred (30 women, 70 men) elite boxers participating in the Australian national championships were weighed at the official weigh-in and 1 h before each competition bout. Regain in BM after weigh-in was compared between finalists and nonfinalists, winners and losers of each fight, men and women, and weight divisions. Boxers were surveyed on their pre- and post-weigh-in nutrition practices.
The lightest men’s weight category displayed significantly greater relative BM regain than all other divisions, with no difference between other divisions. BM prebout was higher than official weigh-in for men (2.12% ± 1.62%; P < .001; ES = 0.13) and women (1.49% ± 1.65%; P < .001; ES = 0.11). No differences in BM regain were found between finalists and nonfinalists, winners and losers of individual bouts, or between preliminary or final bouts. BM regain was significantly greater (0.37% BM, P < .001; ES = 0.25) before an afternoon bout compared with a morning bout.
Boxers engage in acute BM-loss practices before the official competition weigh-in, but this does not appear to affect competition outcomes, at least when weight regain between weigh-in and fighting is used as a proxy for the magnitude of acute loss. While boxers recognize the importance of recovering after weigh-in, current practice is not aligned with best-practice guidance.
Gary J. Slater, Anthony J. Rice, David Jenkins, Jason Gulbin and Allan G. Hahn
To strengthen the depth of lightweight rowing talent, we sought to identify experienced heavyweight rowers who possessed physique traits that predisposed them to excellence as a lightweight. Identified athletes (n = 3) were monitored over 16 wk. Variables measured included performance, anthropometric indices, and selected biochemical and metabolic parameters. All athletes decreased their body mass (range 2.0 to 8.0 kg), with muscle mass accounting for a large proportion of this (31.7 to 84.6%). Two athletes were able to maintain their performance despite reductions in body mass. However, performance was compromised for the athlete who experienced the greatest weight loss. In summary, smaller heavyweight rowers can successfully make the transition into the lightweight category, being nationally competitive in their first season as a lightweight.
Kellie R. Pritchard-Peschek, David G. Jenkins, Mark A. Osborne and Gary J. Slater
The aim of the current study was to investigate the effect of 180 mg of pseudoephedrine (PSE) on cycling time-trial (TT) performance. Six well-trained male cyclists and triathletes (age 33 ± 2 yr, mass 81 ± 8 kg, height 182.0 ± 6.7 cm, VO2max 56.8 ± 6.8 ml ⋅ kg−1 ⋅ min−1; M ± SD) underwent 2 performance trials in which they completed a 25-min variable-intensity (50–90% maximal aerobic power) warm-up, followed by a cycling TT in which they completed a fixed amount of work (7 kJ/kg body mass) in the shortest possible time. Sixty minutes before the start of exercise, they orally ingested 180 mg of PSE or a cornstarch placebo (PLA) in a randomized, crossover, double-blind manner. Venous blood was sampled immediately pre- and postexercise for the analysis of pH plus lactate, glucose, and norepinephrine (NE). PSE improved cycling TT performance by 5.1% (95% CI 0–10%) compared with PLA (28:58.9 ± 4:26.5 and 30:31.7 ± 4:36.7 min, respectively). There was a significant Treatment × Time interaction (p = .04) for NE, with NE increasing during the PSE trial only. Similarly, blood glucose also showed a trend (p = .06) for increased levels postexercise in the PSE trial. The ingestion of 180 mg of PSE 60 min before the onset of high-intensity exercise improved cycling TT performance in well-trained athletes. It is possible that changes in metabolism or an increase in central nervous system stimulation is responsible for the observed ergogenic effect of PSE.
Jessica M. Stephens, Shona Halson, Joanna Miller, Gary J. Slater and Christopher D. Askew
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.
Alisa Nana, Gary J. Slater, Arthur D. Stewart and Louise M. Burke
Dual energy X-ray absorptiometry (DXA) is rapidly becoming more accessible and popular as a technique to monitor body composition, especially in athletic populations. Although studies in sedentary populations have investigated the validity of DXA assessment of body composition, few studies have examined the issues of reliability in athletic populations and most studies which involve DXA measurements of body composition provide little information on their scanning protocols. This review presents a summary of the sources of error and variability in the measurement of body composition by DXA, and develops a theoretical model of best practice to standardize the conduct and analysis of a DXA scan. Components of this protocol include standardization of subject presentation (subjects rested, overnight-fasted and in minimal clothing) and positioning on the scanning bed (centrally aligned in a standard position using custom-made positioning aids) as well as manipulation of the automatic segmentation of regional areas of the scan results. Body composition assessment implemented with such protocol ensures a high level of precision, while still being practical in an athletic setting. This ensures that any small changes in body composition are confidently detected and correctly interpreted. The reporting requirements for studies involving DXA scans of body composition include details of the DXA machine and software, subject presentation and positioning protocols, and analysis protocols.
Kristen L. MacKenzie-Shalders, Neil A. King, Nuala M. Byrne and Gary J. Slater
Increasing the frequency of protein consumption is recommended to stimulate muscle hypertrophy with resistance exercise. This study manipulated dietary protein distribution to assess the effect on gains in lean mass during a rugby preseason. Twenty-four developing elite rugby athletes (age 20.1 ± 1.4 years, mass 101.6 ± 12.0 kg; M ± SD) were instructed to consume high biological value (HBV) protein at their main meals and immediately after resistance exercise while limiting protein intake between meals. To manipulate protein intake frequency, the athletes consumed 3 HBV liquid protein supplements (22 g protein) either with main meals (bolus condition) or between meals (frequent condition) for 6 weeks in a 2 × 2 crossover design. Dietary intake and change in lean mass values were compared between conditions by analysis of covariance and correlational analysis. The dietary manipulation successfully altered the protein distribution score (average number of eating occasions containing > 20 g of protein) to 4.0 ± 0.8 and 5.9 ± 0.7 (p < .01) for the bolus and frequent conditions, respectively. There was no difference in gains in lean mass between the bolus (1.4 ± 1.5 kg) and frequent (1.5 ± 1.4 kg) conditions (p = .91). There was no clear effect of increasing protein distribution from approximately 4–6 eating occasions on changes in lean mass during a rugby preseason. However, other dietary factors may have augmented adaptation.