[Show abstract][Hide abstract] ABSTRACT: Objectives:
There is increasing evidence that physical activity (PA) positively affects cognitive function (CF). Existing research has focussed on this association in children and the elderly, with less research available in young to middle-aged adults who constitute a substantial proportion of the population.
A systematic review investigating the relationship between habitual PA (≥12 months) and CF in young to middle-aged adults (18-50 years).
A search was conducted using AMED, CINAHL, MEDLINE, PsychINFO, AUSPORT MED and SPORTDiscus databases. Eligible studies had to report descriptive statistics for CF and PA levels in healthy participants 18-50 years. Effect sizes (ES) (Hedges g) were calculated where possible.
The initial search netted 26,988 potentially relevant manuscripts, with four more identified through hand searching. Fourteen were included for review. A range of validated platforms assessed CF across three domains: executive function (12 studies), memory (four studies) and processing speed (seven studies). Habitual PA was assessed via questionnaire/self-report methods (n=13, 8 validated) or accelerometers (n=1). In studies of executive function, five found a significant ES in favour of higher PA, ranging from small to large. Although three of four studies in the memory domain reported a significant benefit of higher PA, there was only one significant ES, which favoured low PA. Only one study examining processing speed had a significant ES, favouring higher PA.
A limited body of evidence supports a positive effect of PA on CF in young to middle-aged adults. Further research into this relationship at this age stage is warranted.
[Show abstract][Hide abstract] ABSTRACT: Background:
Sound nutrition knowledge and a balanced diet are essential for operational readiness and optimal health of military personnel. Few studies have examined nutrition knowledge in this population.
To assess the level of general nutrition knowledge across military occupations (ie, officers [OFFRs], physical training instructors [PTIs], cooks [CKs], and soldiers [SOLs]) compared with a civilian, community (C) sample.
Convenience sample of Australian military (M) and C participants.
Main outcome measures:
General nutrition knowledge measured using the validated General Nutrition Knowledge Questionnaire (GNKQ). Knowledge scores and the influence of demographic characteristics (eg, age, sex, level of education, and living arrangement) within and between M and C groups were evaluated.
Analysis of variance, general linear models, independent-samples median test, t tests, χ(2) test, and Spearman's correlation.
A sample of 1,295 participants were recruited with 622 (48%) from C. The M sample (n=673) consisted of SOLs 62.1%, OFFRs 9.1%, PTIs 12.8%, and CKs 16.0%. Mean age was higher for C than M (35.5±14 y vs 29.7±9.2 y; P<0.001). However, SOLs were younger and OFFRs older than other groups (P<0.001). The M sample had more men (91.1% vs 39.4%; P<0.001). The OFFRs, PTIs, and C members had similar total GNKQ scores (62.8%, 61.9%, and 64.7%, respectively) with these groups higher (P<0.001) than CKs and SOLs (56.4% and 50.6%, respectively). Across all participants, there was a positive relationship between total GNKQ score and age, female sex, and tertiary education (all P values <0.001). Significant differences identified in total GNKQ score between groups remained after adjusting for demographic factors. Young men (M or C) without tertiary education had the lowest GNKQ scores.
Because low general nutrition knowledge may be detrimental to dietary intake, health, and operational readiness in military personnel, nutrition education programs particularly targeted at SOLs and CKs seem warranted.
No preview · Article · Sep 2015 · Journal of the American Academy of Nutrition and Dietetics
[Show abstract][Hide abstract] ABSTRACT: Background: Young women of reproductive age have higher iron requirements due to menstruation, and often restrict energy and iron rich foods due to weight concerns. They are therefore at a greater risk of iron deficiency (ID) and iron deficiency anaemia (IDA), both of which often go undiagnosed.
Objectives: A non-invasive method of assessing risk of ID in young women would be a valuable clinical tool. This study aimed to develop a short, inexpensive clinical assessment to identify young women at increased risk of ID/IDA.
Design: As part of a large (n=300) cross-sectional study of young (18-35y), healthy weight (HW) (BMI 18.5-25) and obese (OB) (BMI≥30) women designed to investigate the relationship between iron status and cognitive function, a food frequency questionnaire (FFQ) (DQESv2 Cancer Council) to assess iron intake and a blood draw to assess iron status were undertaken.
Outcomes: Thus far, a total of 262 young women (HW: n=147; OB: n=115) completed the FFQ and blood draw. Of these women, 15% had ID and 6.6% had IDA. The mean intake of iron was significantly lower in those with ID/IDA (10.8±6.0mg/day) versus those with normal iron status (13.7±7.1mg/day) (p=0.007). With regards to intakes measured by FFQ, 32% with ID and 35% with IDA had an intake below the Estimated Average Requirement (EAR). The HW and OB groups had similar proportions of women with ID/IDA. Modelling to assess the potential contribution of heavy menstrual loss for improving the capacity of FFQ data to inform risk of ID/IDA in young women will be presented.
[Show abstract][Hide abstract] ABSTRACT: Non-alcoholic fatty liver disease (NAFLD) is an independent predictor of CVD in otherwise healthy individuals. Low
-3 PUFA intake has been associated with the presence of NAFLD; however, the relationship between a biomarker of
-3 status – the Omega-3 Index – and liver fat is yet to be elucidated. A total of eighty overweight adults (fifty-six men) completed the anthropometric and biochemical measurements, including the Omega-3 Index, and underwent proton magnetic resonance spectroscopy assessment of liver fat. Bivariate correlations and multiple regression analyses were performed with reference to prediction of liver fat percentage. The mean Omega-3 Index was high in both NAFLD (intrahepatic lipid concentration≥5·5 %) and non-NAFLD groups. The Omega-3 Index, BMI, waist circumference, glucose, insulin, TAG, high-sensitive C-reactive protein (hsCRP) and alanine aminotransferase (ALT) were positively correlated, and HDL and erythrocyte
-3 ratio negatively correlated with liver fat concentration. Regression analysis found that simple anthropometric and demographic variables (waist, age) accounted for 31 % of the variance in liver fat and the addition of traditional cardiometabolic blood markers (TAG, HDL, hsCRP and ALT) increased the predictive power to 43 %. The addition of the novel erythrocyte fatty acid variable (Omega-3 Index) to the model only accounted for a further 3 % of the variance (
=0·049). In conclusion, the Omega-3 Index was associated with liver fat concentration but did not improve the overall capacity of demographic, anthropometric and blood markers to predict NAFLD.
Full-text · Article · Jul 2015 · The British journal of nutrition
[Show abstract][Hide abstract] ABSTRACT: Unlabelled:
This study investigated the association between general nutrition knowledge and dietary quality in a convenience sample of athletes (≥ state level) recruited from four Australian State Sport Institutes. General nutrition knowledge was measured by the validated General Nutrition Knowledge Questionnaire and diet quality by an adapted version of the Australian Recommended Food Score (A-ARFS) calculated from food frequency questionnaire data. Analysis of variance and linear modeling were used to assess relationships between variables.
mean (Standard Deviation). A total of 101 athletes (Males: 37; Females: 64), 18.6 (4.6) years were recruited mainly from team sports (72.0%). Females scored higher than males for both nutrition knowledge (Females: 59.9%; Males: 55.6%; p = .017) and total A-ARFS (Females: 54.2% Males: 49.4%; p = .016). There was no significant influence of age, level of education, athletic caliber or team/individual sport participation on nutrition knowledge or total A-ARFS. However, athletes engaged in previous dietetic consultation had significantly higher nutrition knowledge (61.6% vs. 56.6%; p = .034) but not total A-ARFS (53.6% vs. 52.0%; p = .466). Nutrition knowledge was weakly but positively associated with total A-ARFS (r = .261, p= .008) and A-ARFS vegetable subgroup (r = .252, p = .024) independently explaining 6.8% and 5.1% of the variance respectively. Gender independently explained 5.6% of the variance in nutrition knowledge (p= .017) and 6.7% in total A-ARFS (p = .016). Higher nutrition knowledge and female gender were weakly but positively associated with better diet quality. Given the importance of nutrition to health and optimal sports performance, intervention to improve nutrition knowledge and healthy eating is recommended, especially for young male athletes.
No preview · Article · Jun 2015 · International journal of sport nutrition and exercise metabolism
[Show abstract][Hide abstract] ABSTRACT: Competitive bodybuilders are well known for extreme physique traits and extremes in diet and training manipulation to optimize lean mass and achieve a low body fat. Although many of the dietary dogmas in bodybuilding lack scientific scrutiny, a number, including timing and dosing of high biological value proteins across the day, have more recently been confirmed as effective by empirical research studies. A more comprehensive understanding of the dietary intakes of bodybuilders has the potential to uncover other dietary approaches, deserving of scientific investigation, with application to the wider sporting, and potential health contexts, where manipulation of physique traits is desired.
Our objective was to conduct a systematic review of dietary intake practices of competitive bodybuilders, evaluate the quality and currency of the existing literature, and identify research gaps to inform future studies.
A systematic search of electronic databases was conducted from the earliest record until March 2014. The search combined permutations of the terms 'bodybuilding', 'dietary intake', and 'dietary supplement'. Included studies needed to report quantitative data (energy and macronutrients at a minimum) on habitual dietary intake of competitive bodybuilders.
The 18 manuscripts meeting eligibility criteria reported on 385 participants (n = 62 women). Most studies were published in the 1980-1990s, with three published in the past 5 years. Study methodological quality was evaluated as poor. Energy intake ranged from 10 to 24 MJ/day for men and from 4 to 14 MJ/day for women. Protein intake ranged from 1.9 to 4.3 g/kg for men and from 0.8 to 2.8 g/kg for women. Intake of carbohydrate and fat was <6 g/kg/day and below 30 % of energy, respectively. Carbohydrate intakes were below, and protein (in men) intakes were higher than, the current recommendations for strength athletes, with no consideration for exploration of macronutrient quality or distribution over the day. Energy intakes varied over different phases of preparation, typically being highest in the non-competition (>6 months from competition) or immediate post-competition period and lowest during competition preparation (≤6 months from competition) or competition week. The most commonly reported dietary supplements were protein powders/liquids and amino acids. The studies failed to provide details on rationale for different dietary intakes. The contribution of diet supplements was also often not reported. When supplements were reported, intakes of some micronutrients were excessive (~1000 % of US Recommended Dietary Allowance) and above the tolerable upper limit.
This review demonstrates that literature describing the dietary intake practices of competitive bodybuilders is dated and often of poor quality. Intake reporting required better specificity and details of the rationale underpinning the use. The review suggests that high-quality contemporary research is needed in this area, with the potential to uncover dietary strategies worthy of scientific exploration.
[Show abstract][Hide abstract] ABSTRACT: Background/Aims: Non-alcoholic fatty liver disease (NAFLD) is an independent predictor of CVD. Omega-3 PUFA supplementation has been shown to improve NAFLD. This study aimed to examine the relationship of the Omega-3 Index (O3I; a biomarker of omega-3 status) with liver fat (intrahepatic lipid concentration; IHL%).
Methods: Eighty overweight/obese, healthy, non-smoker adults (56 males) undertook MRI and proton magnetic resonance spectroscopy (1H-MRS) to measure abdominal adiposity and IHL% within seven days of undergoing anthropometric measurements and providing a blood sample for biochemical and erythrocyte lipid analysis. Correlations with liver fat were examined and linear regression for the prediction of IHL% was performed. Mean±SEM are reported.
Results: O3I was high in participants with (9.0±0.3) and without (8.4±0.3) NAFLD, and was positively correlated with IHL% (r=0.255, P=0.029), although further analysis revealed this was stronger and statistically significant for males (r=0.425, P=0.001) and not females (r=0.020, P=0.925). Linear regression showed that O3I and erythrocyte n-6/n-3 ratio together significantly explained 28% of the variance in IHL% (P=0.046). The addition of BMI, waist and age raised the predictive power to 58% (P<0.001). Further addition of biochemical markers (TAG, HDL, high-sensitive CRP (hsCRP)) increased the total variance explained by the model to 66%.
Conclusions: In overweight/obese adults, O3I was unexpectedly positively associated with IHL%, however gender differences apparent in this cohort warrant further research. In overweight obese adults, simple anthropometric and demographic measures may be of equal or greater utility than erythrocyte PUFA analysis in identifying those at increased risk of NAFLD.
Funding source(s): Blackmores; Diabetes Australia.
[Show abstract][Hide abstract] ABSTRACT: In athletes, caffeine use is common although its effects on sleep have not been widely studied. This randomised, double-blind, placebo-controlled crossover trial investigated the effects of late-afternoon caffeine and carbohydrate-electrolyte (CEB) co-ingestion on cycling performance and nocturnal sleep. Six male cyclists/triathletes (age 27.5 +/- A 6.9 years) completed an afternoon training session (TS; cycling 80 min; 65 % VO2max) followed by a 5 kJ kg(-1) cycling time trial (TT). Caffeine (split dose 2 x 3 mg kg(-1)) or placebo was administered 1 h prior and 40 min into the TS. A 7.4 % CEB (3 ml kg(-1) every 15 min) was administered during the TS, followed 30 min after by a standardised evening meal. Participants retired at their usual bedtime and indices of sleep duration and quality were monitored via polysomnography. Data: mean +/- A SD. All participants performed better in the caffeine TT (caffeine 19.7 +/- A 3.3; placebo 20.5 +/- A 3.5 min; p = 0.006), while ratings of perceived exertion (caffeine 12.0 +/- A 0.6; placebo 12.9 +/- A 0.7; p = 0.004) and heart rate (caffeine 175 +/- A 6; placebo 167 +/- A 11 bpm; p = 0.085) were lower in the caffeine TS. Caffeine intake induced significant disruptions to a number of sleep indices including increased sleep onset latency (caffeine 51.1 +/- A 34.7; placebo 10.2 +/- A 4.2 min; p = 0.028) and decreased sleep efficiency (caffeine 76.1 +/- A 19.6; placebo 91.5 +/- A 4.2 %; p = 0.028), rapid eye movement sleep (caffeine 62.1 +/- A 19.6; placebo 85.8 +/- A 24.7 min; p = 0.028) and total sleep time (caffeine 391 +/- A 97; placebo 464 +/- A 49 min; p = 0.028). This study supports a performance-enhancing effect of caffeine, although athletes (especially those using caffeine for late-afternoon/evening training and competition) should consider its deleterious effects on sleep.
Full-text · Article · Aug 2014 · Arbeitsphysiologie
[Show abstract][Hide abstract] ABSTRACT: Glycemic index (GI) manipulation of pre-event meals has been used as a dietary strategy to enhance endurance exercise performance. The existing literature investigating this strategy appears equivocal however, a meta-analysis has not been conducted. PURPOSE: This systematic review evaluated the effect of a low GI (LGI) or high GI (HGI) pre-exercise meal on exercise performance using meta-analysis. METHODS: A systematic search was conducted to identify relevant randomized, crossover trials. Manuscripts were included if they used: non-sedentary, healthy participants aged ≥16 y; a LGI (<55) and HGI (>70) meal consumed 30-180 min prior to exercise; exercise protocols that included a time trial (TT) or time to exhaustion test (TTE) only, or a submaximal bout followed by a TT or TTE. Additional sub-analysis was conducted for studies where carbohydrate (CHO) was also consumed during exercise. After data extraction of participant, meal and exercise data, effect sizes (ES) and 95% confidence intervals (95% CI) were calculated for each study and an overall effect for each exercise protocol was determined. Data: ES (95% CI). RESULTS: The initial search yielded 3,431 citations. After exclusion of ineligible studies, 21 articles were included. Studies used a mix of active male and female participants (VO2peak - females: >44; males: >50 ml.kg-1.min-1). The CHO content of pre-exercise meals ranged from 0.17 g to 2 g.kg-1 of body mass. No significant effect of pre-exercise meal GI on TT performance was observed [ES: 0.17 (-0.16 to 0.51); p=0.31]. In submaximal + TT studies where no CHO was ingested during exercise, performance improved non-significantly with a HGI meal [ES: -0.28 (-1.01 to 0.44); p=0.45]. In studies where CHO was consumed during exercise, a LGI meal non-significantly enhanced performance [ES: 0.30 (-0.25 to 0.85); p=0.28]. TTE performance was not significantly improved by either meal type, although LGI was favored [ES: 0.40 (-0.31 to 1.11); p=0.27]. No consistent metabolic responses (glucose, insulin, lactate and respiratory exchange ratio) during exercise were observed with either a LGI or HGI meal. CONCLUSION: There was no clear ergogenic benefit of consuming either a LGI or HGI pre-exercise meal for endurance exercise performance.
[Show abstract][Hide abstract] ABSTRACT: Although iron deficiency is common in women especially during dieting, weight management trials rarely examine the longitudinal impact of genetics on iron. This study examined the associations between the TMPRSS6 rs855791 polymorphism and iron indices at baseline and after a 12-month trial comparing two weight loss diets (higher-protein, higher-haem iron (HPHI) vs lower-protein, lower-haem iron (LPLI)). A total of 76 young overweight women (18-25y; BMI⩾27.5 kg/m(2)) were included at baseline, with 27 (HPHI: n=15; LPLI: n=12) completing the 12-month trial. At baseline, C allele homozygotes exhibited higher serum iron (P=0.047) and lower hepcidin (P=0.023) compared with T allele carriers. After 12 months, no genotypic differences were observed for ferritin and soluble transferrin receptor, although C homozygotes on HPHI showed higher serum iron and transferrin saturation (P<0.05). Results indicate that rs855791 can influence iron metabolism to some extent, but its impact on storage and functional iron status is small relative to dietary protein/iron manipulation.European Journal of Clinical Nutrition advance online publication, 7 May 2014;; doi:10.1038/ejcn.2014.82.
No preview · Article · May 2014 · European journal of clinical nutrition
[Show abstract][Hide abstract] ABSTRACT: The present systematic review examined the relationship between nutrition knowledge and dietary intake in adults (mean age ≥ 18 years). Relevant databases were searched from the earliest record until November 2012. Search terms included: nutrition; diet or food knowledge and energy intake; feeding behaviour; diet; eating; nutrient or food intake or consumption. Included studies were original research articles that used instruments providing quantitative assessment of both nutrition knowledge and dietary intake and their statistical association. The initial search netted 1 193 393 potentially relevant articles, of which twenty-nine were eligible for inclusion. Most of them were conducted in community populations (n 22) with fewer (n 7) in athletic populations. Due to the heterogeneity of methods used to assess nutrition knowledge and dietary intake, a meta-analysis was not possible. The majority of the studies (65·5 %: community 63·6 %; athletic 71·4 %) reported significant, positive, but weak (r< 0·5) associations between higher nutrition knowledge and dietary intake, most often a higher intake of fruit and vegetables. However, study quality ranged widely and participant representation from lower socio-economic status was limited, with most participants being tertiary educated and female. Well-designed studies using validated methodologies are needed to clarify the relationship between nutrition knowledge and dietary intake. Diet quality scores or indices that aim to evaluate compliance to dietary guidelines may be particularly valuable for assessing the relationship between nutrition knowledge and dietary intake. Nutrition knowledge is an integral component of health literacy and as low health literacy is associated with poor health outcomes, contemporary, high-quality research is needed to inform community nutrition education and public health policy.
Full-text · Article · Mar 2014 · The British journal of nutrition
[Show abstract][Hide abstract] ABSTRACT: The control of eating behaviours such as hunger and disinhibition is problematic for women during weight management. Higher-protein (HP) diets have been shown to promote greater weight reduction than higher-carbohydrate (HC) diets, but their impact on eating behaviours is relatively unexplored. This study compared two iso-energetically restricted (5,600 kJ/day) diets differing in protein (HP: 32 %, HC: 20 %) and carbohydrate (HP: 41 %, HC: 58 %) on appetite ratings, restraint, disinhibition, perceived hunger and binge eating in 36 (HP: n = 21, HC: n = 15) young (18-25 years), healthy women with BMI ≥27.5 kg/m(2) who completed a 12-month clinical weight management trial. Dietary compliance and self-worth were also assessed. Results showed that both diets induced improvements in restraint and disinhibition from baseline (p < 0.01), with HP participants losing a non-significantly greater amount of weight than HC participants (HP: 9.6 ± 2.6, HC: 4.1 ± 1.4 kg, p = 0.07). Despite reasonable compliance, no significant appetite and eating behaviour differences were observed between the diets. Reduction in disinhibition (regardless of diet) significantly predicted weight loss (β = 0.574, p < 0.001) and self-worth improvement (β = -0.463, p = 0.002), while HP intake predicted greater self-worth change (β = -0.371, p = 0.011). This study demonstrates that young women can improve restraint and disinhibition on a weight management programme, with the reduction in disinhibition shown to be a key predictor of weight loss. HP intake may offer some advantage for increasing self-worth but not eating behaviours. As HP diets are popular, these findings warrant confirmation in a larger sample.
No preview · Article · Mar 2014 · Eating and weight disorders: EWD
[Show abstract][Hide abstract] ABSTRACT: Objective:
The purpose of this study was to assess the effect of high intensity interval training (HIIT) versus continuous aerobic exercise training (CONT) or placebo (PLA) on body composition by randomized controlled design.
Work capacity and body composition (dual-energy X-ray absorptiometry) were measured before and after 12 weeks of intervention in 38 previously inactive overweight adults.
There was a significant group × time interaction for change in work capacity (P < 0.001), which increased significantly in CONT (23.8 ± 3.0%) and HIIT (22.3 ± 3.5%) but not PLA (3.1 ± 5.0%). There was a near-significant main effect for percentage trunk fat, with trunk fat reducing in CONT by 3.1 ± 1.6% and in PLA by 1.1 ± 0.4%, but not in HIIT (increase of 0.7 ± 1.0%) (P = 0.07). There was a significant reduction in android fat percentage in CONT (2.7 ± 1.3%) and PLA (1.4 ± 0.8%) but not HIIT (increase of 0.8 ± 0.7%) (P = 0.04).
These data suggest that HIIT may be advocated as a time-efficient strategy for eliciting comparable fitness benefits to traditional continuous exercise in inactive, overweight adults. However, in this population HIIT does not confer the same benefit to body fat levels as continuous exercise training.
Full-text · Article · Jan 2014 · Journal of obesity
[Show abstract][Hide abstract] ABSTRACT: Objective. The purpose of this study was to assess the effect of high intensity interval training (HIIT) versus continuous aerobic exercise training (CONT) or placebo (PLA) on body composition by randomized controlled design. Methods. Work capacity and body composition (dual-energy X-ray absorptiometry) were measured before and after 12 weeks of intervention in 38 previously inactive overweight adults. Results. There was a significant group × time interaction for change in work capacity (), which increased significantly in CONT (%) and HIIT (%) but not PLA (%). There was a near-significant main effect for percentage trunk fat, with trunk fat reducing in CONT by % and in PLA by %, but not in HIIT (increase of %) (). There was a significant reduction in android fat percentage in CONT (%) and PLA (%) but not HIIT (increase of %) (). Conclusion. These data suggest that HIIT may be advocated as a time-efficient strategy for eliciting comparable fitness benefits to traditional continuous exercise in inactive, overweight adults. However, in this population HIIT does not confer the same benefit to body fat levels as continuous exercise training.
Full-text · Article · Jan 2014 · Journal of obesity
[Show abstract][Hide abstract] ABSTRACT: Young overweight women are at risk of iron and zinc deficiency. This study assessed iron, zinc and inflammatory status during a 12-month weight loss trial in young women (18-25 y; BMI >=27.5 kg/m2) randomised to a higher-protein (HP: 32% protein; 12.2 mg/day iron; 11.7 mg/day zinc) or lower-protein (LP: 20%; 9.9 mg/day; 7.6 mg/day respectively) diet with contrasting haem iron and zinc content. In completers (HP: n=21; LP: n=15), HP participants showed higher median ferritin (52.0 vs 39.0 μg/L; p=0.021) and lower median soluble transferrin receptor-ferritin index (sTfR-F; 0.89 vs 1.05; p=0.024) although concentrations remained within normal range for both diets. Median C-reactive protein (CRP; HP: 3.54; LP: 4.63 mg/L) and hepcidin (HP: 5.70; LP: 8.25 ng/mL) were not elevated at baseline, and no longitudinal between-diet differences were observed for zinc and CRP. Compared to those with <5% weight loss, HP participants losing >=10% weight showed lower median sTfR-F (0.76 vs 1.03; p=0.019) at six months. Impact of >=10% weight loss on iron was more apparent in LP participants who exhibited greater mean serum iron (20.0 vs 13.5 μmol/L; p=0.002), transferrin saturation (29.8% vs 19.4%; p=0.001) and lower sTfR (1.24 vs 1.92 mg/L; p=0.034) at 12 months. Results show normal iron and zinc status can be maintained during 12 months of energy restriction. In the absence of elevated baseline inflammation and hepcidin, a more favourable iron profile in those with >=10% weight loss may reflect stronger compliance or the potential influence of iron regulatory mechanisms unrelated to inflammatory hepcidin reduction.
No preview · Article · Dec 2013 · Asia Pacific Journal of Clinical Nutrition
[Show abstract][Hide abstract] ABSTRACT: This chapter focuses briefly on the available evidence supporting the relevance of attaining a desirable weight or body composition for optimizing sports performance and why this may be challenging for athletes. The chapter examines dietary strategies for assisting athletes to safely manipulate weight and body composition. Morphological attributes generally considered important to sports performance include body mass or weight, stature, and skeletal muscle or fat mass. Diet and training can significantly alter body mass and composition. Genetic factors ultimately underpin the limit to which the physique characteristics can be manipulated. Weight management programs for athletes need to consider energy and fuel needs for training. The recommendation for an athlete to undertake weight or fat loss should be given serious consideration, even though dieting and losing weight appear to be commonplace in the community.
[Show abstract][Hide abstract] ABSTRACT: Purpose:
The purpose of this study was to establish whether sensory factors associated with cold-beverage ingestion exert an ergogenic effect on endurance performance independent of thermoregulatory or cardiovascular factors.
Ten males performed three trials involving 90 min of steady state cycling (SS; 62% VO2max) in the heat (32.1 ± 0.9 °C, 40 ± 2.4% relative humidity) followed by a 4 kJ/kg body mass time trial (TT). During SS, participants consumed an identical volume (260 ± 38 g) of sports beverage (7.4% carbohydrate) every 15 min as either ice slushy (-1 °C; ICE), thermoneutral liquid (37 °C; CON), or thermoneutral liquid consumption with expectorated ice slushy mouthwash (WASH).
Rectal temperature, hydration status, heart rate, and skin blood flow were not different between trials. Gastrointestinal (pill) temperature was lower in ICE (35.6 ± 2.7 °C) versus CON (37.4 ± 0.7 °C, p = .05). Heat storage tended to be lower with ICE during SS (14.7 ± 8.4 W.m(-2), p = .08) and higher during TT (68.9 ± 38.6 W.m(-2), p = .03) compared with CON (22.1 ± 6.6 and 31.4 ± 27.6 W.m(-2)). ICE tended to lower the rating of perceived exertion (RPE, 12.9 ± 0.6, p = .05) and improve thermal comfort (TC, 4.5 ± 0.2; p = .01) vs. CON (13.8 ± 1.0 and 5.2 ± 0.2 respectively). WASH RPE (13.0 ± 0.8) and TC (4.8 ± 0.2) tended to be lower versus CON (p = .07 and p = .09 respectively). ICE improved performance (18:28 ± 1:03) compared with CON (20:24 ± 1:46) but not WASH (19:45 ± 1:43).
Improved performance with ICE ingestion likely resulted from the creation of a gastrointestinal heat sink, reducing SS heat storage. Although the benefits of cold-beverage consumption are more potent when there is ingestion, improved RPE, TC, and meaningful performance improvement with WASH supports an independent sensory effect of presenting a cold stimulus to the mouth.
Full-text · Article · Oct 2013 · International Journal of Sport Nutrition and Exercise Metabolism
[Show abstract][Hide abstract] ABSTRACT: To comprehensively describe anthropometric characteristics of Australian junior elite rugby league players and assess potential anthropometric dissimilarities between players of varying positional groups, ethnicity (Polynesian vs. non-Polynesian) and playing level (junior vs. professional; using published data from Australian professional players).
Height, body mass, eight skinfolds, five girths and two bone breadths were measured with body fat (BF%) and somatotype calculated using population-appropriate equations. Data: mean±SD.
This study recruited 116 junior players. Mean age, mass and BF% were 17±1y, 87.0±11.6kg and 14.0±4.6% respectively. Compared to backs, forwards had greater mass (92.6±12.2 vs. 80.9±7.1kg), skinfolds, girths, femur breadth, BF% (16.1±4.8% vs. 11.8±3.2%) (all p<0.01), and were more endo- and mesomorphic, but less ectomorphic (all p<0.001). Compared to other positional groups, props had greater mass, adiposity, calf girth and endomorphy, while adjustables (fullbacks, five-eighths, halfbacks, hookers) had the shortest stature (all p<0.01). Polynesians exhibited greater height (181.0±5.7 vs. 178.7±6.3cm), mass (90.6±11.7 vs. 84.7±11.1kg), arm and calf girths, bone breadths and mesomorphy (7.6±1.2 vs. 6.7±1.1) than non-Polynesians (all p<0.05). Juniors had lower height, mass, waist and smaller sum of skinfolds than professional players (all p<0.05).
Greater mass, mesomorphy, adiposity and bone size in forwards is desirable for tackling and attacking and may protect against high impact forces sustained in this position. Advantageous anthropometric attributes exhibited in Polynesian players may influence selection into junior elite rugby league teams. Anthropometric data from this study may assist other junior players and coaches with training, dietary modification and position allocation.