Search Results

You are looking at 1 - 10 of 10 items for

  • Author: Elizabeth M. Broad x
Clear All Modify Search
Restricted access

Elizabeth M. Broad, Ronald J. Maughan and Stuart D.R. Galloway

The effects of 15 d of supplementation with L-carnitine L-tartrate (LC) on metabolic responses to gradedintensity exercise under conditions of altered substrate availability were examined. Fifteen endurance-trained male athletes undertook exercise trials after a 2-d high-carbohydrate diet (60% CHO, 25% fat) at baseline (D0), on Day 14 (D14), and after a single day of high fat intake (15% CHO, 70% fat) on Day 15 (D15) in a double-blind, placebo-controlled, pair-matched design. Treatment consisted of 3 g LC (2 g L-carnitine/d; n = 8) or placebo (P, n = 7) for 15 d. Exercise trials consisted of 80 min of continuous cycling comprising 20-min periods at each of 20%, 40%, 60%, and 80% VO2peak. There was no significant difference between whole-body rates of CHO and fat oxidation at any workload between D0 and D14 trials for either the P or LC group. Both groups displayed increased fat and reduced carbohydrate oxidation between the D14 and D15 trials (p < .05). During the D15 trial, heart rate (p < .05 for 20%, 40%, and 60% workloads) and blood glucose concentration (p < .05 for 40% and 60% workloads) were lower during exercise in the LC group than in P. These responses suggest that LC may induce subtle changes in substrate handling in metabolically active tissues when fattyacid availability is increased, but it does not affect whole-body substrate utilization during short-duration exercise at the intensities studied.

Restricted access

Alan J. McCubbin, Gregory R. Cox and Elizabeth M. Broad

This case study describes the nutrition plans, intakes and experiences of five ultra-marathon runners who completed the Marathon des Sables in 2011 and 2013; age 37 (28–43) y, height 184 (180–190) cm, body mass 77.5 (71–85.5) kg, marathon personal best 3:08 (2:40–3:32). MdS is a 7-day, six-stage ultra-running stage race held in the Sahara Desert (total distance of timed stages 1–5 was 233.2 km in 2011, 223.4 km in 2013). Competitors are required to carry all equipment and food (except water) for the race duration, a minimum of 8,360 kJ/day and total pack weight of 6.5–15 kg. Total food mass carried was 4.2 (3.8–4.7) kg or 0.7 (0.5–1.1) kg/day. Planned energy (13,550 (10,323–18,142) kJ/day), protein (1.3 (0.8–1.8) g/kg/day), and carbohydrate (6.2 (4.3–9.2) g/kg/day) intakes on the fully self-sufficient days were slightly below guideline recommendations, due to the need to balance nutritional needs with food mass to be carried. Energy density was 1,636 (1,475–1,814) kJ/100g. 98.5% of the planned food was consumed. Fluid consumption was ad libitum with no symptoms or medical treatment required for dehydration or hyponatremia. During-stage carbohydrate intake was 42 (20–64) g/hour. Key issues encountered by runners included difficulty consuming foods due to dry mouth, and unpalatability of sweet foods (energy gels, sports drinks) when heated in the sun. Final classification of the runners ranged from 11th to 175th of 970 finishers in 2013, and 132nd of 805 in 2011. The described pattern of intake and macronutrient quantities were positively appraised by the five runners.

Restricted access

Elizabeth M. Broad, Ronald J. Maughan and Stuart D.R Galloway

Twenty nonvegetarian active males were pair-matched and randomly assigned to receive 2 g of L-carnitine L-tartrate (LC) or placebo per day for 2 wk. Participants exercised for 90 min at 70% VO2max after 2 days of a prescribed diet (M ±SD: 13.6 ± 1.6 MJ, 57% carbohydrate, 15% protein, 26% fat, 2% alcohol) before and after supplementation. Results indicated no change in carbohydrate oxidation, nitrogen excretion, branched-chain amino acid oxidation, or plasma urea during exercise between the beginning and end of supplementation in either group. After 2 wk of LC supplementation the plasma ammonia response to exercise tended to be suppressed (0 vs. 2 wk at 60 min exercise, 97 ± 26 vs. 80 ± 9, and 90 min exercise, 116 ± 47 vs. 87 ± 25 μmol/L), with no change in the placebo group. The data indicate that 2 wk of LC supplementation does not affect fat, carbohydrate, and protein contribution to metabolism during prolonged moderate-intensity cycling exercise. The tendency toward suppressed ammonia accumulation, however, indicates that oral LC supplementation might have the potential to reduce the metabolic stress of exercise or alter ammonia production or removal, which warrants further investigation.

Restricted access

Elizabeth M. Broad, Ronald J. Maughan and Stuart D.R. Galloway

In a randomized, placebo-controlled, double-blind crossover design, 15 trained males undertook exercise trials during two 4 wk supplementation periods, with either 3 g L-Carnitine L-tartrate (LCLT) or 3 g placebo (P) daily. Total carbohydrate and fat oxidation during 90 min steady state cycling were not different between 0 or 4 wk within LCLT or P trials (mean ± standard deviation: carbohydrate oxidation P0 99 ± 36, P4W 111 ± 27, LCLT0 107 ± 33, LCLT4W 112 ± 32 g, respectively; fat oxidation P0 99 ± 28, P4W 92 ± 21, LCLT0 94 ± 18, LCLT4W 90 ± 22 g, respectively). Subsequent 20 km time trial duration was shorter after P (P0 31:29 ± 3:50, P4W 29:55 ± 2:58 min:s, P < 0.01), with no significant change over LCLT (LCLT0 31:46 ± 4:06, LCLT4W 31.19 ± 4.08 min:s). Four weeks LCLT supplementation had no effect on substrate utilization or endurance performance.

Restricted access

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.

Restricted access

Elizabeth M. Broad, Louise M. Burke, Greg R. Cox, Prue Heeley and Malcolm Riley

Fluid losses (measured by body weight changes) and voluntary fluid intakes were measured in elite basketball, netball, and soccer teams during typical summer and winter exercise sessions to determine fluid requirements and the degree of fluid replacement. Each subject was weighed in minimal clothing before and immediately after training, weights, and competition sessions; fluid intake, duration of exercise, temperature and humidity, and opportunity to drink were recorded. Sweat rates were greatest during competition sessions and significantly lower during weights sessions for all sports. Seasonal variation in dehydration (%DH) was not as great as may have been expected, particularly in sports played indoors. Factors influencing fluid replacement during exercise included provision of an individual water bottle, proximity to water bottles during sessions, encouragement to drink, rules of the game, duration and number of breaks or substitutions, and awareness of personal sweat rates. Guidelines for optimizing fluid intakes in these three sports are provided.

Restricted access

Louise M. Burke, Gary Slater, Elizabeth M. Broad, Jasmina Haukka, Sofie Modulon and William G. Hopkins

We undertook a dietary survey of 167 Australian Olympic team athletes (80 females and 87 males) competing in endurance sports (n = 41), team sports (n = 31), sprint- or skill-based sports (n = 67), and sports in which athletes are weight-conscious (n = 28). Analysis of their 7-day food diaries provided mean energy intakes, nutrient intakes, and eating patterns. Higher energy intakes relative to body mass were reported by male athletes compared with females, and by endurance athletes compared with other athletes. Endurance athletes reported substantially higher intakes of carbohydrate (CHO) than other athletes, and were among the athletes most likely to consume CHO during and after training sessions. Athletes undertaking weight-conscious sports reported relatively low energy intakes and were least likely to consume CHO during a training session or in the first hour of recovery. On average, athletes reported eating on ~5 separate occasions each day, with a moderate relationship between the number of daily eating occasions and total energy intake. Snacks, defined as food or drink consumed between main meals, provided 23% of daily energy intake and were chosen from sources higher in CHO and lower in fat and protein than foods chosen at meals. The dietary behaviors of these elite athletes were generally consistent with guidelines for sports nutrition, but intakes during and after training sessions were often sub-optimal. Although it is of interest to study the periodicity of fluid and food intake by athletes, it is difficult to compare across studies due to a lack of standardized terminology.

Restricted access

Adam J. Zemski, Shelley E. Keating, Elizabeth M. Broad and Gary J. Slater

Rugby union athletes have divergent body composition based on the demands of their on-field playing position and ethnicity. With an established association between physique traits and positional requirements, body composition assessment is routinely undertaken. Surface anthropometry and dual-energy X-ray absorptiometry (DXA) are the most common assessment techniques used, often undertaken synchronously. This study aims to investigate the association between DXA and surface anthropometry when assessing longitudinal changes in fat-free mass (FFM) and fat mass (FM) in rugby union athletes. Thirty-nine elite male rugby union athletes (age: 25.7 ± 3.1 years, stature: 187.6 ± 7.7 cm, and mass: 104.1 ± 12.2 kg) underwent assessment via DXA and surface anthropometry multiple times over three consecutive international seasons. Changes in the lean mass index, an empirical measure to assess proportional variation in FFM, showed large agreement with changes in DXA FFM (r = .54, standard error of the estimate = 1.5%, p < .001); the strength of association was stronger among forwards (r = .63) compared with backs (r = .38). Changes in the sum of seven skinfolds showed very large agreement with changes in DXA FM (r = .73, standard error of the estimate = 5.8%, p < .001), with meaningful differences observed regardless of ethnicity (Whites: r = .75 and Polynesians: r = .62). The lean mass index and sum of seven skinfolds were able to predict the direction of change in FFM and FM 86% and 91% of the time, respectively, when DXA change was >1 kg. Surface anthropometry measures provide a robust indication of the direction of change in FFM and FM, although caution may need to be applied when interpreting magnitude of change, particularly with FM.

Restricted access

Adam J. Zemski, Shelley E. Keating, Elizabeth M. Broad, Damian J. Marsh, Karen Hind and Gary J. Slater

During preseason training, rugby union (RU) athletes endeavor to enhance physical performance characteristics that are aligned with on-field success. Specific physique traits are associated with performance; therefore body composition assessment is routinely undertaken in elite environments. This study aimed to quantify preseason physique changes in elite RU athletes with unique morphology and divergent ethnicity. Twenty-two White and Polynesian professional RU athletes received dual-energy X-ray absorptiometry assessments at the beginning and conclusion of an 11-week preseason. Interactions between on-field playing position and ethnicity in body composition adaptations were explored, and the least significant change model was used to evaluate variations at the individual level. There were no combined interaction effects with the variables position and ethnicity and any body composition measure. After accounting for baseline body composition, Whites gained more lean mass during the preseason than Polynesians (2,425 ± 1,303 g vs. 1,115 ± 1,169 g; F = 5.4, p = .03). Significant main effects of time were found for whole body and all regional measures with fat mass decreasing (F = 31.1–52.0, p < .01), and lean mass increasing (F = 12.0–40.4, p < .01). Seventeen athletes (nine White and eight Polynesian) had a reduction in fat mass, and eight athletes (six White and two Polynesian) increased lean mass. This study describes significant and meaningful physique changes in elite RU athletes during a preseason period. Given the individualized approach applied to athletes in regard to nutrition and conditioning interventions, a similar approach to that used in this study is recommended to assess physique changes in this population.

Restricted access

Matthew W. Hoon, Andrew M. Jones, Nathan A. Johnson, Jamie R. Blackwell, Elizabeth M. Broad, Bronwen Lundy, Anthony J. Rice and Louise M. Burke

Context:

Beetroot juice is a naturally rich source of inorganic nitrate (NO3 ), a compound hypothesized to enhance endurance performance by improving exercise efficiency.

Purpose:

To investigate the effect of different doses of beetroot juice on 2000-m ergometer-rowing performance in highly trained athletes.

Methods:

Ten highly trained male rowers volunteered to participate in a placebo-controlled, double-blinded crossover study. Two hours before undertaking a 2000-m rowing-ergometer test, subjects consumed beetroot juice containing 0 mmol (placebo), 4.2 mmol (SINGLE), or 8.4 mmol (DOUBLE) NO3 . Blood samples were taken before supplement ingestion and immediately before the rowing test for analysis of plasma [NO3 ] and [nitrite (NO2 )].

Results:

The SINGLE dose demonstrated a trivial effect on time to complete 2000 m compared with placebo (mean difference: 0.2 ± 2.5 s). A possibly beneficial effect was found with DOUBLE compared with SINGLE (mean difference –1.8 ± 2.1 s) and with placebo (–1.6 ± 1.6 s). Plasma [NO2 ] and [NO3 ] demonstrated a dose-response effect, with greater amounts of ingested nitrate leading to substantially higher concentrations (DOUBLE > SINGLE > placebo). There was a moderate but insignificant correlation (r = –.593, P = .055) between change in plasma [NO2 ] and performance time.

Conclusion:

Compared with nitratedepleted beetroot juice, a high (8.4 mmol NO3 ) but not moderate (4.2 mmol NO3 ) dose of NO3 in beetroot juice, consumed 2 h before exercise, may improve 2000-m rowing performance in highly trained athletes.