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Kristy Martin, Disa Smee, Kevin G. Thompson and Ben Rattray

Purpose:

Nitrate supplementation improves endurance exercise and single bouts of high-intensity activity, but its effect on repeated sprints is unclear. This study is the first to investigate the effects of acute dietary nitrate supplementation during a high-intensity intermittent-sprint test to exhaustion.

Methods:

Team-sport athletes (9 male, age 22.3 ± 2.1 y, VO2max 57.4 ± 8.5 mL · kg−1 · min−1; 7 female, age 20.7 ± 1.3 y, VO2max 47.2 ± 8.5 mL · kg−1 · min−1) were assigned to a double-blind, randomized, crossover design. Participants consumed 70 mL of concentrated beetroot juice containing a minimum of 0.3 g of nitrate (NT) or 70 mL of placebo (PL) 2 h before a repeated-sprint protocol involving repeated 8-s sprints with 30-s recovery on a cycle ergometer to exhaustion.

Results:

Fewer sprints (NT = 13 ± 5 vs PL = 15 ± 6, P = .005, d = 0.41) and less total work (NT = 49.2 ± 24.2 kJ vs PL = 57.8 ± 34.0 kJ, P = .027, d = 0.3) were completed in NT relative to PL. However there was no difference in overall mean power output or the mean power output for each individual 8-s sprint.

Conclusions:

These findings suggest that dietary nitrate is not beneficial for improving repeated-sprint performance, at least when such sprints are near-maximal and frequent in nature. The lack of an effect of nitrate at near-maximal oxygen uptake supports the suggestion that at greater exercise intensities nitrate does not have an ergogenic effect.

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Disa J. Smee, Anthony Walker, Ben Rattray, Julie A. Cooke, Ben G. Serpell and Kate L. Pumpa

Given the importance of body composition in maintaining optimal physical and functional capacities, the use of appropriate, field-based assessment tools should be a priority to assist in maintaining the occupational safety of firefighters and the community. For ease, body mass index has often been used to assess these changes. However, it is limited in its accuracy. The purposes of this study were twofold: (a) to compare the validity of different measures of body composition against dual-energy X-ray absorptiometry (DXA) in urban firefighters and (b) to assess these measures in their ability to provide meaningful interpretation of criteria-driven categories of adiposity. A total of 64 male firefighters (age = 44.0 ± 9.5 years) underwent full anthropometric profiling (predictor equations used to determine body fat percentage [BF%]), bioelectrical impedance analysis (BIA), and DXA assessments. Participants’ body mass index was calculated, and BF% and lean mass were determined along with criteria-driven categorizations of adiposity. Anthropometric (skinfolds) predictor equations (e.g., mean bias = −4.4% for BF%) were typically closer to DXA measures, compared with BIA (9.4% for BF%). However, when determining categories of criteria-driven adiposity, BIA (42.9% overweight or obese) provided closer estimates to the DXA-determined distribution (44.6%) than anthropometric-based measures (up to 40%). Body mass index appears an inappropriate measure for accurately determining categories of adiposity with 64.1% classified as overweight or obese. Given the logistical constraints of anthropometric profiling, and the closeness of BIA to DXA in adiposity categories, BIA may be a suitable alternative to DXA for assessing body composition in professional urban firefighters.

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Lachlan J.G. Mitchell, Ben Rattray, Paul Wu, Philo U. Saunders and David B. Pyne

Purpose: Critical speed (CS) and supra-CS distance capacity (D′) are useful metrics for monitoring changes in swimmers’ physiological and performance capacities. However, the utility of these metrics across a season has not been systematically evaluated in high-level swimmers. Methods: A total of 27 swimmers (mean [SD]: 18 females, age = 19.1 [2.9] y, and 9 males, age = 19.5 [1.9] y) completed the 12 × 25-m swimming test multiple times (4 [3] tests/swimmer) across a 2-y period. Season-best times in all distances for the test stroke were sourced from publicly available databases. Swimmers’ distance speciality was determined as the event with the time closest to world record. Four metrics were calculated from the 12 × 25-m test: CS, D′, peak speed, and drop-off %. Results: Guyatt responsiveness index values were calculated to ascertain the practically relevant sensitivity of each 12 × 25-m metric: CS = 1.5, peak speed = 2.3, D′ = 2.1, and drop-off % = 2.6. These values are modified effect sizes; all are large effects. Bayesian mixed modeling showed substantial between-subjects differences between genders and strokes for each variable but minimal within-subject changes across the season. Drop-off % was lower in 200-m swimmers (14.0% [3.3%]) than in 100-m swimmers (18.1% [4.1%], P = .003, effect size = 1.10). Conclusions: The 12 × 25-m test is best suited to differentiating between swimmers of different strokes and events. Further development is needed to improve its utility in quantifying meaningful changes over a season for individual swimmers.

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Courtney J. McGowan, David B. Pyne, Kevin G. Thompson and Ben Rattray

Purpose:

Targeted passive heating and completion of dryland-based activation exercises within the warm-up can enhance sprint freestyle performance. The authors investigated if these interventions would also elicit improvements in sprint breaststroke swimming performance.

Methods:

Ten national and internationally competitive swimmers (~805 FINA (Fédération internationale de natation) 2014 scoring points; 6 men, mean ± SD 20 ± 1 y; 4 women, 21 ± 3 y) completed a standardized pool warm-up (1550 m) followed by a 30-min transition phase and a 100-m breaststroke time trial. In the transition phase, swimmers wore a conventional tracksuit and remained seated (control) or wore tracksuit pants with integrated heating elements and performed a 5-min dryland-based exercise routine (combo) in a crossover design.

Results:

Performance in the 100-m time trial (control: 68.6 ± 4.0 s, combo: 68.4 ± 3.9 s, P = .55) and start times to 15 m (control: 7.3 ± 0.6 s; combo: 7.3 ± 0.6 s; P = .81) were not different between conditions. It was unclear (P = .36) whether combo (–0.12°C ± 0.19°C [mean ± 90% confidence limits]) elicited an improvement in core temperature maintenance in the transition phase compared with control (–0.31°C ± 0.19°C). Skin temperature immediately before commencement of the time trial was higher (by ~1°C, P = .01) within combo (30.13°C ± 0.88°C [mean ± SD]) compared with control (29.11°C ± 1.20°C). Lower-body power output was not different between conditions before the time trial.

Conclusions:

Targeted passive heating and completion of dryland-based activation exercises in the transition phase does not enhance sprint breaststroke performance despite eliciting elevated skin temperature immediately before time trial commencement.

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Courtney J. McGowan, David B. Pyne, Kevin G. Thompson, John S. Raglin and Ben Rattray

Context:

An exercise bout completed several hours prior to an event may improve competitive performance later that same day.

Purpose:

To examine the influence of morning exercise on afternoon sprint-swimming performance.

Methods:

Thirteen competitive swimmers (7 male, mean age 19 ± 3 y; 6 female, mean age 17 ± 3 y) completed a morning session of 1200 m of variedintensity swimming (SwimOnly), a combination of varied-intensity swimming and a resistance-exercise routine (SwimDry), or no morning exercise (NoEx). After a 6-h break, swimmers completed a 100-m time trial.

Results:

Time-trial performance was faster in SwimOnly (1.6% ± 0.6, mean ± 90% confidence limit, P < .01) and SwimDry (1.7% ± 0.7%, P < .01) than in NoEx. Split times for the 25- to 50-m distance were faster in both SwimOnly (1.7% ± 1.2%, P = .02) and SwimDry (1.5% ± 0.8%, P = .01) than in NoEx. The first 50-m stroke rate was higher in SwimOnly (0.70 ± 0.21 Hz, mean ± SD, P = .03) and SwimDry (0.69 ± 0.18 Hz, P = .05) than in NoEx (0.64 ± 0.16 Hz). Before the afternoon session, core (0.2°C ± 0.1°C [mean ± 90% confidence limit], P = .04), body (0.2°C ± 0.1°C, P = .02), and skin temperatures (0.3°C ± 0.3°C, P = .02) were higher in SwimDry than in NoEx.

Conclusions:

Completion of a morning swimming session alone or together with resistance exercise can substantially enhance sprint-swimming performance completed later the same day.