Effects of dietary nitrate, caffeine, and their combination on 20-km cycling time trial performance.

This is the accepted manuscript version of the following article: M. Glaister, J. R. Pattison, D. Muniz-Pumares, S. D. Patterson, and P. Foley, “Effects of Dietary Nitrate, Caffeine, and Their Combination on 20-km Cycling Time Trial Performance”, The Journal of Strength and Conditioning Research,Vol. 29(1): 165-174, January 2015. The final published version is available at: http://journals.lww.com/nsca-jscr/Pages/aboutthejournal.aspx ©2015 by the National Strength & Conditioning Association.The aim of this study was to examine the acute supplementation effects of dietary nitrate, caffeine, and their combination on 20-km cycling time trial performance. Using a randomized, counterbalanced, double-blind Latin-square design, 14 competitive female cyclists (age: 31 ± 7 years; height: 1.69 ± 0.07 m; body mass: 61.6 ± 6.0 kg) completed four 20-km time trials on a racing bicycle fitted to a turbo trainer. Approximately 2.5 hours before each trial, subjects consumed a 70-ml dose of concentrated beetroot juice containing either 0.45 g of dietary nitrate or with the nitrate content removed (placebo). One hour before each trial, subjects consumed a capsule containing either 5 mg·kg of caffeine or maltodextrin (placebo). There was a significant effect of supplementation on power output (p = 0.001), with post hoc tests revealing higher power outputs in caffeine (205 ± 21 W) vs. nitrate (194 ± 22 W) and placebo (194 ± 25 W) trials only. Caffeine-induced improvements in power output corresponded with significantly higher measures of heart rate (caffeine: 166 ± 12 b·min vs. placebo: 159 ± 15 b·min; p = 0.02), blood lactate (caffeine: 6.54 ± 2.40 mmol·L vs. placebo: 4.50 ± 2.11 mmol·L; p < 0.001), and respiratory exchange ratio (caffeine: 0.95 ± 0.04 vs. placebo: 0.91 ± 0.05; p = 0.03). There were no effects (p ≥ 0.05) of supplementation on cycling cadence, rating of perceived exertion, (Equation is included in full-text article.), or integrated electromyographic activity. The results of this study support the well-established beneficial effects of caffeine supplementation on endurance performance. In contrast, acute supplementation with dietary nitrate seems to have no effect on endurance performance and adds nothing to the benefits afforded by caffeine supplementation.Peer reviewedFinal Accepted Versio

Commentaries on viewpoint : physiology and fast marathons

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Accumulated oxygen deficit during exercise to exhaustion determined at different supramaximal work rates

The aim of the study was to determine the effect of supramaximal exercise intensity during constant work-rate cycling to exhaustion on the accumulated oxygen deficit (AOD) and to determine the test-retest reliability of AOD. Methods: Twenty-one trained male cyclists and triathletes (mean ± SD for age and maximal oxygen uptake [VO 2 max] were 41 ± 7 y and 4.53 ± 0.54 L/min, respectively) performed initial tests to determine the linear relationship between VO 2 and power output, and VO 2 max. In subsequent trials, AOD was determined from exhaustive square-wave cycling trials at 105%, 112.5% (in duplicate), 120%, and 127.5% VO 2 max. Results: Exercise intensity had an effect (P = .011) on the AOD (3.84 ± 1.11, 4.23 ± 0.96, 4.09 ± 0.87, and 3.93 ± 0.89 L at 105%, 112.5%, 120%, and 127.5% VO 2 max, respectively). Specifically, AOD at 112.5% VO 2 max was greater than at 105% VO 2 max (P = .033) and at 127.5% VO 2 max (P = .022), but there were no differences between the AOD at 112.5% and 120% VO 2 max. In 76% of the participants, the maximal AOD occurred at 112.5% or 120% VO 2 max. The reliability statistics of the AOD at 112.5% VO 2 max, determined as intraclass correlation coefficient and coefficient of variation, were .927 and 8.72%, respectively. Conclusions: The AOD, determined from square-wave cycling bouts to exhaustion, peaks at intensities of 112.5-120% VO 2 max. Moreover, the AOD at 112.5% VO 2 max exhibits an 8.72% test-retest reliability

The physiological demands of elite epée fencers during competition

The aim of this study was to determine the physiological demands of epée fencing performance. Eight elite male epée fencers competed in a competition consisting of 7 Poule and 7 Direct Elimination (DE) fights. Core temperature (TC), heart rate (HR), movement patterns, training load, and differentiated ratings of perceived exertion (RPE) were collected for all Poule and DE fights. Expired gas, and energy expenditure (EE) were measured using breath-by-breath gas analysis during selected fights, along with blood lactate concentration. Maximal HR and RPE were greater in DE than Poule fights. There was a tendency for greater increases in TC in DE compared to Poule fights (p = 0.052). Blood lactate concentration decreased during the competition from Poule to DE suggesting reliance on phosphocreatine and aerobic energy sources during fencing. High oxygen consumption (~50 ml.kg−1.min−1) and EE (~13 kcal.min−1) were recorded in both Poule and DE. Fencers covered 3 times more distance in DE than Poule fights. High training load scores were also recorded. This is the first study to show an increased physiological strain, with high aerobic and anaerobic demands, as fencing competition progressed from Poule to DE. Additionally, there was a considerable energy demand exhibited during epée competition