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Mark Glaister

Tests of repeated-sprint ability provide a simple way to evaluate the basic physical characteristics of speed and endurance necessary to excel in various multiple-sprint sports. Furthermore, such tests help overcome the complications associated with field-based evaluations of this type of exercise. Nevertheless, despite over 40 y of research, many issues regarding our understanding of multiple-sprint work remain unresolved. This commentary aims to raise awareness of issues relating to methodology, physiological responses, and the effectiveness of various ergogenic and training strategies; to promote a greater understanding; and to drive future research.

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Mark Glaister and Conor Gissane

The aim of this study was to carry out a systematic review and meta-analysis of the effects of caffeine supplementation on physiological responses to submaximal exercise. A total of 26 studies met the inclusion criteria of adopting double-blind, randomized crossover designs that included a sustained (5–30 min) fixed-intensity bout of submaximal exercise (constrained to 60–85% maximal rate of oxygen consumption) using a standard caffeine dose of 3–6 mg·kg−1 administered 30–90 min prior to exercise. Meta-analyses were completed using a random-effects model, and data are presented as raw mean difference (D) with associated 95% confidence limits (CLs). Relative to placebo, caffeine led to significant increases in submaximal measures of minute ventilation (D = 3.36 L·min−1; 95% CL, 1.63–5.08; P = .0001; n = 73), blood lactate (D = 0.69 mmol·L−1; 95% CL, 0.46–0.93; P < .00001; n = 208), and blood glucose (D = 0.42 mmol·L−1; 95% CL, 0.29–0.55; P < .00001; n = 129). In contrast, caffeine had a suppressive effect on ratings of perceived exertion (D = −0.8; 95% CL, −1.1 to −0.6; P < .00001; n = 147). Caffeine had no effect on measures of heart rate (P = .99; n = 207), respiratory exchange ratio (P = .18; n = 181), or oxygen consumption (P = .92; n = 203). The positive effects of caffeine supplementation on sustained high-intensity exercise performance are widely accepted, although the mechanisms to explain that response are currently unresolved. This meta-analysis has revealed clear effects of caffeine on various physiological responses during submaximal exercise, which may help explain its ergogenic action.

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Daniel Muniz-Pumares, Charles Pedlar, Richard J. Godfrey and Mark Glaister

Purpose:

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 [V̇O2max] were 41 ± 7 y and 4.53 ± 0.54 L/min, respectively) performed initial tests to determine the linear relationship between V̇O2 and power output, and V̇O2max. In subsequent trials, AOD was determined from exhaustive square-wave cycling trials at 105%, 112.5% (in duplicate), 120%, and 127.5% V̇O2max.

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% V̇O2max, respectively). Specifically, AOD at 112.5% V̇O2max was greater than at 105% V̇O2max (P = .033) and at 127.5% V̇O2max (P = .022), but there were no differences between the AOD at 112.5% and 120% V̇O2max. In 76% of the participants, the maximal AOD occurred at 112.5% or 120% V̇O2max. The reliability statistics of the AOD at 112.5% V̇O2max, 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% V̇O2max. Moreover, the AOD at 112.5% V̇O2max exhibits an 8.72% test–retest reliability.

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Mark Glaister, Colin Towey, Owen Jeffries, Daniel Muniz-Pumares, Paul Foley and Gillian McInnes

Purpose: To investigate the influence of torque factor and sprint duration on the effects of caffeine on sprint cycling performance. Methods: Using a counterbalanced, randomized, double-blind, placebo-controlled design, 13 men completed 9 trials. In trial 1, participants completed a series of 6-s sprints at increasing torque factors to determine the torque factor, for each individual, that elicited the highest (T optimal) peak power output (PPO). The remaining trials involved all combinations of torque factor (0.8 N·m−1·kg−1 vs T optimal), sprint duration (10 s vs 30 s), and supplementation (caffeine [5 mg·kg−1] vs placebo). Results: There was a significant effect of torque factor on PPO, with higher values at T optimal (mean difference 168 W; 95% likely range 142–195 W). There was also a significant effect of sprint duration on PPO, with higher values in 10-s sprints (mean difference 52 W; 95% likely range 18–86 W). However, there was no effect of supplementation on PPO (P = .056). Nevertheless, there was a significant torque factor × sprint duration × supplement interaction (P = .036), with post hoc tests revealing that caffeine produced a higher PPO (mean difference 76 W; 95% likely range 19–133 W) when the sprint duration was 10 s and the torque factor was T optimal. Conclusion: The results of this study show that when torque factor and sprint duration are optimized, to allow participants to express their highest PPO, there is a clear effect of caffeine on sprinting performance.