The contribution of energy systems in different repeated sprint protocols: The effect of work/rest ratios

The aim of this study was to investigate the effects of rest intervals, sprint distance, and number of repetition on performance variables, physiological responses, and to examine the contributions of energy systems in repeated sprint protocols when total distance variable controlled. Sixteen trained male football players participated in this study. Four repeated sprint protocols which had a total distance of 300 m were applied in random order by combinations of 20 x 15 m and 10 x 30 m with standard recovery duration and individual recovery of 1:5 work:rest ratios. Sprint duration, oxygen consumption (VO2), blood lactate concentration (LA), heart rate (HR) and ratings of perceived exertion (RPE) were measured during the tests. The contributions of the aerobic, lactic, and alactic systems were calculated from the VO2, LA values, and the recovery VO2 kinetics using mono-exponential models, respectively. Variance analysis with repeated measurements using Bonferroni correction was applied to examine hypothesized differences. The findings indicated that the effects of the protocols on total sprint duration, total exercise duration, and the percentage of performance decline were significantly different (p<0.05). Comparing the effects of protocols revealed differences (p<0.05) for each parameter except maximum HR. The percent contribution of the alactic energy system to total energy expenditure was similar (p>0.05), however, the percentages of lactic and aerobic energy systems were significantly different (p<0.05) for 3 different protocols. Additionally, this study suggested that the protocols with individual resting ratio could be preferred to improve the alactic system, however, 10 x 30 m protocol with individual resting ratio seemed more reasonable for improving both the alactic and lactic systems.