Acute effects of two different initial heart rates on testing the Repeated Sprint Ability in young soccer players

Aim. The aim of this paper was to investigate the acute effects of two different initial heart rates intensities when testing the repeated sprint ability (RSA) performances in young soccer players. Methods. Since there are many kinds of pre-match warmups, we chose to take as an absolute indicator of internal load the heart rate reached at the end of two different warmup protocols (60 vs. 90% HRmax) and to compare the respective RSA performances. The RSA tests were performed on ifteen male soccer players (age: 17.9±1.5 years) with two sets of ten shuttle-sprints (15+15 m) with a 1:3 exercise to rest ratio, in different days (randomized order) with different HR% (60 and 90% HRmax). In order to compare the different sprint performances a Fatigue Index (FI%) was computed, while the blood lactate concentrations (BLa-) were measured before and after testing, to compare metabolic demand. Results. Signiicant differences among trials within each sets (P<0.01) were found. Differences between sets were also found, especially comparing the last ive trials for each set (Factorial ANOVA; P<0.01), effect size values conirming the relevance of these differences. Although the BLa- after warmup was higher (36%) between 90% vs. 60% HRmax, after the RSA test the differences were considerably low (7%). Conclusion. Based on physiological information's this methodological approach (testing with initial 90%HRmax) relects more realistically the metabolic background in which a soccer player operates during a real match. This background may be partially reproduced by warming up protocols that, by duration and metabolic commitment, can reproduce conveniently the physiological conditions encountered in a real game (e.g. HRmax≈85-95%; BLa->4 mmol/L-1).