Efectos del entrenamiento interválico sobre la condición física y percepciones de disfrute de jóvenes futbolistas: compa-raciones entre protocolos de intervalos cortos y largos

This study aims to compare the effects of short- versus long-interval training (IT) protocols on physical fitness and enjoyment levels in young soccer players. Twenty-four male soccer players in the under-15 category (aged 14 to 15 years) participated in this study. The training protocols lasted seven weeks, with training sessions held twice a week (Tuesdays and Thursdays), and assessments conducted pre- and post-training. Evaluations included the 30-15 Intermittent Fitness Test, Bipodal Horizontal Jump, and Unipodal Horizontal Jump. The long-interval training protocol consisted of three sets of three minutes at 80-90% of the final speed reached in the 30-15 Intermittent Fitness Test (vIFT). The short-interval protocol consisted of three sets of three minutes, with 20 seconds of action followed by 10 seconds of passive recovery, totaling three minutes, at 100-110% of vIFT. Both protocols included a passive recovery period of 1 minute and 30 seconds between sets. Sessions were conducted after the team's regular game-based training. At the beginning of week five, the 30-15 IFT was repeated to adjust training session intensity. During all training sessions, the rating of perceived exertion (RPE 0-10) and session duration (minutes) were recorded, allowing for the calculation of internal load, monotony, and strain indices. At the end of the training period, players completed the Feeling Scale, a questionnaire measuring enjoyment of both short and long IT. Results showed that both short and long IT protocols increased distance in the bipodal horizontal jump, the unipodal horizontal jump on the right leg, and vIFT. Only short IT improved performance in the unipodal jump on the left leg, with no significant differences between groups. Internal load, monotony, and strain showed no differences between the IT protocols. However, the short IT group reported higher enjoyment compared to the long IT group. In conclusion, both training programs improved aerobic fitness and horizontal jump performance, but players who underwent short IT reported greater enjoyment.