A comparative analysis of acute effects induced by speed endurance and repeated-sprint training in soccer players

Purpose: This study aimed to compare the acute physiological and mechanical responses elicited by two commonly used high-intensity training modalities, speed endurance training (SET) and repeated-sprint exercise (RSE), in moderately trained soccer players. Methods: Fourteen male soccer players (age 21 ± 2 years, height 181 ± 5.5 cm, body mass 74 ± 8.3 kg) were randomly assigned to either speed endurance training (SET; 6 × 15-s all-out shuttle runs with 90 s passive recovery) or repeated-sprint exercise (RSE; 3 × 6 × 5-s all-out linear and shuttle runs with 20 s recovery between repetitions and 3 min between series). External load was assessed using GPS technology, while heart rate (HR), blood lactate concentration (La−), and session rating of perceived exertion (s-RPE) were used to quantify internal load. GPS-derived mechanical variables included distance covered at different speed thresholds, number of accelerations and decelerations, maximal speed, and estimated metabolic power. Physiological measures also included mean and peak HR, time spent in five HR intensity zones, and post-exercise blood lactate concentrations. Results: RSE induced a higher neuromuscular load, reflected by more accelerations and decelerations > 3 m s−2 and greater distances covered at metabolic power zones 10–25 W kg−1. SET elicited higher blood lactate responses, indicating greater anaerobic contribution. Both protocols produced comparable top speeds and sprint decrement, and similar HRpeak and time spent at 80–90% HRmax, suggesting adequate aerobic stimulus. Conclusions: SET and RSE elicit distinct responses, reflecting differences in metabolic and neuromuscular demands. These findings provide practical insights for coaches, suggesting that SET may be preferentially used to increase metabolic stress, whereas RSE may be more suitable when targeting neuromuscular load and acceleration–deceleration demands, thereby supporting informed training periodization in soccer.