This study examined whether performing heavy back squats before exercise affects jumping ability and repeated sprint performance in trained soccer players. Twenty male university soccer players completed two testing sessions in a randomized crossover design. In one session, participants performed a standardized warm-up only. In the other session, they performed the same warm-up followed by three sets of three back-squat repetitions at 90% of their one-repetition maximum. The two sessions were separated by one week. After each condition, participants completed a countermovement jump test and an 18 × 40-meter repeated sprint test. The study aimed to determine whether the heavy back-squat activity improves early explosive performance and whether it increases fatigue during prolonged repeated sprint exercise.