Effects of sprint distance and repetition number on energy system contributions in soccer players

BACKGROUND/OBJECTIVE: This study aims to compare the effect of sprint distance and repetition number on performance, physiological responses, and energy systems contributions. METHODS: Eighteen male university league soccer players (age: 19.9 ± 1.6 years, height: 177.9 ± 4.7 cm, body mass: 72.4 ± 6.3 kg, percentage body fat: 8.9 ± 1.8, training experience: 7.4 ± 1.6 years) completed two different repeated sprint protocols: 20 × 20 m (20 × 20) and 10 × 40 m (10 × 40) with 15s and 30s rest intervals, respectively. Oxygen uptake (VO(2)) were measured during the rest, exercise, and recovery phases. Rest and peak blood lactate concentrations were determined. Using VO(2) and lactate values, the energy system contributions were calculated using a mono-exponential model and mathematical calculations. Energy systems contributions and total energy expenditure (TEE) were calculated both for the entire protocol (overall) and for the sprints only. RESULTS: Ratings of perceived exertion (RPE), peak and mean heart rate (HR) responses were significantly higher in the 20 × 20 whereas lactate response was higher in the 10 × 40. TEE was similar between the 10 × 40 (586.3 ± 60.8 kJ) and 20 × 20 (595.6 ± 57.5 kJ). For overall estimations, the 10 × 40 and 20 × 20 presented similar results of oxidative (47.5 ± 5.4 vs 45.7 ± 5.1 kJ min(−1)) and phosphagen (44.7 ± 5.4 vs (42.9 ± 4.8 kJ min(−1)) systems contributions whereas glycolytic contribution was higher in the 10 × 40 (15.5 ± 2.2 vs 12.8 ± 2.3 kJ min(−1)). For sprints only estimation, the phosphagen (257.6 ± 31.5 vs 225.2 ± 28.2 kJ min(−1)), glycolytic (89.4 ± 13.4 vs 67.3 ± 12.5 kJ min(−1)), and oxidative (76.9 ± 6.9 vs 72.0 ± 7.9 2 kJ min(−1)) systems contributions were higher in the 10 × 40. CONCLUSIONS: Although HR and RPE responses were higher in the 20 × 20, phosphagen (during sprints) and glycolytic (during both sprints and overall protocol) were higher in the 10 × 40 protocol. Therefore, the 10 × 40 protocol seems more reasonable for developing or evaluating the anaerobic systems.