Effects of linear and change of direction high-intensity interval training on physical performance of elite female soccer players.

The aim of this study was to determine the effects of linear and change of direction high-intensity interval training (HIIT) on physical performance in elite female soccer players. Thirty elite female soccer players (age: 19.6 ± 4.6 years; height: 166.5 ± 4.8 cm; body weight: 60.5 ± 8.3 kg; BMI: 21.9 ± 2.9 kg/m²) were randomly allocated to HIIT linear (HIIT_LIN) and HIIT change of direction (HIIT_COD) training groups. The HIIT_LIN group performed linear running for 15, 20 or 25 s by keeping constant pace during the entire distance. In contrast, the HIIT_COD group performed three changes of direction (COD) with a 180° turn during each interval run at 15, 20 or 25 s. Physical performance was assessed using sprinting, agility, vertical jumps, repeated sprint ability (RSA) and 30-15 Intermittent Fitness Test (30-15 IFT). In both groups, all physical performance measurements improved (p ≤ 0.05), except RSAbest in HIIT_LIN (p = 0.45). Both interventions significantly improved speed over 10 m, 20 m, 30 m, Pro-agility, Zig-zag, RSAavg, fatigue index, maximal oxygen uptake, and velocity at 30-15 IFT, while moderate improvements were observed in countermovement jump (CMJ), CMJ with arm swing and squat jump. However, HIIT_COD did not achieve superior improvements in any of the aforementioned measurements compared to HIIT_LIN. Based on the obtained results, we concluded that different types of HIIT training have a positive effect on physical performance in elite female soccer players.