Author(s): KAWAHARA, F., YASUMATSU, M., Institution: RIKKYO UNIVERSITY, Country: JAPAN, Abstract-ID: 1121

INTRODUCTION:
Flywheel training improves physical performance of soccer players. Previous studies have primarily focused on male soccer players, whereas research on female players is limited (1). The purpose of this study was to clarify the effects of a 5-week flywheel squat program on body composition and physical performance in female soccer players.
METHODS:
Twenty female university soccer players participated, with 12 who completed at least 75% of the training program analyzed. The intervention period was the preseason. Tests included body composition, jumps (CMJ with arm, standing long jump, rebound Jump), 40m sprint, and COD tests (Y-test, V-test). Testing was conducted three times: Pre, Middle and Post (After 3 and 5 weeks). The experiment lasted 8 weeks, with the 5-week intervention phase (2 sessions per week). Athletes received two familiarization sessions. Exercises included squats using a flywheel (Kbox 3, Exxentric AB, Bromma, Sweden). The athletes selected the inertial load with the higher average eccentric power (0.05 or 0.075 kg · m²). Loads were set twice. At least 48 hours separated training sessions. Athletes were instructed to perform the concentric phase as quickly as possible and the eccentric phase with maximum deceleration toward the end. Training was progressive (Week 1-3: 8 reps × 2 sets; Week 4-5: 8 reps × 3 sets). For statistical analysis, Repeated measures ANOVA or Friedman's Test was performed. Effect sizes were calculated using Partial Eta Squared or Kendall's W. For statistical significance, we considered an alpha level of 0.05.
RESULTS:
In body composition, Lean body mass (p < 0.01, η2p = 0.44, Pre < Mid, Post) significantly increased. Body fat percentage significantly decreased (p < 0.01, η2p = 0.40, Pre > Mid, Post). In the field tests, 30m time (p < 0.01, η2p = 0.60, Pre > Mid, Post), 40m time (p < 0.01, η2p = 0.71, Pre > Mid > Post) , CMJ with arm (p = 0.02, η2p = 0.30, Pre < Mid), standing long jump (p < 0.01, η2p = 0.56, Pre < Mid, Post), and V-test (p < 0.01, η2p = 0.47, Pre, Mid > Post) showed significant improvement. On the other hand, ground contact time during the rebound jump significantly increased (p < 0.01, η2p = 0.49, Pre < Mid, Post).
CONCLUSION:
In contrast to the previous study (1), this study showed improvements in many field test measures. While most variables improved from Pre to Mid, the V-test only showed significant changes from Mid to Post. These results suggest improvements in body composition and jumping were observed during the first three weeks, which subsequently led to significant improvements in deceleration. Conversely, the significant increase in ground contact time should be considered when introducing flywheel training in sports requiring high power output in short durations.

(1) Pecci et al. (2023) Effects of 6 weeks in-season flywheel squat resistance training on strength, vertical jump, change of direction and sprint performance in professional female soccer players. Biology of Sport, 40(2), 521-529.