The effects of French contrast method on explosive power and speed-related skills in female soccer players: a randomized controlled trial

The purpose of this study was to examine whether the addition of a 6-week French Contrast Method (FCM) to routine soccer training affects agility, vertical jump height and 30-m sprint performance in female soccer players. A pretest–posttest control-group design was used. Twenty-four female soccer players (≥ 3 years of playing experience; regular training) participated. The experimental group performed a 6-week FCM program in addition to routine soccer training, while the control group continued routine soccer training only. Agility, vertical jump and 30-m sprint tests were administered at baseline and post-intervention. Within the scope of the study analyses, the primary outcomes (agility, vertical jump, and sprint performance) were derived from within-group pretest–posttest comparisons, whereas the secondary outcomes were obtained from findings related to the participants’ descriptive characteristics. The group × time interaction was found to be significant in the Illinois Agility Test (F = 16.813, p = 0.0004, ηp² = 0.433). Performance time decreased from 18.44 ± 0.59 s to 17.09 ± 0.36 s (Δ = −1.35 s) in the experimental group, while the change was limited in the control group (Δ = −0.22 s); the mean difference between groups was − 1.13 s (95% CI: −1.54 to − 0.72). A significant group × time interaction was also detected in vertical jump performance (F = 12.415, p = 0.002, ηp² = 0.361), with an increase of + 3.31 cm in the experimental group and + 0.77 cm in the control group (between-group difference: +2.54 cm; 95% CI: −0.64 to 5.72). In contrast, the group × time interaction was not significant for the 30 m sprint performance (F = 0.869, p = 0.361, ηp² = 0.038). These results indicate that the FCM training program is effective in improving female soccer players’ agility and vertical jump performance, but does not create a significant difference between groups in 30 m sprint performance. These findings not only extend the scientific literature but also provide actionable strategies for coaches and practitioners.