Long-Term Effects of Resisted Sled Sprint Training on Acceleration Performance in Female Professional Soccer Players

Resisted sprint training (RST) is widely used to enhance acceleration capacity; however, evidence concerning on long-term effects to RST in professional women’s remains limited. Methods: This study examined the chronic effects of a six-week resisted sled sprint training intervention using a single-group longitudinal pilot design in professional female soccer players. Twenty-two players were assessed at baseline (T1), with fourteen completing the post-intervention assessment (T2) and seven available at the two-month follow-up (T3). Athletes completed one weekly RST session with loading progressively increasing from 20% to 80% of body mass and total sprint volume ranging from 100 to 200 m per session. Sprint performance and kinematic variables of the first three acceleration steps for both limbs were assessed before the intervention, immediately after and at a two-month follow-up. Within-group changes across time were analyzed using a one-way ANOVA with Bonferroni post hoc comparisons, with the level of significance set at p ≤ 0.05. Results: Sprint times significantly improved following the intervention (T1-T2), with a 2.61% improvement in acceleration performance over the 0-20 m phase. This improvement was accompanied by increases in center of mass projection angle and toe-off distance, resulting in a more forward-oriented sprint posture. At follow-up, sprint performance showed partial retention of these changes. These adaptations were accompanied by greater hip and knee extension of the ipsilateral limb at toe-off, without evidence of adverse sagittal-plane kinematic alterations during the early acceleration phase. Conclusions: The results indicate that once-weekly RST was associated with preliminary improvements in acceleration performance in professional female soccer players and induces technical adaptations that did not appear to negatively affect sprint mechanics during the initial acceleration phase. Given the absence of a control group and the substantial attrition at follow-up, these findings should be interpreted as exploratory.