The aim of this study was to investigate the effects of heavy sled towing using a load corresponding to a 50% reduction of the individual theoretical maximal velocity (ranged 57–73% body mass) on subsequent 30 m sprint performance, velocity, mechanical variables (theoretical maximal horizontal force, theoretical maximal horizontal velocity, maximal mechanical power output, slope of the linear force–velocity relationship, maximal ratio of horizontal to total force and decrease in the ratio of horizontal to total force) and kinematics (step length and rate, contact and flight time). Twelve (n = 5 males and n = 7 females) junior running sprinters performed an exercise under two intervention conditions in random order. The experimental condition (EXP) consisted of two repetitions of 20 m resisted sprints, while in the control condition (CON), an active recovery was performed. Before (baseline) and after (post) the interventions, the 30 m sprint tests were analyzed. Participants showed faster 30 m sprint times following sled towing (p = 0.005). Running velocity was significantly higher in EXP at 5–10 m (p = 0.032), 10–15 m (p = 0.006), 15–20 m (p = 0.004), 20–25 m (p = 0.015) and 25–30 m (p = 0.014). No significant changes in sprint mechanical variables and kinematics were observed. Heavy sled towing appeared to be an effective post-activation potentiation stimulus to acutely enhance sprint acceleration performance with no effect on the athlete’s running technique.

Background: Post-activation potentiation refers to the acute and temporary enhancement of performance in explosive movements after performing a conditioning activity, such as plyometrics. The current study aimed to investigate the acute effects of horizontal leg bounding on 30 m acceleration performance, 5 m split times, and sprint kinematics (step frequency and length, flight and contact time). Methods: Fourteen young sprinters, nine females and five males, performed two experimental conditions and one control condition in randomized and crossover orders. The experimental conditions included 3 × 10 repetitions of alternate-leg horizontal bounding or 3 × 5 repetitions of single-leg horizontal bounding for each leg. Active recovery was performed in the control condition. A 30 m sprint test was executed before and 5 min after each condition. Results: Sprint times at 5 m (p = 0.014) and 10 m (p = 0.041) were improved after performing alternate-leg horizontal bounding. Additionally, an increase in running velocity (p = 0.017) and step frequency (p = 0.028) was observed in the 0–5 m segment of the sprint. Sprint performance and kinematics showed no significant differences after performing single-leg horizontal bounding. Conclusions: Alternate-leg horizontal bounding, which is a sprint-specific exercise that emphasizes a horizontal impulse, can be used effectively to improve performance in the initial phase of sprint acceleration.