Comparison of Mechanical Hurdle-Resisted, Sled-Resisted and Standard Sprint Training in U18 Female Hurdlers: A Preliminary Randomized Trial

To compare hurdle-resisted sprint training (EGH), sled-resisted training (EGS), and hurdles-only training (CG) on performance and kinematics using a smallest-effect-size-of-interest (SESOI) framework, fifteen U18 female hurdlers (16.3 ± 1.3 years) were randomized to EGH, EGS, or CG (n = 5 each) for a 7-week intervention (7 microcycles). EGH used individualized resistance (10% velocity decrement), while EGS used fixed ~13% body-mass resistance. Outcomes included 30 m hurdle time (30 mH), Technique Index, and exploratory kinematics. Primary analysis used baseline-adjusted robust ANCOVA with permutation and linear mixed models (LMM) as sensitivity checks. A smallest-effect-size-of-interest (SESOI) of −0.066 s (~1.2%) was pre-specified. Adjusted ANCOVA favored EGH over CG (−0.19 s; 95% CI [−0.45, 0.06]; p = 0.11). The point estimate exceeded the SESOI, though the CI captured both meaningful and trivial effects. Sensitivity analyses maintained this directional pattern, but LMM estimates varied in magnitude, suggesting model dependence. The EGH–EGS contrast was smaller and uncertain (−0.15 s; p = 0.10). Exploratory baseline-adjusted kinematic contrasts showed no clear differences at the first hurdle, but highlighted nominal differences in the EGH group at the second hurdle (greater take-off distance, p = 0.030) and third hurdle (shorter flight and landing times, p < 0.05), which should be interpreted as hypothesis-generating. In this preliminary trial, the data are compatible with a range of effects from negligible to practically meaningful for hurdle-resisted sprint training relative to both control and sled-resisted conditions. All estimates are accompanied by wide compatibility intervals, precluding confirmatory conclusions. These findings establish protocol feasibility, provide estimation-based preliminary evidence with openly available individual-level data, and motivate adequately powered multi-center replication trials.