Acute effect of running retraining interventions on low & high-frequency components of the impact signals.

Running-related injuries (RRIs) have been linked to high-frequency components of impact-related variables. The influence of running retraining interventions on low- (LoF) and high-frequency (HiF) components of impact-related variables remains unexplored. This study investigated the effects of different retraining strategies on LoF and HiF components of impact-related variables. Twenty-six habitual rearfoot runners completed four overground running conditions: no instructions (CON), forefoot strike (FOR), increased cadence by 10% (CAD), and a combination of both (CADFOR). Three-dimensional kinematics were recorded, while ground reaction forces were processed to separate LoF and HiF signals (10 Hz as cut-off value). Compared to CON, HiF impact peak was reduced in FOR (p <0.001, d = 2.0), CAD (p = 0.006, d = 0.6), and CADFOR (p <0.001, d = 2.3). HiF instantaneous vertical loading rate was significantly reduced only in FOR (p <0.001; d = 0.6) and CADFOR (p <0.001; d = 0.7). Notably, adopting a forefoot strike pattern reduced HiF components of impact-related variables nearly three times more than cadence increase alone. The combination of forefoot strike and increased cadence produced the largest reduction in HiF impact components, suggesting it may be the most effective retraining strategy for potentially lowering RRI risk.