Economy benefits of running in advanced footwear technology shoes remain with plantarflexion fatigue

We investigated the effects of plantarflexion fatigue on running economy (RE) response to advanced footwear technology (AFT) in a group of heterogenous runners. Secondary aims were to examine the relationships between plantarflexion power and RE responses to AFT, and effects of plantarflexion fatigue and footwear on biomechanical measures. Sixty-four runners completed two laboratory sessions. Session one involved a peak oxygen uptake test. Session two included two RE tests in both a Control and AFT shoe before plantarflexion fatigue, and two rounds of plantarflexion fatigue before reassessment of RE in one of the two shoes (counterbalanced). Plantarflexion power was assessed at baseline, and before and after each fatigue protocol. Video-based running biomechanics were recorded during all RE tests. RE measures were improved in AFT (35.3 ± 5.0 mL/kg/min, 12.5 ± 1.8 W/kg, 4.18 ± 0.40 J/kg/m) versus Control (36.8 ± 5.2 mL/kg/min, 13.1 ± 1.9 W/kg, 4.37 ± 0.40 J/kg/m), and better pre-fatigue (35.7 ± 5.1 mL/kg/min, 12.7 ± 1.8 W/kg, 4.25 ± 0.40 J/kg/m) than post-fatigue (36.4 ± 5.2 mL/kg/min, 12.8 ± 1.9 W/kg, 4.30 ± 0.42 J/kg/m). Plantarflexion power decreased 6.5% post-fatigue. Despite these significant effects of AFT and plantarflexion fatigue on RE, no interactions were observed (P ≥ 0.476). Baseline plantarflexion power and changes in power did not correlate with AFT responses (P ≥ 0.566). Statistically significant differences indicated AFT reduced ground contact time and foot strike angle and increased cycle time and duty factor, with plantarflexion fatigue increasing cycle time and duty factor; however, estimates of differences were generally within the limits of instrumental resolution. Plantarflexion fatigue and plantarflexion power were not associated with RE responses to AFT, opposing the idea that plantarflexion strength explains variability in AFT response. Trial registration: Australian New Zealand Trials Registry, ACTRN12624000753550, 18th June 2024.