Does plantarflexion fatigue influence running economy response to advanced footwear technology?

Abstract

Background: Previous research found an average 4.0% increase in running economy (RE) with runners wearing shoes with advanced footwear technology (AFT), however there is large inter-individual variability. Serval speculations have arisen to explain this variability, one being runners needing strong enough plantarflexion strength to fully benefit from AFT shoes. Therefore, this study will investigate the effects of plantarflexion fatigue on RE response to AFT shoes. Methods: Sixty-four participants (age, 33.5 ± 15.6 y; sex, 32 male, 32 female; VO2peak, 49.4 ± 8.3 mL/kg/min) completed two sessions. Session one collected demographic information and conducted an incremental VO2peak test on a treadmill. Session two included a plantarflexion power test and four RE tests in the Control and AFT shoe in a counterbalanced mirrored crossover design. These RE tests were followed by two rounds of a plantarflexion fatigue protocol, including pre-plantarflexion (PRE) and post-plantarflexion (POST) power tests. Each fatigue protocol was followed with a calf muscle fatigue and soreness visual analogue scales, along with a RE test in a counterbalanced shoe condition. Results: RE improved 4.0 to 4.3% in the AFT compared to the Control shoe. Plantarflexion fatigue induced 1.6 to 2.4% decline in RE. There were no significant interaction between shoe conditions and time (P > 0.691). Baseline plantarflexion power did not significantly correlate to AFT response (P > 0.132), nor did the change in plantarflexion power (PRE to POST) to the change in AFT response (PRE to POST) (P > 0.930). Conclusion: Overall, AFT improved RE while plantarflexion fatigue negatively affected RE. Isolated plantarflexion fatigue did not alter AFT response and plantarflexion power was not linked to AFT response, refuting speculations that runners need strong enough plantarflexion strength to fully benefit from AFT. Since isolated plantarflexion fatigue is not generalisable to running induced fatigue, investigating the effects of running induced fatigue on RE response to AFT is recommended.