Improving running economy through altered shoe bending stiffness across speeds

Adding carbon fiber to shoe soles may not improve running economy: a muscle-level explanation

“…7 ), none of the respective active muscle volumes changed across footwear conditions (active muscle volume = total muscle volume × relative activation) 37 . This is now the fourth study that failed to replicate Roy and Stefanyshyn’s classic investigation 12 , which stated that adding carbon fiber plates to shoe soles improves running economy 14 – 17 . Since the classic investigation, only Oh and Park 13 reported that adding carbon fiber plates to running shoes elicited a relative footwear stiffness that improves running economy at 2.4 m/s.…”

“…How does adding carbon fiber plates to shoe soles affect athlete plantar flexor dynamics during running? Adding carbon fiber plates to shoe soles increases the footwear’s 3-point bending stiffness 12 , 13 , 15 , 17 , 24 , 25 , 28 and typically shifts the athlete’s center of pressure more anterior along the foot during ground contact 24 , 25 , 28 , 29 . These altered biomechanics generally yield a longer moment arm between the ground reaction force ( F GRF ) and the ankle-joint center ( ) 13 , 24 .…”

“…In particular, we sought to investigate how footwear 3-point bending stiffness affects soleus fascicle dynamics and running economy. Based on the reported interactions between adding carbon fiber plates to shoe soles, footwear 3-point bending stiffness 12 – 15 , 17 , 24 , 25 , 28 , 29 , and ankle-joint dynamics 13 , 14 , 24 , 29 , we hypothesized that running with shoes that have stiffer carbon fiber plates would increase soleus fascicle force generation while decreasing its operating length and shortening velocity during the ground contact. We also hypothesized that an optimal footwear bending stiffness would minimize soleus active muscle volume and aerobic energy expenditure.…”

“…These views persist even though it is inconclusive whether adding carbon fiber to shoe soles improves running economy [12][13][14][15][16] or distance-running performance. To date, two studies have reported that adding optimally stiff carbon fiber plates to shoe soles improves running economy by 0.8 12 and 1.1% 13 , while data from four other studies suggest that adding carbon fiber plates to shoe soles does not affect running economy [14][15][16][17] .…”

Intra- and inter- session reliability of a new method for evaluating toes flexor strength: preliminary study

“…Several studies have recently highlighted that the longitudinal bending stiffness of the shoes is associated with a decrease in running energy cost (Madden et al 2016). More specifically, McLeod et al (2020) have reported that shoe construction needs to be personalised in regard to longitudinal bending stiffness when running economy is valued. Consequently, the ability to measure foot muscle strength and particularly at the metatarsophalangeal (MTP) joint is necessary for researchers and shoe companies.…”