Does an increase in energy return and/or longitudinal bending stiffness shoe features reduce the energetic cost of running?

Abstract

Does an increase in energy return and/or longitudinal bending stiffness shoe features reduce the energetic cost of running?. European AbstractPurpose This study focused on the effects of shoe energy return and shoe longitudinal bending stiffness on the energetic cost and biomechanics of running. Methods The energetic cost of running and biomechanical variables altering running economy (ground contact times, stride frequency, vertical and leg stiffness, ground reaction force impulses, alignment between the resultant ground reaction force and the leg) were measured for nineteen male recreational runners. Participants ran overground under their ventilatory anaerobic threshold (10.8 ± 1.1 km h −1 on average) using four shoe prototypes with features combining low or high magnitudes of energy return and longitudinal bending stiffness. Results Neither the energy return, nor the longitudinal bending stiffness, or the interaction of these shoe features altered the energetic cost of running. High energy return shoes induced significant increased ground contact time from 274.5 ± 18.3 to 277.1 ± 18.7 ms, and significant decreased stride frequency from 1.34 ± 0.05 to 1.33 ± 0.05 Hz. High bending stiffness shoes induced significant increased ground contact time from 273.8 ± 18.2 to 277.9 ± 18.7 ms, significant increased vertical stiffness from 23.2 ± 3.4 to 23.8 ± 3.0 kN m −1 , and significant decreased net vertical impulse from 245.4 ± 17.2 to 241.7 ± 17.5 BW ms. Conclusions Increased energy return and longitudinal bending stiffness induced subtle changes in the running biomechanics, but did not induce any decrease in the energetic cost of running.

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

“…Theoretically, how does the addition of 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, 23, 24 and typically shifts the athlete’s center of pressure more anterior along the foot during ground contact. 23, 24, 27 These altered footwear biomechanics theoretically increase plantar flexor force generation and decrease the respective muscle fiber’s operating lengths, such changes require more metabolic energy expenditure per contraction.…”

“… The moment arm between the plantar flexor MTs and ankle-joint center is indicated by r MT . 30 When athletes run with carbon fiber plates added to their shoe soles, they often exhibit generally similar GRF magnitudes 13, 15 and longer plantar flexor MT moment arms 13, 23 compared to running in conventional footwear. To counteract the greater GRF-ankle flexion moment from adding carbon fiber plates to shoe soles, plantar flexor MT forces increase (Eq.…”

“…In particular, we sought to investigate how footwear 3-point bending stiffness affects muscle dynamics and running economy. Based on the reported interactions between adding carbon fiber plates to shoe soles, footwear 3-point bending stiffness, 12–15, 23, 24, 27 and ankle-joint dynamics, 13, 14, 23, 27 we hypothesized that running with shoes that have stiffer carbon fiber plates would increase soleus (plantar flexor muscle) force generation while decreasing soleus operating length and shortening velocity during the ground contact. We also hypothesized that an optimal footwear bending stiffness would minimize active soleus volume and aerobic energy expenditure.…”

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

“…Despite the rampant use of carbon fiber plates in athletics [8][9][10] , policy makers are regulating the use of these plates in distance-running footwear based on the notion that they provide wearers an 'unfair advantage' over competitors without such technology 11 . 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] .…”

Evidence of variable performance responses to the Nike 4% shoe: Definitely not a game-changer for all recreational runners

“…Similarly, inserting carbon fibre plates to midsoles to increase the longitudinal bending stiffness of running footwear has also been shown to improve RE ~1% [28], although the location of the plate [29], running speed [30], and induced changes in running biomechanics [29,31] can influence this relationship. The 'cost of cushioning' concept and 87% of stored mechanical energy return from the NIKE midsole potentially involve lesser muscular efforts to moderate impacts, which could underpin the 3.6 to 4.5% improvement in RE compared to OWN across running intensities alongside the lighter shoe mass and stiffer midsole, although more mechanistic investigations are required to confirm these assumptions.…”