Abstract
Custom made foot orthoses (CFO) with specific material properties have the potential to alter ground reaction forces but their effect on running mechanics and comfort remains to be investigated. We determined if CFO manufactured from ethyl-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) materials, both compared to standardized footwear (CON), improve running economy (RE), running mechanics, and comfort at two running speeds. Eighteen well-trained, male athletes ran on an instrumented treadmill for 6 min at high (HS) and low (LS) speeds corresponding to and 15% lower than their first ventilatory threshold (13.8 ± 1.1 and 11.7 ± 0.9 km.h−1, respectively) in three footwear conditions (CON, EVA, and TPU). RE, running mechanics and comfort were determined. Albeit not reaching statistical significance (P = 0.11, η2 = 0.12), RE on average improved in EVA (+2.1 ± 4.8 and +2.9 ± 4.9%) and TPU (+0.9 ± 5.9 and +0.9 ± 5.3%) compared to CON at LS and HS, respectively. Braking force was decreased by 3.4 ± 9.1% at LS and by 2.7 ± 9.8% at HS for EVA compared to CON (P = 0.03, η2 = 0.20). TPU increased propulsive loading rate by 20.2 ± 24 and 16.4 ± 23.1% for LS and HS, respectively compared to CON (P = 0.01, η2 = 0.25). Both arch height (P = 0.06, η2 = 0.19) and medio-lateral control (P = 0.06, η2 = 0.16) showed a trend toward improved comfort for EVA and TPU vs. CON. Compared to shoes only, mainly EVA tended to improve RE and comfort at submaximal running speeds. Specific CFO-related running mechanical adjustments included a reduced braking impulse occurring in the first 25% of contact time with EVA, whereas wearing TPU increased propulsive loading rate.
Highlights
Custom foot orthoses (CFO) are increasingly used to alter the magnitude and resultant direction of ground reaction forces (GRF) under the foot by modifying foot-surface interaction
Albeit not reaching statistical significance (P = 0.11, η2 = 0.12), Running Economy (RE) on average improved in ethyl-vinyl acetate (EVA) (+2.1 ± 4.8 and +2.9 ± 4.9%) and thermoplastic polyurethane (TPU) (+0.9 ± 5.9 and +0.9 ± 5.3%) compared to compared to standardized footwear (CON) at LS and HS, respectively (Figure 2)
We reported improved RE (P = 0.11, η2 = 0.12) mainly when using EVA (+2.1 ± 4.8 and +2.9 ± 4.9%), at HS and LS respectively, compared to CON (P = 0.11, η2 = 0.12)
Summary
Custom foot orthoses (CFO) are increasingly used to alter the magnitude and resultant direction of ground reaction forces (GRF) under the foot by modifying foot-surface interaction. The magnitude of the reduction in subtalar joint inversion moment, altering GRF production during locomotion, directly depends on the amount of customization by molding and/or posting (McCormick et al, 2013) This individualized surface geometry, in combination with materials used, likely determine comfort, cushioning, and bending stiffness (Mundermann et al, 2003a,b; Kirby and Werd, 2014). RE on average improved by ∼8% when male endurance trained runners ran at five preset speeds ranging ∼11–15 km.h−1, while wearing CFO compared to a shoe fitted support (Burke and Papuga, 2012) In these aforementioned studies, stride pattern was not characterized to offer a possible biomechanical explanation for CFO-related adjustments in RE. The use of different running shoes between runners (Burke and Papuga, 2012) and set (i.e., absolute) running speeds for a range of runners with rather different levels of overall aerobic fitness (Hayes et al, 1983; Burke and Papuga, 2012) participate to increase interindividual variability in the response to a CFO intervention
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