Acute intense fatigue does not modify the effect of EVA and TPU custom foot orthoses on running mechanics, running economy and perceived comfort

Abstract

We determined whether fatigue modifies the effect of custom foot orthoses manufactured from ethyl-vinyl acetate (EVA) and expanded thermoplastic polyurethane (TPU) materials, both compared to standardized footwear (CON), on running mechanics, running economy, and perceived comfort. Eighteen well-trained, males ran on an instrumented treadmill for 6 min at the speed corresponding to their first ventilatory threshold (13.8 ± 1.1 km/h) in three footwear conditions (CON, EVA, and TPU). Immediately after completion of a repeated-sprints exercise (8 × 5 s treadmill sprints, rest = 25 s), these run tests were replicated. Running mechanics, running economy and perceived comfort were determined. Two-way repeated measures ANOVA [condition (CON, EVA, and TPU) × fatigue (fresh and fatigued)] were conducted. Flight time shortened (P = 0.026), peak braking (P = 0.016) and push-off (P = 0.032) forces decreased and vertical stiffness increased (P = 0.014) from before to after the repeated-sprint exercise, independent of footwear condition. There was a global fatigue-induced deterioration in running economy (− 1.6 ± 0.4%; P < 0.001). There was no significant condition × fatigue [except mean loading rate (P = 0.046)] for the large majority of biomechanical, cardio-respiratory [except minute ventilation (P = 0.020) and breathing frequency (P = 0.019)] and perceived comfort variables. Acute intense fatigue does not modify the effect of custom foot orthoses with different resilience characteristics on running mechanics, running economy and perceived comfort.

No Effect of EVA and TPU Custom Foot Orthoses on Mechanical Asymmetries during Acute Intense Fatigue

“…Although CFOs slightly modified SA scores in some individuals tested in our study, the evidence regarding the effects of inserts on asymmetry is not strong regarding who may benefit and in which way. Previously, we did not observe any significant difference in the time course and magnitude of mechanical adjustments in response to repeated treadmill sprints when comparing shoe only to EVA or TPU inserts [19,20]. Reportedly, healthy individuals walking on a treadmill showed altered frontal and transverse plane foot kinematics with increasing stiffness of CFOs, leading to a reduction in rearfoot eversion and an increase in rearfoot abduction [30].…”

“…This study was part of a larger project investigating the effects of CFOs on stride mechanics during repeated treadmill sprints, but the primary outcome measures reported here (SA scores) are distinct from previous analyses [19,20]. This study used a counterbalanced randomized crossover design.…”

“…The sprints were conducted on an instrumented motorized treadmill (ADAL3D-WR, Medical Development-HEF Tecmachine, France), as described elsewhere [19,20]. The treadmill was mounted on a highly rigid metal frame, set at 0 • incline, fixed to the ground through four piezoelectric force transducers (KI 9077b; Kistler, Winterthur, Switzerland) and installed on a specially engineered concrete slab to ensure maximal rigidity of the supporting ground.…”