Plantar loading and cadence alterations with fatigue

Purpose: The purpose of this investigation was to identify changes in loadi ng characteristics of the foot associated with fatigue during running. Meth ods: Nineteen healthy subjects ranging from 20 to 30 yr (mean = 22.3, SD = 2.4) were equipped with the Pedar in-shoe measurement system (Novel GmbH) f or the assessment of planter loading. After acclimation to the treadmill, s ubjects were progressed through the Ohio State protocol for exercise testin g until fatigue was reported using Borg's RPE scale. Six right footsteps we re recorded at 150 Hz for each subject's comfortable running pace under nor mal and fatigued conditions. A series of repeated measures multiple analysi s of variance was performed for all dependent variables analyzed in this st udy including peak force (PF), force-time integral (FTI), peak pressure (PP ), and pressure-time integral (PTI) for all regions of the plantar surface. Results: Decreased step time, significantly smaller values under the heel for PP, PF, FTI, CT, and PTI, and trends toward increased medial forefoot l oading were identified while subjects were running under fatigued condition s (alpha < 0.05). Conclusion: These results suggest that subjects change ru nning technique and plantar surface loading characteristics in response to fatigued conditions through increased cadence, decreased loading of the hee l, and increased medial forefoot loading.