Plantar loading and cadence alterations with fatigue.

PURPOSE

The purpose of this investigation was to identify changes in loading characteristics of the foot associated with fatigue during running.

METHODS

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) for the assessment of plantar loading. After acclimation to the treadmill, subjects were progressed through the Ohio State protocol for exercise testing until fatigue was reported using Borg's RPE scale. Six right footsteps were recorded at 150 Hz for each subject's comfortable running pace under normal and fatigued conditions. A series of repeated measures multiple analysis of variance was performed for all dependent variables analyzed in this study 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 loading were identified while subjects were running under fatigued conditions (alpha < 0.05).

CONCLUSION

These results suggest that subjects change running technique and plantar surface loading characteristics in response to fatigued conditions through increased cadence, decreased loading of the heel, and increased medial forefoot loading.