A quantification of lower limb coordinative variability during running with different levels of midsole cushioning
Cushioned material between the foot and the ground during the stance phase of running dampens haptic feedback information used by higher control centres to inform subsequent movement executions. The purpose of this investigation was to examine whether this constraint on the motor system would manifest in reduced coordinative variability in lower limb joint couplings and a more 'rigid' gait pattern, implying increased consistency of tissue stress during time periods of limb loading. Ten midfoot and 10 rearfoot experienced distance runners, all of whom were habitual in their categorized footstrike pattern and free of any pain or injury, ran on a treadmill while barefoot and in shoes with minimalist (New Balance Minimus) and maximalist (Hoka Stinson One One) amounts of midsole cushioning. No differences in leg segment coordinative variability were observed between footwear conditions in either group of runners. Peaks in variability were often observed around periods of gait transition, primarily in foot shank couplings. Further, a novel observation was the altered spatiotemporal properties of the segments' phase plots between footwear conditions, manifesting in altered joint coupling patterns. The effect of increased midsole cushioning material on proprioceptive acuity during stance was not a sufficient disturbance to the motor system to manifest in altered levels of coordinative variability. Healthy, experienced runners likely display learned coordination patterns containing 'normal' levels of variability. Preliminary observations of altered joint coupling patterns between footwear conditions may have significant implications for healthy mechanical function. Prospective investigations should be employed to assess for any association between injury risk and individual specific levels of coordinative variability.
Footwear Science