During the swing phase of gait, the effective length of the leg-distance from the hip joint center to the toe-must be made shorter than the distance from the hip to the floor to avoid toe-stubbing or tripping while walking. Critical toe clearance occurs approximately halfway through swing phase when the distance between the toe and the floor reaches a local minimum. Analytical techniques derived in this study were used to evaluate: (1) the sensitivity of toe clearance to the swing leg hip, knee, and ankle joint angles; and (2) the sensitivity of the hip-toe distance to the swing leg knee and ankle joint angles. The toe clearance, hip-toe distance, toe clearance sensitivity (TCS), and hip-toe distance sensitivity (HTDS) were calculated for each frame of data during the swing phase of 10 able-bodied subjects. A minimum toe clearance of 1.9+/-0.5cm occurred at about 51% of the swing phase during able-bodied gait. At that particular time, the toe clearance was found to be most sensitive to the angle of theankle (17.1cm/rad), then the hip (9.5cm/rad), and lastly the knee (2.5cm/rad). The hip-toe distance was found to be about twice as sensitive to the angle of the ankle (-15.3cm/rad) than to that of the knee (-7.6cm/rad) at the time of critical toe clearance. The methodology developed here and the baseline information calculated for able-bodied subjects could be used to evaluate the effects that different gait pathologies have on swing-phase toe clearance and hip-toe distance.
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