Toe clearance variability during walking in young and elderly men.

Falls during walking are a major cause of injury and death in the elderly. From a falls perspective, a critical gait event is minimum toe clearance (MTC), as failure to achieve foot-ground clearance results in a trip and potentially a fall. MTC exhibits stride-to-stride variability, which must be minimised to avoid the occurrence of toe-ground contact events. Gait kinematics were acquired from 10 young and nine elderly men for 1000 sequential strides during treadmill walking. The swing toe was modelled as the endpoint of a 21 degree-of-freedom kinematic chain. Central tendency and dispersion of MTC, stance foot angles and stance and swing leg joint angles at the time of MTC (time(MTC)) were compared between the young and elderly. The relationship between joint angle variability and MTC variability was also examined in both age groups. No age-related differences in median MTC were identified, however within-subject variability of MTC was greater for the elderly than the young. The elderly also displayed less stance hip extension, greater swing hip flexion and less stance hip adduction at time(MTC) than the young. No age-related differences in stance foot or joint angle variability were identified. MTC variability was most strongly correlated with swing ankle plantar-dorsiflexion variability for the young group and stance ankle adduction-abduction variability for the elderly. In conclusion, elderly men exhibit greater MTC variability than young men, which in the absence of an age-related increase in median MTC, may increase the risk of tripping in the elderly.