Ageing and limb dominance effects on foot-ground clearance during treadmill and overground walking.

BACKGROUND: Foot-ground clearance during the gait cycle swing phase is a critical locomotor adaptation to uneven terrain and non-optimal lower limb control has been linked to tripping and falling. The aim of this research was to determine ageing effects on bilateral foot-ground clearance during overground and treadmill walking.

METHODS: Ageing and walking surface effects on bilateral foot trajectory control were investigated in 11 older (mean age 73.8 years) and 11 young (mean age 22.5 years) participants. First maximum clearance after toe-off, minimum foot-ground clearance and second maximum clearance prior to heel contact were determined from sampled 3-dimensional marker coordinates during preferred-speed treadmill walking and walking overground.

FINDINGS: Preferred walking speed was lower in treadmill walking for both groups. In both groups non-dominant minimum foot-ground clearance and first maximum clearance were greater than for the dominant foot. A high positive correlation was found between these two swing foot clearances when older adults walked on the treadmill. Second maximum clearance was reduced in the older group but this was the only overall age effect. Treadmill walking reduced minimum foot-ground clearance relative to overground locomotion except in the older adults' non-dominant limb that revealed greater vertical clearance height in the non-dominant foot.

INTERPRETATION: Decreased second maximum clearance in the older group may be linked to reduced dorsiflexion. Greater minimum foot-ground clearance in the older adults' non-dominant foot may reflect functional asymmetry, in which the non-dominant limb primarily secures or stabilizes gait. The high positive correlation between first maximum and minimum foot-ground clearances suggests that intervention designed to increase first maximum clearance may also increase minimum foot-ground clearance. A direction for future research is to further understand ageing effects on lower limb trajectory variables in response to a range of walking surface characteristics.