A Comparison of Treadmill and Overground Walking Effects on Step Cycle Asymmetry in Young

27 Although lower limb strength becomes asymmetrical with age, past studies of ageing effects on gait 28 biomechanics have usually analysed only one limb. This experiment measured how ageing and 29 treadmill surface influenced both dominant and non-dominant step parameters in older (Mean 74.0 30 yr) and young participants (Mean 21.9 yr). Step-cycle parameters were obtained from 3-D 31 position/time data during preferred-speed walking for 40 trials along a 10 m walkway and for 1032 minutes of treadmill walking. Walking speed (Young 1.23 m/s, Older 1.24 m/s) and step velocity 33 for the two age groups was similar in overground walking but older adults showed significantly 34 slower walking speed (Young 1.26 m/s, Older 1.05 m/s) and step velocity on the treadmill due to 35 reduced step length and prolonged step time. Older adults had shorter step length than young adults 36 and both groups reduced step length on the treadmill. Step velocity and length of older adults’ 37 dominant limb was asymmetrically larger. Older adults increased the proportion of double support 38 in step time when treadmill walking. This adaptation combined with reduced step velocity and 39 length may preserve balance. The results suggest that bilateral analyses should be employed to 40 accurately describe asymmetric features of gait especially for older adults. 41 42