Aim: The aim of this study was to investigate the differences between older and younger adults in the attenuation of impact during descent from a step. Strategies that have been implicated in reducing either the magnitude of vertical ground reaction force (vertical GRF) or the time taken to reach the maximum vertical GRF in the stepping leg were explored. Study Design: The study was an experimental, laboratory based, repeated measures design. Participants: Twenty participants took part in this exploratory study. Ten in the older group of 60-80 years, mean 65.3 (SD 5) years and ten in the younger age group of 20-30 years, mean 22.8 (SD 2.5) years. Main Measures: The vertical GRF and the time taken to reach maximum vertical GRF were measured to ascertain impact during step descent. Electromyography and kinematic variables were measured to determine the effect they may have on the impact. The variables measured were the maximum joint range of motion of the hip and knee during early stance in step descent. Surface electromyography from four lower limb muscles was recorded to ascertain the magnitude of muscle activity at impact. The relationship in an antero-posterior direction of the upper body and stepping leg at initial contact (IC) was also investigated. Results: There was a significant difference in both the amount of knee flexion and the amount of activity of the vastus lateralis muscle during impact between older and younger adults. Older adults had significantly less knee flexion during a step descent activity than younger adults (F(1,18)=5.48; p=.031).Older adults had significantly more vastus lateralis activity during a step descent activity than younger adults (F(1,18)=5.21; p=.035). Conclusions: Older and younger adults use different strategies in both muscle activation and joint range of motion around the knee of the leading leg during the step descent. Older adults used more vastus lateralis activity perhaps to increase stiffness in the knee, leading to a reduction in range of motion at impact. Although no change in vertical GRF was detected in this study, both of these strategies have the potential to increase the impact of a step and therefore cause jarring and possible damage. This study recruited healthy active older adults and differences in impact may be observed in an older or less active population, or in those with joint pathology such as osteoarthritis.

Aim: The aim of this study was to investigate the differences between older and younger adults in the attenuation of impact during descent from a step. Strategies that have been implicated in reducing either the magnitude of vertical ground reaction force (vertical GRF) or the time taken to reach the maximum vertical GRF in the stepping leg were explored. Study Design: The study was an experimental, laboratory based, repeated measures design. Participants: Twenty participants took part in this exploratory study. Ten in the older group of 60-80 years, mean 65.3 (SD 5) years and ten in the younger age group of 20-30 years, mean 22.8 (SD 2.5) years. Main Measures: The vertical GRF and the time taken to reach maximum vertical GRF were measured to ascertain impact during step descent. Electromyography and kinematic variables were measured to determine the effect they may have on the impact. The variables measured were the maximum joint range of motion of the hip and knee during early stance in step descent. Surface electromyography from four lower limb muscles was recorded to ascertain the magnitude of muscle activity at impact. The relationship in an antero-posterior direction of the upper body and stepping leg at initial contact (IC) was also investigated. Results: There was a significant difference in both the amount of knee flexion and the amount of activity of the vastus lateralis muscle during impact between older and younger adults. Older adults had significantly less knee flexion during a step descent activity than younger adults (F(1,18)=5.48; p=.031).Older adults had significantly more vastus lateralis activity during a step descent activity than younger adults (F(1,18)=5.21; p=.035). Conclusions: Older and younger adults use different strategies in both muscle activation and joint range of motion around the knee of the leading leg during the step descent. Older adults used more vastus lateralis activity perhaps to increase stiffness in the knee, leading to a reduction in range of motion at impact. Although no change in vertical GRF was detected in this study, both of these strategies have the potential to increase the impact of a step and therefore cause jarring and possible damage. This study recruited healthy active older adults and differences in impact may be observed in an older or less active population, or in those with joint pathology such as osteoarthritis.

No / We often complete step downs in the absence of visual feedback of the lower-limbs, and/or of the area on the ground where we intend to land (e.g. when descending a step whilst carrying a laundry basket). Therefore, the present study examined whether information from lower visual field (lvf) provides any advantage to the control of step descent. Ten healthy subjects (age 24.4 ± 9.4 years) completed repeated step downs over three-step heights with visual information available from either full or upper visual fields (lvf occluded), and for specific intervals relative to step initiation. Visuomotor control of step descent was assessed by determining pre-landing kinematic measures and landing mechanic variables for the initial landing period. Findings indicate that whilst there were only limited effects on pre-landing kinematic measures under lvf occlusion, individual’s ability to plan/control landing mechanics was significantly different in such conditions compared to when they had access to full field vision. These changes were consistent with participants being uncertain regarding precise floor height when access to lvf was restricted, and consequently led them to adapt their landing behaviour but without fundamentally altering their stepping strategy. Compared to when vision was available throughout, the occlusion of vision (full or upper visual field) from toe-off or mid-swing onwards caused very few differences in landing behaviour. This suggests that the contribution of information from lvf to the control of landing behaviour occurs predominantly prior to or during movement initiation and that ‘online’ vision is used only in the latter portion of the descent phase to subtly ‘fine tune’ landings.