GAIT IMPAIRMENTS
AMONG elderly adults are correlated loss of physical function, admission to nursing homes, and increased risk of falling.
Thus, the maintenance of gait is an integral component of interventions aimed at maintaining mobility and independence. Therefore, an understanding of the specific neuromuscular factors that alter gait is important to develop and evaluate effective interventions for those at greatest risk of disability. Reductions in muscle strength and power capacity may
contribute to age-related changes in gait. In particular, ankle plantarflexors generate significant power during normal gait,
such that impairments to these muscles could induce changes in the coordination of walking. Indeed, ankle muscle power capacity decreases significantly with age, with healthy elders showing power reductions of 20% to 40% relative to young
adults. These decrements may contribute to the most consistently observed kinetic change in elderly gait, which is reduced
ankle power generation during late stance.4,7-9 Evidence in support of this relation is a high correlation between ankle
power output during gait and measures of lower-extremity strength.
Furthermore, Judge et al7 found that healthy elderly adults tended to increase hip flexor power rather than ankle plantarflexor power to increase walking speed, suggesting a potential compensatory mechanism for plantarflexor weakness. McGibbon and Krebs11,12 showed that elderly adults with physical impairments tend to exhibit even more pronounced reductions in ankle power output during walking. In a related study, they showed that functionally limited elderly generated more energy from the hip and low back as a possible compensation for reduced plantarflexor power ouptut. However, it remains unclear whether the reduced power output, relative to healthy elderly, is actually attributable to limitations in muscle power development or to other reasons such as reduced flexibility. Discerning the relative effects of these factors is highly relevant for informing interventions to improve walking
performance.
The purpose of the present study was to compare peak joint powers and joint angles between comfortable and fast walking speeds among a group of elderly adults who exhibit reductions in physical performance. We tested our hypothesis that peak ankle powers would not change when impaired elderly increase walking speed, but that peak hip power output would increase significantly with speed. Support for this hypothesis would suggest that ankle power capacity may be saturating and thus may be a limiting impairment in this population. We also compared joint powers and kinematics of the low-performance elderly with a healthy elderly cohort to provide additional data by which to understand the kinematic and kinetic changes that can arise with impairment.
GAIT IMPAIRMENTS
AMONG elderly adults are correlated loss of physical function, admission to nursing homes, and increased risk of falling.
Thus, the maintenance of gait is an integral component of interventions aimed at maintaining mobility and independence. Therefore, an understanding of the specific neuromuscular factors that alter gait is important to develop and evaluate effective interventions for those at greatest risk of disability. Reductions in muscle strength and power capacity may
contribute to age-related changes in gait. In particular, ankle plantarflexors generate significant power during normal gait,
such that impairments to these muscles could induce changes in the coordination of walking. Indeed, ankle muscle power capacity decreases significantly with age, with healthy elders showing power reductions of 20% to 40% relative to young
adults. These decrements may contribute to the most consistently observed kinetic change in elderly gait, which is reduced
ankle power generation during late stance.4,7-9 Evidence in support of this relation is a high correlation between ankle
power output during gait and measures of lower-extremity strength.
Furthermore, Judge et al7 found that healthy elderly adults tended to increase hip flexor power rather than ankle plantarflexor power to increase walking speed, suggesting a potential compensatory mechanism for plantarflexor weakness. McGibbon and Krebs11,12 showed that elderly adults with physical impairments tend to exhibit even more pronounced reductions in ankle power output during walking. In a related study, they showed that functionally limited elderly generated more energy from the hip and low back as a possible compensation for reduced plantarflexor power ouptut. However, it remains unclear whether the reduced power output, relative to healthy elderly, is actually attributable to limitations in muscle power development or to other reasons such as reduced flexibility. Discerning the relative effects of these factors is highly relevant for informing interventions to improve walking
performance.
The purpose of the present study was to compare peak joint powers and joint angles between comfortable and fast walking speeds among a group of elderly adults who exhibit reductions in physical performance. We tested our hypothesis that peak ankle powers would not change when impaired elderly increase walking speed, but that peak hip power output would increase significantly with speed. Support for this hypothesis would suggest that ankle power capacity may be saturating and thus may be a limiting impairment in this population. We also compared joint powers and kinematics of the low-performance elderly with a healthy elderly cohort to provide additional data by which to understand the kinematic and kinetic changes that can arise with impairment.
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