Mechanical energy transfer during gait in relation to strength impairment and pathology in elderly women

Objective: To examine the relationships among strength impairment, pathology and the mechanical energy transfers across the leg and low-back joints in a sample of frail elderly women with functional limitations. Background: Past studies suggest mechanical energy analyses may be useful for identifying compensatory strategies used by elders during gait, but also suggest that age and strength are not the only factors that determine the extent of compensatory strategy use. Methods: Gait data for 75 functionally limited women 60–90 years of age were analyzed. Subjects were categorized by strength and pathology diagnoses. Inverse dynamics was used to compute concentric (positive) and eccentric (negative) mechanical energy expenditures of the ankle, knee, hip and low-back during the stance phase of gait. Joint mechanical energy expenditures were compared between strength and diagnoses groups, and relationships among joint mechanical energy expenditures examined within groups. Results: Weaker subjects demonstrated lower concentric ankle and eccentric knee mechanical energy expenditures, and higher eccentric low-back mechanical energy expenditures, than stronger subjects. Subjects with orthopaedic impairments demonstrated higher eccentric low-back mechanical energy expenditures than subjects with other impairments. Inverse correlations were found between ankle mechanical energy expenditures and hip and low-back mechanical energy expenditures for subjects with orthopaedic impairments. Conclusions: Elders with weak leg muscles and orthopaedic impairments increased hip and low-back mechanical energy expenditures, apparently to compensate for reduced ankle and knee mechanical energy expenditures. Further research is warranted to determine what long-term influences these compensatory strategies have on function and disability.