Lifting strategy and stability in strength-impaired elders.
METHODS
Ninety-six subjects underwent biomechanical analysis of freestyle box lifting.


OBJECTIVE
To relate lifting strategy to lower extremity muscle strength and postural stability in functionally limited elders.


BACKGROUND
Back pain and postural instability in elders is rampant and poorly understood. Much of the literature on lifting relates to young subjects.


METHODS
Lifting strategy for 91 functionally limited elders was classified by timing of peak power in the back and knee joints. Isometric hip and knee extensor strength and postural stability were compared among strategy classifications. Postural stability was analyzed by measuring center of gravity (CG) displacement during lifting.


RESULTS
Three lift strategy groups were established: back-lift, or back dominant strategy (BDS); leg-lift, or leg dominant strategy (LDS); and leg-dominant back-first mixed strategy (LDB). Subjects with relatively strong hip and knee extensors used leg dominant strategy; subjects with relatively strong knee, but weak hip, extensors used leg-dominant back-first mixed strategy; and subjects with weak hip and knee extensors used back dominant strategy. Leg dominant strategy and leg-dominant back-first mixed strategy engendered less center of gravity displacement and thus were posturally more stable than the back dominant strategy.


CONCLUSIONS
Subjects apparently chose their lift strategy based on their hip and knee extensor strength. Weaker elders using a less stable back dominant strategy could be susceptible to falls and subsequent long bone and vertebral body fractures. Clinicians could identify at-risk elders by muscle testing. Beyond emphasizing strength and endurance exercise in elderly patients, weak elders should be taught to use a leg dominant lifting strategy, or if they are not physically able, to use a combined back/leg strategy.
Puniello
M S
MS
Massachusetts General Hospital Biomotion Laboratory and the MGH Institute of Health Professions, Boston 02114-4719, USA.
McGibbon
C A
CA
Krebs
D E
DE
D000368:Aged; D000369:Aged, 80 and over; D001415:Back / Q000502:physiology; D016330:Frail Elderly; D006801:Humans; D007596:Joints / Q000502:physiology; D007866:Leg / Q000502:physiology; D017770:Lifting; D008875:Middle Aged