Influence of lower extremity strength of healthy older adults on the outcome of an induced trip.
OBJECTIVE
To determine whether decreased lower extremity strength contributes to trip-related falls in older adults.


METHODS
A cross-sectional sample of older adults were safety-harnessed and tripped while walking using a concealed, mechanical obstacle. Lower extremity strength was compared between trip outcome groups.


METHODS
A biomechanics research laboratory.


METHODS
Seventy-nine healthy, community-dwelling adults aged 65 and older (50 women).


METHODS
Ankle, knee, and hip flexion and extension strength were measured isometrically and isokinetically. Measured strengths were subjected to a factor analysis. Strength factor scores were compared between those who recovered from the trip and those who fell by three previously identified mechanisms: during-step, after-step, and elevating-response falls.


RESULTS
Seven common factors, one associated with each direction of exertion at each joint and one with the time rate of moment increase, explained 88% of the variance in measured strength. The during-step (n=5) fallers were significantly stronger in the ankle extension (plantarflexion), knee flexion, overall extension, and total strength factors than those who successfully recovered using a similar, lowering strategy (n=26). The elevating-response faller (n=1) was stronger in the plantarflexion and overall extension factors than most of those who recovered using a similar, elevating strategy (n=11). Two of three after-step fallers were among the weakest subjects tested.


CONCLUSIONS
Weak older adults and the strongest older adults may be at greater risk of falling from a trip, although by different mechanisms. High strength may increase the likelihood of a during-step or elevating-response fall; decreased strength may increase the likelihood of an after-step fall.
Pavol
Michael J
MJ
Department of Biomedical Engineering, Lerner Research Institute, The Cleveland Clinic Foundation, Ohio, USA. mpavol@uic.edu
Owings
Tammy M
TM
Foley
Kevin T
KT
Grabiner
Mark D
MD
D000058:Accidental Falls; D000368:Aged; D000843:Ankle Joint; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005163:Factor Analysis, Statistical; D005260:Female; D006621:Hip Joint; D006801:Humans; D007537:Isometric Contraction; D007719:Knee Joint; D008297:Male; D018709:Statistics, Nonparametric