Affiliations: Faculty of Kinesiology and Physical Education,
University of Toronto, Toronto, ON, Canada | Department of Kinesiology, University of Waterloo,
Waterloo, ON, Canada | Northern Ontario School of Medicine, East Campus,
Laurentian University, Sudbury, ON, Canada | School of Rehabilitation Science, McMaster University,
Hamilton, ON, Canada
Note: [] Corresponding author: Jack P. Callaghan, Department of
Kinesiology, Faculty of Applied Health Sciences, University of Waterloo,
Waterloo, ON N2L 3G1, Canada. Tel.: +1 519 888 4567, ext. 37080; Fax: +1 519
746 6776; E-mail: callagha@uwaterloo.ca
Abstract: BACKGROUND: Theoretical and empirical data support the notion that
distal lower extremity joint dysfunction could influence the low-back injury
potential of workers, but the impact of unilateral ankle immobilization on
low-back loading during lifting has yet to be examined. OBJECTIVE: To examine the influence of unilateral ankle
immobilization on the kinematics and kinetics of lifting. METHODS: With and without their right ankle immobilized, 10 men
performed laboratory-simulated occupational lifting tasks. Together with force
platform data, three-dimensional kinematics of the lumbar spine, pelvis, and
lower extremities were collected, and a dynamic biomechanical model was used to
calculate peak compressive and shear loads imposed on the L4/L5 intervertebral
joint. RESULTS: In comparison to the unaffected conditions, ankle
immobilization generally resulted in less knee (0.001 ⩽ p ⩽ 0.07)
and greater lumbar spine (0.001 ⩽ p ⩽ 0.35) sagittal motion when
lifting. Associated with this compensatory movement strategy were greater L4/L5
anterior/posterior reaction shear forces (0.001 ⩽ p ⩽ 0.25). However,
there were cases when individual compensatory movement strategies differed from
the "group" response (i.e., subjects increased their sagittal knee motion on
the affected side about 8% of the time); this resulted in increased peak L4/L5
joint compression forces without changing the peak L4/L5 anterior-posterior
shear forces. CONCLUSIONS: Ankle dysfunction can alter the way in which
individuals move and load their low-backs when lifting. The different ways in
which individuals compensate for personal movement constraints could alter the
potential site and mechanism of occupational low-back injury.
Keywords: Secondary injury, movement compensation, motion constraint, kinetic chain
