Doctoral Dissertations

Date of Award

12-1989

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Education

Major Professor

Wndell P. Liemohn

Committee Members

Jack Wassweman, Jean Lewis, Edward Holey, John C. Hungerford, Dennis O'Connell

Abstract

In back care programs the erect-torso squat lifting technique is sometimes recommended without concern for the strength of the person's trunk and leg musculature, which if insufficiently developed, may restrict the persons ability to lift in this manner when instructed to do so. The purpose of this study was to evaluate the effects of different levels of strength on body posturing during lifting. In this investigation forty two apparently healthy male university students underwent a battery of tests to determine their respective levels of strength. From this group six were identified as being of a high level of strength and six were identified as being of a low level of strength. These 12 subjects received instruction on how to perform a manual lifting task; the task was to displace a 90 kg box from the floor to the height of the umbilicus using the flexed-knee method of lifting. Cinematographic techniques were used to examine the (a) angular positioning of the knee and torso and (b) moment arm of the box lifted relative to the body's center of gravity. In addition, a lumbar monitor was used to record angular positioning of the low back. Differences were found between the high and low strength groups for posturing of the knee, torso, and lumbar spine. Throughout most of the duration of the lift the high strength subjects demonstrated more pronounced knee flexion and greater trunk extension as is seen in the usually recommended squat method of lifting. The low strength subjects were more variable in their lifting postures; some lifted in a manner similar to the high strength subjects and others selected a more extended-knee, flexed-torso posturing. Based on the results of this study it was concluded that variations in the levels of strength may be accompanied by differences in body posturing during lifting.

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