Application of Ergonomics to the Low Back - Fundamentals and Assessment Tools for Occupational Ergonomics - page 571

28
Application of
Ergonomics to the
Low Back

28.1 Overview . . . ............................. 28-1
28.2 Assessment of Weight Lifted . . . .............. 28-2

28.3 Assessment of Trunk Moment . . .............. 28-2

28.4 Assessment of Trunk Posture . . . .............. 28-3

28.5 Assessment of Trunk Motion . . . .............. 28-5

28.6 Assessment of Other Manual Material

Handling Modes .......................... 28-5

28.7 Assessment of Whole-Body Vibration . . . ....... 28-6

28.8 Assessment of Psychosocial Work

Characteristics and Responses Kermit G. Davis, III

University of Cincinnati

. . .............. 28-6

28.9 Summary of Assessment Tools . . .............. 28-7

28.1 Overview

Before an individual can accurately assess the workplace, there must be a basic understanding of the prin-
ciples of ergonomics, particularly with respect to how they relate to risk of injury. When evaluating the
risk of low back injury, it is important to start with a load-tolerance relationship, whether that is a phys-
ical, social, or psychological load. In other words, exposures in the workplace exert loads on the body,
which the body must respond to, and, at some point, a tolerance is exceeded causing the injury and
resulting in an injury (McGill, 1997). The most likely tolerance relating to low back injuries is structural
tolerance — loading on the spine. Another potential tolerance that may also contribute to risk assessment
is pain sensation, particularly with respect to psychosocial work factors (this will be discussed further
later). Based on this load-tolerance viewpoint, one must understand what factors contribute to the
loading on the spine structures and their corresponding tolerances. Once these factors are identified,
the proper assessment tools can be identified and developed to measure the levels of the specific risk
factors that would exceed the tolerances of the spine structures. Thus, assessment tools can only be
effective if they can accurately identify when tolerances are exceed either cumulatively or acutely
and, often times, must be multifactorial in nature.
Many factors in the workplace may contribute to the loading on the lower back. Some of these factors
are the weight of the object being lifted, height of origin and destination, horizontal distance (moment arm)
at origin and destination, task asymmetry at origin and destination, repetition (lift rate), mode of
exertion (lifting, squat lifting, stoop lifting, lowering, pushing, pulling, carrying, etc.), feet position,

28-1