| Summary: | Mismatch of human capabilities and the physical requirements of the job they are employed
to do, are often the focus of attention for ergonomists. Efforts to address these mismatches
require that the determination of both the characteristics of the job demands, as well as the
capabilities of the individual or population are objectively quantified.
A heavy manual handling task that was inherent in the performance of a specific job within a
military environment became the focus of this study. Concern was raised regarding the safety
and efficiency of the current employee population to carry out this task, with the equipment
and procedures that was originally designed for use by a younger and all male population.
Despite the change in user profile, there were no selection criteria in place for employee
selection that was based on objective quantified measurements of the physical demands of the
job.
Thus, the objectives of the study were as follows:
1. To determine if the lifting and carrying capabilities of the current population of
ammunition handlers can safely match the requirements of the manual
handling tasks inherent in their job.
2. To determine the correlation between aerobic, strength exertion or
anthropometric characteristics of the ammunition handler and their manual
handling capability.
3. To compare the functional strength capabilities between the female and male
ammunition handlers.
A one-time cross sectional study design was used. One hundred and eighty seven subjects
participated in the study, thirty eight of whom were women. The participants were drawn
from a sample of convenience from the worker population and who voluntarily agreed to
participate in the study.
A multi-faceted approach was taken to address the characteristics and capability of the
participants regarding manual material handling. The measured parameters included: basic
anthropometry, an aerobic capacity prediction test, isokinetic arm and leg strength tests and
an isometric back strength test. The participants also underwent a functional lift and carry test
that was designed specifically for this study and made use of the key ergonomics components
for the manual handling task being addressed. Dummy objects were constructed to replicate
the object that is handled, in three different mass configurations; 47 kg, 35 kg and 20 kg.
The results of the functional lift and carry test of the total population were compared to that of
the job requirements in terms of the mass of the object (47 kg), the time duration, the number
of repetitions and the levels to which the object had to be lifted (300 mm, 900 mm and
1500 mm) . The results indicated that only 43% of the total sample group could safely and
effectively match the manual handling requirements of the job. Of that group, 0% of the
women were able to fully meet the requirements.
Correlation tests were applied to the results of the anthropometric variables, the results of the
predicted aerobic capacity test, the arm, leg and back muscle strength tests, with that of the
functional lift and carry capability test results. There were no correlations found between the
functional test and that of the other variables. There was a moderate correlation found
between aerobic capacity and functional lift ability, as well as between right knee concentric
extensors endurance results and that of functional lift ability. Thus, there were no strong
predictive tests that could be used for employment screening purposes; the functional test
remains the closest representation to the job requirements.
The results of the functional test of the men and women subgroups were analysed for effect
size. There was a large effect size calculated (d>0.80) between the functional lift ability of
the men and the women of all levels for all masses. The implication is that a task must first
be designed to be non gender biased before a policy of open employment for heavy manual
handling tasks can be successfully implemented.
The findings of the study confirm that the entire current worker population would probably
not be able to safely and effectively perform the manual handling task they were required to
do within their post profile. The implications are that the risks for musculoskeletal injuries,
fatigue, uneven workload distribution and poor performance are high. The capabilities of the
workers do not match that of the job demands. However, should the mass of the object that is
handled be replaced with an object of similar capability and characteristics, but having a mass
of not more than 20 kg, more than 98% of the sample population would then be able to safely
and effectively perform the task.
The ergonomics interventions required to improve the mismatch of the job requirements to
capabilities would include 1) redesign of the manual handling task or 2) implementing a
functionally based selection criterion for employees to be posted in the specific job profile. === Thesis (M.Sc. (Human Movement Science))--North-West University, Potchefstroom Campus, 2005.
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