2007, Piran, Slovenia

Working Environment
METHODS
Students and workers (males and females) between 18-35 y were selected as subjects. A total
of 20 subjects participated. Subjects were recruited in a heterogeneous way so that some
subjects were regular physical activity and some were non-regular physical activity. All
subjects were right handed. These twenty (N=20) subjects were divided in to two groups:
First group, 10 males (college) and 10 males (worker). All of them are healthy and have no
history of hand dysfunction.
Upper limb posture was determined with the seven degrees of freedom model (SDFM)
(Roman- Liu et al., 1999). This model sets the minimum number of degrees of freedom that
can define upper limb posture considering the shoulder joint, elbow and wrist. According to
SDFM, the upper limb is defined by seven angles (q1, q2, q3, q4, q5, q6, q7) Fig. 1 (Roman-
Liu, D.; Tokarski, T. 2005). Some of the selected upper limb postures are hypothetical and
they do not usually occur in Workplace or sports settings however, they can be appropriate for
measurements and for making Comparisons. (Roman-Liu, D.; Tokarski, T. 2005). All
subjects were introduced and instructed about the equipment and the RPE scale. Prior to
actual testing, each subject was made to sited, and strapped with the chair, and instructs to use
the right arms only. Throughout the study, subjects were present with weights and instruct to
lift them with arm hold them for about three seconds. The left arm always constant (dead
weight) while the right arm always lifted variable Weights. After lifting, and during holding
the weights, subjects are instructed to compare the variable weight (right arm) against the
constant weight (left arm) and rate the variable weight using the RPE scale. Subjects were not
told about the actual weights they were lifted.
Figure 1. Definition of upper limb posture by seven angles: (q1) arm horizontal adduction/abduction; (q2) arm
flexion; (q3) arm humeral rotation: medial rotation (-), lateral rotation (+); (q4) elbow flexion; (q5) pronation (-),
supination (+); (q6) ulnar deviation (adduction) (-), radial deviation (abduction) (+);(q7) volarflexion (extension)
(-), dorsiflexion (flexion) (+).
DISCUSSION
This study provided the following conclusions:
1. Two training sessions proved to be sufficient to learn to use Borg's CR-10 scale.
2. There was a strong positive correlation between the weights lifted and RPE values.
3. College male subjects perceived the weights differently without and with fatigued muscles.
But worker male subjects perceived the weights differently as compare to college male
subjects. This may be due to the physical (the factors Physical exertion and Physical
discomfort) and mental (the factors Lack of motivation and Sleepiness) dimensions of
perceive fatigue.
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