Civil Engineering Reference
In-Depth Information
A reduction in the quantity of data used to describe cumulative loading on the low back substantially
increased the amount of error. The approaches that used a representative posture to quantify cumulative
loading for a few portions of a cycle resulted in substantial error (square — 70%, work
rest — 27%,
component — 39%, work only — 35%) relative to the complete data set at 30 Hz (Figure 13.15).
/
(a)
(b)
2500
2500
2000
2000
1500
1500
1000
1000
500
500
Gold standard
5Hz
0
0
0
0.5 1.0 1.5
2.0 2.5
3.0 3.5 4.0
0
0.5 1.0
1.5
2.0 2.5
3.0 3.5 4.0
Time (s)
Time (s)
(c)
(d)
2500
2500
2000
2000
1500
1500
1000
1000
500
500
Square
Work/Rest
0
0
0
0.5 1.0 1.5
2.0 2.5
3.0 3.5 4.0
0
0.5 1.0 1.5
2.0 2.5
3.0 3.5 4.0
Time (s)
Time (s)
(e)
(f)
2500
2500
get
place
return
lift
2000
2000
1500
1500
1000
1000
500
500
Work only
Component
0
0
0
0.5 1.0 1.5
2.0 2.5
3.0 3.5 4.0
0
0.5 1.0 1.5
2.0 2.5
3.0 3.5 4.0
Time (s)
Time (s)
FIGURE 13.15 A schematic representation of actual data demonstrating the six approaches used to calculate the
cumulative loading at L4
L5. (a) Gold standard — rectangular integration of all frames collected at 30 Hz. (b)
5 Hz - rectangular integration of data sampled at 5 Hz based on the methods of Kumar (1990). (c) Square —
loading at the beginning of lift multiplied by the duration of the task based on the methods of Norman et al.
(1998). (d) Work
/
rest — work, loading at the beginning of lift multiplied by the time the mass was in subjects
hands, and rest, loading during upright standing multiplied by remaining time of the cycle. (e) Work only — the
work component of work
/
rest alone. (f) Component — cycle divided into four components of the task: get load,
lift load, place load, and return. The
/
in (a) indicates the start point of the lifting phase. (From Callaghan et al.
(2001) Ergonomics, Taylor & Francis, 44 (9), 825-837. With permission.) http://www.tandf/co.uk/journals.
†
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