Environmental Engineering Reference
In-Depth Information
•
Biomechanical
. Compressive forces on the L5/S1 disc are not tolerable
over 650 kg (1,430 lbs) in most workers, which would result in conditions
above the MPL.
•
Physiological
. Metabolic rates would exceed 5.0 kcal/min for most indi-
viduals working above the MPL.
•
Psychophysical
. Only about 25 percent of men and less than 1 percent
of women workers have the muscle strengths to be capable of performing
work above the MPL.
At the Action Limit (AL)
•
Epidemiological
. Musculoskeletal injury incidence and severity rates
increase moderately in populations exposed to lifting conditions described
by the AL.
•
Biomechanical
. A 350 kg (770 lbs) compression force on the L5/S1 disc
can be tolerated by most young, healthy workers, which would result in
conditions at the AL.
•
Physiological
. Metabolic rates would exceed 3.5 Kcal/min for most indi-
viduals working above the AL.
•
Psychophysical
. Over 75 percent of women and over 99 percent of men
could lift loads described by the AL.
The AL and MPL are calculated as follows:
AL
(
kg
)
=
40
(
15
/H )(
1
−
0
.
004
|
V
−
75
|
)(
0
.
7
+
7
.
5
/D)(
1
−
F/F
max
)
(1)
AL
(
lb
)
=
90
(
6
/H )(
1
−
0
.
01
|
V
−
30
|
)(
0
.
7
+
3
/D)(
1
−
F/F
max
)
MPL
=
3
(
AL
)
(2)
where:
H
=
Horizontal location (centimeters or inches) forward of midpoint
between the ankles at the origin of lift
V
=
Vertical location (centimeters or inches) at the origin of lift
D
=
Vertical travel distance (centimeters or inches) between the
origin and destination of lift
F
=
Average frequency of lift (lifts/minute)
F
max
=
Maximum frequency, which can be sustained (see Table 2.1)
Ta b l e 2 . 1
F
max
Table
V >
75 (30) Standing
V
≤
75 (30 in) Stooped
1 hour duration
18
15
8 hours duration
15
12
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