ERGONOMICS OF MANUAL MATERIALS HANDLING - Environmentally Conscious Materials Handling - page 44

• Vertical location . Vertical height of the hands above the floor (at origin of
lift). V is measured vertically from the floor to the mid-point between the
hand grasps, as defined by the large middle knuckle.
VM = ( 1 − 0 . 003 | V − 75 | ) in cm, or

) in inches
If V > 175 cm (70 in.), then the vertical multiplier becomes 0.0. It is
assumed that V cannot be less than zero (not lifting a load below floor
level).
• Distance component . Vertical travel distance of the hands between the
origin of the lift and destination of lift.
DM

VM = ( 1 − 0 . 0075 | V − 30 |

= ( 0 . 82 + 4 . 5 /D) in cm

1 . 8 /D) in inches
D is assumed to be at least 25 cm (10 in.) and no greater than 175 cm
(70 in.). If D< 25 cm ( < 10 in.), then use D

= ( 0 . 82 +

DM

= 25 cm or D = 10

inches in the equations just given.
• Asymmetry component . Refers to a lift that begins or ends outside the
midsagittal plane of the body, which is the plane going through the middle
of the body separating the body into left and right sides. The AM decreases
about 0.14 for each 45 degrees of asymmetry of lift.
AM

0 . 0032 A ,where A is the angle of asymmetry
The angle A is limited to the range of 0 to 135 degrees. If A > 135 degrees,
the AM

= 1 −

0.
• Frequency component . This is defined by the number of lifts per minute, the
task duration, and the height of the origin of lift. Lifting frequency should
be observed and measured over at least a 15-minute period. Lift duration
has been defined in three time intervals rather than the two intervals of the
1981 guide. The durations are as follows:
• Short . One hour or less, followed by a recovery time period of 1.2 times
the work time (e.g., 30 minutes work, followed by at least 36 minutes
of recovery would be considered short duration).
• Moderate . More than one hour but no more than two hours, followed by
a recovery period of at least 0.3 times the work time (e.g., 100 minutes
of work, followed by 30 minutes of recovery).
• Long . More than two hours work up to eight hours. The height of the
origin of lift differentiates between lifts above or below knuckle height
(75 cm or 30 in.).
For frequencies of less than one lift every five minutes ( F

= 0andRWL =

≤ 0 . 2), use

F = 0 . 2. In the 1981 guide, F max values were 12, 15, or 18 lifts/min,