Suppose you want to find the female population percentage for lifting tote pans.
Your measurements include (see guidelines below):
Tote pans weigh 29 pounds
Hand distance away from body of 7 inches
An initial hand height at start of 30 inches
A hand height at end of task of 50 inches, and
Tote pans are lifted once every 5 minutes
First you must select the correct “Table” from the Select Task
menu. Since you are looking for female population percentages, select;
Female - Lifting Task Ending Between Knuckle Height & Shoulder Height (≥28”
Enter the Object Weight of 29 lb.
Select from the Lifting Distance pull down menu 20 inches.
Select from the Hand Distance pull down menu 7 inches.
Select from the Frequency - One Lift Every pull down menu 5 minutes.
Select Compute Population Percentage. This is the population percentage
of female workers able to perform this task without overexertion or fatigue.
Many times measurements will lie in-between those values in the pull
down menus e.g. Hand Distance, Frequency, Lifting, Lowering, Carrying Distance,
and Hand Heights. If so, round off to the higher or lower value depending on
whether the value is above or below the middle value of the measurements. For
example, for same Female - Lifting Task Ending Between Knuckle Height & Shoulder
Height (≥28” and ≤53”) task; for a measured Lift Distance
of 16 inches than select 20 inches and for a measured Lift Distance of 14 inches
then select 10 inches etc.
Liberty Mutual Tables is intended to be a flexible tool. If you would
like to see the population percentage differences between a Lifting Distance
of 20 inches and 10 inches then select one and then the other and Compute Population
Percentage each time. Compare population percentage results. Same would be true
for entering Object Weights any other measurements including Hand Distance.
This is how What-If scenarios can be performed using Liberty Mutual Tables.
Hand Distance is the distance from the front of the body to the hands.
(Note that this is a different measurement from the 1991 Revised NIOSH Lifting
Guide). Hand Distance will normally be half the width of the object being handled
unless the object is purposely held away from the body.
For Pushing and Pulling Tasks you will need to obtain a force gage or
force measurement device and enter the initial force, in pounds, needed to start
the object moving. Take several measurements and enter the highest value particularly
when floor or wheel conditions are poor. For pushing tasks, you can measure
the force by pulling. However, while the effect on the worker may be different
between a push and pull, the measured force will be the same. Also obtain the
sustained force measurement to keep the object moving. All measurements should
be taken at an acceleration representative of the task as performed in the actual