4.2 NIOSH Lifting Guide
National Institute for Occupational Safety and Health
Human Limits Considered
  • In NIOSH Lifting Guide
Based on risk injury potential
- Corresponds to cadaver data
Based on compression limits for L5/S1 disk
Based on Energy Expenditure Levels
Based on muscle-strength  capabilities
The greater the predicted compressive forces, the greater the number of lower back pain incidents
Compression Data
  • Looks at existing studies on dead bodies
  • 20 studies reporting disc endurance
  • Studies are old because it is a trade-off protecting dead people's rights. 
  • Findings: 
NIOSH Action Limit
  • Below this line there is no problem/no need to worry about injuries
NIOSH Max. Permissible Limir
  • Above this line it can be very very dangerous
1. Injury potential increases for some people
1. Injury potential increases for most people 
2. A 350 kg (770 lb) compression on the L5/S1 disc 
2. A 650 kg (1430 lb) compression on the L5/S1 disc 
3. A metabolic rate of 3.5 kcal/min 
3. A metabolic rate of 5.0 kcal/min 
4. 75% of females are capable of exerting the necessary muscle strength
4. 25% of females are capable of exerting the necessary muscle strength
NIOSH LIfting Guide Equations
To figure out safety standards.
Recommended Weight Limit (RWL)
RWL = LC x HM x VM x DM x AM x FM x CM
  • No discounting factor can be greater than 1
  • If factor = 0 you should never do this activity
  • Optimal conditions: symmetric lifting position with no torso twisting, occasional lifting, good coupling, <= 25 cm vertical distance of lifting
RWL = 
FM x
AM x
DM x
VM x
HM x
LC x
Horizonal Location
  • Distance of the hands away from the midpoint of the ankles.
  • How far away the load is from horizonal center of mass (point between the ankles)
Load Constant
  • Maximum weight under ideal conditions
  • LC = 23 kg OR 51 lbs
Assymmetric Lifting
  • Angular measure of how far the object is displaced from the front (mid-sagital plane) of the worker's body at the beginning or ending of the lift, in degrees. 
Vertical Travel Distance
  • Absolute value of the difference between the vertical heights at the destination and origin of the lift
  • How much is lifted UP
Vertical Location
  • Distance of hands above the floor
  • Harder to lift if it is on the floor
Coupling Multiplier
  • Classificaation of the quality of hand to object coupling (Ex; handle cut out, grip)
Lifting Frequency
  • Average number of lifts per minute over a 15 minute period
Lifting Index (LI)
LI = (Load weight)/(Recommended Load Weight

LI = 1 is action limit
LI = 3 is max permissible limit.
Steps to Solve NIOSH Qustions:
1. Select a unit system: 1 lb = 0.45 kg or 1 inch = 2.5 cm
2. Find initial position of the lift and the values of H, V, D, A, F and C
3. Computer RWL and LI
4. Compare LI with action limit and permissible limits:
- If LI <= 1 SAFE
- If 1 < LI <= 3 increased RISK for SOME workers
- LI > 3 MANY workers at HIGH risk
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