1 ISE Manual handling is associated with 27% of all industrial injuries 670,000 injuries/yr in the United States 60% of all money spent on industrial injuries 93,000,000 lost workdays/yr

2 ISE Approaches to recommendations Biomechanical  emphasizes forces and torques  load limit does not vary with frequency Physiological  emphasizes energy requirements and cardiovascular demands  important for repetitive lifting Psychophysical  combination of the above  predicts “real” capability based on performance under controlled conditions

3 ISE Manual handling variables Individual Technique Task Goals:  increase the strength of the worker  decrease the stress due to technique and task  both

4 ISE Pushing and pulling strength factors Handles One hand vs. two hands Body posture Application height Direction

5 ISE Push/pull summary Two hands are usually better than one. Force capability goes down as it is exerted more often. Initial force capability is higher than sustained capability. Pushing capability is higher than pulling. Push at waist level; pull at thigh level.

6 ISE Task modifications Measure the force required to move all wheeled equipment; periodically check the forces. Install vertical push/pull bars on carts. Push rather than pull loads. Avoid muscle-powered pushing and pulling for ramps, long distances, and frequent moves. Use mechanical aids and momentum. Reduce force by reducing friction.

7 ISE Holding Problems  Holding gives a static load combining body weight and object weight.  Low-back pain arises from spine biomechanics. Solutions  Reduce the magnitude and duration of the torque.  Use balancers.  Limit high loads to short durations.

8 ISE Carrying guidelines Replace carrying with pushing or pulling. Minimize the moment arm of the load relative to the spine. Consider carrying large loads occasionally rather than light loads often. Use teamwork. Consider using balancers, manipulators, conveyors, or robots. Reduce lifting by raising the initial location. Avoid carrying objects up and down stairs.

9 ISE Lifting guidelines 51 lbs is the maximum that can be lifted or lowered (load constant). Recommended weight limit (RWL) is load constant multiplied by various factors. Lifting index = load weight / RWL

10 ISE NIOSH lifting example At initiation,  Horizontal location, H 1 = 10 in.  Vertical location, V 1 = 40 in.  Vertical location, V 2 = 51 in.  Angle of asymmetry, A = 0  Frequency, F = 12 /min.  Load = 14 lbs.  Duration = 2 hr. What is the RWL? What is the Lifting Index, LI?

11 ISE Basic NIOSH lifting formula (pg. 253) RWL = LC × HM × VM × DM × FM × AM × CM  RWL = recommended weight limit  LC = load constant (51 lbs.)  HM = horizontal multiplier  VM = vertical multiplier  DM = distance multiplier  FM = frequency multiplier  AM = asymmetry multiplier  CM = coupling multiplier Note: review the conditions under which this will not apply – turned around, they make a good set of criteria for lifting task design!

12 ISE Multiplier formulas Horizontal multiplier HM = BIL / H BIL = Body interference limit H = Horizontal location Vertical multiplier VM = 1 – VC × | V – KH | VC = Vertical constant = for inches, for cm. V = Vertical location KH = Knuckle height (assume 30 in.)

13 ISE Multiplier formulas (cont.) Distance multiplier DM =.82 + DC/D DC = Distance constant = 1.8 for inches, 4.5 for cm. D = Vertical travel distance Asymmetry multiplier AM = 1 –.0032A A = Angle of symmetry

14 ISE Multiplier formulas (cont.) Frequency multiplier See Table 13.9, pg Lifting frequency = mean number of lifts in a 15-minute period Lifting duration /session in hours may be:  Short =.001 h to ≤ 1 h with recovery time of ≥ 1.2 × duration  Moderate = >1 h ≤ 2 h with recovery time of ≥.3 × duration  Long = >2 h but ≤ 8 h

15 ISE Multiplier formulas (cont.) Coupling multiplier See Table 13.10, 13.11, Fig Depends on:  Height of initial and final hand–container coupling  Whether coupling is good, fair, or poor

16 ISE Solution … HM = VM = DM = FM = AM = CM = RWL = LI =

17 ISE Force limits FL = A × F × DIST  A = Age factor  F = Frequency factor  DIST = Distance factor Differences between force limits and NIOSH guidelines.  Different factors  Different criteria  FL permissible load ~1.8 times that of NIOSH

18 ISE Resources Manual Handing Guide (Mital et al.) Biomechanical software  ErgoIntelligence MMH  2D Static Strength Prediction Program  3D Static Strength Prediction Program

19 ISE Guidelines for manual handling Three categories:  Select individual 1.Select strong people based on tests.  Teach technique 2.Bend the knees. 3.Don’t slip or jerk. 4.Don’t twist during the move.  Design the job 5.Use machines. 6.Move small weights often. 7.Get a good grip. 8.Put a compact load in a convenient container. 9.Keep the load close to the body. 10.Work at knuckle height.

20 ISE Examples to discuss