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dmcfarlane
06-05-2005, 03:34 PM
Dear colleagues,

Is there an expert on the biomechanics of the shoulder joint for load-pushing tasks? Potiki has suggested a handle height of 940 to 1000 mm on the basis of the 50th percentile female elbow height (Potiki, 1994). This is probably feasible for most cruising situations but it is not always feasible when applying a maximal force (during the initial shove for instance).

My observations of trolley-pushing tasks suggest that the preferred grip height for pushing hospital trolleys varies from elbow height to chest height.

My observations suggest that workers prefer a grip point at upper chest height when they have to apply maximum force (such as propelling a trolley up a ramp for instance). Workers tend to bend forwards to use their body weight and push with their arms near shoulder height in such situations.

They tend to bend their elbows only when applying low forces (on empty trolleys on flat. Even if they are using mainly arm muscles (as opposed to shoulder muscles) a chest height grip might be preferable to waist height as it is important not place loads too low as this reduces the effectiveness of the lever action of the forearm. This is especially when the arm is in as an internal elbow angle greater than 105 degrees reduces the effectiveness of the leverage of the joint to less than a quarter of the maximum possible (Tichauer, 1978).

Can anyone tell me what current biomechanics says about the preferred height for pushing when applying one's body weight?

Regards,

David.

References

* J. Potiki. (1994), Treatise for Master of Safety Science, "Trial of a task/user/environment methodology to develop ergonomic guidelines for the dEsign and use of manually handled hospital trolley", (University of New South Wales, Kensington NSW), page 250.

* E. Tichauer, (1978), "The Biomechanical Basis of Ergonomics" (New York: John Wiley & Sons), page 11, esp. figure 9.




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