We are happy to provide source documentation to substantiate the oft-cited maximum lifting limit of 35 lbs for most patient handling tasks. The following two links should answer any questions you might have on the recommended weight limit. The first link, http://www.cdc.gov/niosh/awards/hamilton/pdfs/hum_5.pdf, provides an extensive evaluation of the NIOSH source equation and measurements involved in a cross sectional epidemiologic study.
The second link, an AJN article by NIOSH scientist Dr. Tom Waters, explains how the complexities involved in patient handling tasks lead to the 35 lb recommended limit. In particular, we wish to underscore the following statement in the article: "For most patient-lifting tasks, the maximum recommended weight limit is 35 lbs.-but even less when the task is performed under less than ideal circumstances, such as lifting with extended arms, lifting when near the floor, lifting when sitting or kneeling, lifting with the trunk twisted or the load off to the side of the body, lifting with one hand or in a restricted space, or lifting during a shift lasting longer than eight hours."
You can review an abstract of the Waters AJN article here.
The Lift Doctor hopes you find that these documents provide a satisfactory explanation.
The Lift Doctor*