An interactive app that will tell you how much you can safely lift from various positions and how frequently – what will they think of next?
I saw this app on the Washington State Department of Labor & Industries website. It shows how to safely lift from various positions, with what frequency, and with how much weight. I don't think a person could follow these guidelines and still work in construction (the maximum weights are simply too low). Though I do agree with the implied instructions to lift from waist-height whenever possible, hold what you are carrying close, and avoid twisting your back while carrying anything heavy.
You can demo it by clicking here. Check it out – it's kind of interesting, thought.