What action is advisable when setting down a load to avoid injury?

Bending at the knees is advisable when setting down a load to avoid injury because this technique engages the strong muscles of the legs instead of the weaker muscles of the back. By bending at the knees and maintaining a straight back, the body is positioned to better support the weight and minimize strain on the spine. This proper lifting method helps to distribute the weight more evenly throughout the body, thus reducing the risk of developing musculoskeletal injuries, which are common when lifting improperly.

The other options do not provide a safe approach to dealing with heavy loads. Dropping a load quickly can lead to accidents and injuries, both to the individual and to anyone nearby. Using a back support can be helpful but does not replace proper lifting techniques. Pushing instead of lifting may be appropriate in certain scenarios but is not always feasible and does not directly address the act of setting down a load safely. Therefore, bending at the knees is the most effective method for safely setting down a load while protecting oneself from injury.