the.com/body mechanics

means The proper way of moving, lifting, and positioning your body to do physical work efficiently while minimizing strain and injury, especially on the spine and joints.

from A 20th-century compound built from plain English parts: 'body,' from Old English 'bodig' (the trunk of a person), and 'mechanics,' from Greek 'mēkhanikē' (the art of machines, related to 'mēkhanē,' a contrivance or device). The pairing treats the human frame like a load-bearing structure with levers and fulcrums — which, biomechanically, it is. The term gained traction through nursing and physical therapy training, where teaching people to bend at the knees instead of the back became a matter of professional survival, not just folk wisdom.