Final answer:
The nurse instructs the use of large muscle groups for lifting to more evenly distribute the workload and prevent injury. This practice is backed by the principles of statics and muscle recruitment, as larger muscles can exert greater forces and handle heavier loads more efficiently.
Step-by-step explanation:
The rationale for a nurse instructing a nursing assistant to use large muscle groups when lifting is primarily to distribute the workload more evenly across the muscles, reducing the risk of injury. Statics, which is the study of forces and their effects on matter in static equilibrium, is relevant because it helps understand the strains in our muscles and bones when performing tasks such as lifting. Large muscles like those in the thighs or the back encompass large motor units which are responsible for gross movements and can exert greater forces due to the recruitment of more muscle fibers. This recruitment of muscle fibers allows the body to handle heavier loads more efficiently, preventing excessive force on smaller muscle groups and reducing the chance of strain. Therefore, using larger muscle groups when lifting can prevent undue stress on parts of the body such as the back, where muscles have smaller effective perpendicular lever arms and are more prone to injury when used inappropriately.