Final answer:
The principles in question relate to maintaining proper posture and spinal alignment. Proper posture avoids back strain, and when lying in a supine position, supports for the back and knees may be required. Adjusting stance for stability and balance when carrying weight is also an aspect of good posture.
Step-by-step explanation:
Observe principles of proper posture. Remember that proper alignment is based on a straight spinal alignment or rolled or folded towels may be needed to support the small of the back and raise the knees or head in the supine position. Someone with good posture stands or sits in such a way that their center of gravity is directly above the hips, which is crucial to avoid back strain and disk damage. Additionally, when lying down, the body can be described as prone or supine, depending on whether the face is down or up, respectively. Posture is a function that develops in infancy, and maintaining correct spinal alignment is essential for balance and stability in various positions and activities.
For instance, adjusting one's stance when carrying additional weight helps keep the center of gravity above the base of support, which is particularly important for stability. This technique is used by a person carrying a child piggyback or by students carrying heavy books or bags, as they adjust their stance to maintain their balance. Using props such as towels for support when lying in a supine position helps maintain proper spinal alignment and contributes to overall posture and health.