The goal is to achieve perfect spinal alignment with no pressure points. Different sleeping positions requitr different degrees of mattress support and firmness.
WHEN SLEEPING ON YOUR STOMACH.
A stomach sleeper generally needs a firmer mattress. The degree of firmness depends on body weight. with the heaviest part of the body being the central or hip area, good support is needed here to prevent a concave position, where the hips are lower than the head and feet. This causes tremendous stress on the lower back.
WHEN SLEEPING ON YOUR SIDE.
A side sleeper requires a slightly softer mattress or mattress top (pillow top) to accept the impression of the shoulder and hip. In this position, the body is resting on the ankle, knee, hip and shoulder. There are no major muscle groups in the first 3 locations, thus putting most of the burden of weight on the shoulder muscle. A too firm mattress can lead to excessive stress on the joint causing stress, pain and lack of circulation, resulting in tingling and numbness in the arm, hands and fingers. A too firm mattress can cause pain on this pressure point by not providing enough pushback on the surrounding areas. A too soft mattress will allow the hips to sink, causing an un-alignment of the spine, which will cause back and neck pain.
WHEN SLEEPING ON YOUR BACK.
A back sleeper has the most leeway, and may choose any mattress type that comfortably supports body weight and shape. The proper mattress fit supports the neck and shoulders, the lumbar and behind the knees. The body should come in contact with the mattress from head to toe.
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