If a mattress is too hard, you get support, but comfort is compromised, which can lead to body pain and poor sleep in the long run. A very firm mattress puts extra pressure on the shoulders, hips, and joints, which can cause numbness or body stiffness, especially for side sleepers. When a mattress is too hard, the body cannot maintain its natural curve, leading to increased back pain and muscle tension.
A medium-firm mattress provides a balanced level of support and comfort for most people, while an overly firm mattress is only suitable for certain specific medical conditions.