Choosing the Right Chair
Your chair needs to fit YOU, as your needs may be different from others you share your space with. Most chairs can be adapted but good chairs are not always expensive and often already in your home, desk chair, outdoor chair. Comfort is important but the spine will not generally like a C curve or feet up position.
In sitting, support your spine behind you in an inward curve at the waist, unless you have severe degeneration or if this too uncomfortable.
Remember: the bottom goes right at the back of the chair before you sit, then put the support in the hollow of the back. The feet should be on the floor, so you may need a low box to put them on if you have short legs.
Remember the 90/90 rule: 90 degrees at the hips, 90 degrees at the knees and 90 degrees at the ankle.
Choosing a chair for recreation
You will become the shape of the chair you sit in if a large proportion of your day is spent sitting, over a long period of time. To reduce delayed back pain from sitting get up often and stretch backwards or go for a walk or lie down flat for 5 minutes. A comfortable chair often feels comfortable until you move, so you tend not to move as much as you should. A good chair is easy to get out of and sits you in the supported, comfortable upright position.
The back of the chair needs to support your back by moulding into the spine at the base, and preferably the top of the back should be no higher than the shoulder blades. You do not need a chair to support your neck, your neck will automatically be supported when the lower back curve is supported with an inward curve. Roll up and tape a towel to support the inward curve especially when in soft furniture.
If the back of the chair or couch comes up higher than the shoulder blades, the top edge of it will push your head forward and, even if it is not uncomfortable, the unnatural posture can lead to neck pain or headaches next day or at night.
Sit square in the chair