Take breaks to rest your back! Humans aren't "designed" to hold the same position for hours on end. Even short (20 second, even) breaks can be extremely helpful

Take breaks to rest your back! Humans aren't "designed" to hold the same position for hours on end. Even short (20 second, even) breaks can be extremely helpful: Lie on your back. Knees bent / legs up, so your back is fully supported by the floor. Arms at your sides, hands on your stomach or whatever the most neutral position is. Small pillow / book under your head to keep that portion of your spine properly curved. Source: family member is an Alexander Technique teacher, also personal experience.