In the UK now we hit the height of the holiday season. Long journeys heavy luggage, bad beds, little sleep and likely too much alcohol!
If you want to avoid stiff necks and bad backs heed some of the following advice.
Laying on your side reading your kindle or a book for a prolonged period requires the muscles of the neck on the upper side to work hard holding the head still. Later in the evening or next day these muscle shorten and can then pull the first and second Rib up irritating the ulnar nerve referring issues to the hand. So change sides regularly and stretch the neck muscles after prolonged reading.
When getting into bed make sure the pillow suppports the neck, especially after few glasses of wine.
The same principles apply to the lower back muscles.
A good start would be to do a few mobility exercise first thing in morning and stretches.
Visit the website stretching pages.
In any event enjoy your holidays.