Small neck muscles - Zero gravity (almost)

Position yourself on your back and make sure that legs are hip-width apart. Possibly you want to put a towel under your knees, and one towel folded twice lengthwise underneath your lumbar spine and one folded twice lengthwise under your cervical spine - just to make up for the lordosis. Cushioning should not be heavy - by all means, just make sure you do not arch over the surface. Hands can be put on your stomach or besides you, palms facing upwards.
Now, look up with some effort WITHOUT letting your head move. Keep this position for a few breaths - now INHALE deeply, upon EXHALING; look down as if you wanted to see your belly button.
Now, this movement lengthens the muscles that have been working while you looked up. It is called isometric tension and post-isometric relaxation. (It's like in humans: if you worked hard, you are more likely to enjoy your vacation - the same way muscles relax better if they worked before.)
Doing this - just looking up straight - allows the neck to re-position itself, sort of "get back on track, parallel". But it lies in the nature of the vertebrae that movement also involves rotation and lateral flexion. So we want to also care for the oblique muscles which allow us to turn and bend sideways.
You just repeat the exercise - looking up and after a few breaths - down to your belly button, but this time you look into one corner with both eyes (and in the next cycle, to the other side). This way, all muscles in the neck are engaged, and eventually get lengthened.
Below, you'll find a picture for print out! Have a good day/ evening after doing the exercise.