Low energy hip flexion.
The “low energy” bit of the title means that there is little to no effort or exertion to do this; plus no risk of pulling any muscle or bending/twisting incorrectly that could do your more harm than good. But, the hardest part for many folk may be getting down on the floor to do this because it requires a hard surface and a chair to rest one leg on. Yes yeh, the riskiest part might be actually getting down of the floor 
And here’s the actual video clip explaining how to do it and the knock on benefits of getting the spine realigned.
Again, this is one I used to do in yoga and still feels good to do occasionally, particularly when I have a pinch somewhere in the shoulders. And of course I have an artificial left hip I like to take good care of to last as long as it can.
You can see from those skeletal images how much of a knock on affect it has all the way up the spine and into shoulders. Your central nervous system runs down that column and branches out from there to all over your body.
Miss alignment of the spine can cause all kinds of muscle and tendon issues a throughout the body: shoulder, arm, hand, fingers; hip, thigh, knee, feet, toes issue. You’d be surprised the amount of muscle and joint issues stem just from the hip tightness; trapped nerves, sciatica, painful knees can be released or eased just by looking after your back, your spine.
I think this could be beneficial for stroke arms and legs, to do just prior to any rehab exercise you do to get the most out the exercise itself. By unlocking the spine in this way, you might be surprised how much it may unlock in your arm/hand, leg/foot after a while.
It suggests you 10-15 mins each side. After that you could try a few movements while your down there, such as trying to move your stroke arm or leg out to the side. Test out a range of movements; if you can already get your out to the side, then try getting it above your head. Dorsiflexion of your foot…pointing and raising the toes, rotation of the ankle etc.
These are just a few random examples from the sort of things we all do in our stroke rehab routine and I’m sure you can all think of lots more
I’ve been racking my brains to do this on the bed for those who can’t get down on the floor yet. And I suppose the most suitable way of doing it would be to pile pillows under the leg to be bent to a 90° and don’t have a pillow under your head. Just don’t try using a chair on your bed 
It’s worth giving it a go, once or twice a day for a couple weeks and there’s nothing to lose but a bit of time 
Lorraine