Here's a nice refresher that you can do at the office when you've been sitting for a long time. It also gives some relief for a tired lower back. It's called
Complete Breath
Stand up, legs together.
Stretch your arms over head as high as they'll go.
Even better if you can grab on to the top of a door frame and use that to help the stretch.
Breathe in as much air as you possibly can.
Stretch as much as you can - but not to the point of pain
Hold it gently for a heart beat or two.
Let go of the stretch by letting your arms float to your sides, while
Slowly letting go of your breath.
(Breathing out through your mouth is OK. This can be done as if you're blowing air over a bottle.)
Breathe out every last bit of air and then
Repeat as much as you like!
The key to making this refreshing is to make the stretches as full as possible and to make your breathing as full and as empty as possible. Do it vigorously.