There are young people today that move like old people from eating too much junk food and not getting enough exercise.
Let the skin be like water, let the flesh hang from the bones.
Try this now. If you can't do it, you can do Headstand instead. If you don't want to do that, go home!
You have to get serious about your practice!
Don't teach too many postures; just the main ones, and hold them for a long time.
The Spiritual Sun already blazes within.