Many of the exercises that we do in the west to 'stay fit' are vigorous and energetic; work the muscles and make them bigger; cause you to get exhausted, sweaty and hot.
There is nothing wrong with this type of exercise but we have to understand that they are not inherently nourishing. They take energy from the inside and move it to the outside. This is one reason why, contrary to popular perception, athletes die younger than the general population; they have exhausted the body.
The Chinese were aware of this and so devised nourishing exercises which they called Qi Gong - the literal translation is Qi Work. Instead of jumping around and flailing arms the exercises are slow, meditative and internally powerful. To an observer it looks like very little is happening and so to a Western eye can appear next to pointless.
Over time, these exercises build awareness of the internal organs of the body, and this awareness starts translating into better internal health. These exercises work on the inner body (not the muscles and bones) freeing up and strengthening the internal organs.
One of the beautiful aspects of these exercises is that because they are nourishing rather than exhausting, you can do them at any time and it will make you feel stronger.
This is a video of Dr Keown performing a series of exercises called the Twelve (or Eight) Brocades. His 'technique' isn't perfect but that is beside the point. The point is to practice them!