A fitness program developed by the Royal Canadian Air Force in the 1950s is still a good program to follow. Prince Philip used it for almost his whole life. It is a 10-15 minute workout for a lot of different fitness levels depending on how in shape you are. It scales from beginner to champion athlete.
You can watch the original 5BX video here.
You can also get a electronic copy of the booklet here.
Or a copy of the XBX booklet for women here.
If you want to follow a 5BX video, here is a simple one to follow.