Calisthenics is for life.
When you put your legs on the ground and stand up out of a chair or off the bed, that's a body squat.
If you use your hands to push down and life yourself up out of a chair to a standing position, that's a triceps dip.
If you're laying on your stomach for whatever reason and use your arms to push yourself up, then extend a leg and stand up, that's a pushup to a lunge.
These are exercises you can do daily, that you do naturally that you can do for the entire duration of your life word to Jack Lalaine.
Otherwise you're going to be one of those obese or frail people who one day sit in a chair, lay in a bed or fall on the floor and don't have the strength to get back up.