I'm very heartened by the numerous replies and encouragement to do some pushups.

A friend of mine is a personal trainer, I'll be seeing her next week and will ask her to show me how to do both push ups and sit ups (the former I really can't do while the later I end up moving in a walrus lurching style from one end of a hall or room to the other and look very dorky doing too)

I have a walking app to track my daily walking (usually a min 1½ - 2 miles (2 - 3Klm) per day) so push ups might become a thing I do, too. (Just as an aside, I got advised to "walk up all flights of stairs briskly" for a very short burst of exercise which I've been doing for close to twelve months now).