I have had bikes all my life that might be part of the reason the old bones are complaining now with more than I care counting been broken living hard and fast the falls take a price on a body.
The normal script of walk more for good lungs is held back by my old mate Arthur Rightus a pain in the just about everywhere, that makes the idea of a bike the obvious choice not going out on it gives it all weather work time - light weight does not take up much room in the house (prob in bedroom) and above all not expensive my economy is no better than the rest of the country.
Exercise bike suggestions on a post card as they used to say.