Need more exercise?

I have been contemplating this.
The Senior Cat says he does not get enough exercise. He was out in the garden for a short time  yesterday - before it started to rain. This is his "exercise" now - slowly pottering around the pots we have at waist height. 
He used to walk around the block and then walk around the block with his walker. That's too much now.
He has never played sport. His attempts to teach children to play sport at school ended up with a dislocated shoulder when he tried to throw a cricket ball. In the schools where he was the only male teacher and expected to teach the boys how to play football they kindly told him to "stand there and just watch us sir". The Senior Cat is, by his own description, "clumsy" and "the owner of two left feet".   
At one time he used to ride his bike to the school he was teaching at. He said it set a good example for the children - and probably the staff as well.  He continued to ride the bike until he was in his eighties and his knees started to trouble him. Middle Cat bought him a walking machine and he used that for another five or six years. 
The machine now sits there idle. It gets no exercise at all. I ride my trike - and yes, I should get more exercise than I do but at least I get some.  I should use the machine, especially if it is cold and wet and I don't feel much like getting cold and wet too. 
But there are people I know who get no exercise at all. They think they exercise. They do their housework at weekends and they sweep up the leaves in autumn. Someone else comes in to mow the lawn - if they have one. 
One of those people is in the process of having the lawn removed and a "no work" garden put in. 
   "All it will require is a bit of watering and someone to come in once in a while and tidy things up," he proudly told me, "It's all natives so it has to be a good thing."
I have watched this "garden" taking shape. I suppose it will suit him but, to me, it lacks colour and life. It doesn't mix well with the surrounding houses. It won't be green and cool. 
This same man complains that he sometimes doesn't know what to do with himself, especially if there is no sport to watch on television. 
I had to drop a prescription and some books in to his elderly neighbour yesterday. Her garden is still neat. Yes, someone else comes in to mow the lawn now and the "young lad" (he's almost 40) down the street a bit came in and did some pruning for her. 
    "I've got so much to do this week, " she told me, "Thanks for picking these up." 
She would have walked to the chemist and the library and back but she wanted to finish getting a garden bed ready so she could go to the garden shop with her daughter-in-law tomorrow.
     "And I'll be down to see all those wonderful things at the show next week."
She shakes her head over her neighbour's garden. 
     "That's not going to exercise his body or his brain."
We both agreed that exercise takes many forms and exercise of the mind is one.