Thanks to a fitness app called GPP Intensity, I've found a great exercise called burpees. Very simple but completely knackering.
A fit young person is supposed to do 12 in 30 seconds, followed by several other killer activities, and repeat all of it several times without a break. I managed just 4 burpees in 30 seconds before I needed a complete rest. Pathetic.
But I came back to it in the course of the day, and it makes you really feel alive. It loads up the heart so you can feel it going boom! boom!
Now, I know what you're thinking - I'll give myself a coronary. But nobody in my family has ever had heart trouble. Mind you, we've all had cancer. It balances up.
PS Note to self - never try burpees first thing in the morning or you'll set off the shagger's back. Actually, do the yoga beforehand and you'll probably be warmed up enough. How do fit people manage to have time left over to do normal living?