My wife and I are in our 60s, I am ex military and have always regarded exercise as a necessary evil, my wife tried it when I joined a civilian gym and took to it like a duck to water. We have been following the 5+2 diet for over a year and have reached a plateau, me at 168-172 lbs. We feel as fit as we ever have, but our (my) lifestyle is far too sedentary.

This morning I tried the first HIT exercises as shown in the Micheal Moseley programme, which was repeated here in the UK last night.

I was surprised at the physical results, which really made me feel as though I had just completed an hour in the gym (or been beaten up!). I intend to do three days a week at 3×20 seconds of extreme effort exercise biking, and two normal gym workouts a week, of about 45 minutes each, mostly aerobic.

Is this sensible and how should I warm up/warm down for the HIT sessions?