WARNING, for you older folks, GET A CHECKUP before you start something like this, I have done it and it can be brutal, but effective. If you refuse to see a doctor, than ease into this please, over a series of several weeks.
Steady as she goes. And make it fun.
If it gets too miserable (and it can get too miserable if you push too hard), you will quit.
It's a wonderful program and there are REAL results. But take it slow and increase the intensity very slowly.
This program will produce great results, the most important of which is that you will feel great. I have done HIIT for a few months and noticed a great change in mood (way up) and a big change in fitness.
I will add a caveat. I overdid it a little while ago and burned out. I caught my first cold in 20 years.
I was out for a week and felt miserable. Ergo, don't overdo it.
That said, you probably won't.
I am an exercise maniac. I was doing an hour of hard cardio which included barf-inducing HIIT in the last 20 minutes.
Not a good thing to do.
I am back at it but I am taking 3 steps back and planning to move ahead at a steady, reasonable pace.
Two words of warning: cardiac arrest
Great interval training for developing trunk and arms: shoveling snow.