I have been using the HIIT method for 32 days, i hadn't lifted weights in 25 years but i jumped in feet first and have been seeing and feeling gains every day, I'm a paraplegic so my routine is from the waist up..
Started out with 15 minute sessions twice daily with whey protein between sessions, 32 days later i am HIIT'n it for 30 minutes sessions twice daily, early morning and late evening..
When your muscles are used to being relaxed they don't want to cooperate so you have to shock the muscles into submission so they start growing..
I love it, no more than 60 seconds between individual workouts and pushing it, also on strict high protein low calorie diet and have dropped 3 pants sizes since i began, my goal is to go from 44 waist to a 34 waist in 60 days..
Summer Bodies are Built during the Winter