You need a heart rate meter, otherwise it's kinda hard to gauge whether you are doing it right or not. The elliptical machines fit this category well, treadmills are not recommended, but running outdoor is okay. Next calculate your maximum heart rate, take 220 minus your age and you get your max heart rate. e.g I am 20 years old, my max heart rate would be 220 minus 20 and i get 200. The more intense the exercise, the higher the heart rate .
Please consult with your doctor before you start HIIT, it's very tiring. Before you begin HIIT and if you are a newbie to exercise, i suggest you get used to cardiovascular exercises 1st.
Beginners HIIT regime 4 cycles :
5 minutes jog. ( aim to increase heart rate 70%)
1 minute run ( aim for HR 75%)
30 seconds jog ( don't walk)
1 minute run ( aim for for HR 75-80%)
30 seconds jog
1 minute sprint ( aim for HR 80 -85%)
30 seconds jog
1 minute sprint as fast as possible( aim for HR 80-85%)
5 minutes jog cool down ( don't skip this)
advanced HIIT Regime 10 cycles
5 minutes jog warm up ( aim for HR 70%)
1 minute run aim for HR 75%
30 seconds jog ( don't walk)
1 minute run ( aim for for HR 75%)
30 seconds jog
1 minute run ( aim for HR 75%)
30 seconds jog
1 minute run ( aim for HR 75-80 %)
30 seconds jog
1 minute run ( aim for HR 75-80 %)
30 seconds jog
1 minute run ( aim for HR 75-80 %)
30 seconds jog
1 minute sprint ( aim for HR 80-85 %)
30 seconds jog
1 minute sprint ( aim for HR 80-85 %)
30 seconds jog
1 minute sprint ( aim for HR 80-85 %)
30 seconds jog
1 minute sprint ( aim for HR 80-85 %)
30 seconds jog
5 minutes cooldown
You can't sprint at the beginning of the cycles, otherwise you will run out of steam by the 5th cycle, slowly build up then sprint at the last 4 cycles. DO NOT SKIP THE COOLDOWN IT'S DANGEROUS. Imagine your heart going real fast at 85% and suddenly, you skip the cooldown and sit down- it's like putting a sudden flooring brake on your speeding car, what can happen ? Car overturns.