HIIT stands for High Intensity Interval Training, which is a short bout of high cardio effort followed by a low-moderate intensity rest period. One of my favorite HIIT protocols I follow is a 30 second sprint followed by 90 seconds of active recovery.
True HIIT training can be done 1-3 times a week and should range from 10-30 minutes for all out effort style training. High intensity intervals should be around 85-95% of your max heart rate. When the workout go past 30 minutes you’ll start to see the intensity diminish, so its best to keep these workouts short and intense.
There are no definitive guidelines for choosing work-to-rest ratios but a good place to start is 1:2 or 1:3 ratio to see how you feel and how your heart rate is responding. Individuals physical fitness levels vary greatly and will impact the amount of rest needed to recover from a high intensity interval. Progressive overload applies to HIIT as well, so increasing the intensity or duration needs to change in intensity or duration over time. Start with 2-4 intervals to start and work your way up. I typically stop after no more than 8 intervals, any more than that and most people will be overtraining and burn out eventually.
For fasted morning HIIT workouts use a BCAA or 10 g of protein prior to training to reduce muscle breakdown during workout. Also, using green tea (highly recommended) or other types of caffeine prior to your fasted workout session can also increase fat burn. Taking L-carnitine 30 minutes prior to exercise has also been shown to increase fat burning.
Next time you hit the cardio machines try this HIIT workout: 5 minutes of light cardio for a warm up, followed by 2-4 high intervals for 30 seconds. Follow the high interval with a low to complete rest interval for between 60-90 seconds. After you’re finished with your intervals cool down for 5-10 minutes of moderate intensity, steady state cardio.