HIIT stands for High Intensity Interval Training. It is a method of working out that saves time, which we are all short on. The high intensity exercises can range anywhere from between 5 or 10 seconds to 5 or 10 minutes. The periods of recovery can vary as well. Ideally, every interval that is high intensity should be as intense as you can possibly make them.
During the high intensity interval the goal is to reach 100% of your maximum heart rate and to hold it there for as long as you can sustain. Depending on how long it takes lactic acid to build up and creatine phosphate to deplete will determine how long you can hold your maximum or close to maximum heart rate.
If you are beginner and can’t go really intensely you should start out by making your high intensity period slightly less intense and shorter in duration. You can also make your recovery period longer if necessary. Within a few more exercise sessions with HIIT, you should be able to pick up the intensity. When you want more results, the idea is not to increase the duration of exercise but to increase the intensity of the exercise.
There have been some studies comparing HIIT to continuous training. It was found after one study that participants rated HIIT as more entertaining then running continuously for 45 minutes. A typical HIIT routine lasts about 20 to 30 minutes in duration.
For weight loss, subjects doing HIIT with sprints and recovery periods of 4 minutes were compared to those jogging at 65% of their max heart rate between 30 and 60 minutes. At the end, the HIIT group lost a total of 5.8% of their fat mass and the HIIT group lost 12.4% of their fat mass. This makes HIIT look much more effective than jogging; however, I don’t know many people that jog at only 65% of their maximum heart rate. Personally, when I jog, my heart rate goes to about 80% of my heart rate. I’d like to know the comparison between those running at 80% of their heart rate compared to the HIIT sprint study group.
One reason why HIIT is more effective in burning fat has to do with what is called Excess Post Exercise Oxygen Consumption (EPOC) otherwise known as the “after burn effect.” With high intensity exercise you end up consuming a lot more oxygen after the exercise is finished because during the intense periods of the exercise your body cannot fully supply all the oxygen it demands. It is believed that post-exercise, when you are consuming oxygen to make up for what you couldn’t consume with exercising so hard you are also burning more calories in the process. It is believed that up to 48 hours after a HIIT workout you burn more calories via increased oxygen delivery than you would with continuous exercise training.
VO2 is considered a means to measure your overall fitness. V for volume, O2 for oxygen, VO2 max refers to a person’s overall capacity to transport and use oxygen during exercise. As you get more fit, your VO2 improves. What’s interesting is the increase in VO2 from HIIT and continuous training. 27 patients were divided into two groups, a HIIT group that used 95% of their maximum heart rate and a continuous training group that used 70% of their maximum heart rate. After 12 weeks, the HIIT group improved their VO2 by 46% and the continuous training group improved their VO2 by 14%.
Check out the graph below to see how traditional exercise or continuous training compares to HIIT.
I’m taking the cardiovascular workout from Bill Phillip’s Body-for-LIFE as an example HIIT routine. The program is a total of 20 minutes. I’ve tried it both running on the treadmill and cycling. For the first two minutes you do an intensity that is light, for me that is level 10 on the bike. Then on the third minute I go up one level to level 11. On the fourth minute I go up to level 12. On the fifth minute I go up to level 13. On the sixth minute I’m at level 14. At level 14, I’m giving it basically everything I’ve got except I may just be able to go to level 15. At level 14 or the sixth minute, hopefully my heart rate is around 92-95% of its maximum. If it isn’t, I should peddle harder and faster until it is. After the sixth minute, I start a new interval and I back down to level even. Then I progress a level upwards each minute until I reach level 14 again which is the 10th minute. I’m halfway done at the 10th minute.
Then I start again at level 11 for the 11th minute and go all the way back up to level 14 again by the 14th minute. The last interval is different. When I get to level 14, instead of going back down to level 11, I go up one more level to level 15 which really burns. I’m giving it everything that I have at level 15. I finish that minute which is the 19th minute and then drop all the way back to level 10 for the final 20th minute. When you are at the 19th minute, or your highest point, strive to be at 100% of your heart rate for as long as you can be. You may only be able to hold it for 10 seconds that is fine, hold it as long as you can, hopefully the whole minute. That’s it! To calculate your maximum heart rate take 220 and subtract your age from that.
This protocol is an intermediate to advanced level HIIT routine. You start by doing 30 seconds of high intensity work, striving to reach a max heart rate of 100%. You then do a one-minute recovery period at about 60-70% of your maximum heart rate.
Then you do another interval for a 30
second period of high intensity work, then lower the intensity for another one
minute of recovery. You do this for a total of 13 intervals. At the end of the
workout you’ll be at 19.5 minutes of workout duration. The ratio of high
intensity to recovery is 1:2.