Are you tired of that pudge around your belly?  Do you despise doing steady state cardio for 20-45 minutes at a time?  Did you know that you can burn more fat and improve your heart health and endurance in just a fraction of that time?  Sound too good to be true?  Is this starting to sound like an infomercial for the latest vibrating hula ab workout gizmo?  Put your wallet back in your pocket, this info is for real!  Research over the past 20 years has made a hugely compelling case that high intensity interval training is superior to steady state cardio in just about every way.  In this brief post, I’ll break down what you need to know.

What is high intensity interval training (HIIT)?  It a nutshell, it’s exercising very hard in short bursts lasting anywhere from 20 seconds to 3 minutes at a time, with lower intensity exercise in between.  “Very hard” means getting your heart rate up to 80-90% of max, where max can be estimated at 220 minus your age.  Typically 4-8 rounds are done, and the entire workout is over in 4 to 20 minutes.  In contrast, steady state cardio consists of lower intensity exercise done for 20 or more minutes at a time, often up to 45-60 minutes.

Benefits of HIIT

1. Improves cardiovascular health – multiple studies have shown that HIIT increases VO2 max (a measure of cardio health) and elasticity of arteries and veins more effectively than non-interval training.
2. Improves endurance dramatically – in one study, after just two weeks of HIIT (six sessions total), participants roughly doubled the amount of time they could bicycle at 80% of their pre-study VO2 max.  Roger Bannister famously broke the 4 minute mile using interval training for 30 minutes a day, beating all of his peers who trained 3 or more hours per day.
3. Burns more fat and calories – studies have shown that 15 minutes of HIIT burns more calories than 1 hour of jogging on a treadmill.
4. Builds more muscle – HIIT stimulates both fast and slow twitch muscle fibers, while steady state cardio stimulates slow twitch fibers only. In addition, HIIT has been shown to increase the body’s production of growth hormone which helps build muscle.
5. Increases metabolism – according the American College of Sports and Medicine, HIIT helps you consume more oxygen than a non-interval workout and results in burning additional calories and fat for up to 24 hours after you exercise.
6. Improves glucose regulation – In one study, participants improved their insulin sensitivity by 23% after just 2 weeks of HIIT with only 18 minutes of total exercise. This is good news for all of us but especially for type 2 diabetics.
7. Time efficient– get an effective heart healthy workout completed in as little as 4 minutes

How to get started with HIIT

It’s very simple to put together an HIIT workout!  Pick an exercise that gets your heart rate up quickly, preferably one that you enjoy doing.  You’ll find the best ones for raising you heart rate are full body exercises like the airdyne bike, versaclimber, rowing, running, or swimming.  The stepmill is also very good.  Start at an easy pace for about 5 minutes to warm up.  Now you’re ready for the actual workout.  Here are some examples of how to do the intervals.

Example 1 (less intense): go as hard as you can for 60 seconds, then go easy for 2 minutes.  Repeat for 5 rounds (15 minutes total).

Example 2 (more intense): go as hard as you can for 20 seconds, then go easy for 10 seconds.  Repeat for 8 rounds (4 minutes total).  This is known as the Tabata protocol, named after Dr. Tabata’s ground breaking 1996 study that showed it improved aerobic capacity more than 60 minutes of steady state cardio.

Example 3: Run up a hill as fast as you can, then walk or jog back down slowly, repeat 4-7 times.

Example 4: Play a game of competitive soccer, which involves sprints alternated with jogging.

The variations are endless.  As long as you push yourself very hard for anywhere from 20 seconds to 3 minutes to get your heart rate up in that 80-90% range, then back off for a period to recover, and repeat, you’ll reap the benefits.  One to three HIIT sessions per week are recommended.  I’d also recommend either resistance training or moderate activity another 2-4 days per week depending on your goals.

A word of caution

HIIT has become hugely popular in the fitness world for good reason, but there are some instances where it’s not appropriate to do.  First and foremost, someone who has medical issues such as a heart condition or high blood pressure should consult their doc first.  Secondly, HIIT tends to put more stress on the muscles and cardiovascular system than steady state cardio, so if you try to add HIIT to an already intense training program, you could push your body into an overreaching/overtraining state.  That’s one reason you rarely see pre-contest bodybuilders doing HIIT.  If your body’s in need of recovery, low impact steady state cardio is the better option.  For the rest of us, HIIT can be a highly effective and efficient way to get healthy and lean, and in my opinion is much less boring than walking on the treadmill for 45 minutes.  Try it and let me know if you agree!