I roughly remember my first HIIT cardio workout. I had read an article in Muscle Media 2000, written by Shawn Phillips (in 1993 I think) describing a way to do cardio to burn fat like crazy. When I went to my gym and performed HIIT on the treadmill, people gave me some crazy looks. I’ve been experimenting and studying up on HIIT cardio ever since…and after close to 20 years, I’m still in learning mode. In this post I’m going to break apart a study that compares short 30 seconds intervals with longer 3 minute intervals. This study found that the 30 second intervals could be more effective than 3 minute intervals. I’d like to give you some practical ways on how to use the findings in this study.
[Rugby is an example of the effect that sprint intervals have on the body. Obviously these guys train in a number of ways, but the tempo of the game contributes to low body fat levels displayed by all of the players.]
Greater Calorie Burning With Less Pain?
Let’s be honest…if you are willing to kill yourself, you can burn a lot of calories and eventually get super lean. Ever see the movie 300? That movie is an example of people who lived and breathed fitness and tortured themselves for months to get lean. The “brute force” method of fitness works, but who wants to live like that? I think training should be enjoyable and something that you want to do for life. Luckily a study found that 30-30 HIIT Intervals, done properly, felt easier and actually burned more calories than a longer more painful work-to-rest ratio.
Link to Study: Physiological Responses During Interval Training With Different Intensities and Duration of Exercise
“In conclusion, this study revealed that IT duration of 30 seconds in comparison to 3 minutes allowed the athlete to perform a longer session with a higher total VO2, mean VO2, and HR yet at a lower BLC. The study also indicated that a submaximal intensity of 90% of MPO allowed the athlete to perform a longer session with a higher total than IT duration performed at 100% MPO.”
[I’ll try to make these findings of the study easier to digest.]
4 Different Types of HIIT Intervals Were Compared:
1. 30-30 HIIT Interval @ 90% Maximum Power Output:
30 seconds of effort at 90% alternated with 30 seconds of recovery at 50%. This was to be done for 30 minutes or until the subject couldn’t maintain the required Maximal Power Output.
2. 30-30 HIIT Intervals @ 100% Maximum Power Output:
30 seconds of effort at 100% alternated with 30 seconds of recovery at 50%. This was to be done for 30 minutes or until the subject couldn’t maintain the required Maximal Power Output.
3. 3min-3min HIIT Intervals @ 90% Maximum Power Output:
3 minutes of effort at 90% alternated with 3 minutes of recovery at 50%. This was to be done for 30 minutes or until the subject couldn’t maintain the required Maximal Power Output.
4. 3min-3min HIIT Intervals @ 100% Maximum Power Output:
3 minutes of effort at 100% alternated with 3 minutes of recovery at 50%. This was to be done for 30 minutes or until the subject couldn’t maintain the required Maximal Power Output.
Intervals Allow Hard Work With Lower Blood Lactate
Let’s discuss why intervals are effective in the first place compared to just training hard at a steady rate. Intervals allow you to spend a greater amount of time doing intense exercise at lower blood lactate levels than simply “running hard”. The active rest is what prevents lactic acid buildup in the muscles. HIIT cardio allows you to spend more total time at high intensity levels without feeling it as much as simply training hard non-stop.
Less Pain & Fatigue With the Same Total Time at High Levels
Let’s say that you do intervals of 30 seconds walking and 30 seconds running. Your average running speed is 10.5 mile per hour and you do intervals for 20 minutes. That is 10 total minutes of running at 10.5 miles per hour. If you ran at that pace for 10 minutes straight, you would be gasping for air as well as feel a burn in your legs after a minute or two. Alternating running with walking is what allows you to get this same amount of higher intensity exercise in without the pain and fatigue caused by lactic acid buildup. Same amount of work with less of a perceived effort.
Shorter Intervals Created a Larger “Oxygen Debt”
The shorter intervals had a 90% greater oxygen uptake than the longer intervals. This created a larger oxygen debt. Why is oxygen debt important? When you train at an intense level, like sprinting, your body can’t supply oxygen at a fast enough rate to fuel the muscles. After the intense effort is completed, your body has to basically repay that “borrowed energy”…it owes oxygen to get those muscles back to their normal state. The more energy your body borrowed during an intense effort the more oxygen it owes…this is called Oxygen Debt. The larger the oxygen debt created by your workout the longer it will take to repay it…with the benefit of more calories burned for a longer period of time after you are done exercising.
The problem with training all out is that lactic acid buildup can shut the muscles down. You obviously want to train hard, but not to the point where you can’t complete the next interval. So the finding here is that hard intervals are better than pushing your limit each and every sprint. How hard is 90%? Well you can use heart rate to kind of give you an estimate if you are pushing hard enough. It looks like the average heart rate of the 30-30 intervals at 90% was 171 beats per minute. Although using heart rate is not an exact measurement of effort, if you are in the 170 range at least part of the time doing your intervals…you will be close to the right intensity level.
Short Intervals Are An Efficient Way to Burn Calories
The 30-30 interval protocol is a good one for burning calories without feeling it as much as longer intervals. I’d consider this a good “go-to” interval routine. This 30-30 HIIT cardio workout is one you could do without risking over-training and you would get decent results, but you will get better overall results if you mix in longer intervals.
Why Do Longer Intervals At All?
Longer intervals increase your VO2 max. VO2 max is the maximum amount of oxygen in milliliters someone can use in 1 minute, per kilogram of body weight. Simply put, it is how much oxygen can you use per minute. Fit people can use more oxygen per minute than people who are out of shape. It has been shown that people with a higher VO2 max will burn more calories doing the same activity as someone with a lower VO2 max. Longer intervals improve VO2 max better than shorter intervals. My post on that: Brief Exercise Found to Be Much More Effective for “Fit” People
Long Intervals Allow the Short Intervals to Work Better
Like I mentioned at the beginning of this article, I have studied the heck out of HIIT cardio workouts for close to 20 years now. What I have found is that longer intervals hurt more, but get you in better shape (improve VO2 max). This allows you to get more out of the shorter intervals, which don’t hurt as much. I recommend cycling longer intervals with shorter intervals (I have a whole HIIT cardio course that I’m rewriting this fall and releasing in 2012 that will cover this in detail).
A Real Example of an Easy 30-30 Workout
I like to do my toughest HIIT cardio workouts early in the week and save the 30-30 stuff for the last few days of the week. I don’t worry too much about hitting 90% intensity exactly…I simply track heart rate to give me an estimate. Here is one of my “go-to” 30-30 hiit workouts on an Elliptical.
- 30 seconds on level 11.
- 30 seconds on level 15.
- Alternated for 15-20 minutes.
- Try to get heart rate to 175-180 by the last minute or two.
- Steady state at level 12 for 15 minutes.
- Keep heart rate at 165+ during steady state portion.
Note: In my free ebook and Video Course, Abs Blueprint, I cover exactly what I do to get the most fat burning effects out of my cardio sessions. Make sure and read that ebook and watch the videos if you haven’t already.
My Practical Advice from The Findings of This Study?
Adjust your intervals based on your fatigue levels. If you have physically demanding job, or simply don’t want to feel worn down, then shorter intervals are the way to go. If you want to push hard, improve your VO2 max and don’t mind a little more fatigue…then mix in the longer intervals into your HIIT cardio workout routine.
Hi Rusty,
I was wondering if cardio kickboxing has the same effects as a HIIT workout. Depleting glycogen.
Here’s a program I use in my martial arts class. 30 sec. Bodyweight exercise followed by a 30 sec. active rest jumping jacks, light run or some type of footwork). This is a 16 minute workout. Starting with an upper body exercise. Then a lower body exercise and then an an exercise. Then we repeat that sequence for 16 minutes. After two weeks we we add five seconds to the work portion. Two weeks later we do the same thing, and then add five more seconds again. By the sixth week you’re doing 45 sec. of work and 15 sec. of active rest. At the two month mark we change exercises and start all over. We do a light warm up and stretch first and end the workout with a slightly more involved stretching routine. Makes for a total of about 25-27 minute workout.
Great workout.
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very very good job and research..