In recent years, there has been quite the over-popularization of the concept of high-intensity interval training (HIIT), along with a rather major backlash against traditional forms of aerobic training, for fat loss. It’s not uncommon to read how low intensity aerobics is useless for fat loss, everybody should just do intervals, regular aerobics makes you lose muscle, etc. I have seen it claimed that aerobics will make you fatter, stress the adrenals, and all manners of fascinating claims.
Nevermind that, over the decades, bodybuilders have gotten into contest shape with (often endless amounts of) cardio, runners, cyclists and swimmers are extremely lean, etc. Somehow, aerobic training has gotten a bad rap.
While I have written about this in a previous article series, I wanted to revisit the topic again since I see the same (usually incorrect) ideas being thrown about.
Where Did this Idea Come From?
I think what happened is that for about 2 decades, aerobic training has been (over) emphasized over all other kinds of activity. As well, people got the absolutely wrong idea about how to use it for fat loss so you have people trotting along on the treadmill at an intensity that is just slightly higher than sitting on the couch, burning a couple of hundred calories in an hour and wondering whey they aren’t losing fat.
So folks, usually with a heavy resistance training bias or background, overreacted. And the backlash began. Basically, people get a little over-enthusiastic about a certain type of training (or eating), take it to some absurd extreme, get into problems, find an alternative and decide that the first type of training is useless, overrated, etc, etc, blah, blah, blah and they jump to the opposite extreme. They jump from one extreme to the other until, hopefully, they come back to some happy medium.
Well, I’m a happy medium kind of guy and I try to avoid that kind of binary either/or thinking; I find it more useful to examine training tools in terms of their pros and cons, benefits and disadvantages. So let’s examine both steady state aerobics and interval training for fat loss (endurance performance is a separate topic) in that fashion. In part 1, I’m going to define some terms and examine both types of activity; in part 2 (two weeks from now), I’ll talk about how to decide which is best depending on the specifics of the situation
Defining Steady State and High-Intensity Interval (HIIT) Training
To make sure we’re all on the same page and my discussion going forward is clear, let me start by defining my terms.
Steady State Training
This describes any form of aerobic/cardiovascular training where some reasonably steady intensity is maintained for an extended period. So this might be something akin to 20-60 minutes at a steady heart rate of 140-150 (could be higher, could be lower). I’m just going to call this cardio or aerobics, even though I know some people get into longwinded semantic arguments about it. I’m sure everybody knows what I’m talking about.
High-Intensity Interval Training (HIIT)
HIIT refers to any form of activity that alternates higher intensity activity (such as 30-60 seconds almost all out) with periods of lower intensity activity. The rest interval can be passive (sit on your butt) or active (keep moving at a low intensity). While weight training can technically be considered interval training, I’m going to restrict this article to interval training done with standard cardio modes (i.e. running, cycling, stairmaster, etc).
A typical interval workout for fat loss might be a short warmup followed by 5 repeats of 60 seconds near maximum intensity alternated with 60-90 seconds of very low intensity activity, followed by a 5′ cool down. This is often referred to as high intensity interval training (HIIT) which differentiates it from aerobic interval training discussed immediately below.
Aerobic Interval Training
For completeness, I want to mention a third, sort of hybrid, form of training that is usually referred to as aerobic interval training. This is a type of training often used by very untrained beginners who are simply unable to perform 20 minutes or more of continuous aerobic activity. So they might perform 5 minutes of low intensity aerobic activity prior to taking a short break, followed by another 5 minutes of low intensity aerobic training, until they accumulated 20-30 minutes of activity.
Over their first several weeks of training, they would try to increase the duration of each aerobic interval session while decreasing the rest interval. Additionally, many strength and power athletes do a type of aerobic interval training usually referred to as extensive tempo running: this is a low intensity type of aerobic interval training done in short bouts. So a sprinter might run 10 repeats of 200 meters but at a very low intensity (aerobic intensity) with 100 meters of walking in-between. In this article, I’m not talking about aerobic interval training when I compare and contrast traditional aerobic training and interval training; aerobic interval training is sort of a third category that doesn’t apply to this discussion.
Pros and Cons of Steady State and High-Intensity Interval Training
Now, I want to compare and contrast aerobic and interval training in terms of potential pros and cons. This will allow us, in part 2 (two weeks from now) to look at how to integrate the different types of training into real world workout schemes.
Steady State Aerobics: Pros
- Depending on the intensity, steady state aerobics tends to burn more calories during the exercise bout than interval training.
- More appropriate for beginners.
- Can be done more frequently, daily or more often (if desired) although this depends on the duration, intensity and frequency as well as the setup of the rest of the training program.
- Some research finds suggests that regular exercise helps people stick to their diet better. In that interval training can’t (well, shouldn’t) be performed daily, low intensity activity may help people stay on their diets
Steady State Aerobics: Cons
- Most indoor aerobics modes tend to be boring, especially for long durations. Exercise can, of course, be done outdoors but this raises a whole separate set of issues (bicycle safety, running outdoors, traffic, etc) that are beyond the scope of this article. This is a big part of why gyms have music and televisions; I have seen one with a cardio movie theater.
- An excess of endurance training, especially at higher intensities (too close to lactate threshold, a topic for another newsletter) seems to cause muscle loss, decrease strength and power, and cause overtraining. This is major issue for bodybuilders and strength/power athletes but can be avoided by keeping the intensity under control.
- Too much repetition of the same mode of aerobics can generate overuse injuries, both runners and cyclists are prone to knee problems, swimming causes rotator cuff issues (and the cold water tends to increase hunger), etc. This can be avoided by non-endurance athletes by rotating the type of activity being done.
- Unless people are tremendously aerobically fit, it can be difficult to burn a huge number of calories unless the duration of each workout is just ridiculous. So, at moderate intensities, the average person might burn 5-10 calories/minute; a 145 lb person burns about 100 calories per mile walking or running. So over an hour aerobic session, you might achieve 300-600 calories burn. While this can certainly add up if done daily, it’s still a fairly small expenditure. The people trotting along on the treadmill or spinning on the bike at low intensities, often for only 30 minutes, are burning jack all calories. Which are usually more than compensated when that person figures that they must be burning at least 1000 calories and rationalizes that cheeseburger and milkshake because of it. This is one of those weird ironies: very high caloric expenditures through aerobics are reserved for trained endurance athletes, and they typically don’t need it. The people who need to be burning a lot of calories through aerobic activity usually aren’t able to, at least not initially.
Before continuing, I should probably bring up one of the more idiotic arguments against steady state aerobics here. The argument goes something along the lines of “Aerobic training is useless because, as you adapt and become more efficient, the same workout that burned a significant amount of calories over 40 minutes takes 60 minutes because you’re getting more efficient.”
This is about as logical as saying that weight training is ineffective because the same weight that was difficult for 12 repetitions is now too light, and you have to do more repetitions with it. Except that, in the case of weight training, the suggestion would be to add weight to the bar. I will discuss exercise efficiency in more detail later in this series.
And the same exact thing can be done with aerobic training: as the body adapts (and you become fitter), you can increase your caloric expenditure by increasing the intesity of your workout. So say that you were doing the stairmaster at level 8 and a heart rate of 140 beats per minute for 40 minutes. Now you’ve adapted and level 8 is only a heart rate of 130. Well, you could go to an hour, or you could increase the intensity to level 9 and burn more calories during those same 40 minutes.
In addition, exercise efficiency doesn’t vary that much; in cycling for example, it varies between about 20-25%. So even if you increase your efficiency by 5%, this would only change the caloric expenditure for a given exercise bout by that same 5%. A 400 calorie workout becomes a 380 calorie workout. This is hardly a change worth decrying steady state aerobics before.
High-Intensity Interval Training: Pros
- For a given time investment, interval training leads to a greater fat loss and this occurs despite a smaller calorie burn during activity. This is because interval training generates a much larger EPOC (excess post-exercise oxygen consumption) which are the calories burned post exercise.
- Interval training may improve the muscle’s ability to use fat for fuel more effectively than aerobic training (note: recent studies have also suggested that interval training can generate very rapid improvements in endurance performance in a very short period but this is beyond the scope of this article).
- Time efficient: Not everybody has the time to devote to an hour (or more) of aerobic training per day. A properly set up interval workout may only take 15-20 minutes.
- Time seems to pass faster: Compared to regular aerobics, which can be mind numbingly dull (especially if done indoors), the change in intensity with intervals seems to make the workout pass faster.
High-Intensity Interval Training: Cons
- The intensity of intervals makes them inappropriate for beginners. One exception is a style of training called aerobic intervals which I mentioned above. But high intensity interval training is simply inappropriate for beginning exercisers, for the same reason that high intensity weight training is inappropriate.
- Intervals are high intensity training, this has implications for the overall training setup (discussed in more detail in part 2) and integration with the rest of your program (i.e. weight training). Simply put: if you think you can train legs in the weight room 2-3X/week and do intervals an additional 2-3X/week on alternate days, you are incorrect unless you are deliberately trying to overtrain or get injured.
- Higher risk of injuries: this depends somewhat on the type of activity with high impact activities such as sprinting carrying a higher injury risk (especially for heavier individuals) than intervals done on the bike or Stairmaster.
- Limited in how many days they can be performed. Two to three days per week is about the maximu for interval training, most endurance athletes won’t do intervals more than twice/week. Have I heard of people trying to interval daily? Yes. Do I think it’s a good idea? No.
- Intervals hurt, especially intervals in the 60-90 second range where muscular acid levels are very high. If you’re not willing to push yourself, you won’t get much out of interval training. You know the warnings on most aerobics machines, that tell you to stop if you feel signs of exhaustion or fatigue; that’s what a properly done interval program should feel like. Sensations of burning in your legs (from high acid levels in the muscle) along with extreme discomfort are not only common but expected. Some people also report nausea initially, this can be made worse if they have eaten too close to training.
A Few Semi Random Comments Before I Continue
As I mentioned above interval training hurts. It’s difficult and you have to be willing to push to make them effective. Put differently, if someone is not going to work sufficiently hard at interval training, then there’s really no question about intervals versus aerobics. A half-effort interval workout doesn’t accomplish any of the things that interval training is trying to accomplish; if you aren’t willing to push yourself on the intervals, you should simply do regular aerobic training.
And the reality is that thousands of people have lost fat without ever doing intervals. So while intervals may be more time efficient, and may generate more fat loss for the time invested, there’s certainly no requirement to do them to get leaned out. Can they be more effective under specific conditions? Absolutely. Are they mandatory to get lean? Of course not.
Additionally, I want to point out that intervals are not a year round kind of thing, even if that’s how people are using them. Endurance athletes typically only include them for intensive periods of 3-4 weeks, or occasionally for periods of up to 8 weeks. Yet somehow general fitness exercises are trying to do intervals year round. Folks shouldn’t be dieting more than 6-8 weeks without a break in the first place, they sure as shit shouldn’t be doing intervals for more than that without a break.
This is in addition to many people taking a good idea and being idiots about it; I have heard of people performing 2 hours of intervals (20 minutes on each piece of cardio equipment) following a lower body weight workout. That’s not productive training, that’s exercise addiction. I’ve heard of people doing intervals daily (or more). Elite endurance athletes typically only perform intervals 1-2X/week, what makes you think you need more?
Finally, and I’ll come back to this below, there’s no fundamental reason that this has to be an either/or choice in the first place. Endurance athletes typically do 3-5 steady state aerobics sessions and 1-2 interval sessions per week, there’s no reason that a dieter can’t do 2 interval sessions and 2-3 aerobic sessions/week as part of their fat loss efforts. Or, depending on the specifics of their training, a maximum of 3 interval sessions and 1-2 standard aerobic sessions.
The Importance of Context
Hopefully readers can see that neither steady state nor high-intensity interval training can be considered good or bad in absolute terms. It always comes down to context. So now let me look at where one or the other type of exercise might be the most appropriate for a given context.
A beginner just starting an exercise program will be best served with low to moderate intensity aerobics. They can begin to incorporate short intervals (15-30 seconds at a slightly higher intensity) after their first 4 weeks of regular training if desired. The only exception, as mentioned above would be something called aerobic interval training which is an entire separate topic.
Basically, beginners need to break in to aerobic training the way they break into any kind of training: slowly and gradually. Someone completely out of shape simply has no business working at the kinds of intensities demanded by interval training. The risk of injury is too high, the benefits too small. Even the original interval study (by Tremblay) had a 4 week break in period prior to beginning the intervals.
Once again, after 4 weeks or more of consistent aerobic training (where consistent means at least three times/week for a minimum of 20 minutes at a moderate intensity and beginners should gradually be increasing the duration of their cardio sessions as their fitness improves), beginners can begin to use interval training to continue improving fitness or increase fat loss. When intervals are first introduced, a small number of short intervals should be performed.
I would routinely have beginners start with 30-60 seconds pushing their normal cardio pace a bit and then resting for 4-4.5 minutes. This would be done throughout the entirety of their cardio session to begin introducing them to working a little bit more intensely. Over several weeks, the length of the interval would increase as the rest interval decreased.
Intermediate Trainees/Those Already Weight Training
This is where it gets more complicated because there are so many different ways that people might be training. As mentioned above, interval training is another high intensity workout and that has to be considered within the context of the overall training structure.
Local overtraining (of the legs) is a very real issue when you try to add interval training to a heavy leg training schedule. Someone who is trying to train legs twice (or more) per week and who adds intervals to that load can quickly run into problems. This applies to bodybuilders, powerlifters, and any other athlete who has to develop multiple capacities at once. There are a couple of solutions. This is why I didn’t include intervals in the Ultimate Diet 2.0; it already included 3-4 lower body workouts/week. Adding intervals would have just made overtraining a near guarantee.
The first is to cut back leg training (which should really be done on a diet anyhow, I’ll talk about training for fat loss in another newsletter) to reduce the overall training load. Basically, leg training should be moved to maintenance loads, with a reduction in volume, frequency, or both (intensity should never be reduced).
If you were training legs for 6-8 sets twice/week you can cut back to 2-3 sets twice/week or perhaps 4 sets once/week and maintain leg strength (and size) for quite some time. Adding two days of intervals to your training, plus 1-2 regular aerobic sessions, works just fine (see comments below on sequencing). If leg training is cut back to once/week, or the volume performed more frequently is very low, intervals might be possible up to three times/week.
Athletes Who Need to Lean Out
This is another complicated situation because the term ‘athlete’ covers a lot of ground. Are we talking about an endurance cyclist who needs to drop some weight to be more effective on the climbs, a strength/power athlete who is cutting to make weight for a meet, a wrestler or boxer who needs to cut some fat.
The endurance athlete is probably already doing intervals and is already doing an absolute pile of long duration endurance training. Frankly, they are probably just better adding a bit more endurance work (30′ of extra low intensity stuff) to their main workouts or cutting back their calories a bit.
Strength/power athletes have to worry about any non-strength work cutting into their strength and performance. Many powerlifters, for example, perform a type of interval conditioning training involving sled dragging and this is arguably more specific to their sport.
A great many of these types of athletes are also carrying a lot of body weight (whether muscle or body fat) and that makes high impact activities such as running a problem. Intervals can probably be worked in 1-2 days/week along with the addition of fairly low intensity (think brisk walking) cardio another 2-3 days/week. Overtraining and performance drop should be watched for closely.
Bodybuilders dieting, either for a contest, or to prepare for the next mass gaining phase, are somewhat separate from other athletes so I’m going to discuss them separately. Bodybuilding is, fundamentally, not a performance sport. So, strictly speaking, bodybuilders (unlike a powerlifter or olympic lifter) aren’t intensely concerned with poundage drops. However, dieting bodybuilders are concerned with muscle mass loss and this can be huge issue for naturals, especially if they are trying to reach contest shape.
Big drops in training poundages or intensity tends to cause muscle loss when you don’t have anabolics to stave it off; natural bodybuilders should be somewhat concerned of such. I would say that, contest bodybuilders, perhaps even moreso than the general public, has a tendency to overtrain on a diet.
It’s not uncommon for bodybuilders to increase training frequency and volume, along with adding an absolute pile of aerobic activity (2 hours/day is not uncommon), all combined with a caloric deficit. This is, of course, illogical as hell: why would you add more training during the one time period you can’t adapt to it. Is it any wonder that natural bodybuilders overtrain and lose so much muscle trying to diet down?
To a great degree, I’d approach the choice of intervals versus aerobics for a bodybuilder similar to that of anybody else, even if I know most won’t listen to me: they should reduce their weight training volume and/or frequency during dieting.
Intensity, in terms of weight on the bar should not be reduced. Basically they should do a handful of heavy sets to maintain muscle mass; if they simply must do more work, they can do some high rep short rest work akin to the depletion workouts in the Ultimate Diet 2.0 or something similar. There are a lot of metabolic type weight workouts (whether bodyweight, weight or kettlebell based) floating around.
To this, intervals can be added two to three times/week maximum with low to moderate intensity aerobic activity being performed several more times per week.
Sequencing Steady State and High-Intensity Interval Training
Ok, I guess I could have really summed up the above by simply saying that beginners should stick with plain old aerobics and everybody else will need to either
- Cut back their leg training to incorporate intervals
- Just stick with regular aerobic training
In any event, I want to talk a bit about how to sequence intervals with weight training. I’m going to assume that the person in question is training lower body twice/week, doing intervals twice per week and doing aerobics on 2-3 other days. That would at least be close to an ideal situation under most circumstances.
There are basically two ways to go about it. The first is to do the interval workouts on non-leg training days. The advantage to this is that you get to be fresher for all of the workouts, since they are all being done rested. The disadvantage is that the chances of overtraining are higher because legs are being trained intensely 4 days/week. That is, if you do interval training 2X/week and train legs 2X/week on separate days, your legs are getting hit hard 4 days/week. This can be too much.
My preferred method is to do the interval training on the same days as your leg training. Preferably the workouts would be split up (i.e. intervals in the morning, weights in the evening, or vice versa) but that isn’t always possible. Intervals can be done after lower body lifting but I’d highly recommend staying away from anything that requires coordination. Trying to run sprints after heavy leg training is an excellent way to blow out your knee or turn an ankle; doing intervals before lifting just makes your lifting inefficient. You wouldn’t want to exhaust yourself with interval training before weights either, another excellent way to get hurt.
So let’s say we have an individual using a 4 day/week upper/lower split routine who wants to do 2 days of intervals and 2 days of aerobic training. Here’s how I would suggest sequencing it.
- Monday AM: HIIT PM: Lower body weights
- Tuesday AM: Aerobics PM: Upper body weights
- Wednesday: Off (brisk walking would be allowed for active recovery)
- Thursday: AM: HIIT PM: Lower body weights
- Friday: AM: Aerobics PM: Upper body weights
- Saturday Off (brisk walking would be allowed for active recovery)
- Sunday: Completely off (everyone should take at least one day off per week).
Next, let me get a little bit technical and look at one of the physiological effects that HIIT is based upon, namely the Excess Post-Exercise Oxygen Consumption or EPOC.