Confused about HIIT and afterburn effect

aleggett321

I've just started mixing up my exercise routine by adding HIIT twice a week, alternating with 60 minute moderate intensity cardio, light weights and yoga. I've read about 15 or 20 Googled articles on the supposed afterburn effect of HIIT. Some debunk it as myth while others praise it as a fat burning miracle. I'd love to hear your opinions or research.

AJ_G

There is an afterburn effect associated with HIIT but it is blown way out of proportion. To be honest it's almost negligible. I've seen different numbers, but most agree the afterburn is on the order of 10-15% of the calories burned during the HIIT, so if you burned 400 calories during an HIIT session, the afterburn is 40-60 calories, which is relatively nothing. The main advantages of HIIT is that it is resistant to Metabolic Adaptation, and it is high intensity meaning it can actually help build your leg muscles unlike steady state cardio.

meshashesha2012

There is an afterburn effect associated with HIIT but it is blown way out of proportion. To be honest it's almost negligible. I've seen different numbers, but most agree the afterburn is on the order of 10-15% of the calories burned during the HIIT, so if you burned 400 calories during an HIIT session, the afterburn is 40-60 calories, which is relatively nothing. The main advantages of HIIT is that it is resistant to Metabolic Adaptation, and it is high intensity meaning it can actually help build your leg muscles unlike steady state cardio.

this, AND you really have to be doing HIIT, not just the intervals many people mistake for HIIT

here's an interesting article by lyle mcdonald that discuss this (and excerpts i thought were relevant:
http://www.bodyrecomposition.com/research-review/research-review-effects-of-exercise-intensity-and-duration-on-the-excess-post-exercise-oxygen-consumption.html

n one study, subjects who exercised for 80 minutes at 70% VO2 max (about 80% of maximum heart rate) had an EPOC lasting 7 hours. But it only amounted to about 80 calories extra burned. Not to mention that only the most well trained individuals could sustain such a workload in the first place. As well, this still represented a rather small proportion of the total calorie burn from the exercise bout itself. That is, most of the calories burned were from the 80 minutes of exercise, the small EPOC only added a bit to that. Yeah, every little bit helps but which is going to contribute more to fat loss: the 700-800 calories burned during the exercise bout itself or the 80 calories burned afterwards?

alo i'd be willing to bet that any additional fat loss people see when they do HIIT is more related to the fact that HIIT effects the hormones that control appetite so you aren't as hungry as often. i know when im in a HIIT cycle i pretty much have to set alarms to remind myself to eat

tigersword

^Pretty much that. If you're only doing it for the "afterburn," you're pretty much wasting your time. HIIT is good for getting a short workout in when pressed for time. It's also good for variety. That's about it. As for it building muscle? That's also a myth. The high intensity parts, if done right, MAY be anaerobic in nature, but it's still not a progressive overload situation. It may improve muscle endurance, but absolutely will not add muscle mass.

AJ_G

^Pretty much that. If you're only doing it for the "afterburn," you're pretty much wasting your time. HIIT is good for getting a short workout in when pressed for time. It's also good for variety. That's about it. As for it building muscle? That's also a myth. The high intensity parts, if done right, MAY be anaerobic in nature, but it's still not a progressive overload situation. It may improve muscle endurance, but absolutely will not add muscle mass.

My apologies, that's what I was trying to say when I said "help build muscle". No HIIT does not build muscle, but it is a better compliment to a muscle building program involving progressive overload then steady state cardio is. My bad

Rocky_ZG

this, AND you really have to be doing HIIT, not just the intervals many people mistake for HIIT

Right. I often see people writing about HIIT and how their high intensity interval is 1-2 minutes.
With real HIIT they should not be able to do the max intensity for more than 20-30 seconds. I find it difficult to sprint with max speed for more than 15-20 seconds. I can make 30+ seconds with slightly slower running speed but then it is not HIIT as I see it.
Even Usain Bolt couldn't sustain max sprint speed for 1-2 minutes, and repeat that for 6, 8 or 10 consecutive intervals.

aleggett321

Thank you all. This is pretty much what I expected to hear. Burning hundreds of calories while driving or grocery shopping would be nice but didn't make sense to me.
I started with HIIT while I was traveling for a month because it could be worked in at the hotel gyms without taking an hour out of a busy schedule. I really enjoy it as an alternative on a busy day. Plus I like the way my legs are shaking afterward!
I can't do more than 20 seconds all out/ 40 seconds recovery. I hope I'm doing it right.
Thanks again to all who responded.

tigersword

this, AND you really have to be doing HIIT, not just the intervals many people mistake for HIIT

Right. I often see people writing about HIIT and how their high intensity interval is 1-2 minutes.
With real HIIT they should not be able to do the max intensity for more than 20-30 seconds. I find it difficult to sprint with max speed for more than 15-20 seconds. I can make 30+ seconds with slightly slower running speed but then it is not HIIT as I see it.
Even Usain Bolt couldn't sustain max sprint speed for 1-2 minutes, and repeat that for 6, 8 or 10 consecutive intervals.

My personal favorite are the people who go on about their 45 or 60 minute "HIIT" sessions. If you can go an hour, you aren't doing HIIT. :laugh:

jimmmer

this, AND you really have to be doing HIIT, not just the intervals many people mistake for HIIT

Right. I often see people writing about HIIT and how their high intensity interval is 1-2 minutes.
With real HIIT they should not be able to do the max intensity for more than 20-30 seconds. I find it difficult to sprint with max speed for more than 15-20 seconds. I can make 30+ seconds with slightly slower running speed but then it is not HIIT as I see it.
Even Usain Bolt couldn't sustain max sprint speed for 1-2 minutes, and repeat that for 6, 8 or 10 consecutive intervals.

My personal favorite are the people who go on about their 45 or 60 minute "HIIT" sessions. If you can go an hour, you aren't doing HIIT. :laugh:

Don't even get me started on 40 minute "tabata" routines... :P

Azdak

Another key area of misunderstanding regarding the "fat burning" effects of HIIT comes from the fact that the challenges to losing fat are different depending on one's level of body fat. For some one who is obese, the problem is fat oxidation--i.e. the ability to metabolize fat as a fuel is impaired. As body fat % lowers, the problem changes to one of fat mobilization--i.e. releasing stored body fat so that it can be used for fuel. HIIT leads to an increased catecholamine release, which is thought to lead to increased mobilization of fat stores.

So, those who are the biggest proponents of HIIT are likely to be the ones who most benefit from it--hence the increased advocacy. However, it also leads to the benefits of HIIT being overgeneralized.

I think there is also misunderstanding due to the nature of many of the research projects that have investigated this subject. In most comparison studies, a HIIT workout is compared to a lower-level steady state cardio routine (50%-65% of max). In research, it is necessary to have clear differences between the experimental treatments, so that is appropriate. However, in real life, that can also lead to overly shallow conclusions and, again, overgeneralization of the results.

In real life, the average exerciser will benefit quite well from a balanced approach that includes steady-state cardio, tempo training, and some interval training. They don't need to do all-out HIIT workouts (although there is nothing wrong with doing them, as long as the personal can physically tolerate the effort). The specific benefits of true HIIT (i.e. increased fat mobilization) are not an issue, and they can realize the fitness benefits of HIIT with higher-intensity (but not all-out effort) workouts.

If you asked most people, they would say that the effects of HIIT are this:

HIIT workout

---

> increased fat burning

---

> increased "afterburn"

---

> decreased body fat

This is partially true (except for the effects of the "afterburn") for certain individuals (lower body fat percentage already).

However, for the average exerciser, the actual HIIT improvement paradigm looks more like this:

Increased intensity ----> increased fitness

---

> ability to work at a higher workload

---

> increased total workout calorie burn

---

> higher daily calorie deficit

---

> increased weight loss

The point being that the primary benefit of higher-intensity workouts is increased fitness, and that that can be achieved with a wide variety of workouts, not just tabata et al.

It's easy to observe that some people are "not doing true HIIT", but the fact is that most people don't need to do "true HIIT" and in fact will not derive that much extra benefit from doing so. (we can quibble over the definition of "most", but the idea is still the same) The main thing is to make sure that people are doing the types of workouts that are most appropriate for their experience, goals, and ability at any given point in time.

Star_1234

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