To me this just appears to be the fat burning zone myth blown out of proportion, i.e training at 70% of estimated max heart rate burns more percentage of energy as fat as oppossed to higher intensities like 85-90% max heart rate. mr Beradi although I think you are right about doing continued cardio as oppossed to interval sessions for greater fat loss, yet working at higher intensities will create greater EPOC (exercise post oxygen consumption) which has been shown by Horton and Hill 1998 when they compared two groups (one exercisisng at 5 mets for 45 mins and the other for 30 mins at 10 mets) and all individuals within the 10 mets group exhibited higher EPOCs compared to the low intensity groups (some showing up to 500kj difference) - as such when doing continous cardio I personally would do a slightly shorter session but at a greater intensity - and therefor are more effeicient as you say. as such I feel alot of the misconceptions relating to this subject is due to this type of information being misunderstood and taken to extremes (e.g sprinting instead of continous activities) -please feel free to flame me if im wrong.
British lifter, you are EXACTLY right. People often misconstrue the evidence. For example I wonder just how many guys posting here know what the hell an kJ is. It’s like, “Wow, 500kJ, that must be HUGE”. Well to get cals from kJ, youve gotta divide by 4.18 so 500kJ is only about 119 kcals.
In addition, MOST of the moderate vs high intensity exercise studies on fat loss and EPOC were using 2 CONTINUOUS exercise groups at different % of max. And while the higher intensity continuous groups had higher EPOC, when the TOTAL calorie expenditure for the exercise + EPOC is calculated, they are not all that different. 100 cals is good, but not if I have to freakin train like Im training for the tour de france on the bike. Id rather lose the 100 cals and go easy on the bike while reading t-mag or something. By doing this, I may be sparing muscle. But this is probably a personal preference thing.
There definately are studies showing HIIT does have a big EPOC but most just compare the metabolism after 20 min of sprints to the metabolism of a control group who is resting. Well,no shit metabolism is going to be higher after Ive just sprinted vs lying around all morning.
There is only 1 study I know of that DIRECTLY compares HIIT and continuous and yes, it does show that HIIT is better for fat loss than continuous exercise. But I havent read the full papers yet so until I do so, I cant say if they are any good or even how much more fat was lost. The abstract doesnt even say how long the bouts were so until you go read the paper, dont use it support the notion that 20 min sprint sessions are better than continuous.
So really, the bulk of the evidence points to moderate intensity continuous exercise as being a bit better for total calorie loss. Besides, as Cy pointed out, people have been getting lean using continuous exercise for centuries.
But again, Im pretty certain that moderate intenstiy continuous, high intensity continuous, and HIIT will ALL lead to fat loss. Im just trying to OBJECTIVELY determine which may be the best. And Im trying to get weight lifters to recognize that continuous exercise is not the EVIL that most people in the industry are preaching.
John:
I know you were going to look up the paper, but this link contains a table that describing the duration, etc. of the Tremblay study.
http://www.planetkc.com/exrx/FatLoss/HIITvsET.html
Hey Ted, GREAT link. For anyone interested in following this discussion go check out the following link:
In addition, check out the fat loss section. The one study done comparing HIIT vs endurance training is referenced. But also of MORE PRACTICAL relevance is the other study under "endurance and weight training". The combination of wts + continuous exercise (both brief 15 min sessions sessions) lead to more weight loss than 30 min of endurance training. Again, since I recommend doing cardio after weights, I believe this speaks to my whole point.
HIIT may work well for fat loss. But after resistance training, why would you go and do HIIT? After lifting, you've already got the post exercise calorie burn waiting for you. Beyond that, just do some continuous exercise and burn some more calories DURING the session.
Oh yeah, and in the other HIIT study on that site, just because there was a 3-fold reduction in SKINFOLDS, that doesnt mean there was 3x the fat loss. For example, in the study the HIIT group lost 14 mm from 6 sites while the other group lost 5 mm from the 6 sites. Plugging some average skinfold numbers into my computerized equations in the lab, the 14 mm loss would translate to about a 1.2% loss in bodyfat % (going from 11.1% to about 8.9%) while the 5 mm loss would translate to a .8% loss in bodyfat (going from 11.1% to 10.3%). Again, not that big of a difference especially since both bouts were pretty much 30 minutes of activity (1 was continuous and the other was interval). The whole misconception that 20 min of HIIT is better than 60 min in continuous is clearly misguided and not supported by the research.
So, from the literature, EPOC isnt that different and fat loss isnt that different. So I still suggest that continuous mod intensity after weights is superior.
See people, just cause you read an abstract or some guy's opinion of a study, doesnt mean that you understand what happened. Ive been in school a long time to learn how to analyze this stuff. And when you do further analysis on your own, you can get at the truth. Remember, authors of studies start with biases also. If they think HIIT is better, their interpretation of the data may lead them to conclude that it is better. In the study above HIIT was "better" but the reviewers make it sound as if it is MUCH better when the differences were minor at best.
JB, good points. I think another thing that people don’t take into account is that HIIT is tougher on your than slow endurance training. When you use HIIT you may have to cut back on your leg workouts because of the level of entensity. Got a question for ya… How do ya feel about HIIT being used by strength athletes to lose weight? Do you feel that it’s more appropriate than slow endurance exercise if your focus is strength rather than hypertrophy? I figure there’s three ways to go about it… 1) incorporate slow endurance training into part of your cycle, drop some fat and lose a little strength, then re-gain the strength in the next part of your cycle… 2) incorporate HIIT (which would probably help preserve strength levels, but you’d have to back off on your leg workouts in the gym, which seems counter productive)… 3) Very little cardio (just to keep your aerobic base up) and focus on cutting calories. Which seems best to you?
J.B., thanks for another great post! In response to your last thread,and
having read more than a few abstracts in Quantum Physics, I became aware
that the scientists’ expectations almost always influenced the outcome
of the experiment.(Yes, even with no tampering!) So I can see how these
studies too frequently reflected the hypotheses of the researchers!
Thank, you again, for your research.It supports a belief I’ve always held:
well-placed cardio-vascular training will not send us into catabolic death!
Ok, I went to the library and found the Tremblay study. Not bad but there needs to be some clarification…
First, the HIIT lost more fat, yes. But they started out heavier and fatter than the other group (weight and skinfolds at the start were 63kg and 94.2 mm for the HIIT group and 60kg and 79.2 for the continuous group). So they were about 7 lbs heavier and certainly had more fat to lose and we all know the fatter you are when you start, the easier the fat comes off.
Secondly, when using standardized equations, the HIIT group dropped from 15% fat to 13.6% fat. While the continuous group dropped from 14% fat to about 13% fat. Since these data were not published, I had to analyze it myself. I know this contradicts what I posted earlier, but earlier, I just used guestimates and now I used the data from the study.
So Im not surprised the HIIT group did better. They were fatter and heavier. But .4% fat is not that much of a difference if you ask me.
John, is it possible that the reason I felt like death when I did longer duration cardio as opposed to when I did HIT cardio could be because I follow a pretty low-carb diet when dieting? If I had upped the complex carb intake somewhat while doing longer duration, moderate intensity cardio, would I have felt better and lost more fat? Granted I never really made the effort to get my bodyfat “super-low” (never below 8%), but if I wanted to get down to 4 or 5%, do you think it would be impossible without doing some longer duration cardio? Thanks for your input.
I could not agree more with Mr. Berardi about either the Tremblay study or any other. When reading a study of this sort, one must be aware that all too often there are any number of covariates at work, possibly affecting the data itself and possibly affecting the interpretation of the analysis.
We've all heard the phrase: "Statistics don't lie." Well, that's true, but only when we add the caveat: "about the sample from which they are taken." I'm not saying that anyone conducting a study like this is unethical, I'm just saying that one has to be extremely careful when reading the results.
Notice also in the Trembly outline that nothing was said about extra physical activity in either group. Therefore applying the results of such a study to bodybuilding is highly questionable.
One more observation: though I agree with Mr. Berardi about lower intensity cardio being more beneficial after resistance training, imagine doing a whole bunch of sprints after a vicious quad workout. I think the ab-workout you'd get from puking all over yourself would be great every once in a while.
obviously no one seems to pin down the one exercise that will lose the most amount of fat, probably 'cause we all are different in physiological sense.
one thing that has struck me is that no one seems to have picked up on the release of epinephrine and GH during the HIIT, surley if epinephrine is increased, thus activating beta-2 recpetors and Protein kinase and then nuclear HSL, the fat burning effect will be greater?, coupled with E/C/A or PPA with l-TYR and caffiene this would surely lead to an increase in lipolysis and for a longer duration.
Also the increase in GH after would surely lead to a nice amount of fat being burnt, i agree with the statement that the exercise (no matter what form) should be conducted after weights,as anecdotal evidence suggests training on an empty stomach is too catabolic for me and people i train with.
Stu, you make a couple of good points…
however I would like to address a couple of things…first…although we are all physiologically different, most basic metabolic processes during exercise are VERY similar between individuals. So for those who want to say that there is no “optimal way” to do certain things, they are probably wrong. There may be subtle differences, but sweeping differences, no.
As far as catecholamine response to exercise, high intensity exercise does increase GH and epi/norepi. But unfortunately, during the bout at HIIT intensities, fat oxidation is inhibited. Epi/Norepi increase glycolysis in the muscle and liver, which increases both glucose as well as protons and acidity in the muscle/blood. This inhibits ffa oxidation in adipose tissue and muscle. Also, ffa transport in the muscle is inhibited by this activity. So during the exercise at high intensity, the catecholamine response actually helps to inhibit fat mobilization and oxidation. CNS stimulants would not make this situation much better because ultimately the major limitation during HIIT is the transport of fats once in the muscle.
Interestingly, it's been shown that continuous exercise at 65% of VO2 utilizes the most fat from intramuscular and adipocyte sources. But as intensity increases and epi/norepi goes up above 65%, fat oxidation actually decreases and blood glucose/muscle glycogen are used preferentially while the ABSOLUTE and RELATIVE amounts of fat oxidation are actually decreased. Here is an example. At 65% of max, at 1000kJ of energy expenditure, about 400 will be glycogen, and 50 will be glucose. The rest, 550kJ will be fats. But at 85% of max, at 1400 kJ of energy expenditure, only 300kJ will be fats while the other 1100 is glycogen and glucose. So you can see that when some argue that "sure a lower intensity burns a greater % of fat, doing higher intensity burns more absolute fat", they are wrong when moving above 65% of max.
There may be some extra fat burnt due to the hormonal situation that persists AFTER the exercise is done but remember that the extra cals are just a few more than regular continuous exercise. In addition there have been tons of studies showing that the % of fat oxidation after continuous exercises is increased above rest anyway.
I did a study where i had sex first thing in the morning on an empty stomach. I lost 15.69 pounds of fat in 6.9 days. i think thats a pretty significant amount. That might be the optimal amount and time for cardio.
BRAVO!!! I can not agree with you more, People will argue with you with there own little “examples” of “what works for them” because if they are wrong in what they are doing their “church of latter day fitness” is wrong! may I repost a little part of what you said, “although we are all physiologicaly different, most basic metabolic processes during exercise are VERY similar between individuals so for those who want to say there is no “optimal way” to do certain things, they are probably wrong. There may be subtle differences, but sweeping differences, no.” BRAVO BRAVO BRAVO!!!
Is there any evidence that aerobic exercise increases EPOC after the first 30 post-exercise minutes? Is there any evidence to the contrary? If there is, could someone post it? Thanks in advance.
I don’t care what you say Goldberg-I really hope you were joking because nobody with a brain would belive you lost 15lbs of fat in 6 days! (let alone just by having sex after you wake up)