Are we green?
All the best of the season to you, and i wish you great strides for the new year.
i replied to Holto privately about this question of my research area, which he has not yet acknowledged to me directly or on the board - that's curious, but it's holto's perogative.
I'm also not sure what the big deal is about my area of research: i'm not speaking ex cathedra; i generally point to places where what i've said is supported. So i'm mainly translating/presenting research here. Anyone can check out those sources and judge for themselves whether i've presented it accurately: that's why i put the links in or point to programs or whatever that inform that perspective.
I hope my posts can therefore be taken on their merits.
best of the season to all
Last edited by mc wb; 12-16-2007 at 11:03 AM.
This was partly due to you briefly discussing the letters "Dr." in front of your signed user name when replying to posts, that was called into question by user(s).
While many people question eachother and have differing opinions pertaining to researched areas/studies (that often conflict eachother), I feel that if someone throws the letters Dr. in front of their name, they did it for a specific reason, and they should be prepared to answers questions from members of this site pertaining to such (especially after being asked 5 direct times and 1 indirect time).
I was not e-ttacking you, if it was perceived.
Last edited by Slim Schaedle; 12-16-2007 at 11:32 AM.
I wrote a little article on this. You may find it helpful.
Any references there, much obliged, with thanks.
if i may also offer a clarification, about tabata, which you also mention in your piece: for that *specific* protocol, cadence is critical, which is something that many people miss. It is not only the 20sec on "really brutally hard" and 10sec off for 8 repeats - i'm not saying that that isn't a dam hard interval you've described; it is just not the tabata protocol for improving VO2 max, which just happened to have a side benefit of getting at subcutaneous fat.
While it is possible to do 20hard/10stop of any activity, it would be very difficult to do the tabata on anything other than a bike or perhaps a rowing machine (on treadmills, people can collapse). Indeed, the only way the protocol has been successfully measured is on a bike, because of the use of specific cadence and load as measures.
There has been critique of tabata for VO2 max, and consequently at least one other protocol has been strictly defined to improve on tabata for VO2max work. This one uses kettlebells to stimulate VO2max (and have a consequent effect on fat loss): again, cadence (no. of swings per minute) and load (size of kettlebell) are key components.
A side benefit of kettlebell VO2 work is that swings and snatches with KB's have direct cross over benefit for powerlifting/weightlifting.
But i offer this as an aside. The tabata work was not focused on fat loss; it was focused on VO2max improvements and determinng the most efficient intervals for that. The point is intervals are great for helping fat utilization/burning.
It was interesting to read your hill workouts.
A couple of questions: Do you, by the way, have any references that point towards the interval periods of work/rest you recommend? I'm always looking for this kind of reference, and would be much obliged.
I may have missed it, but you don't seem to mention heart rate related to the degree of incline in your intervals. For athletic training, in any case, it's usual to determine either bike or eliptical gearing or treadmill incline or speed based on % of heart rate targeted for that interval. Tabata, for instance, definitely uses %VO2max as a measure for determining gearing and mere mortals without this kind of apparatus use %ofMaxHR. Some more formal presentations on HIIT definitely use HR% as measures.
Others just say "go all our for x" rather than gating it at some measurable output or work level. I don't quite understand how this kind of interval work is determined as effective or not, since there's no direct correlation to HR%max either to confirm how you're doing on a given day or to note improvement over time, or to know, more importantly, if a given gearing or incline is either right for you, or pushing into over training/over work. Is there a reason, therefore, you in particular don't use heart rate?
with thanks and
best of the holidays
These work like a hot damn in this regard.
With reference to the value of heart rate when doing HIIT, for those who may be interested, fyi
I've never checked my pulse while doing any of my training. I have no intention of starting now. The only reason I do these is to build up VO2 max in a hurry - without having to do so much cardio I lose mass or risk converting too much transitional fibre to slow twitch analogues.
this piece by dr. mark tallon. You'll notice there's a point of diminishing return in going beyond 75% VO2max rate (approx 85% max heart rate) for the fat burning effect.
best of the season,
Last edited by mc wb; 12-25-2007 at 07:16 AM.
The above exchange about HIIT - and the rationale proposed by Built for doing it -- "What we hope to effect with HIIT is catecholamine release" -- took me by surprise. My awareness of interval work in terms of research on both improving VO2max and consequent effect in fat burning was different than this model. Indeed, that this stress-induced effect was of less consequence than the long term oxidative metabolism revving.
The following is a meditation to unpack this rationale.
If i'm reflecting Built's position correctly, the main reason for HIIT is to motivate the release of fat to be burned. Catecholamines are definitely one hormone that is invoked naturally when the body is under stress. The release of fat for energy use is one of the consequences.
I haven't been able to find any research that conclusively shows that the kind of stress produced by intervals causes the release of catecholamines. The closest i've found is a reference from Men's Health to very new work that has yet to be peer-reviewed (published) , where the authors only hypothesize around catecholamines release being a reason for the big fat burn experienced in a VERY SPECIFIC protocol: 8sec sprint; 12 secs low to no work for 20 mins. This sounds remarkably like Tabbata with the emphasis on fat loss rather VO2max improvement. I'll be interested to see the final full version of this work once it's been through peer review. The reason peer review is so important: experts in the field look at the protocol/methodology of the study, at the stats, to see if the method is reasonable and repeatable for the claims made; that some other factors weren't involved in getting the results etc. But right now, this is all speculation until the paper is either published or else made available for scrutiny.
This doesn't mean that catecholamine release is not happening, it's just that i have seen no work to indicate at what kind of intensity, for instance, catecholamines are released in interval work, or that this particular hormone is responsible etc etc.
But beyond the role or not of catecholamines, there's a lot of science we do have about HIIT. I'll come onto that in a moment.
The subsequent part of Built's presented model, if i'm hearing it right, is that low level cardio following the intervals acts like a hoover to suck up all that loosened off fat "before they [the fat] reesterify and redeposit on your ass".
There's no doubt that low level cardio (sub 60%MHR) burns fat and has a nice effect on the heart. Lots of people lose weight just by walking, after all. A 20min low level cardio session is going to burn maybe 100calories, and every little bit helps, for sure. More on another model for why post hiit light cardio might be useful is presented below.
Before that, the question i have with this model is that it seems to focus more on the activity - the particular fat released and potentially burned in the session - than the whole impact of the activity for the 24-48hours post the interval session - something which science has definitely shown occurs.
Don't misunderstand me: there's obvious value in the interval itself, not just its side effects: intervals certainly cause a lot of energy burning directly during the event. There may also be catecholamines operating. But beyond this speculation, there's good research around a different way of looking at HIIT.
A bit of history: the primary training rationale for intervals over CONSTANT steady state HIGH intensity work is to improve both VO2max and lactate threshold: intervals are more efficient at increasing VO2/lactate threshold performance. The work/break/work/break enables the boundary to be pushed higher/harder. The important bit in here is oxygen uptake. The more efficiently you can utilize oxygen the better you can perform athletically: respiration reflects a bunch of over systems improving - it's a great measure.
Now, a simple side effect of greater O2 uptake is greater oxidation of fat. In high intensity activities, we mobilize phosphagen stores, then glycogen (blood sugar) - these are our anaerobic metabolic systems. They don't work independently of each other; one predominates under certain conditions.
My understanding is that intense activity causes glycogen stores to be effectively maxed out. That means that other energy sources have to be used. That's fat. Fat can only really be burned in the presence of O2. Hence the Aerobic system (aerobic just means with oxygen).
How this ties in with intervals: first EPOC, then life. Excess post exercise oxygen consumption, or oxygen debt developed by exertion - all to do with ATP, lactic acid and getting that acid cleared out of the system. Repaying that 02 debt has your 02 metabolism operating at a higher than normal rate. The 02 metabolism uses fat as its primary energy source. Thus, intervals which drive up o2 debt, keep the 02 metabolism revving to repay that debt. Depending on the intensity and duration, that debt can take 2-3 days to repay. (a few articles cited here)
In other words, the biggest benefit of intervals is the upped 02 metabolism, which (a) burns fat and (b) stays revved a long time (as in days) after HIIT
This is not to say that there is no catecholamine release that is related to lipase which is an enzyme that gets the fat out to be used for energy. What i would suggest is that while that is a good thing, that is not the biggest fat-burning benefit of HIIT. We know that this release occurs when lifting HEAVY - or when the whole flight of fight response is triggered.
It may signal that glycogen stores have likely been sapped, and a shot of carbs would actually be a good thing (fat doesn't burn well without carbs present; it's important to restore glycogen availability to the liver/muscles).
Likewise, there are good reasons for cooling down post HIIT with aerobic work. As summarised by eric cressey
Following the bout of HIIT, a brief (i.e. 5-15 minutes) session of low-intensity aerobics might work to enhance fat loss. It appears that inadequate blood flow to adipose tissue during high-intensity exercise is the culprit behind reduced fat oxidation (26). As a result, immediately upon cessation of high-intensity exercise, there is a marked increase in the concentration of plasma free fatty acids (2). By exercising at an intensity that relies primarily on the use of plasma fatty acids (i.e. less than 60% of heart rate reserve), you will maximize adipose tissue lipolysis and fat oxidation.
2. Rasmussen BB, Holmback UC, Volpi E, Morio-Liondore B, Paddon-Jones D, Wolfe RR. Malonyl coenzyme A and the regulation of functional carnitine palmitoyltransferase-1 activity and fat oxidation in human skeletal muscle. J Clin Invest 2002 Dec;110(11):1687-93.
26. Samra JS, et al. Effects of epinephrine infusion on adipose tissue: interactions between blood flow and lipid metabolism. Am J Physiol. 1996 Nov;271(5 Pt 1):E834-9.
Bottom line with respect to fat burning: getting the oxidative metabolism revved up means fat burning. A great way to get the oxidative metabolism revved is HIIT to drive oxygen debt. O2 debt LASTS - so that rev can be burning calories - burning fat - for a looong time post HIIT. Because aerobic exercise (sub 60% intensity) doesn't induce this o2 debt, its effects are more limited to the calories burn during just that particular session.
Forgive me if this entire cycle is known to all folks reading here. It's been helpful for me to think about HIIT and really work through the process in light of established research.
Time to go work out,
ps - if you're interested in sources to walk through intervals, EPOC and the rest, there are a couple of well regarded texts,
The NSCA's Essentials of strength and conditioning
Exercise Physiology: Human Bioenergetics and Its Applications Brooks, Fahey and Baldwin - 4th Edition.
There's a lot of articles on the "hierarchy of substrates" used in intervals too - how this is done with rats frequently is rather sad (i prefer human studies).
Checking Pubmed or Medline will bring them up.
There's also a couple year old summary by Kravitz
Last edited by mc wb; 12-25-2007 at 08:08 AM. Reason: added refs
Wow. Good read. Thanks.
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