Friday, March 2, 2012

Low Volume + High Intensity is the Best "Health Investment" Obese Babyboomers Can Make! Plus: Doing More "Cardio" Than 3x30min Can Make Sense to Maximize VO2max

Image 1: It's not too late to do something for your health. Just make sure you or your loved ones back the right horse - and this si not the nag trotting along the race track in what it believes was the "fat burning zone" ;-)
If you are, as I would hope, a regular here at the SuppVersity. I do not have to tell you that "cardio", and I am using this term here to refer to exercise that is in fact (and not just supposedly) heart healthy and will help you improve your conditioning, does not, or, I should say should not consist of doing hours of steady state aerobic exercise in the "fat burning zone". A question I do yet often get (and rightly so!) is how much is enough and what is too much? And while I stick to my experience based recommendation that 2-3x HIIT sessions at 15min are plenty (assuming you also lift weight), I don't want to deny you the latest results of a recently published study by scientists from the Duke University (Duscha. 2012), which could shed some light on the "optimal" dosage of the "classic" steady state variety of "cardio training" for the not-so athletic part of the population - I know this ain't you, but maybe your aunt or uncle ;-)?

Important message #1 - "Any exercise is better than none!"

"Another study with obese subjects?", you may now say - and yes, it is, but let's look at it this way: By 2030 50% of you, my dear American friends, will be obese (USA Today. 2011). And if the government didn't keep pushing the "demarcation line" up every year, you would already have passed the 50% mark by now (I guess, we Germans are not much better though ;-). The 163 obese subjects (age: 40-65, mean: 52y; BMI: 25-35kg/m², mean: 30kg/m²; bodyfat: 33.5%) in the Duke study are thusly very well representative of (at least) one out of three of your formerly babybooming neighbors and maybe even some of your relatives.
Figure 1: Outline of the study protocol (left) and adherence of the subjects in the individual groups to the prescribed form of exercise (created based on information from Duscha. 2012)
As my mini-overview of the study design in figure 1 goes to show, the subjects were randomized to one out of three exercise groups which different in both the weekly volume, as well as the average intensity of the exercise sessions. As you can imagine, the subjects were in pretty bad shape at the beginning of the study, which is why the first three of the 9-months study period were spend "accommodating" the study participants to their respective jogging (high intensity) or walking (low intensity) regimen, on which they then remained for the subsequent 6 months.
Image 2: I am not particularly fond of heart rate monitors, but especially for people who are just starting to work out for the first time in their lives, they can actually be a valuable tool.
Progress comes from providing new stimuli: Whether you are obese or lean, a professional athlete or a sedentary couch potato. If you want to make progress you got to expose your body to new stimuli on a regular basis. And as I have mentioned this in several previous blogposts, already - taking the stairs can be a very powerful new stimulus for someone whose farthest "walk" of the day takes him from the couch to the fridge. Even for really big losers, it does yet not take too long until taking the stairs comes quite handy and the importance of continuous progression the subjects in the study monitored by the means of a heart rate monitor, is obligatory - not to train in a non-existent fat-burning zone, but to make sure that a) you are still demanding enough of yourself to make progress and b) that you are not at the point where running faster and running longer becomes counter-productive.
From an epidemiological point of view, the first, and probably most important result of the 6-months exercise intervention, probably is that no matter what you do, you will benefit from getting your ass of the couch! Now, given the fact that most people consider doing that "inconvenient" and thusly refuse to do it, the 2nd most important result of the study is that despite the fact that the subjects had already been hand-picked for "high adherence" from a cohort from the Studies of Targeted Risk Reduction Interventions Through Defined Exercise, the subjects  in the low volume + high intensity exhibited a 4% and 6% greater adherence to the exercise regimen than their peers in the "classic low intensity" group and the high volume + high intensity group, respectively.

Important message #2 - "More is not always more"

Although adherence is one of the most commonly overlooked, yet crucially important determinants of how successful any dietary and/or exercise intervention may be, an adherence rate of across-the-board >80% is more than just "above average" and goes to show you that the subjects were highly motivated to get in better shape. If we now assume that your aunt, uncle, mom or dad was one of them, the question still remains, which of the regimen would be the "best" for her/him to do?
Figure 2: Relative increases in Peak VO2, citrate synthase activity and capillary density after 6 months on training regimen with different volume / intensity; text quotes the conclusion (data calculated based on Duscha. 2012)
If you take a look at the relative increases in VO2Max, citrate synthase (a marker of mitochondrial health and fatty acid oxidation capacity) and density, it appears quite obvious that "more" and "harder", as in high volume + high intensity, would be the way to go - at least if increased conditioning and building a bigger metabolic engine are your relative's main concerns.
Figure 2: Cost-benefit analysis (expressed relative to low volume + low intensity group) for increases in Peak VO2, citrate synthase activity and capillary density after 6 months on training regimen with different volume / intensity (data calculated based on Duscha. 2012)
And while this may be the case, if we just rely on absolute increases, the image looks slightly different, when we plot those against the effort (for figure 1 I used the workload, but the graph looks identical, if you plot it relative to the time the subjects spent training). In fact, the cost-benefit analysis in figure 2 reveals that contrary to what the data in figure 1 suggested, VO2Max and citrate synthase do not improve to an equal extent with the increase in volume in the high volume + high intensity group: While you get a whopping and very worthwhile additional increase in VO2Max from doing 175min/week of high intensity exercise (vs. 114min/week; note: these are the actual, not the prescribed values), the additional hour results in a comparatively mediocre +33% increase in citric acid synthase - or put another way: If you invest +58% more work, you get a very "profitable" +128% in VO2max, whether the extra work is worth the +33% increase in citric acid synthase, which could as well be a simple result of the increased energy consumption and the correspondingly increased turnover rate of the citric acid cycle is yet questionable.

Bottom line: 3x a week 30-40min = plenty, but...

If we wanted to summarize the results of our analysis and turn it into some wise-ass advice you can give to your obese friends and/or relatives this could sound like this: "Look, it does not take much! Three times a week 30 minutes of exercise is plenty and this type of exercise is matched to your individual capacity. You will be puffing a little, but I promise the results are well worth it. It will not only improve your conditioning, but also help you build a bigger metabolic engine that will help you shed that pouch today and keep you healthy into the old ages, in the future".
Image 3: For the babies of the babies, intensity is even more important than for their formerly babybooming granddads and -mothers
And what about my kids? In case you missed the piece on HIT exercise for obese boys from February, 14th, 2012, I highly recommend you read up on that, if you are wondering what type of exercise your daughter/son, granddaughter/-son, niece or nephew could (or should) do to avoid the same fate as 17% of her/his obese peers, who are destined to develop diabetes and heart disease in later life. For them, even more so than for your uncle, aunt, mom or dad, intensity holds the key to success - cf. "HIT the Cravings - Eat Less, Improve Your Health & Lose Weight"
What is important though, is that you keep an eye on your protégé(e) and switch her/him over to a more explosive combination of resistance training and HIIT, when the 30-40 minutes of "classic" aerobic training are no longer demanding. If you fail to do that and your mentee just keeps escalate the dosage, the only one who will benefit from that is Gary Taubes, because it would prove his theory that "exercise does not help with weight loss" and what's worse, according to a decently written editorial in the latest issue of the British Journal of Sports Medicine there is "emerging evidence" of "a potential link between life-long intensive endurance competition and acquired cardiac pathology" (Wilson. 2012) - yet another reason to make sure not to forget to make the switch, before you or the babyboomer you take care of becomes a marathon junkie!