Part of the problem with this study is the same as that seen in most studies in exercise science -- they only study untrained participants and last, say, 10 weeks (or 8, in this case) And then there are the tiny tiny sample sizes (14 individuals??). The fact is, doing almost anything is better than doing nothing. That's good news for the people who do nothing, I guess, because you can literally start parking two blocks from work every day and start seeing improvement.
But because of this novice effect, we don't really get a sense from the studies what the actual optimal ways of exercising are. It's after that initial period (say, 10 weeks) of going from doing nothing to doing something that you start to hit plateaus and have difficulty improving. This is the point where the difference between various forms of exercise would start to become clear, and yet that's when studies always stop.
Is doing 3 sets of 5 better than 5 sets of 5? Is HIIT better than long, slow distance for cardiovascular conditioning? We have lots of anecdotal evidence of how to improve physical conditioning past the initial novice period, but very little in the way of rigorous studies. So for now and the foreseeable future, if we are to decide what to do once doing literally anything is no longer enough to make improvements, we'll just have to rely on "bro science" and the experience of various coaches who see a lot of trainees to decide how best to exercise.
You seem to be missing the practical upshot: If you are middle aged, not exercising, and moderately overweight, HIT twice a week is an effective way to "significantly" improve your aerobic capacity, physical function, and reduce your blood glucose levels. Whether HIT is the optimal way to accomplish that is not the question they were investigating. It's a small sample size but was effective for all eight participants. It works in practice, whether or not you understand why it works theory. There are lots more interesting questions around the edges that can be explored now.
Everything works. HIT works. Riding your bike once a week works. Walking every day works. Taking up tennis, or soccer, or frisbee works. The point is, short-duration studies on the untrained provide little to no information. It would have been much more interesting to test and compare 3-5 different exercise modalities.
bcbrown covered this pretty well in their response to your comment, but I just wanted to reinforce: it's well established that doing almost anything will show improvements for untrained people. So this study, like most studies, doesn't really tell us anything. On the other hand, many people start exercising, feel great for a few weeks, and then start to not feel so great, and stop seeing improvements. This is the point where we need to start focusing research. There is good anecdotal evidence for what to do next, but it needs to be backed up by studies.
Also, you can hardly claim to know anything quantitatively when your sample size is 14.
This is a great example of what I'm talking about. He even claims to be based on science! But where are the studies this program is based on? I'm betting they are mostly studying untrained individuals for about 10 weeks with low sample size.
To be clear, I didn't write my previous comment because I'm looking for workout advice.
Lot of mentions of whether or not the person is sedentary/just starting off. I'm no expert in these areas, but an interesting additional bit of info on HIIT in highly trained individuals:
Anyone else think it's odd that the control group had a mean BMI of 24 (i.e: high end of normal range) and the HIT group had a mean of 29 (high end of overweight, almost obese)?
The "McMaster Studies" showed similar, that short sprint/rest interval training (30 second sprint, 4 minute rest, 250% of VO2 max) was equally effective as moderate long distance (90-120 minutes of 65% of VO2 max).
An excellent book called Which Comes First, Cardio or Weights? by Alex Hutchinson discussed that research and more recent research that followed up on it. Basically the gains from those two types of training come from improving different pathways, which explains why both sprinters and distance athletes tend to get the best results from incorporating both types of training in their regimens.
He is not really an academic but from a practical point of view Alex Viada explains how he programs his weekly training around his requirements in powerlifting and long distance running (which are on the opposite ends of the spectrum in terms of energy systems): http://www.atlargenutrition.com/blog/2012/11/hybrid-athlete-...
I'm personally a die-hard fan of HIT. I've never been able to keep up cardio regiments like jogging or biking simply because it takes too much time in my schedule and I get extremely bored 20+ minutes into either of those activities.
Not to brag, but HIT has kept me in very good shape. As a software engineer who cares about efficiency, 15-20 minutes of HIT versus 60-90 minutes of jogging/biking just makes more sense to me. Throw on joint pain from jogging on concrete and the perils of high-speed biking, HIT on a machine is a no-brainer.
I use a rowing machine. When I'm relatively untrained, I start with rowing at a steady rate, working up to 20 minutes. Then I add in HIIT, starting at 20 seconds work/ 40 seconds recovery. When I can do 6-8 intervals, I'll change the rest/work ratio to 30/30, then 20/10. For the work intervals, I row as hard as I can, a pace of around 1:30-1:40 per 500m. For recovery, I row as slow as I can, around 4:00/500m.
Study attempts to determine whether high intensity training (HIT) consisting of 10 6-second sprints w/ a one minute recovery between sprints performed twice weekly improves metabolic health and decreases type 2 diabetes risk in untrained middle aged (35-58 y/o) people. It appears yes.
also, a bmi of 29 (yes, yes, all you bodybuilders and powerlifters and strongman I know all about it) is tubby but not quite obese. It's kind of shocking how little effort this is. [1] is a good visual illustration of what a 29bmi looks like
Most of the commentary from there probably pertains.
One thing I noticed in this study is that (unlike a few other articles where I couldn't find the primary sources), they didn't do a warmup period:
"The HIT training protocol was similar to that used previously by Jakeman et al. [20]. 16 sessions of HIT were spread over an eight week period, with one or two days of rest between each sprint. There was no warm-up or cool down in the training sessions. Each training session consisted of 10 repeated 6-s all-out cycling efforts against 7.5% of body weight for males and 6.5% for females (Monark peak bike Model 894E, Monark Exercise AB, Vansbro, Sweden), added to the bike once the participant was cycling at 100 rpm with 1 min of passive recovery between sprints." [emphasis mine]
Yeah, I was surprised by the fact that such a short duration of exercise (11 minutes of exercise twice / week) could have such a large impact on health. I wish there were more details on how much exercise each group had before the study -- my question is whether HIT on its own is good enough, or does it require normal exercise as well?
Conventional wisdom says that you're not really working out unless you spend 10-25 minutes on warm up, an hour or more on working out, and some stretching to finish off and/or a cool down. That isn't even counting the time to go to the gym or the park, or the shower afterwards. No wonder people are inactive.
What conventional wisdom is that? The standard for warm up is 5 minutes isn't it? And a standard work out is 20-25 minutes as far as I'm aware. You can do a whole work out in 30 minutes.
My runs are 5 minutes warm up, I spend those 5 minutes walking to get from my house to a park, then 20-25 minutes running around the park (c25k plan) and then 5 minutes of walking back. You can fit that into almost any part of your day.
What about dressing up for the jog and afterwards showering and dressing up again? Also most people don't have a park in a 5 minute walking distance. I would say for most people they take 10-30 minutes to get to the training place, train at least 20 minutes and then 10-30 minutes back again and then 5-10 minutes of shower. Now that is quite a large part of the day.
But because of this novice effect, we don't really get a sense from the studies what the actual optimal ways of exercising are. It's after that initial period (say, 10 weeks) of going from doing nothing to doing something that you start to hit plateaus and have difficulty improving. This is the point where the difference between various forms of exercise would start to become clear, and yet that's when studies always stop.
Is doing 3 sets of 5 better than 5 sets of 5? Is HIIT better than long, slow distance for cardiovascular conditioning? We have lots of anecdotal evidence of how to improve physical conditioning past the initial novice period, but very little in the way of rigorous studies. So for now and the foreseeable future, if we are to decide what to do once doing literally anything is no longer enough to make improvements, we'll just have to rely on "bro science" and the experience of various coaches who see a lot of trainees to decide how best to exercise.