Dear Michael,

you are referring to the 2007 report by Wisloff et al? Still a very interesting finding for secundary prevention. We have been doing some work on HIIT and also on calcium signaling (at least in ECs) but I'm not 100% convinced that it is calcium handling. If you look at CRT calcium signaling is not a major target. But I believe miR-222 has some potential .we have analyzed it during different HIIT protocols based on the work of Liu et al. and cardiac hypertrophy. I'm still working on this trying to correlate functional changes in MRI after HIIT and miR-222. Are you planning any interventions?

Regards

BORIS

Well, more his review paper: Wisloff U, Ellingsen O, Kemi OJ. High-intensity interval training to maximize cardiac benefits of exercise training? Exerc Sport Sci Rev 2009;37,139-46. I don't think its ALL calcium handling, but Wisloff makes a fairly convincing argument that left ventricle ejection fraction increases with 4x4@90%. Probably you have to have cardiac hypertrophy to have increased stroke volume, but more rapid sequestration of calcium to better SERCA pumps to improve the relaxation rate in diastole is needed to reduce the resistance to fill. I'm retired, so the only interventions I'm interested in are my own training!

I've seen a lot of papers using HIIT, but they seem to stray from the classic - and seemingly most effective - 90%HR max for 4 min with 3 min rest, repeated 4 times. I think this training protocol strength trains the heart, increasing LVEF, but I'd like to know more about the mechanism, and the sensors that control the molecular signaling response that produces increased VO2 max, increased LVEF...and less death.

I found Liu X, Xiao J, Zhu H, Wei X, Platt C, Damilano F, Xiao C, Bezzerides V, Bostrom P, Che L, Zhang C, Spiegelman BM, Rosenzweig A. miR-222 is necessary for exercise-induced cardiac growth and protects against pathological cardiac remodeling. Cell Metab 2015;21,584-95. Interesting read.

I also read your paper Schmitz B, Rolfes F, Schelleckes K, Mewes M, Thorwesten L, Kruger M, Klose A, Brand SM. Longer Work/Rest Intervals During High-Intensity Interval Training (HIIT) Lead to Elevated Levels of miR-222 and miR-29c. Front Physiol 2018;9,395. What a lot of work, and its really interesting! Well done. We could never get funding for a training study like this in the US. The nerds control the $ and exercise is not considered science.

I think that the rest period are important for some reason, but just a hunch. I get this hunch from Helgerud J, Hoydal K, Wang E, Karlsen T, Berg P, Bjerkaas M, Simonsen T, Helgesen C, Hjorth N, Bach R, Hoff J. Aerobic high-intensity intervals improve VO2max more than moderate training. Medicine and Science in Sports and Exercise 2007;39,665-71. I have attached a graphic that shows their results. Better increases in VO2 max and stroke volume with 4x4@90%. I think it's the stimulus of having to get back to 70% for the 3 minutes between. However, 15 sec on/15 sec off seems to give almost the same response. Granted these are healthy young males.

Here is the graphic from Helgerud J, Hoydal K, Wang E, Karlsen T, Berg P, Bjerkaas M, Simonsen T, Helgesen C, Hjorth N, Bach R, Hoff J. Aerobic high-intensity intervals improve VO2max more than moderate training. Medicine and Science in Sports and Exercise 2007;39,665-71.

Dear Michael,

I can only agree, there is still data needed to understand the molecular and cellular effects of HIIT. I am currently trying to understand the importance of the rest period and will be coming up with some more data comparing 30 s to 180 s rest period. Concerning interventions: I'm personally doing 4x30x30 all-out ;)

Thanks for your appreciation of our interventional study on miR-222!; its of course science and may lead to better prevention once we understand what is actually happening during HIIT.

Helgerud et al. nicely showed what one can achieve in 8 weeks of HIIT. Most liekely the third session each week was not necessary (some studies suggest two per week is enough). Also very interesting is the strong effect on HR recovery. You can see this in our paper on miR-222 but also in Stöggl and Sperlich 2014 Article Polarized training has greater impact on key endurance varia...

Have you started your training yet?

Regards

Hi Boris,

Thanks so much for that paper. I have been reading it and digesting the results. My first impression reminds me of a quote by Farquar and Farquar, the first authors to have a graphic in any published report, "Data in a table is like sunshine in a cucumber - you knows it's in there somewhere, but it's difficult to get it out". So I made a few figures to understand the stats and the magnitudes.

It strikes me that the POL group does get the best VO2 improvement, but also that group started a little lower than the HIIT group. Training status might make a difference. Also the "economy" looks much better with the HIIT group, and I think this might suggest increased LVEF (stroke volume). This protocol should be replicated, hopefully in older people too.

I guess I'm doing POL training now: lifting 3x a week; 3 hour mountain bike rides 2-3x a week and 4x4@90 HIIT on a stationary bike at the spin studio (the instructors hate me because I don't follow their class). Really, I'm a mountain biker and what to stay healthy to do that...and not, you know, die.

Being older (60) has certain additional challenges that I have to cope with. I can't squat hard because my hamstrings get very sore and it takes me 3-4 days to recover. I'm on crestor, a statin, 40 mg, and I don't really gets DOMS anywhere else by my hamstrings. Doing a HIIT workout makes squats hard the next day, and I can only do 6 reps of 4 sets because I get lightheaded. I try to exhale on the extension, but I think my tired heart can't cope with the valsalva. I'm working on it.

I try not to mix lifting and endurance or HIIT work on the same day because there is some evidence of reduced effectiveness of both for concurrent training. This from Vernon Coffey and others.

I think Stoggl's work is excellent because they have shown that HIIT should be in addition to your regular endurance workout. My one concern for athletes is that VO2 peak is not the right metric for race success. It does put you in the top range, but only explains something like 70% of your finish time, just a guess.

I like Ronnestad BR, Hansen J, Nygaard H. 10 weeks of heavy strength training improves performance-related measurements in elite cyclists. J Sports Sci 2017;35,1435-41. and

Vikmoen O, Ronnestad BR, Ellefsen S, Raastad T. Heavy strength training improves running and cycling performance following prolonged submaximal work in well-trained female athletes. Physiol Rep 2017;5.

Both these papers chose a maximal effort short time trial after the end of a long endurance task, like a race and the sprint at the end. This seems much closer to "train to win" for elite athletes than VO2 max. VO2 max is for health.

Now, why won't someone do Polarized training on 50+ year old who are at risk for cardiac issues, but have not yet had an event? It seems like this is when we should spend our research dollars and save health care dollars by making these people healthier. Maybe I'm showing my age.

Regards,

Michael

We should rename this discussion already. So many helpful infos and a number of interesting papers and thoughts.

B

Just came across this one on SERCA and exercise training:

Article Endurance Training in the Spontaneously Hypertensive Rat Con...

HIIT is better than continuous long training, Higher VO2 uptake and oxigen kinetiks. Minimal myocardial microinjuries, and better reconditioning. And isometric staine training is better than isotonic exercise. Exercise myocardial modulation involves too much molecular mechanisms

,isometric staine training is better than isotonic exercise' to achieve which outcome?