Hold the Presses! More Good News about HIIT!

I began doing high intensity interval training (HIIT) about 7 years ago after reading a study that said that it provided the cardio and respiratory benefits of a longer workout in a shorter time, and it is a strong stimulator of stem cell growth. Stem cells are the miracle cells we are born with that cause healthy growth in our childhood and teens. They reduce in number during our lifetime and have a minimal but important presence in later life. It made sense that stimulating their production would have benefits on my own health and longevity, so I decided to give HIIT a try.

To start, I zeroed in on the HIIT training specifics. It’s an entirely different exercise regimen than I was used to! It was hard to push myself to close to maximal effort for 10 or 15 or 20 seconds or as long as 60 seconds, depending on the routine. Then I would rest and repeat, 5 or 10 or even 15 times. I felt so good afterward, flooded with endorphins and accomplishment, that it further reinforced my commitment to HIIT.

Then, on a stress test 4 years ago and a follow-up one last year, my cardiologist was floored by my METs score of over 13. One MET, or metabolic equivalent, is the amount of oxygen consumed when you sit still. A score of 13 METs indicates a VO2 max of 47. (VO2 max, or ventilation rate of oxygen, is the amount of oxygen a person can use during intense exercise.) This score placed me in the top 2 percent of people in the decade younger than me! She said she was humbled and added, “Whatever you’re doing, keep doing it.”

So, with all this in mind, I just read an article by Peter Attia, author of Outlive: The Science & Art of Longevity. In the article, he said he was astounded by two newer studies on what he calls maximal aerobic capacity and its relation to cardiovascular health as well as all-cause mortality. Attia is an MD and is usually on the skeptical side when it comes to studies with big claims. He usually points out flaws in studies and the controls and sample groups used. The fact that he touts these two articles, and gives them so much credit, means that he has vetted their sources, methods, and sample populations and agrees with the findings. At age 51, he added that he is including more high aerobic capacity practices in his already rigorous personal health and longevity plan.

So, here’s the deal with both of these studies (see notes 1,2.) Out of 120,000 participants for 8 years in one study and 750,000 participants for 10 years in the other, the top percentile by VO2 max participants (representing 2% of the total people studied) had a 5 times lower risk of dying from all-cause mortality than the lowest percentile group, which represented 25% of the total people studied. The groups in between all had higher rates of all-cause mortality than the top group, the risk scaling up in each group as VO2 max declined.

The takeaway here is that if you are in the lowest group, the 25%, your chance of dying is 5 times greater over the next 8-10 years than if you are in the highest group. Remember, cardiovascular fitness is not only about heart disease. It is also about cancer, diabetes, dementia, and all sorts of other health problems as well.

Does this mean you should mostly do HIIT exercise? Not by a long shot. Attia warns of two dynamics if you overdo it. The first is HIIT burnout, in which you are not allowing enough time to recover from the intensity of a HIIT workout. The second is something he calls an aerobic base. This is the steady conditioning you get from regular Zone 2 type exercise and probably the place you want to start if you’re not used to HIIT training. I have found that once a week, and sometimes twice, is the HIIT rhythm that works for me, combined with 3 or 4 Zone 2 sessions every week. You can read more about all this in my book, A Life Yet to Live: Finding Health, Vitality and Joy after 60.

The new research on HIIT training is great news for anyone who wants to stay healthy and live long. Now, you just have to do it!

1 Mandsager K, Harb S, Cremer P, Phelan D, Nissen SE, Jaber W, “Association of Cardiorespiratory Fitness with Long-term Mortality among Adults Undergoing Exercise Treadmill Testing.” JAMA Network Open, 2018;1(6):e183605, doi:10.1001/jamanetworkopen.2018.3605

2 Kokkinos P, Faselis C, Samuel IBH, et al. “Cardiorespiratory Fitness and Mortality Risk Across the Spectra of Age, Race, and Sex.” Journal of the American College of Cardiology, 2022;80(6):598.609. doi:10.1016/j.acc.2002.05.031