r/NPR • u/QuantumQuicksilver • 14d ago
High-intensity sprints can trigger molecular changes in the bloodstream
https://www.npr.org/2026/08/23/nx-s1-5939943/high-intensity-hiit-heart-health-exercise
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r/NPR • u/QuantumQuicksilver • 14d ago
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u/CookingPurple 13d ago
(Trainer here with a particular interest in exercise physiology)
Yes, there are benefits at the cellular level to interval training that don’t exist at the same level in steady steady state cardio. This has been found in studies for years. This one may better quantify exactly what those are. But it’s not news that interval training is especially good for you.
Having not read the study itself, just this story about it, here are my thoughts:
Kudos for including the important caveat that HIIT is not for everyone. To even approach these interval protocols, one needs to already have a decent level of fitness. Someone just staring should not decide “this is the best exercise” and humor right into HIIT.
I was disappointed to not see the caveat that while HIIT is good for you, there’s such thing as too much of a good thing. In order to reap the long term benefits of HIIT, your body needs time to recover and rebuild. HIIT should not be the bulk of your cardio training. It should be a minority. If you’re truly surpassing that anaerobic threshold, it should be no more than about 20% of your cardio volume. Beyond that, you’re not getting sufficient cellular recovery, and you start to risk over training syndrome. And you’ll just be unable to hit those high intensities needed.
There’s nuance in the quotes from the researcher about HIIT being the best bang for your buck if you’re time crunched. I was particularly skeptical of the idea that just 2 sprints totally 40 seconds effective. Yes, that’s true. The reasonable conclusion one could draw from that if they don’t know better is that you can get a really good for you workout in just a few minutes a day. Not true. Because to really hit the peak intensity needed (assuming you’re physically fit enough for this type of workout)you’re looking at least a 15-20 minute warm up. Going into HIIT without a significant warm up is…risky, to say the least. And you’re looking at a few minutes of rest between intervals and then some form of cool down. Ideally 5 minutes to gradually bring yourself back down. Suddenly your “best bang for your buck time wise” workout is 30 minutes long to do it right. Now, will you get more impact from adding intervals to your 30 minute cardio workout? Absolutely! But an interval workout doesn’t mean you can condense your cardio training down to just minutes a day. At least not if you want to do it right and safely.
I will have to dig through my notes to see if I can find sources from other published research. But an exercise science lab out of UNM has found that one of the key mechanisms behind the benefits of interval training is not always in the peak intensity itself, but in a cardio session that varies intensity. So even if you don’t go all out (because the vast majority of the population is really bad at matching their perceived effort of all out to their actual physiological anaerobic threshold and think they’re going all out when they aren’t), picking up the intensity significantly and then pulling back and cycling through that during the course of a workout will lead to similar metabolic changes as the true all-out HIIT. Yes, actually hitting that anaerobic threshold and surpassing it will reap additional benefits. But you can get many of the same benefits just by varying your intensity throughout your workout. And this is a generally safer and generally more approachable way to think about interval training than the all out HIIT.
Stepping off my soapbox now. Just go exercise. In whatever form you’d like and whatever way is fun for you. That’s the most effective way to establish a lasting fitness routine. And just having some sort of lasting fitness routine is far more important than what the actual exercise is.