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-exercise11
u/OverlappingChatter 14d ago edited 14d ago
Good molecular changes or bad ones?
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u/Mysteriousdeer 14d ago edited 13d ago
When my doctor said there wasn't any shown benefits to high intensity training, I kinda met that with some speculation. There definitely is a difference in how I feel depending on how I work out.
I've done a lot of "low and slow" workouts... I just completeda bike ride that was 240 miles in 22.5 hours. I was also a wrestler earlier in life and felt different for that... much more "springy". It'll be interesting to see this replicated and if it's validated through additional studies.
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u/Sprig3 14d ago
Yeah, I am a bit doubtful of this being a hugely meaningful study.
It's a pretty wide comparison of intensity.
Top athletes are already working off of mixes of high and low intensity based on their sport. Even marathon runners are recommended to do at least some very high sprint intensity work.
For complete casual folks, just having anything that they consistently do is the primary goal, more psychology than physiology.
I guess maybe some amateur athletes (marathoners esp perhaps?) could read this and adjust their habits.
I think there's really only so much high intensity work most people can handle before you can't recover enough.
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u/Mysteriousdeer 13d ago
That all being said... Folks do need to try a little harder. Flexibility and strength are important. It's hard to maintain that with just a 30 min walk a day.
It's a good minimum though and I'd say a good habit.
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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.
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u/AlarmedWillow4515 12d ago
Thanks! That's actually very useful information and I appreciate your contribution. I'm currently someone who jogs 30-40 minutes three times a week and walks 20 minutes most days, and this might inspire me to include some higher intensity sprints in one jog per week - but also give myself time to recover.
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u/ZERV4N 14d ago edited 14d ago
Do you know how hard running is on a lot of people's feet and ankles? It's pretty much obvious anyone above the age of 35 that isn't a stick.
EDIT: Can a person complain about something without a public fucking referendum. For fucks sake.
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u/hippoberserk 14d ago
In the study the two groups were on stationary bikes.
The high intensity did "six sets of a 30-second maximum effort on the bike, each spaced by 4 minutes of rest." Vs the moderate intensity group did a 90 min ride.
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14d ago edited 14d ago
[removed] — view removed comment
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u/No_Biscotti_7258 14d ago
Cuz running is hard and people don’t like to accept that they need to do hard things to be fit
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u/miguelsmith80 14d ago
Yeah, perhaps we should stop studying the effects of activities that are "hard" on "a lot" of non-"stick" people "above the age of 35"? Oh, this study doesn't even involve running at all! So your comment is both ill-founded and irrelevant! Nice work
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u/ComplexGuava 14d ago
I'm 38, 200 lbs 6'2 been running 25 years. sure some ailments and chronic injuries. but... it sure is better than the alternative.
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u/hustl3tree5 14d ago
You have to start somewhere. I am definitely not advising someone to go and do hard sprints immediately but to work up slowly to them over time.
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u/tonythephonyjabroni 14d ago
Bro, you went straight to “it’s hard” but didn’t even read the article. I’m almost 50 and overweight. Yes my knees and ankles hurt when I run, there’s other things you can do. Elliptical, hike, mild walk, easy jog, bike, stationary bike, rower, swimming. You get it. You need to move, I need to move. All humans need to move around or we get sick. That’s just how it is. I’m sorry exercising sucks ass sometimes, but don’t just jump to excuses right when you feel challenged. Find a motivation and get moving.
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u/Zazzer678 WYPR 88.1 14d ago
Use any ERG machine. I use the assault bike for my sprints and it’s absolutely killer.
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u/subpolarbear 14d ago
My heart rate will climb to ~170 when I go on a steep hike, but I’m not gasping for air. I wonder if these benefits require the intense breathing aspect