High-Intensity Exercise

This post is by Phil Price, not Andrew.

Several months I noticed something interesting (to me!) about my heart rate, and I thought about blogging about it…but I didn’t feel like it would be interesting (to you!) so I’ve been hesitant. But then the NYT published something that is kinda related and I thought OK, what the hell, maybe it’s time for an update about this stuff. So here I am.

The story starts way back in 2010, when I wrote a blog article called “Exercise and Weight Loss: Shouldn’t Somebody See if there’s a Relationship?” In that article I pointed out that there had been many claims in the medical / physiology literature that claim that exercise doesn’t lead to weight loss in most people, but that those studies seemed to be overwhelmingly looking at low- and medium-intensity exercise, really not much (or at all) above warmup intensity. When I wrote that article I had just lost about twelve pounds in twelve weeks when I started doing high-intensity exercise again after a gap of years, and I was making the point that before claiming that exercise doesn’t lead to weight loss, maybe someone should test whether the claim is actually true, rather that assuming that just because low-intensity exercise doesn’t lead to weight loss, no other type of exercise would either.

Eight years later, four years ago, I wrote a follow-up post along the same lines. I had gained some weight when an injury stopped me from getting exercise. As I wrote at the time, “Already this experience would seem to contradict the suggestion that exercise doesn’t control weight: if I wasn’t gaining weight due to lack of exercise, why was I gaining it?” And then I resumed exercise, in particular exercise that had some maximum short-term efforts as I tried to get in shape for a bike trip in the Alps, and I quickly lost the weight again. Even though I wasn’t conducting a formal experiment, this is still an example of what one can learn through “self-experimentation,” which has a rich history in medical research.

Well, it’s not like I’ve kept up with research on this in the mean time, but I did just see a New York Times article called “Why Does a Hard Workout Make You Less Hungry” that summarizes a study published in Nature that implicates a newly-discovered “molecule — a mix of lactate and the amino acid phenylalanine — [that] was created apparently in response to the high levels of lactate released during exercise. The scientists named it lac-phe.” As described in the article, the evidence seems pretty convincing that high-intensity exercise helps mice lose weight or keep it off, although the evidence is a lot weaker for humans. That said, the humans they tested do generate the same molecule, and a lot more of it after high-intensity exercise than lower-intensity exercise. So maybe lac-phe does help suppress appetite in humans too.

As for the interesting-to-me (but not to you!) thing that I noticed about my heart rate, that’s only tangentially related but here’s the story anyway. For most of the past dozen years a friend and I have done bike trips in the Alps, Pyrenees, or Dolomites. Not wanting a climb up Mont Ventoux or Stelvio to turn into a death march due to under-training, I always train hard for a few months in the spring, before the trip. That training includes some high-intensity intervals, in which I go all-out for twenty or thirty seconds, repeatedly within a few minutes, and my heart rate gets to within a few beats per minute of my maximum. While I’m doing this training I lose the several pounds I gained during the winter. Unfortunately, as you may recall we have had a pandemic since early 2020. My friend and I did not do bike trips. With nothing to train for, I didn’t do my high-intensity intervals. I still did plenty of bike riding, but didn’t get my heart rate up to its maximum. I gained a few pounds, not a big deal. But a few months ago I decided to get back in shape, thinking I might try to do a big ride in the fall if not the summer. My first high-intensity interval, I couldn’t get to within 8 beats per minute of my usual standard, which had been nearly unchanged over the previous 12 years! Prior to 2020, I wouldn’t give myself credit for an interval if my heart rate hadn’t hit at least 180 bpm; now I maxed out at 172. My first thought: blame the equipment. Maybe my heart rate monitor isn’t working right, maybe a software update has changed it to average over a longer time interval, maybe something else is wrong. But trying two monitors, and checking against my self-timed pulse rate, I confirmed that it was working correctly, I really was maxing out at 172 instead of 180. Holy cow. I decided to discuss this with my doctor the next time I have a physical, but in the mean time I kept doing occasional maximum-intensity intervals…and my max heart rate started creeping up. A few days ago I hit 178, so it’s up about 6 bmp in the past four months. And I’ve lost those few extra pounds and now I’m pretty much back to my regular weight for my bike trips. The whole experience has (1) reinforced my already-strong belief that high-intensity exercise makes me lose weight if I’m carrying a few extra pounds, and (2) made me question the conventional wisdom that everyone’s max heart rate decreases with age: maybe if you keep exercising at or very near your maximum heart rate, your maximum heart rate doesn’t decrease, or at least not much? (Of course at some point your maximum heart rate goes to 0 bpm. Whaddyagonnado.)

So, to summarize: (1) Finally someone is taking seriously the possibility that high-intensity exercise might lead to weight loss, and even looking for a mechanism, and (2) when I stopped high-intensity exercise for a couple years, my maximum heart rate dropped…a lot.

Sorry those are not more closely related, but I was already thinking about item 2 when I encountered item 1, so they seem connected to me.

 

from Hacker News https://ift.tt/coAd1lg