[rojeee]

It's a good question that I don't really know the answer to but I can offer some experience. I do a lot of running and 80% of my training is below the aerobic threshold, with 20% above (so anaerobic). After aerobic sessions you recover quickly and can do them day in day out for prolonged periods of time with no increase in chronic stress. E.g. running 100km/week. Effects are higher HRV, lower cortisol and lower resting heart rate. Anerobic workouts, on the otherhand (including any weights sessions I do), need to be done sparingly. The day after a hard workout your HRV will be lower, resting heart rate will be higher, cortisol will be higher. Too many anerobic sessions in a row and you'll start getting into over-training syndrome territory, so you really need to be careful! So I guess the TL;DR is the only way anerobic exercise decreases stress/cortisol is by not doing it or doing it sparingly. E.g. It is my opinion that people who only lift weights are probably unhealthy because they have consistently high levels of chronic stress.

[misev]

I do a lot of running as well and have observed the same effects. After anaerobic sprints or a race of up to 10k, sleep HRV drops / HR is higher and running HR:pace is elevated for up to a week. However, usually this is then followed by some improvement in all of these metrics compared to the baseline before the hard workout. Anaerobic exercise builds/maintains especially fast-twitch muscles, and higher muscle mass has positive influence on many health markers; as we get older we slowly lose muscle mass, but the losses are predominantly fast-twitch muscles [1]. So I believe anaerobic workouts are very important, despite causing quite some stress temporarily. Totally agree they require a lot of recovery inbetween.

Unrelated, out of curiosity, when you say 80% of your training: is it in mileage/time? Or some effort metric like TRIMP, calories, avg. HR, or so? Or something else?

1. https://pubmed.ncbi.nlm.nih.gov/7493202/

[rojeee]

That's good you've observed the same effects and definitely agree that anaerobic training improves fitness and teh associated markers over time. When in my teens I did a lot of running but back then I didn't have a HR monitor and probably most of my training was anaerobic and still managed to improve well over the years. I suspect I was taking on high levels of stress which ultimately led me to quit running when I started university.

Interesting that you mention sleep HRV. I use the Oura ring and have observed that my sleep HRV is super super low at the moment, like 15/20ms but when I check it in the morning with my polar H10 strap then it will usually come out between 60-80ms. Tried to figure out what causes it but not had any luck so far. I don't think I'm over-training or have any other issues.

I follow Phil Maffetone's training methodology [1], which has worked quite well for me. So currently, 80% of my training by distance/time is between 135bpm and 145bpm. The training is mostly steady runs between 7km to 25km. The remaining 20% is a mixture of progression runs, speed training, and intervals.

Initially, for the first 6 months of training, all my training was below 145 bpm and was quite slow at 6min/km but now I can do 4.30min/km at 140bpm and I'm still getting faster!

Cheers

[1] https://philmaffetone.com/method/

[misev]

Coincidentally I have the Oura ring too, and my sleep HRV oscilates around 100ms; haven't compared with a strap in the morning though. Strange that you get such low values, maybe something faulty with the ring, or finger placement? It's possible also that the absolute values are not extremely accurate, but the relative trends are. Garmin for example requires a strap to measure HRV stress, even though the watch has an optical HR sensor, which leads me to think optical sensors are not so precise.

What an amazing improvement to 4:30 pace at 140 bpm btw! I've had a similar relative improvement over the first year when I think about it, from around 7:00 to 5:20-5:30 at 140 bpm. But my training was mostly 1km intervals at high end of zone 3 (still quite below threshold), translating to a lot of tempo running on average, plus one session of 200s or 400s faster intervals per week. Been stuck with little progress for a while though, and was thinking to try a more polarized approach like yours with higher volume; thanks for explaining it!