I think a more practical and logical explanation is that fatigue (or elevated perceived exertion at a given absolute workload) is limiting your output, as opposed to some central overtraining mechanism. That's my best guess without seeing a more detailed profile of this phenomenon. Additionally, if you haven't been training in the higher heart rate zones, the energy systems utilized therein are going to be less capable and it's going to feel a whole lot harder.

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https://connect.garmin.com/modern/profile/domingjm

Thanks - I should add my performance hasn't changed just my HR is v low.

There is tons of new research being done on parasympathetic versus sympathetic and whether you care about performance or health and longevity. We tend to work our nervous system way too hard with the training we do to promote good performance at the sacrifice of health and longevity. If you think these professional athletes are " healthy" we are all kidding ourselves. Mark Allen did an interview about this as well. Years and years of stressful training hurts the body in the long term. We need parasympathetic mode to balance out the craziness we put our bodies through, but none of us are too good at that are we? This is also why the 80/20 training is becoming more popular. You can't go full-send 100% of the time and expect to be in the game long. Just like all these crazy age groupers doing 5 IM in a year. They will pay for it when the surgeries start piling up and in the later years. Primal Blueprint podcast discusses this issue alot.

Sympathetic is fight or flight, you body and cortisol levels are always on go.

Parasympathetic is rest and digest mode. Where the cells regenerate and the healing happens.

The trend now is to monitor heart rate variability in the AM to see how stressed your body is. Of course this is the trend right now, I am sure they will come out with something new in a few months. Sleep, rest, and recovery cannot be discounted for sure.

this year I've noticed that my HR has dropped significantly, - 130-140 used to be cruising pace, now that feels quite tough and 110 to 120 would be a long run or ride.

.[/quote]
Ive had this, this year. Turns out I'm low on iron and as a result low on haemaglobin.

Without experimentally administering parasympathetic or sympathetic agonists and antagonists, it's not really possible to definitively determine whether you're experiencing some aberrant nervous system thresholding or not.
If I was you, I would look back at some of my really high intensity efforts and try to replicate those (I'm presuming that you're healthy enough for vigorous exercise). Try to use a run workout where you're able to achieve a higher heart rate. Compare your performance and your resultant heart rate. Theoretically, a given work rate will elicit a given heart rate, or at least within several beats if your fitness hasn't changed dramatically.

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https://connect.garmin.com/modern/profile/domingjm

I'm starting to think this has been my problem for the last few years.

Thanks tuckandgo.

The best analogy that I have for parasympathetic over-reaching is that of Type II diabetes. Ordinarily, stress (training, life etc.) leads to a predictable hormone response - the pituitary releases ACTH which tells the adrenals to release cortisol (to respond to the stress). If this happens too frequently, the adrenals get 'tired' of receiving the message and so become resistant to it (in the same way that the muscles become 'resistant' to insulin in the case of T2D). They reduce the amount of cortisol that they release leading to less sympathetic drive (lower HRs, lower blood lactates, often lower blood glucose etc.)

Like T2D, there are stages. Fortunately, most people don't make it to the last stage where the pituitary has a hard time producing ACTH. This is full blown over-training (akin to pancreatic damage in diabetes) and it can take years to recover from. If only noticing reduced HR during warm up, that would be the very first sign that recovery is needed. Athletes often get to the point of being unable to lift HR, even for main sets, & at this point, it can take a week or so to bounce back. If athletes don't listen to this and continue to push on, it can lead to serious long term issues (& frankly, at the elite level, retirement from the sport).

Long and short, not a big deal when the small signs show up but definitely take it as a message from your parasympathetic system that your body is getting a bit tired of constantly producing a stress response & would very much appreciate a few days off

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Alan Couzens, M.Sc. (Sports Science)
Exercise Physiologist/Coach
Twitter: https://twitter.com/Alan_Couzens
Web: https://alancouzens.com

Wow.

Thank you :-) .

That is exactly the information that I was after and at a level that I fully understand.
I really appreciate your response and will be using the information, hopefully wisely. Especially as I might have a chronic slightly blunted training response at the moment.

As an FYI - it really is the first bit of info I've come across about HR not rising as an overtraining response, rather than the usual HR too high won't go down.

I've had this previously in big blocks of training, although not for a number of years as I don't train as much these days. Couldn't get my heart rate above 138 no matter how hard I tried. I generally find when I taper my heart rate tends to increase from the lower HRs when I am doing harder efforts.

Truly, happy to help!

Yes, unfortunately, sympathetic overtraining (high heart rates, inability to sleep etc) gets a lot more attention (as do most things anaerobic :-) but the parasympathetic version is quite common among the athletes/sports who do big volume. In my experience, it's par for the course, at some level, during big blocks/training camps.

A really good old article by Dan on this phenomenon here... https://www.slowtwitch.com/..._revisited_3274.html

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Alan Couzens, M.Sc. (Sports Science)
Exercise Physiologist/Coach
Twitter: https://twitter.com/Alan_Couzens
Web: https://alancouzens.com

Yep.

Remember performance does not equal health.

I believe a lot of people get into triathlon and endurance sports to improve their health. Then they get competitive, build performance based goals and sometimes sacrifice their health.

And just in time, this article came out

https://www.npr.org/...-tax-athletes-brains

thanks, interesting reading..

I use HR in the pool these days, check on it after each set of intervals. if I'm not getting 150-plus after a hard set, that's my marker to back off effort for the rest of the workout and take an easy day or three.
Used to see this marker once in a while, as it get older it happens more and more frequently..

I've been giving this some thought and noticed most of my seasons go like this:

Good training up to my first big race in late May - early June.
Normally have a good race.

Summer goes OK, races are OK
Late summer race goes OK but not great. In training I seem to lose a little power and speed. My September races are never as good as my Spring races with a few exceptions.

Going over my logs I noticed this:
I seem to be able to put in a lot of volume and have good training response for 16 to 20 weeks. After that I stop improving and it's difficult to get my HR up while training and racing.

In the seasons where I've had 2 to 3 weeks off (meaning really easy) after my June race, my late summer/fall races go much better. In fact one year (2014) I trained up to USAT Nationals, had a so-so race, took a week easy and then ran the next race faster than I did at nationals. After that I took another 10 days easy, trained up to Rev3 Florida and had the best run I've ever done. I've noticed my HR response in that time period wasn't depressed.

So, perhaps I'm digging myself too deep in a hole and 16ish weeks is my limit with that amount of training. Maybe I need to take that 2-3 weeks easy and then get back to normal or just bring my load down a few hours. I don't think I'll be able to judge the latter so I think I'm going to try scheduling a break every 16-18 weeks to get my HR back up to normal ranges where it isn't depressed anymore and get out of that parasympathetic over-training cycle I seem to be putting myself in.