A note on heart rate variation

A light bike doesn't replace good fitness.

Moderator: Moderator Team

Post Reply
iheartbianchi
Posts: 467
Joined: Sun Mar 24, 2019 9:17 am

by iheartbianchi

I haven't really gone into detail regarding heart rate variation since it seemed so obvious (to me at least), but following a discussion I had with an athlete I thought it be worthwhile to raise this here as well.

Let's take an athlete that has a resting HR of around 50, with a max HR of around 200. This individual went on a very hard ride of 150km or so and 2,500m of climbing, pushing out big watts and achieving heart rates of up to 195 on this ride.

After returning home, this athlete reported feeling "hot" and a heart rate that stayed elevated at around 65-70 for the remainder of the day (this is normal as your body works overtime to repair muscles, compensates for decreased white blood cells, hormonal changes, etc.). This athlete went to bed feeling his heart beating faster than normal, and woke up the next day with an elevated heart rate.

When starting the next morning's ride, the base heart rate was higher, but oddly, didn't go past 170bpm no matter how hard he pushed, despite feeling tired and putting out decent power. He couldn't achieve the same peak power as the day before, but he was able to push the same "aerobic" power albeit with an elevated heart rate, which he found contradictory. He didn't understand what was happening, and blamed it on "heart rate variation."

Let's break down what happened. First, a snapshot of what we are dealing with:

1. He has caused damage to his muscle fibers.
2. He has probably accumulated high amounts of lactic acid in his legs, effectively paralyzing the muscles where the lactic acid is concentrated.
3. His body is devoting significant resources to repair.
4. His blood counts will be off, as he will have effectively "melted" his hemoglobin and WBC counts.
5. His adrenal glands will also be fatigued and the body's hormonal balance will be off.

All "bad" things for an average person, but necessary for athletic performance and improvement.

What happened the next day?

A. Because of 1. and 2. (muscle damage, lactic acid), he has significantly fewer muscle fibers to "recruit" into cycling work.
B. Because of 1, 2, 3 and 4, his resting heart rate will be higher as the heart is pumping oxygen and nutrients to faciliate repair.
C. However, because of A, during a state of cycling exercise his body's oxygen demand is decreased, since fewer muscle fibers are capable of doing cycling work - your oxygen uptake is reduced.
D. Because of C, his heart does not need to pump as often.

All clear? Now what are the implications when you try to "force" training on this next day based on power?

X. Because of A, you are only utilizing a portion of your muscle fibers that you would ordinarily use.
Y. Because of X, you are over-relying on a smaller group of muscles, which are subjected to a greater amount of stress than normal, for the same level of power.
Z. Because of Y, your body will try to compensate through changes in your form, utilization of other parts of your body, or over-reliance on inefficient muscle groups which can strain your connective tissue (such as tendons and ligaments).

And because of X, Y and Z, you can run into the following serious issues:

Issue 1 - injury to the muscles that are now being loaded with the stress
Issue 2 - changes to your biomechanics that are less efficient
Issue 3 - injury to the connective tissues that are now being overburdened trying to compensate for your new less efficient biomechanics
Issue 4 - while your body wants to devote its resources to repairing the damage from Day 1, it is now devoted to pumping its resources to fuel a smaller group of muscles to do all the work, thus proactively and actively blocking your fitness gians from Day 1
Issue 5- you feel miserable because you are working harder to do less work, which work may actually be counterproductive

Issues 1 - 3 result in injury. Issue 4 results in plateau. Issue 5 leads to burnout (not physiological burnout, that's a separate issue).

So what is the takeaway? Heart rate variation isn't some random anamoly or some annoyance that you should dismiss. Until we have the technology to easily scan the current state of your muscle fibers (can't be done yet without a surgical biopsy), your lactic acid levels, your blood counts and adrenal levels, the heart rate is a wonderful proxy that tells you when you need to take it easy and slow down. That is what heart rate variation is telling you, and ditching your heart rate monitor for "annoyingly telling you the true state of your body" and blindly following your power meter zones is a recipe for disaster.
Bianchi Oltre XR4
Celeste Matte
Campy SR 11spd mechanical
Bora Ultra 50 tubs
Viseon 5D / stock bits and parts

Bianchi Specialissima Pantani Edition
Campy R 12spd mechanical
Fulcrum Racing Speed 35 tubs
FSA / Deda bits and parts

by Weenie


Toybota
Posts: 80
Joined: Tue Jan 19, 2021 9:16 pm

by Toybota

Thanks for an another great info.
So.. What would you recommend if I'm doing an HR based interval and I just can't seem to achieve required HR?

Do you just work from RPE?

iheartbianchi
Posts: 467
Joined: Sun Mar 24, 2019 9:17 am

by iheartbianchi

Toybota wrote:
Mon Jun 07, 2021 4:13 pm
Thanks for an another great info.
So.. What would you recommend if I'm doing an HR based interval and I just can't seem to achieve required HR?

Do you just work from RPE?
If you can't achieve the required HR, is this a one-off or a consistent theme? If the latter, there are fundamental issues at play (such as incorrect HR zones, poor muscular strength, injury, significant physiological issue such as burnout or illness, etc.). If it's a one-off that means that you're not fit to do intervals that day (either muscle soreness, lactic acid, energy depletion, lack of sleep, etc.). Really need to know more.

I would never rely on RPE unless a seasoned and trained athlete who is highly tuned to their body.
Bianchi Oltre XR4
Celeste Matte
Campy SR 11spd mechanical
Bora Ultra 50 tubs
Viseon 5D / stock bits and parts

Bianchi Specialissima Pantani Edition
Campy R 12spd mechanical
Fulcrum Racing Speed 35 tubs
FSA / Deda bits and parts

Toybota
Posts: 80
Joined: Tue Jan 19, 2021 9:16 pm

by Toybota

iheartbianchi wrote:
Tue Jun 08, 2021 3:04 am
Toybota wrote:
Mon Jun 07, 2021 4:13 pm
Thanks for an another great info.
So.. What would you recommend if I'm doing an HR based interval and I just can't seem to achieve required HR?

Do you just work from RPE?
If you can't achieve the required HR, is this a one-off or a consistent theme? If the latter, there are fundamental issues at play (such as incorrect HR zones, poor muscular strength, injury, significant physiological issue such as burnout or illness, etc.). If it's a one-off that means that you're not fit to do intervals that day (either muscle soreness, lactic acid, energy depletion, lack of sleep, etc.). Really need to know more.

I would never rely on RPE unless a seasoned and trained athlete who is highly tuned to their body.
Looking back, I was definitly feeling fatigued and had some symptoms of overtraining.
Made a classic mistake of just trying to bulldoze through the intervals using ERG mode with the trainer.

More reason to do intervals based on HR rather than power :D .

Post Reply