Low HR during Sweet Spot (and in general)

Hello people,

I am turning to you with an issue that has been bothering me for several months. During rides or training sessions, my heart rate is particularly low. I am a 33 year old male and my heart rate has never exceeded 170 bpm (and it was while climbing the Pyrenees). I am approximately at 43bpm at rest (measured via Polar H10 during sleep).

I did a ramp test a few days ago so my power is more or less correct. However, my sweet spot sessions average 120 bpm, with a maximum around 140.

My heart rate sensor is working properly (measurements taken in parallel with other devices).

Any idea where this might be coming from? Is this problematic?

Thank you!

NB: this problem occurs even after a break, so overtraining is probably not the reason.


Is this an issue that has been present for several months, or has been bothering you for several months?

What are you comparing your heart rate to? Historical records of your own heart rate, or other people’s?

Are you certain this is actually a problem?

I’m 40 and have been in endurance sport for 25 years, and think I’ve probably worn a heart rate monitor for 20 of them. The max HR I’ve ever recorded in Garmin Connect is 161 and if I get above 135 I’m working pretty hard and most z2 rides/runs are in the teens and 20s.

This is not a performance limiter of any kind as I’ve done pretty well from an amateur overall standpoint.


The “issue” has been present since I started cycling (and recording my HR). It’s probably not a health concern: I’m doing something like 15k km each year on the bike.

But I started structured training 2-3 months ago and my HR range seems to be pretty low in the mid-high intensity sessions: sweet spot HR is around 65-70% at the end of the session.

Ramp test is really done at my maximum capacity (I cannot pedal further, legs are giving up) so FTP should be accurate.

But my main concern is just about “maxing my sessions”: cardio never seems to be challenged when I compare to other riders. I know that I should mainly compare to my own performance, but the difference seems so big that I’m afraid to do suboptimal sessions (even hard days are not that difficult from a cardio perspective).

Here is an exemple of my last sweet spot session:

The two reasons this would happen are as follows

  1. You are overtraining and your body is struggling to raise HR

  2. You are well trained and your fitness (combined with the fact that a ramp test is only an estimation of a certain part of your curve) is making sweetspot a bit more like z2


Compared to what?

What I’m trying to get at here, is that if you’re not seeing a substantial deviation from your own usual heart rate then it’s not likely to be an issue. HR is personal and should not be compared to other people.

HR is very individual. If you are concerned at all go see your doc.

I also have a pretty low HR compared to my riding buddies. In my mid-40s and I max out at 166 and anything above 150 I know I’m working and can feel it. Most SS workouts I end up around 125-130 for and Threshold is generally 140 working up to 145 on longer intervals/efforts. Point of me sharing here is that having a lower HR is not problematic always.

What’s your LTHR?

@Hyalync, I wouldn’t be too troubled about it if you are within a normal range for YOU!

You can’t (and shouldn’t) compare yourself to others. When I started cycling consistently a couple years back (and started tracking my HR) i had those initial concerns as well (my HR max at 49 years of age has never been higher than 170, and RARELY gets even close to that… I hover around low 140’s during extended Threshold work and currently have an LTHR of 149 per a recent update on TrainingPeaks).

I did discuss the concern with my doctor, who assured me if i’m not feeling any adverse effects at any point during training or otherwise, then there’s nothing to worry about. She went on to say I should be more concerned and come see her if I experience any wild, out of the norm swings, which could be the signs of something going on!

Your Sweetspot screenshot shows a max of 145 bpm heart rate. That 85% of your 170 bpm, assuming the latter was from a test to find your maximum HR. I’m 56 and my field tested max HR is 172 bpm. Similar resting HR to you (slightly lower for sleeping). I’d say 145 bpm max achieved is in the right ballpark for those Sweetspot intervals. You’re below threshold and I would not expect cardio for Sweetspot to be overly taxing, it’s more about muscular endurance.

Please don’t compare your max HR to others of the same age. There’s wide variance. I have a friend same age, and his max HR is 195 bpm. If we tried to cycle to each others heart rate zones it would not go well.

No. Looks totally normal to me.

Thank you to everybody in this topic for your answers!

Have you raised these concerns with your doctor? If you are concerned I would start there.