Why such a big difference in heart rate? 2 outdoor rides compared

I am currently in the final week of sweetspot base low volume two. I did these two rides outdoors approximately two weeks apart. The area where I live has a rolling terrain so it is not possible to maintain a steady pace sometimes. The average heart rate for these two rides varies by almost 10bpm which is pretty big. I use a vector 3s powermeter and calibrate them before every ride. I wouldn’t completely agree that this is due to increased fitness as 2 weeks is a small-time to make huge gains in my opinion. The average power and NP for both the rides are similar.

Ride 1:

Temperature: 3ºC on average.

Ride 2:

Temperature 6ºC on average

I felt really comfortable in ride#2

10 bpm is not really a big deal. A lot of things could account for the change. A few factors (but not limited too) are:

Sleep
Stress
Caffine Intake
Humidity
Elevation
Nutrition

It is probably a combination of a bunch of things. Also it could be your HR monitor acting up. If the contact strips aren’t just right or the battery is low or something is bent or damaged, who knows.

I wouldn’t sweat 10 bpm, 20 maybe but not 10.

Not a big deal? it is a big deal. I was much more relaxed overall and was easily able to smile and wave at other cyclists. I was easily able to focus on the road and look well ahead(I usually find it hard to do that when my HR is too high).

My HR monitor was not acting up as I could feel the high heart rate in ride#1. It did make a huge difference overall.

I second “not a big deal.”

A change in sleep amount, or quality, could easily affect my HR by 10bpm.

“Why” is a tough thing to answer with HR. You’d be better off looking at trends over many days as opposed to two rides that are two weeks apart.

I think your problem is anxiety.

Sorry, 10bpm is not a big deal. It happens.

You could definitely be more tired two weeks farther into a training block. I just don’t think you can really compared two different rides two weeks apart like that.

I routinely have the same workout under similar conditions vary by that much, so I don’t think it’s weird. I also have days on rare occasions where I’m in God mode for no discernible reason. So maybe you were just having one of those days.