Heart rate during morning fasted ride

Hi all,

I have a question about heart rate relating to training fasted in the morning.

I am currently in my recovery week after 3 weeks of build. My training plan this week was Tuesday and Wednesday Pettit (https://www.trainerroad.com/app/cycling/workouts/21542-pettit) and Thursday(today) Whorl (https://www.trainerroad.com/app/cycling/workouts/21534-whorl). These workouts are very similar. Pretty much all in zone 2.

I usually workout in the evening after work. This morning I did Whorl first thing after getting up and my heart rate is through the roof.

Here are the 3 workouts data for comparison:

These workouts have roughly the same Intensity Factor (0.64) and are all in zone 2 so I would expect avg HR to be roughly the same for all of them. My max heart rate is 199.

As you can see for the first 2 (done in the evening with some carb intake during the day) my avg HR was around 131. For the ride I did this morning it was 151.

I had noticed this before when I have been training in the morning but a 20 bpm difference seems rather substantial.

Have any of you experienced this? Is this to be expected?

I’m currently travelling and working, so I’m using a borrowed trainer and have to workout in the early morning. Pulse is up to 20 points higher, and I just don’t have go at 5:30. I think I’m going to redo this week when I get home. My usual workout time is late morning after a big breakfast and some coffee.

Interesting, so you pretty much observe the same impact on your HR when working out early.

You’re probably less hydrated, which means HR needs to be higher to keep your cardiac output high enough. Fasting causes you to release fluid (and electrolytes), and fasting is what you’re doing while you sleep (see also, break-fast). I know I’m at my lowest weight in the morning. Conversely, after feeding, and especially by the end of the day I’m at my heaviest.

For sweet spot my pulse is usually in the 140s, climbing to 150 over the course of the workout
This morning I tried Carpathian peak, and started out at 150, rising to 160 I barely made it through the first interval, way under power for the second, and just rode easy for the rest of the workout

You may be getting ill or fatigued?

My heart rate in the morning fasted is no different than any other time of day.

No question on the fatigue. I’m on 24 hr call for 4 days this trip

I train a lot fasted in the morning. Same behaviour, looks normal

I train fasted in the morning and have the same HR as I do when I don’t train fasted. When I first started doing it I saw +10-15 BPM on early morning rides (regardless of fasted state or not).

I agree with the comments above about dehydration likely being the culprit