I am experiencing slightly higher HRs during my runs than when I was carb burning. Nothing too drastic, except yesterday I was getting much closer to my max HR during my parkrun PB attempt (I did it, with a new PB at 24.55!).
Has anyone else felt they are running at a higher HR for the same effort level compared to carb fuelled running?
Cheers
Alec
Right Alec, I’m not getting sucked into this one… do I even look like I know how to run? 
That said, I do remember reading some stuff about this (that HR did go up on Keto for months, but then came down for several) but not entirely sure where. IIRC Cardio stuff is one of the last areas to get keto/fat adapted. Definitely search and you should find something useful.
I would start here since these guys/gals have done a lot of n=1 on HR during training…
I honestly never paid attention to my HR before Keto, so I couldn’t tell you if it’s changed while running.
But I did just read in another thread that it’s common for people to have a temporary increase in resting HR while adapting and that typically it goes back lower than pre-Keto, so maybe this is an extension of that.
But you’ve been adapted for a while, haven’t you?
Guess I’m no help, am I? 
I don’t run. I do 3-4 30 to 40 minute sessions a week on an original airdyne at 65-75% of age adjusted max HR. I’m back to exercise at age 69 after a 30 years layoff. Eearly on my quads were on fire at low levels of effort. I got a chest HR monitor and what I observe after three months is my rate of breathing and HR are appropriate to the level of effort and even declining as you would expect as fitness improves. My speculation abouut my quad muscles is they need a better blood supply via more capillaries to accomodate higher blood flow. I’ll have to wait and see if those develop.
Makes me think of Phinney, when he said he doesn’t understand why people are so excited to run a marathon and travel 26 miles in 3-4 hours when he can cover the same distance in a car in a half hour.
@Baytowvin LOL! 
@Alecmcq Try this advice from Dr. Phinney: take a cup of bone broth about half and hour to forty-five minuted before the event. You may be a bit dehydrated or a bit salt-deprived, and your heart may be working uphill trying to oxygenate you with a lower volume of blood. The bone broth should fix that nicely.
ETA: Thinking more about Dr. Phinney’s remark made me wonder: Why does he drive so slowly? 
I had a big step backwards today with my running. I had worked up to 6 miles on Wednesday and had a rest day yesterday. Today I wanted to try to do 6 again, but I hit a wall at 2.5. My heart rate peaked at 176 and I was running a pretty slow pace. Legs started to feel like jelly again.
Even while walking the next 1.5, my heart rate hovered at 140. This seams really high to me.
I knew I felt off today, energy wise. I should have listened to my body and just taken it easy, but I have a 10k a week from tomorrow and I want to make sure I’m ready.
Not sure why I’m backsliding. I have been feeding my electrolytes all day knowing I was going for a run.
Ughh. I just hope it’s a one day thing and I can get back at it tomorrow. 
LeeAnn
Go easy. We all have off days. Not every run is what we hope for. Go into your race feeling rested and confident. Then give it your very best shot, and leave nothing in the tank. You will then know what your best is. And then you can work to improve it.
I have a target 10k race tomorrow. Targeting a 3 min PB, is going to be tough. But I am now way lighter than for my current PB. Looking forward to it!
Cheers
A
Energy levels back up today! Think I’m going to try another run latter. I’ll keep it slow, but I’d really like to get one more 6 miler in before next Saturday. Today gives me plenty of time to tapper a little the rest of the week.
We shall see how it goes.
I experience the same symptoms during my runs before and after starting on the ketogenic diet. I have gathered quite some data from the runs, but have listed here 4 of my 7 kilometer runs, 2 the month before eto, 2 in the 3rd month of keto.
Distance: 7.3 kilometer
Duration: 42:26 minutes
Average tempo: 5:48min/km
Average heart rate: 171
Max heart rate: 194
Distance: 7.31 kilometer
Duration: 47:52
Average tempo: 6:02 min/km
Average heart rate: 175
Max heart rate: 193
Distance: 7.2 kilometer
Duration: 45:40
Average tempo: 6:19 min/km
Average heart rate: 164
Max heart rate: 178
Distance: 7 kilometer
Duration: 43:43
Average tempo: 6:11 min/km
Average heart rate: 159
Max heart rate: 182
The max heart rate was the one that struck me most during the runs, especially because my breathing was quite normal and I was able to talk during running. So I wondered how it was possible that my heart rate was so high, without raising my level of breathing or exerting my body. It was no problem to just finish the 7 km run, and didn’t feel like my heart rate was higher than before.
So yes, my heart rate is on average higher and my max heart rate specifically is higher, but based on the signals from the rest of the body the runs are much easier. The latter could also come from the weight loss (about 18 - 20 kg at that moment).
My runs sucked for three months after starting keto. No energy, legs felt like I had lead in them and I had to insert walk breaks. Then it all got better and hasn’t been a problem since. Can’t wait to get my mileage back to where it use to be. I got out this morning and love it!
I haven’t got the pre keto data as I only started running once on keto.
As any beginning runner, I had been running way too fast to begin with which have impacted the heart rate.
I have asked for help and advise and implemented following changes.
I slowed down keeping my HR low. I started practicing Chi running method.
I only do easy low HR runs working on my running form as the main focus. Yes, it’s nice to see the faster splits and feel better on the legs but the low HR and good running form are doing the trick.
I run fasted sometimes, even on my monthly three day fast.
Over time, I have improved a lot a my HR have allowed for faster pace.
Point being is that I would stop worrying about it and I would most definitely slow down. The body will catch up.
Look up Floris Gierman on YT for more info on low HR training.
It works so well!
I am a 74year old trail runner with some experience of running. I have been keto for 15 months. For the last year I have noticed that for the first 25 minutes of a run my heart rate is at or above my anaerobic threshold, then it abruptly drops to 15-20 bpm slower and never goes back up again unless I take a break, in which case it will be up for a short time.
I interpret this to be due to my having limited glycogen stores which are used up in the first 25 minutes then I am burning only ketones which my body has a limited ability to produce from fat. My short break allows my liver to produce enough ketones to let me run faster for a little while.
Has anyone else has had this type of experience? Maybe it is just due to my age and the fact that my max heart rate is slow and it is hard for me to run in an aerobic, ie fat burning, state.
I echo your experience on max HRs. I have definitely increased my max HR (supposedly not possible) on keto vs pre-keto. Not quite as much as yours. But up by 5 or so BPM.
I noticed this happening at first but it went back to normal after a few months… And congrats on your PB!!