Is this typical heart rate performance?
 

When I am dieting with a low carb diet, my heart rate will be around 120 with moderate exertion. If I take off a few days or if I eat some carbs my hr will be 130 with the same precieved effort.

I seem to reach higher heart rates easier if I am rested or well fueled. So is this typical?

I don't know about low carb diet, but I see similar results wrt rest. When well rested, I ramp up fairly easily to 160 and I can manage up to 10 minutes at 165-170. When trying to work out for 1+ hour every day, after a few days I find it hard to go above 145.

Oh heck yes. That's the reason that the Serious Cyclists on here don't think low carb is very good for Serious Riding. How you gonna go with no glycogen and no fast acting carbs? So it depends on what you're trying to do. You wanna ride and ramp up your aerobic system, you gotta eat carbs. However you can tootle around forever on a low carb diet as long as you keep the effort down to what a glycogen depleted rider who is burning slow conversion foods can manage.

I think it's the other way around.

When I'm tired or bonked I can't maintain the same heart rate as when I am fresh and well fueled. This is true not only of anaerobic effort, but aerobic efforts too.

For the same rate of perceived exertion, your HR should be lower when you're rested than compared to not being rested. If you're bonking, your HR should be higher than normal for the same exertion. You just don't have the energy to reach the higher exertion therefore the HR doesn't go as high. I never bonk, so I'm not very familiar with doing it. Low carb diet can cause bonking.

Let me be a little more specific. I have a route that I have ridden many times. If I maintain my speed when on low carbs my HR will be lower than if I maintain the same speed after consuming carbs. If I have had a few days off exercising and I am on the same route with the same speed I will have a higher HR than I would have if I had been exercising for the previous 5 days.

It seems that the more I get beat down the lower the HR goes. Maybe I am approaching death. Who knows.

No, it's the other way 'round. Take our word for it if you haven't experienced it. It's much harder to get the HR up when you're tired. It is true that the better trained one is, the lower one's HR is a a specific speed or rate of climbing, but that has nothing to do with RPE. It is also true that when one is dehydrated one will run a higher HR at the same RPE. But in general what the OP is experiencing is completely normal and predictable.

If one is bonking, one's HR will be much lower than normal at the same RPE, in fact it will be impossible to raise a HR above zone 3 no matter how much pain you cause yourself.

I find that same situation when I've had a few days off cycling, my hr spikes on that first ride.

Curiously I can keep 160bpm for hours (not that I'm some kind of super athlete or anything), I seem to be comfortable with a 165 and below for most rides so that early spike from a few days off doesn't have a lot of impact. No idea about the bonking hr stuff, I'm usually too tired to care about the hr reading :lol:

It's a sign that you need a rest, or that your glycogen is depleted because of your diet. Taking the days off may allow you to recover, or to rebuild your glycogen stores.

If you want to figure out which it is, try switching to a diet with a normal amount of carbohydrates. If you still feel beat down, then it's because you're tired. But I bet it's the carbs.

We all are.