Higher Heart Rate in the AM?

I'm not relying on it exclusively.  But if I'm measuring power on the bike, and also track HR then I know what sort of HR zones match well to power levels.  If I'm riding or racing a longer distance and start to see that my power is in the right zone, but HR is too high then maybe my body is telling me I'm not going to be able to sustain that pace.

So - if my HR is different in the am and pm, how do I tell where power and HR should match for different levels of effort?

I'm just following logic, but HR will go up as you are dehydrated.  Less actual blood volume means the heart has to pump more...

In the morning, you are pretty dehydrated after 8 hours of nothing to drink.  That's my theory.

However, I'm not sure if my HR goes up in the morning based on the power meter.  Same power at the same HR.  But I tell you one thing, it FEELS a lot harder in the morning to me.  A Z2 effort in the afternoon seems like a piece of cake.  In the morning, Z2 feels like a tempo run....

The way I see it, you go by one metric to determine effort.

If it's HR, then you use HR, regardless of what your power says.  If it's power, you go by that, regardless of what your HR is.

Yeah, it's great to compare them and all, but as you have discovered, it can be misleading.

As I mentioned on the winter cycling thread before; while heart rate training can be an effective training tool to gauge your effort (in particular lower steady intensities) it has limitations. Understanding these limitations can help the athlete use it more effectively otherwise it can be misleading and confusing at time.

HR can tell you something at one time and something different later in the day even when the stimulus (training intensity) is the same which is easily monitor with a power meter. Why the difference then? Well HR measures cardiovascular strain and that’s about it. It doesn’t really tell you anything going on in our muscles which are where we mainly seek to produce training adaptations and grow metabolic fit. Yes on steady/easy efforts the HR can be a great tool that closely represents the effort on our muscles but on high intense sessions it doesn’t. Furthermore since HR can be affected by other variables like heat, dehydration, diet, lack of sleep, stress, etc it can mislead at one point or another.

In your particular case, who knows! Maybe you are not eating before AM sessions and due to the lack of fuel your body works harder at the same intensity, maybe you are a bit dehydrated in the morning, maybe you are not as rested, maybe you ate something (like caffeine), maybe, maybe, maybe…

How that you have the power to train better (pun intended) rely on your PM for intense sessions exclusively. You can watch your HR for curiosity but as long as you legs respond to the target effort let your HR do its thing. If you still want to pay attention to it, then be more keen to use it on long steady effort where the lack of change in pace will allow it to match better the effort of your working muscles.

For running I would advice you to start training by pace/RPE especially for short intense sessions. I can post later how you can test your critical velocity or just do a 20 min time trial and use VDOT to estimate your training paces and voila! If that is not something you want to try and prefer using HR then understand you have to be very aware of the limitations and in many cases you will have to use RPE to judge whether your HR is acting up or if it indeed is telling you something you should pay attention to. Yes RPE is tricky to develop but by trial and error you will get there.

The reason I like power and pace (plus RPE) rather than HR is that this learning curve becomes shorter and you get to learn to get in tune with your body faster, but that’s my preference.

Thanks for the posts.

Jorge - you mention about training by pace for the run.  Is there a good website or book that would be recommended?

By the way, I'll post more about critical velocity (pace for swim and run) and power over the next few days and explain how to test and train with it...

Thanks all.  I realize that HR is variable based on external factors, but I had not considered dehydration as playing a major component.  Given that I am consistently seeing higher HR in the am, I'll chalk it up to that (since I'm training inside other external factors don't really come into play at the moment).

Jorge - I'll look forward to the new thread.