Understanding Heart Rate (HR) vs Power

From what I’ve read, listened to, and understand, there seems to be a wide dismissal of heart rate as a good method of measuring training efforts, as such, we all use power. With that said, wouldn’t your heart rate act as a barrier for the power I’m able to put out?

As an example, I trained for a marathon (running race) for the last 20 weeks, where I used HR and pace to track my training (e.g. zone 2 HR = certain pace range, etc). Come race week, I had a full week of crap sleep and on race day, the pace I trained in was more in the realm of zone 5 HR, as such, had to slow my pace significantly.

If pace is running’s equivalent of cycling’s power (I know there are running power meters now), couldn’t the scenario I encountered happen on the bike as well (i.e. zone 2 hr = certain power range for training…then race day training power range -> zone 5 hr)?

Am I understanding this correctly? or am I completely wrong and making this more complicated?

A post was merged into an existing topic: Is there still a use case for heart rate?