Originally Posted by
RChung
Did you mean your HR at a given power is lower?
In any event, I'm not sure the ratio of watts/HR is that informative. To the extent that we're talking about aerobic production of power, we know that general metabolic efficiency doesn't change very quickly, so not on the order of five weeks. Likewise, A-V O2 differential doesn't change very quickly over the same time frame. So, over a shortish period of time, power generated aerobically is pretty closely related to cardiac output. Cardiac output is just HR * stroke volume, so watts/HR is mostly a proxy for SV.
Maybe your SV has increased, but probably not because of things you've been doing since Jan 1.
I get what you're saying, as the efficiency factor (EF) isn't really showing aerobic efficiency (watts/O2), but watts/heart beat.
But something significant happened in January versus last year, and it seems to have happened over the span of weeks after I started the training change up (my workout change-up actually started after Thanksgiving).
Here are the power:HR traces for the 4 quarters last year. Pretty consistent until the 4th quarter, where the Pwr:HR up to mid-tempo starts dropping.
Whatever the mechanism, I'd call this progress.