Race Analysis: Reverse Cardiac Drift?

Racing
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So just did Pedalpalooza (highly recommended race!) and going over the data from the day. I’m a litttle confused on what I’m seeing.

A couple caveats:

  • I’m from sea level with FTP 227 or 3.82 w/kg
  • Race is at 8300-9000 ft elevation
  • First time I’ve raced at this elevation
  • I get mild-moderate altitude sickeness (recently on a hike about a month prior to this race)
  • No acclimitization (literally got in the evening before and sent it)
  • I planned to pace at under 190 w (84% FTP altitude adjustment) and aim for 0.8 altitude adjusted IF

Here’s the ride at hand:

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First off, I’m happy with the performance. Nailed the IF and didn’t get altitude sickness. In hindsight, I think I may have left just a little on the table but in the race it felt like I couldn’t push any harder on the climbs.

I’m trying to figure out how I managed to negative split the race while also having a lower NP and lower HR in the second half of the race. My speed over the second half of the race increased from 9.9 mph to 10.4. Maybe I was getting more familiar with the course and carrying more momentum? I’m not sure where I found that speed but I’ll take it.

Interestingly, I also saw my HR drift lower through the race faster than my power decreased. Below is interval.icu charts on this. Is reverse cardiac drift/aerobic decoupling a thing? I was expecting the opposite especially since I’m non-acclimatized. Has anyone else seen this phenomenon? And how can this be explained?

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Impossible to give an exact answer, but you likely answered it yourself. You got to know the course better, your race nerves maybe calmed a bit as the race went on, more relaxed, more efficient, etc……

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I often have negative drift on events, or even big rides, as my anxiety calms down and I get in the flow of the ride.

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I often find this occuring as well. Like I can push “harder” but don’t see the same HR response. For myself I chalk it up to nerves and finally being “warmed up” as I am slow to warm up and often have to spike or hit a wall cardio-wise and usually hit a peak HR before I come back down and can start to fire proper. Could be something physiologically going on that can be more scientifically explained or could just be fatigue/heat/hydration as HR can be influenced by so many factors. Very interesting.

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The start of the reverse cardiac drift does line up with finishing the first lap and I did feel more comfortable on the 2nd and 3rd laps. Shame that I couldn’t push harder on the uphills but altitude be altituding.

I think the 1st vs 2nd half speed difference is moot. I gave it more thought and looked at the elevation change. The 1st half was 1900 ft with a avg gradient 0.8% compared to the 2nd half which was 1200 ft and -0.8%. I suppose one has to compare full laps to determine splits. Wasn’t thinking straight last night…