Correlating heart rate, pain and watts (on the bike)

Triathlon Forum
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I’ve been using a computrainer for a few now and I’m trying to make sense of my perceived effort on the trainer versus out on the road. On the road, I’m never surprised, based on how much pain I’m in, by my heart rate. When I climb, it’s hard for me to keep my heart rate below 150bpm and 155-160bpm is a normal effort where I’m breathing heavy but it doesn’t hurt. I’m comfy.

The correlation is true whether I’m climbing on my road bike or aero on my tri bike. I think I have a good idea of pain vs. heart rate.

Now we go inside on the computrainer and I would expect the same heart rate to equal the same pain, but it doesn’t at all!

A heart rate of 160bpm while I’m on my trainer is very painful. I can sit on a heart rate of 160bpm outside for an hour during a climb and I’m “comfortable,” but on the trainer, I’m pushing really hard at 160bpm and I’m looking forward to my 5 or 10 or 15 minute interval to be over. My average heart rate during the bike in my last half-IM was 160 but I couldn’t imagine sitting on my computrainer and pedaling for 2.5 hours at 160bpm, I think I would pass out.

Or maybe I’m just crazy? Is this just an illusion because riding inside is boring?

What I really want to do is correlate watts with heart rate and pain inside and then take that outside so I can pace myself on my powermeter-less tri bike.

What’s going on here? Anyone else experience anything like this?

Jeff

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  1. Less convective cooling indoors - outside you are moving anywhere from say 10-30 mph. That air is cooling you quite nicely. A body likes to reject heat effectively. Convection is an efficient heat dissipation mechanism. Indoors you still have convection, but it’s a whole lot less. End result - heart rate increases in an effort to cool your body through additional sweating.
  2. Inertia at the wheel - the CT has a low mass flywheel. It requires more effort to maintain a constant speed against the brake. On the road, you have the inertia of the bike and you. That’s a whole lot of inertial mass compared to a small CT flywheel. If you modded your CT with a large mass (talking several tens of lbs, not just a couple) you’d start to creep into that road feel. See for example the Velodyne or Alex Simmons’ homebuilt trainer.
  3. It’s boring - Seriously, where would you rather be? Indoors or out? It will affect your motivation.
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But I’m seeing a lower heart rate given the pain, not higher.

Your second point makes sense, pedaling on the computrainer is relentless. But that begs the question: does X watts on the computrainer feel like X watts outside (with a powertap or whatever)??? Someone with both has got to know the answer to this.

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I’m the same way - my hr on the road is way higher AND it feels easier. I just can’t get my hr up on my rollers for some reason. Normally during the winter I ride indoors quite a bit (Ottawa is just too cold), but this year for some reason I just couldn’t get motivated.

I guess I’ll find out how much indoor riding really helps me in a couple of months, as I’ve only ridden indoors a handful of times. I also haven’t been xc skiing this year, so I might be in a whole heap of trouble. Having a new baby is not conducive to lots of training as many of you guys know…

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I think tigermilk might be on to something with #1.

There is a study that shows a very high correlation of perceived exertion to cooling effect around the face/head area.
Try putting a household fan a few feet from your head and turn it on high and do the same exercise with the computrainer and see if there is a different heart rate correlation to perceived effort.