Why is my HR higher outdoors?

I have been noticing that my heart rate is higher outdoors for the same wattage. I use the same power meter indoors and outdoors (vector 3s) and calibrate it before every ride. I noticed that it is easy to maintain a steady pace on the trainer but I don’t maintain a steady pace outdoors. Could that be a reason? how do I keep my pace steady on an outdoor ride especially on rolling terrain and strong winds? On outdoor rides, I can easily go over my FTP and even go into anaerobic zones which rises my heart rate.

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Hills, heat, humidity to name a few

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I suppose this is potentially a couple of questions…

  1. Why is your heart rate higher outside for the same power; and
  2. How do you keep a steady pace.

The second one is easy, you can’t. You’ll go faster downhill than on the flats and uphill. If you mean how do you keep a steady power, that’s a different question. The answer is usually - gearing! If you find yourself going over FTP when going uphill, and your cadence is sluggish, get easier gearing. There’s no shame in it! An easier gear will mean you can spin more uphill and, more importantly, go uphill at a lower power.

The first, isn’t so easy. I am the same. I figure it’s one of, or a combination of, two things:

  1. You’re a lower inertia rider who finds it easier to ride on trainers (that’s me, my FTP is about 10% higher indoor than outdoor); and/or
  2. Riding outdoor uses more muscles, as you’re balancing, moving around etc, and as a result, energy expenditure is higher and so is heart rate.

It would be helpful to have some numbers to understand how big the difference is between outdoor and indoor

I think you answered your own question. If you are trying to do sweet spot intervals at 90% FTP but every 2 min you spike up to 110% then your HR will definitely be higher than during a straight 90% interval. Also outdoors you may be using more muscle to balance, turn, avoid potholes, etc.
Learning to stay steady during rolling hills and wind is a skill that takes time. You’ll get better at it the more you do it. You get better at anticipating the hills and at the slight changes in RPE that allow you to adjust faster

above: outdoor ride full of rolling hills.

above: indoor ride. Managed to keep it steady for the most part and little to no coasting.

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Thanks for the pics but it’s really difficult to see as all we have are the averages. But based on those, nothing looks too odd. Outdoor ride 204 watts at 150 HR. Indoor, 194 watts at 142. Not hugely different and within the realms of day to day drift…

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And you did a 5 hour indoor ride?!?! Wow, well done that man

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It’s hard to say based on those two rides if your HR is actually higher outside. Yeah the average powers are pretty close to eachother but the seems to be because there are a couple stops and either dropouts or your head unit autopauses. But these zeros would pull your average power down a decent amount. It’s probably more accurate to look at the NP for the rides. When you look at that the outdoor ride is 227W/150HR and the indoor ride is 199W/142HR. Which seems about right to me.

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Thanks! it was a 5 hour zwift group ride. Glad to hear that it is normal.