QUESTION: Hello: I am trying to reconcile my power and heart rate data. During a 2022 New England hillclimb, my normalized power for about 90 minutes was 193 watts, and my average heart rate was 168 bpm. During a one hour indoor training ride this weekend, my normalized power was about the same at 196 watts, but my average heart rate was only 139 bpm. Why would it be so much lower for about the same power? – Mark G
RBR REPLIES: This is an intriguing question, because usually you hear cyclists report that they can achieve higher power numbers riding outdoors compared to indoor training.
There could be a few reasons why your heart rate was lower during your indoor training ride despite having a similar normalized power compared to your New England hill climb.
Environmental factors such as temperature and humidity can affect your heart rate. For example, if your indoor training setup was cooler and less humid compared to the New England hill climb because you have good AC and fans at home, your heart rate may have been lower because of that.
What was the race itself like? It is possible that you blew up early in the hill climb and were pushing much higher watts in the beginning and then dropped down to a much lower wattage on later parts of the climb after you blew up? This could give you a lower normalized power for the overall hill climb even with a really hard start.
Are you using the same bike and power meter on the trainer that you used in the race? It it possible that the power meter on the trainer had not been calibrated with a zero offset? Is it possible that the bike on the trainer was using estimated power and not measuring your actual power? I’ve seen stories of riders winning Zwift races riding a trainer with no power meter because it was exaggerating the estimated wattage.
Instead of just looking at your raw normalized power number, have you looked at your watts per kilogram? If you check your watts per kilogram, you can compare that to the wattage for a typical Zwift A, B or C racer, and then also check it against a typical USAC racer in your category for a reality check for both rides. Which ride seems more reasonable as far as w/kg?
Is your fitness different now than it was then? It is possible that you’ve been training a lot since that race and are just fitter? It’s possible to get quite a bit fitter in a matter of months — and also to lose fitness pretty quickly if you stop training.
Readers, did I leave any ideas out?
overtraining can impact heart rate too.
There is more resistance on a trainer than on the road. Basically, out on the road, you are pedaling directly via chain onto the rear wheel. On a trainer, there is a transmission and other mechanicals that take away power “to the rear wheel” therefore it takes more power to pedal through these added inherent resistances on the trainer
Hi RBR: This is Mark G with replies to your questions: My indoor setup is roughly 65 degF with fans, and the race (MWARBH) was about 71degF to start, and decreasing over the course of the climb to the 50’s. My wattage was pretty consistent, from 240 normalized power at the start to 193 after 90 minutes, with a nearly straight-line decline over the 90 minutes (i.e., no blow-up). I use the same bike and crank-arm power meter both outside and on rollers inside. Both outside and inside are measured with a Sigma bike computer, and I also use Rouvy inside. My watts/kg is similar both inside and outside. I was actually fitter for the race, as I’m just starting to resume my training as of January. In response to Gen, I suppose I could have overtrained. In response to bike Fitness Coach, I use my road bike both inside and outside. Any additional thoughts? Thank you.