Heart rate spike on long rides

Hello friends

Today I did my first long ride as part of long distance triathlon plan. It was the Town Hill 2h45min endurance at 70-75% intensity.

I tried to keep up with my hydration and nutrition plan but towards the second part of the ride my heart rate saw a spike and jumped from a 140 avg to 152 while power didn’t change. Even when power drops slightly the HR will stay high towards the last 45 min.

How can this be improved via training as I need to ride 5+ hours at the same intensity and not burning too many matchs on the bike leg. Or is it the nature of indoor training with the heat and sweat?


HR drift over long endurance rides is pretty common. As you do more training specifically base work that % drift should go down.

Also worth noting that a lot of things impact your hr especially over the course of a long ride inside. Keep up with your fueling and hydration and temperature control to the best of your ability.

It’s called heart rate drift. Keep doing more endurance rides to improve. One way to go is to ride by HR. Keep it at 140 for the whole ride even if you need to throttle power down.

Check out the polarized topic:

In other words, your HR and power decoupled. That’s quite normal given it’s your first long ride.
After a few long rides at that given wattage, your HR and power will stay together more and more (within <5%). TrainingPeaks calculate that for you. https://www.trainingpeaks.com/blog/efficiency-factor-and-decoupling/ i haven’t seen it on TR.

Once you find you’re “coupled” then you increase the duration or increase the wattage. Rinse and repeat.

Once my IM race approaches, I look at which power I can hold for 4h with < 5% of decoupling. that becomes my race target power.
Training your IM bike leg is not just about increasing FTP ; you also need also to extend time at effort (muscular endurance) and train your arms, neck muscles to stay in aero, etc

As for how to train it:

  • long steady ride every week with increasing duration
  • do them as steady as you can That means VI < 1.05 (NP/avg power) = no matches burning
    Of course, it depends on the course and how hilly it is. If it’s hilly, still keep it below FTP.

Hope it helps,

P.S.: Here I assume that hydration, cooling and food were all fine & constant. (if you didn’t fuel continuously and instead ate a bunch of food all of a sudden then I would blame your digestion).

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Thanks for the insights.
Once I get a power meter I also want to get a sense of HR and power outside versus indoor. Too bad I didn’t have it in Ironman Copenhagen last year as I kept my heart rate pretty steady throughout the bike leg.
I guess one alternative would be to incorporate 1 to 2 min rest inside the lond workouts to help bringing the Heart rate down a bit?
Regarding POL training I think the intensity of those long rides on training road are above the Zone 1 or even 2 as its about 75% of FTP. I can’t imagine riding any stronger for IM distance so it is a steady state rather than low aerobic ride.

And by the way there was a LOT of sweat in the saddle that I observed for the first time being seated for 2h45

hydration issue could make your HR spike and heat even more.

Your IF during the race depends also on how fast you go and ensuring you keep energy for the run.
Let’s say we both ride at 70% but it allows you to do 180k in 5 hours while it takes me 6h. 5h @ 70% is 250 TSS allowing you to have a good marathon. 6h @ 0.7 is 300 TSS and I should back off a few % or walk the marathon.