Extreme difficulty increasing HR for high intensity bike sessions

Hi all,

Apologies in advance for quite a long post.

So I am a new, but decent cyclist, who specialises in 70.3 triathlon. Last year I averaged 20 hours training a week, about 12-14 of which was on the bike. This year I’ve dropped it down to 16-18 hours a week, with higher intensity, and about 10 hours on the bike.

I don’t use a power meter, or use any metrics other than HR and MHR, for which I use a chest strap. I realize this is not ideal but please bare with me. My MHR is 200, I’m 36 years old.

On a road bike with clipons, on a fairly hilly course (800-900m gain) I have most recently done a 2:25 90km (avg 37.5kmph) bike split. This was at 80% MHR (160bpm). I suspect I can actually ride at about 165bpm, and have recently picked up a TT bike, so presently it’s looking like I can hit closer to 2:15 for 90km. (~40kmph).

In cycling I struggle, even for 4min intervals, to get my HR over 155 (~77% MHR). Some of the most painful, soul destroying workouts I have done have been 12 x 5min intervals with 2min rest, with steady 160bpm for the intervals, this is only 80% MHR. My quads burn, pain is 10/10 and sheer willpower gets me through, but it’s altogether extremely unpleasant and not something I get excited about repeating, which is at odds to the general enjoyment of doing hard things, central to me.

Now compare that to running, which I’m also reasonable at, 1:20 - 1:23 during my 70.3 events. Running, I can relatively easily complete intervals, tempo, threshold, vo2 max etc sessions, where HR is anywhere from 160 - 190 depending on which session you’re looking at. Regardless of accumulated training fatigue I can go out and avg 160bpm for an hour on the run quite happily. If you asked me to do the same on the bike. I’d probabaly break down and cry - I was being quite serious when I said those 12x5 intervals were soul destroying, and amongst the most un-enjoyable things I’ve ever done.

This inability to do higher HR work on the bike is an issue! Especially when I’m trying to build more cycling intensity into my program, ie weekly interval, tempo, and fortnightly vo2 max sessions.

I’m hoping the brain trust here might have some idea of what’s happening, why, and how I can improve it.

Thanks in advance.

Just singeling in on this sentence. That is essentially a 60min (slightly supra-)threshold effort. Not surprised your heart rate would max out at 80%.

How have you tested max hr?

And have you tried a more standard VO2max session of 6x4 for instance with more rest in between (4+) that should see your HR go higher during the intervals.

ETA: You have determined a specific Max HR for cycling, apart from running right? Running heartreates will always (?) be higher then cycling, because you use more muscle groups.


HR is a funny thing. I’m no coach but to me inability to raise it to your max means one of two near opposite things. You are super fit and its nothing to worry about. Or you are overtraining and worn out and need to rest and is something you need to address :neutral_face:

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Caffeinated gels.

But seriously: how fast are you spinning? Try doing 5x5 with cadence >100. And if you want to do a workout with an hour-ish of hard riding, do longer interval durations with fewer reps.

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If I was in your position, I would follow the protocols coaches have posted online for determining max hr (simple version is warm up, max effort tt, sprint at the end until failure).

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The cycling workout you did is hard. Your fit and it is just an aerobic exercise for you. Running uses more muscles and your heart rate will have an easier time to get higher.

How to get your heart rate higher is to do longer intervals or to shorten your rest in between or increase your cadence.

I think the real issue is what is your goal with the workout.

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I’m kinda confused. Why do you wanna hit max HR on a threshold effort? My max is around 182 and The only way to hit that would be like sprinting very hard after a 1 hour very hard climb. Otherwise I top out at my threshold around 172 bpm and I have too much lactic acid for my heart to go on overdrive and do anything.

Maybe I’m misunderstanding? If you hit your absolute max, from my understanding, you wouldn’t be able to continue your threshold efforts anyway.

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Honestly, probably both. Muscular endurance well behind aerobic capacity, and also over trained.

Sorry 5x5? 5 intervals of 5min duration, is the rest 5min also? Cheers.
Cadence is around 70-80, I’m a powerhouse 100%. I lose speed at higher cadences, and I do do a lot of higher cadence work.

5 intervals each being 5 minutes long with 5 minutes easy spinning rest between them.

Sounds like you are doing the intervals outside on the road. That being the case, you just need to go harder for the five minutes, whether that means keeping your gearing as-is and pushing your cadence up or you need shift into your next cassette while maintaining 70-80 RPM. After 5x5 you should be wasted, no chance of doing 10 or 12 of these. Simply put you are riding too easy.

My suggestion, given your comment about your leg muscles, is that you should shift into an easier gear (one cassette) and push 90 RPMs. This will relieve some of the tension in your legs and shift it to cardio. FWIW, 90 RPM is what I use on the trainer when doing VO2 intervals; when doing longer efforts like SS or threshold I am around 97-100.

Five reps of 5 minutes full gas with 5-10 minutes of rest between sets. You said your goal was to increase your HR on the bike. Grinding away at 70-80 rpm for these won’t get your HR up. I’m also a “powerhouse” and can push 20-30 W more at low cadence or standing for these reps than I can at high revs. Find a slight upward incline and spin it.