HR low but legs wouldn't go?

I done spruce knob on Monday( 2 x 30min SS) with a few standing interval and felt strong. I then done Baird +6 the next( wasn’t planned) and found it brutal but just finished it even though it is only 90sec vo2 stuff. On Wed I done an hour endurance, took Thursday off and tried palisades today but only managed 3 out of the 5 I intervals. Started the 4th but would not have finished it so didn’t want to bury myself altogether. One thing I did notice is that my HR was obviously high today but didn’t reach 180 and my max is 186!!( For eg the last 8 min ftp test I done I spent 5 out of the last 8 mins above 180??Why is this?? Is it because my legs are fatigued today.

It sounds like fatigue to me. HR is a fickle thing but when you are fatigued, your HR may not get high but you legs just can’t put out the power that it has in the past.

You say you added Baird +6 on an off day. How does that trend with your previous weeks? Did you accrue more TSS M-W than weeks previous? If you accrued significantly more TSS this week than previous that sounds like your culprit. If you are going to add a ride on a day off, I would suggest doing something like Petit or Dans. Some kind of low aerobic workout. Adding intensity to an off day is a sure fire way to effect workouts later in the week.

1 Like

No science to back this up, but you might consider that your heart is fatigued as well and doesn’t want to increase rate, which increases myocardial oxygen uptake. I notice when I’m barely making it through an over/under of VO2 workout, My heartrate won’t get up as high as earlier regardless of how much power I’m putting out.

1 Like

You threw in a hard v02 max session on an off day… theres your issue. Its simply fatigue and not correct programming. Put your stuff into plan builder and follow it i say, sometimes you may want to do more but you get better during the recovery days.

If you feel like you want to do more just up the % on the workout thats assigned for you?


Lower then usual HR is a sign of fatigue. Looking at what you’ve been doing its not a real surprise you struggled.

1 Like

I’ve had similar experiences, where my heartrate doesn’t seem to rise, and my legs just have no gas, and I’ve come to attribute it to fatigue.

The following analysis is based on an n of 1, and all of the biological knowledge that comes with a degree in economics, and years of working in construction, financial analysis, BI, data governance and welding (not necessarily in that order)…

I’ve always felt like my heart will be exactly as fast as it needs to in order to deliver oxygen, nutrients, remove waste, cool the body, etc. while doing work. When I’m in an interval, and my legs don’t feel like they have the power I’d expect, or I’m struggling to complete that interval, I’ve often noticed that my heartrate doesn’t climb quite as high as I would’ve expected. On the trainer (in erg mode) that usually tells me that within a few minutes I’ll either be dialing back the intensity, or reaching a point where my legs will just no longer turn. On the trail, it means my pace won’t be quite what I’d expected; I’ve hit the ceiling of my work output for that day.

In my mind, if my heartrate isn’t up to where I would expect on past experience for a given intensity, some aspect of the workload that drives it higher isn’t at a level that justifies the higher rate. This could be driven by a number of factors, but if I just don’t have the legs for a given amount of work, I know I’m too fatigued. No clue if it’s biologically accurate, but it’s helped me turn what is often an unreliable variable into something that can give context against the backdrop of other data.

  1. The heart is a muscle. It gets tired too.
  2. I was experiencing something similar last fall. I was faster than ever but my HR was never maxing out. Sometimes on very hard 1-2 minute vomit inducing efforts I wasn’t getting much over 170 when my max is a hair over 180.
  3. Don’t always trust your HR monitor. I started getting hair brain results from mine and I washed it, fresh battery, all of that and still was bugging out.
  4. Related to number 1 I’ve read that a symptom of over training is the inability to reach max HR. Ian Boswell was just interviewed on the cycling podcast I think and he said, after retiring he hit his highest VO2 number ever and was able to reach max HR again for the first time in years. He blamed over training. He’s on another level but I think the same holds true for non-pros.

I’m always doing bodychecks during my hard(er) workouts.

So sometimes, after a swim with lots of kick sets, the next day i’ll feel soreness in the legs right away in the first interval. That usually tells me that it might feel harder than normal as muscles will be a bit more tired than usual.
Heart couldve kept going but the muscles were just overworked.
Proof of that this week,
Monday had Dade +1 (vo2max)
Tuesday had Master swim club with a shitload of kick sets which got my legs pretty tired
Wednesday, after these 2 days, my rhr was about 5-6 beats higher than normal/recovered RHR
Mt Hale was on the schedule (suprathreshold) which i normally would be able to completed. I ended up doing 3.5/4 intervals, but i felt soreness/muscle unhappiness right from the first interval onwards.
HR was normal but legs just didn’t wanna keep going.
Thursday, i look at my RHR its gone down (as in it’s recovered a bit) so my heart was fine, just the legs were fatigued.

If you can’t get your HR up because your legs can’t cope it is fatigue…pure and simple…on the plus side unless you dig yourself a very big hole a day off or two should cure it!

1 Like

Yeah, thanks all. During my 2 x30mins SS I also done about 10 mins on the 2nd interval at a low climbing cadence so that also could have been a bit of a shock to the legs maybe too.

Yeah, I took a day off and done 2 x 30mi SS Intervals this evening and felt great. Added 5% into workout so things moving along nicely. HR avg was 156 first 1st interval and 163 for 2nd interval. A bit of decoupling but I’ll deal with that for now.

I concour with everything said above. More stress = more fatigue and not enough time for recovery. Your heart is a muscle and needs that recovery as well.

We know this but continue to push the envelope of what our bodies can take