High heart rate but no leg exhaustion

Dear TR experts,

I started TR in January after a decade or more of drinking, smoking, and all other kinds of unhealthy habits. Needless to say, it was time for a change. I’m very happy so far with both the app, community and my personal progress. I started out with an FTP of 177 and have brought this number up to 220 (used ramp test in the beginning but I’m now using the AI since they are so close to each other).

In the past few weeks, however, I have been broken by some workouts and outside rides where my HR seems to skyrocket, regardless of the interval effort. Determination is not the issue here, I find myself having to abort intervals because otherwise, I’d faint. The strange thing is that my legs don’t feel heavy or exhausted at all, it’s almost as if my heart just can’t follow my legs. To give some numbers, my rest HR is 48, my max HR is 205, I rode an interval today where I was at 195 for 10 minutes at which point I started seeing black spots and had to lie down on the floor barely remaining conscious.

I’m a bit at a loss on how to proceed, I’m failing workouts and am left with low morale while my legs feel fit. Does this mean I should focus more on Z2 work, longer but less intense workouts? Is my FTP too high, even though it doesn’t feel like it? Could this be due to nutrition?

FYI I know nothing about the science behind all this, even FTP is a relatively new concept to me so any advice would be greatly appreciated.

Thanks in advance!

At what cadence are you doing these workouts?

Fluctuating between 95 and 100.

My guess is that your heart needs more conditioning at z2 or even at z3 as your leg fatigue seem nonexistent. Your leg muscles have adapted quite well but your heart is behind.


Firstly, a huge congratulations to you! You’ve taken the first, and the biggest step. It will change the rest of your life. :clap::clap::clap::clap:

We have very little information here, but my first guess is that you’re simply so motivated to make this huge change that you’re trying to do too much too fast. If that is the case, it’s a slippery slope, where you could end up overtrained or injured. I know we all love to hear our favorite athletes talk about pushing through the pain, no pain/no gain, etc., but in reality, you should absolutely not be feeling frequent pain, nausea, lightheadedness, etc.

They key to getting fitter and faster is to take a long term approach and focus on consistently working out, taking the time to recover and adapt to the work, and not falling back into old habits. You spent 10 years getting unhealthy, don’t try to get it all back in 6 months.

I’d suggest building a plan that has 1-2 harder workouts a week surrounded by 2-3 relatively easy workouts. Give yourself a couple days off the bike to adapt and recover. Focus on consistently working out and recovering rather than on trying to kill yourself to make fast gains. Better to be consistent over a long period of time than to end up injured and not working out.


The only thing I’d add to the excellent advice from @Pbase is to say it’s never a bad idea to consult your doctor as well. Always good to eliminate any health problems early on so that you can focus on your training without having to worry.

Can you be more specific about the intervals? Instead of naming the TR workout, could you describe the interval %FTP and duration when you were hitting 195bpm for 10 minutes?

Your 195bpm is 95% of HRmax (your 205bpm max).

For example I will hit 95% HRmax on 10 minute intervals at 104-110% ftp. That is expected for some, for others it might be a little lower.

What you saw today might be normal.

Depending on the workout your legs could feel fine (relatively speaking). The force involved in a typical pedal stroke aren’t especially high relative to every day tasks (walking, going up stairs, etc).

It’s an aerobic activity and it can be limited by the heart (and lungs) but it can also be limited by local circulation limiting oxygen in and moving metabolic byproducts elsewhere. It won’t necessarily be both at once.

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If you’re literally seeing spots and at risk of passing out, it might be more than just fatigue or similar. It could be an actual heart problem like a-fib or another arrhythmia. Probably not, but be careful. Passing out on the bike is dangerous.

Is your resting HR normal? Or slightly elevated? If up from normal, you could be getting sick or overtrained.


Today it happened at a 10 minute interval at 104%, I attempted the second interval but was forced to stop after a few minutes. Earlier this week, however, I had the same issue on a sweet spot at 94%, after a few intervals. I found myself extending the recovery valleys from 30s to 5 minutes to cope. Last week I had a 4h outdoor ride (with somebody who’s a lot faster than I am) where I basically rode half the time at 175. I have no power meter on my outdoor bike but the ride absolutely destroyed me. Again, my legs did not feel like the problem.

If riding at these heat rate levels for certain durations is normal, it sure feels like my weakness at the moment. Is there any way I can work on this? I was thinking of maybe trying a traditional base?

Thank you all for the advice (and the welcoming words @Pbase), I will definitely try to look at it more as a long-term investment.

I will also heed your advice on consulting a doctor, better safe than sorry I suppose. My goal is more to have fun than it is to become fast.

The most troubling thing is that, in the beginning, having really heavy legs after a workout was a great motivator and gave me a good feeling. The fact that I’m not feeling that anymore worries me a bit and makes me think I’m failing below what I could do, even though my heart tells me otherwise. Maybe I should be happy that my legs are actually getting stronger.

Perhaps one final question if you’ll allow me; how do your legs usually feel after workouts and the day after? Do you often feel the sting when walking down the stairs or is that typically more of a beginner thing?

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You have gotten some great advice here but the one thing that seems to be missing is base/Z2 work. You’ve talked about no workouts below sweet spot and an outdoor ride that destroyed you. You’r only 3-4 months in and you have not done any base work. If I were you, I’d back off on the workouts and do 4-8 weeks of base work.


Mine generally feel fine after bike workouts as far as general walking around. If I finish a workout and an hour or two later ride (commute) somewhere then they’re tired; noticeable if I’m running late and need to ride somewhere uphill. But outside of that scenario it’s not very noticeable.


My legs almost never feel cooked unless I’ve done 100 miles or something epic.

Day to day, it’s much more a feeling of general fatigue that makes me want to go to bed early.

If you’re after a leg burn, you’d be better off doing squats. They’ll help your cycling too!

Thats about half of a 20-min ftp test at the lower end of target pace. For myself, hitting 95% HRmax while riding above threshold is not too alarming.

Here is my feedback, using a story to give it. I spent a lot of time at a desk for 30 years, not very active. Then had a health scare or two in my late forties / early fifties, walked for a couple years, and then got into cycling. My starting ftp was probably 160-180W, it definitely drops down to around 180 if I take a month or two off the bike. Pretty easy in the beginning driving ftp up to 220-240, simply by consistently doing twice a week hard/all-out spin classes at the gym plus an outdoor ride on the weekend.

Then I bought a road bike and did some centuries and the following year did a double century. Pushed ftp up to 275. Pretty good fitness on about 7 hours of riding a week, with “just enough” structure. I was constantly modifying plans and doing fewer intervals, based on how I felt. It worked.

Then I figured “more structure would be better!” and spent two years on the trainer doing lots of intervals, dropped down to 5 hours/week, and got slower, lost 10-15% of my ftp and more importantly also lost my short power punch.

What fixed that, and improved my overall health, was to increase riding back up to average 7-8 hours/week and doing mostly endurance / zone2 / lower-intensity riding. Perhaps not so surprisingly, reducing intervals and doing mostly low-intensity riding was key. Over 3 years of doing that my power increased back to where I was for the double century. More importantly my resting heart rate dropped 10bpm and heart rate variability increased from low teens to low thirties. Nowadays it takes a lot more high intensity work to drive up my heart rate. Overall healthier, and faster. Perfect combo.

The moral of the story - never underestimate the power of low-intensity riding, never underestimate the impact of off-the-bike stress on your health and ability to recover on the bike, and never overestimate how many intervals you should be doing. Both the heart and legs respond to lower intensity exercise. But the question is how much low-intensity do you need to get faster and healthier? Well that depends on your genetics and your training background. My numbers - averaging 7-8 hours/week and pushing ftp up to 275 - well that worked for me over a 3 year timeframe. Somebody with better genetics, healthier, and a longer training history might need 15 hours a week, and they are better off doing more intervals on my 7-8 hours/week.

I wish you well on your fitness journey!


By the description from the OP I would worry about this exact thing. A friend of mine had this happen and was throwing himself into SVT. Talk with your doctor. Consider a holter monitor and possibly a stress test.

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A few ideas:

  1. How did you determine your FTP? Your FTP may be set too high, in which case the 10 min interval above is more like a solid VO2max interval instead of a slightly-above-threshold interval. This was the case for me. I now take the ramp test result, and reduce by 5%.

  2. Your limiter may be your cardiac capacity, not your muscles. I am in this same boat. I have never paused a workout or reduced the workout intensity due to leg fatigue. It has always been because my heart can’t pump enough. There are a variety of reasons for why this might be the case. For me, I think I just have a small heart, and may also have some mild atherosclerosis (a number of medical tests over the years have led me to this conclusion). Echoing a few of the posts above, worth going to a doc to get some heart diagnostics done (eg stress test, EKG, calcium scan).

FWIW, about 80% of people are limited by muscle fatigue in a ramp test. 20% by heart/breathing.

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Definitely see a cardiologist. I have had a cardiac ablation to fix SVT 5 weeks ago. Back to riding and no high heart rate.