Zone 3 Bike vs. Zone 3 run | 80/20 Endurance

Zone 3 Bike vs. Zone 3 run

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    Curry Gallagher

    My HR on bike is much lower than running for the effort level than I am putting in. I’ve read that can be common for those entering cycling from a run background. Zone 3 running is much easier (RPE) for me even at a higher heart rate (+15 though +20) than zone 3 cycling.

    On my third LTHR test yesterday, my average HR over the 15 minutes came down again and substantially. I know it was too high on my first test and would come down on my 2nd test as I could tell from my workouts using that original metric.

    I am using the same resistance on the same dumb trainer as I’ve used before (I really need to get outside for this test). I was absolutely working hard and my gearing was higher and therefore speed as my cadence remained steady, maybe dropped a little. I feel like its my legs that are struggling on the bike, not my breathing or cardiovasular system.

    Is this common to many? Is this me gaining fitness? Was i just more fatigued yesterday? Do I just not have cycling legs built up?


    I also transitioned from running to cycling to triathlon. I think you experience something totally normal. I had the same thing happening. It will take a while till you build the strength und muscular endurance for cycling. You’ll get there though!


    David Warden


    Totally normal for bike LTHR and run LTHR to be different. Even for an experienced triathlete run will be 5 beats higher on the run than the bike, and for a new cyclist 10+ beats is common.

    If your LTHR is going down… that’s not bad, not not necessarily good. It’s good if your LTHR is going down for a given or higher power output, that’s ideal. Even is power output is the same and LTHR is down, ok, that’s neutral. If power is dropping and LTHR is dropping, that’s fatigue, or something else.

    On your dumb trainer, you really can’t confirm*, but no need to panic. Everything you have written about is normal.


    *You can hack your home trainer to be a power meter by using a speed sensor to your rear wheel. As long as the PSI is exactly the same every ride, and as long as the contact point/pressure is exactly the same every time, then you have a consistent measure of output and can use speed as your power meter. So, if your LTHR test has you at 165, but your speed went up by 0.5mph, that’s progress. It’s really hard to keep the environmental factors always exactly the same each ride for this to be accurate, but it was my first “power” meter setup many years ago and worked fine.

    Curry Gallagher

    Thanks guys. I didnt know about tire pressure needing to be exactly the same for the dumb trainer rides. I have a speed sensor on back wheel which i was using in Sufferfest over the winter for virtual watts.

    I was a little bit wrong about what I thought my run hr is. Since i did the run test yesterday, i noticed that my 20 minute run HR is only about 10 bpm higher on average than my 15 minute bike, not the 15 to 20 i thought it was. My max hr hit was about 12 bpm higher on the run than the bike.

    Is it easier to get HR up outdoors? It seems that way.

    Did 6 x 2.5 minute intervals in zone 4 today (CAn4) and was hitting that zone with no issue on an outdoor ride today. Whereas indoors, I’ve struggled a bit to hit let alone stay in the higher hr marks during some of these workouts, not just cause of lagging HR monitor either.

    I have to note that I felt much faster and very comfortable in upper zone 2 during that portion of the ride. I feel like I am working much harder on the trainer in upper zone 2. My outdoor cadence seems much higher too. Comparing to outdoor rides last year, I feel much stronger/faster. Looking forward to the upcoming longer zone 2 intervals.

    David Warden

    Curry, great update. It’s also completely normal for indoor HR to be 5-10 beats lower than outdoor, both for run and bike.




    I have a dumb trainer (cycleops fluid2) and I was thinking of using it as David mentioned above (speed as power meter).
    Problem: at a sustained speed, this trainer is known for increasing resistance over time (maybe because it warms up).

    Recently I’ve found a test with this trainer and a power meter.
    The guy sustained 90rpm (with the same gear) and the output measured power went from ~245 to ~315 in just 8min!

    So, in my case I’ll keep using heart rate zones..

    By the way.. my biking LTHR is about 10bpms lower than my running LTHR.

    • This reply was modified 1 year, 9 months ago by Liandro.
    Curry Gallagher


    I also have a cycleops and that makes total sense. I’m on the struggle bus on that thing for harder/longer workouts. So much better out on the road.

    So, it sounds like you all are recommending that I purchase a smart trainer. I’ll make sure to blame you all when I break the news to the CFO/wife.

    I’m thinking/hoping that next week’s weather will cooperate for me to do that LTHR test outside on the road.

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