Biking Heart Rate Puzzle

HR is a trailing indicator of how much oxygen your muscles need.  It doesn't go up because you're exerting yourself, it goes up because your muscles etc. need more oxygen and your cardiovascular system is responding.  Higher HR, faster breathing, etc.   And HR and breathing feed into "perceived effort". I've heard plenty of stories where run HR is high but bike HR is low, for the same perceived effort.  And often, it's the perception of effort that is wrong and not the HR. 

Are you really pushing yourself just as hard on the bike?  Running uses many more muscle groups than cycling (which is mostly legs, and maybe just quads if you're a "masher"),  Running uses your arms, your glutes, your hamstrings, quads, even calf muscles in ways cycling does not.  So it's not a surprise that running feels a lot harder, but is it, objectively?

Are you familiar with the 10 point RPE scale and zones?  I did some searching and like the image posted below for discussion purposes. There are many like it, and the terms vary a bit, but it's pretty mainstream.

If you're at "threshold pace" then you're in zone 4, which should be RPE 7 to 8, which means you can speak sentences but not paragraphs. Long sentences = RPE 7, short sentences / phrases = RPE 8, word or two = RPE 9.  Or, for me:

RPE 7 = moderate marathon pace
RPE 8 = hard marathon pace, half marathon pace, 10K pace
RPE 9 = 5K pace
RPE 10 = last K of a 5K

I am going to go out on a limb and say that your "threshold run, one hour, 140 avg HR" that's actually a RPE 5 or 6 "tempo" run, and that you're not pushing yourself as hard on the bike.  And watch your form when cycling.  You may be mashing the pedals like a stairstep machine, which would be using mostly quads. I also find that there is a "tipping point" on the bike, where below a certain pace like 17 mph my HR is low, but just trying to push what seems a bit higher (20 mph) and my HR goes up by 20, 30 bpm.  That's the "threshold" we talk about.

What is your running pace at HR 140?  What is your cycling speed at HR 100?   If you push yourself to HR 140 on the bike, what speed is that? Do you also experience a tipping point? 

(this image looked much better locally, and I have to go now, so you may need to zoom to read it)

(rpe-with-zones.jpg)

If you are not that familiar with HR training, perhaps you should use LTHR and do the related run and bike testing (linked article).  This will provide you with your approx. HR Lactate Thresholds and HR zones that are calculated from each test. BT has a the LTHR zone calculator (see 'Hello, your name'/Settings/Training log settings/HR zone manager). The testing can be done outside or inside (trainer).  There will be a difference in the threshold results as running supports more body weight and uses more muscles.  I have about a 6-8 bpm difference, I knew someone that I once trained with that had ~20 bpm difference.

I used HR on the bike trainer only for a short time then I switched over to virtual power, IMHO a better way to train on the trainer if you plan on doing intervals as it removed the lag issues. requires a few items such as an ANT+ speed sensor, ANT+ USB Dongle and a laptop/PC, software and a trainer that has a known speed vs power curve. If you plan on just doing long sustained trainer rides then HR can be used, still not ideal.

You might have missed the "virtual" part of "virtual power".   Virtual power is wattage calculated by software based on what kind of trainer you have and RPM, and not by an actual power meter measuring device.  TrainerRoad was one of the first, and still one of the best.  Check it out: https://www.trainerroad.com/virtual-power

Cost is about $10 a month, once you have all the stuff Donto listed.  Works really well for indoor training.  Of course, once you're training inside with power, you want power outside too.  But it's an easy way to get into power, and nothing you buy is throw-away. 

I use MaximumTrainer program, its only $15 per year.  Yes it is limited on the rides available but comes with the BT Winter Cycling Program built in as well as a few other rides from a coach.  I also have Marc & Shane's Power Mentoring 13 week long workouts for it.  That's all I need!