mschwett 

specifically, climbing vs flats. not due to fatigue or time of day, this is for me a universal phenomena:

physics (calculated via bikecalculator.com of course) tells me that going 6.5mph up a sustained 7-8% grade at 80rpm in my lowest gear (42t chainring and 42t big cog) takes 240w. that's pretty much what my power meter tells me too. it's hard as ****, and i can do it, but not happily, and after 15 minutes or so of it, my power starts dropping to 200w or so, and eventually further.

the same physics tells me that on flat ground 240w gives me around 22mph. again, that's pretty much exactly my flat no-wind cruising speed, so real life matches the physics closely enough. cadence is around 80rpm on my second smallest (12t) cog. but in that scenario, i feel like i'm at a sustainable power level for a long time, a comfortable but energetic hard cruise. i've done this around the public cycle track for a long time, limited only by eventual boredom, since there's no scenery or hill to get over the top of.

Carbonfiberboy 

I think it might be the phenomenon which makes captaining a tandem so much harder than riding a single at the same apparent effort and HR. On the flat, your legs get a tiny rest every pedal revolution. On a climb, there's weight on your legs the whole time. It's called "crank inertial load" - google.

mschwett 

interesting! seems like the scientific jury is out on whether inertial load truly affects performance, but there seems to be some consensus around a psychological impact at least.

Iride01 

I think because time is part of it's calculation and depends on how much mass is being moved. You can change gears on your bike and still put out the same number of watt's. If you shift to a lower gear then you have to pedal faster. If you shift to a high gear, then you have to pedal slower to maintain the same power.

So when you try to maintain a particular power, don't forget to shift when the conditions change and your legs are giving out whether from too fast a cadence or too much muscle you have to put into the pedals.

mschwett 

here's a real world example. one week apart - no meaningful change in fitness or weather. the grade is a little less (and slightly variable) than my hypothetical, but the average power and heart rate for these two 12 minute efforts is virtually dead on. both were during a 1.5-2 hr ride after a day of rest. slightly higher rate for the laps is because of slightly longer interval since i took morning meds, which slow HR down from what you'd "naturally" expect it to be. if someone told me i had to continue the effort on the left for 7 more intervals, for a total climb of 4,000 feet, i'd go home. the effort on the right i know i could continue for at least 8 hours with steady intake of food and fluid.

GhostRider62

Alls I can say is 243 watts average on 107 BPM HR over 2 hours is damned impressive. Damn. If you are young, your FTP must be at least 400 watts.

For me, the load seems unrelenting on a climb and the forces on the muscles are a little different than on the flats. It feels a little harder at the same load, even when very fit (for me)

mschwett 

i wish lol. 47 y/o. my absolute max HR is 135. heart rhythm issues. FTP around 265, i do have decent endurance at near/threshold levels.

GhostRider62

Ah.....an old diesel like me.

rm -rf

I got a Kickr trainer this winter, and I have a Stages powermeter on the bike. It's way harder for me to keep the same watts range that's quite normal on an outdoor ride. Even though it can coast and has a heavy flywheel too. Surprisingly harder.

mschwett 

right, probably analogous. on flat ground you have that little tiny reduction of resistance every time the pedal goes around that Carbonfiberboy referenced, and you can also coast or cruise at a reduced power for a few seconds or longer without speed taking a huge nosedive. going uphill (or on a trainer with a heavy flywheel, i assume) if you let up, you come to a halt pretty fast. it's just surprising how big of a difference it seems to make.

Carbonfiberboy 

That's really interesting. Indoors, I ride resistance rollers as you probably know. The drums are ABS, so there's little inertia in the rotating mass, hence crank inertial load is very low. I've adapted to this over the decades by smoothing out my pedal stroke, which is what everyone says happens to folks who are habituated to rollers. I consciously try to reduce pedal force by spreading out the pedal force over more degrees. Hence I don't notice any difference in effort w/r to power between indoors, flats, and climbing. As an endurance cyclist rather than a crit or TT racer, climbing is my focus, the only thing that really matters. Thus I do the much-derided OLP and low cadence high power intervals which definitely improve my climbing. Since I'm a slow climber, that's definitely a low inertial load environment.

I think this paper: https://rcnl.rice.edu/PDFs/jb2002.pdf
adequately explains this reasoning.

Carbonfiberboy 

As the OP quoted in post 3, "Peak crank torque was higher during cycling at 90 rpm with high compared with low crank inertial load." Reducing that peak torque is the reason that cyclists prefer a higher cadence on the flat, i.e. their freely chosen cadence increases.

burnthesheep

You'd have to have a God awful CdA and CRR combo to only go 22mph on 240w on a flat road. Like, you'd need to be up on a mountain bike or Dutch with Gatorskins or knobbies.

So, the physics is off on your estimate. You're putting out less than you think at 22mph, and can thus go longer.

In either case without a good meter, it's still guess work. The hill is closer to reality, the steeper it is. But you'd still need to lookup the CRR of your tires. Flat? Nah. It won't work out without one.

GhostRider62

I got a Neo Smart Tact2 recently and it drives me crazy. It is like it is constantly hunting putting little peak torque values into my muscle fibers.

I hate the thing.

mschwett 

really? i’d like to see some data on that, the sources i’ve used mostly agree with this. 240w = 20-22mph:





obviously i am using a power meter for the ride data, not just making it up. of course it could be off, but it matches the bike calculator estimates almost perfectly for slow climbing, which is a pretty simple exercise:

GhostRider62

I am not sure about that on a normal road bike on normal roads with typical parameters....on a TT bike, I can do that in around 185-190 watts.

It would take around 260 watts for a 190 lb rider, 20 lb bike tp go 22mph, Crr 0.005, CdA 0.360 m^2 with Rho 1.22 kg/m3

burnthesheep

The one you posted has zero input for your CdA guess which is the largest influencer on power demands at a speed like 22mph.

The one you posted makes gross assumptions about CdA based on selecting 'drops, bar tops, aerobar' and doesn't even tell you what it is.

I got 225w for 22mph at a pretty soupy thick air density and a 0.320 CdA for road riding. 15w would easily be enough less to explain the longer amount of time you can ride on flat land.

Either way, where's the flat land version of what you just posted for the ride? As you said at that speed you could ride a longer time, you didn't say it was the same power. So it would be helpful to post the same exact thing at the same power for the flat route. Because then we could look at things like your HR ramp over time for the same power level, and note things like the outside temperature that day. Or what mile of the ride you were on for each day. Which could affect the physiology of your time to exhaustion at a given power level.

Either way, this is a more legit calculator.
Cycling Physics Calculator

burnthesheep

Kinda my point, even if we don't agree on the inputs to the calculators. We don't know his CRR or CdA. And 1.22 air density is pea soup.

Changing either just a bit would provide enough difference to explain the time to exertion.

Which is why I just now asked him for the same kind of data for the flat ride. So we can see that the power is the same and see how the HR ramps over that time.

mschwett 

thanks for the link - i’ll check it out! i am quite certain that i’m not very aerodynamic or low resistance - trail jersey, hairy legs, very worn 32mm tires, endurance geometry, on the hoods. here are two flat track examples, again quite close to the bike calculator predictions.

burnthesheep

Thanks for the reply.

Look at the HR avg listed for your 220w part there and then the 260w part. The one for 220w is higher. This doesn't make sense physiologically for a 40w difference. The 220w 15min ride avg should be a lower HR. Not higher.

Either there's a big problem with your meter, or something isn't right here with that data.

mschwett 

the power data pretty clearly corresponds to the speed, and matches whatever model bikecalculator uses, and while the meter could absolutely be off 5% either way, i'm not sure how/why it would be off more for climbing than flat, or one day vs another, etc. small differences, sure.

the heart rate data is also correct, but my heart rate is dependent to a very large degree on how long it's been since i took my meds, to the tune of around 20BPM. if i go for a ride an hour or two after taking them, i'll max out around 110 for a very similar perceived effort to 130 if that same ride was 8 hours later. that's one of the reasons i rely much more on the power/speed/grade data.

GhostRider62

1.22 is not pea soup, it is an average Spring day where I live. Anyway, I got no dog in this hunt. Checking the PM is simple work.

TPL

Electric bicycles require .... natural gas ....crude oil ....coal ....nuclear to charge the battery ....NOT very efficient

Always ride a bicycle WITHOUT a motor ....maximize your efficiency

Riveting

I've always attributed my "extra" endurance while doing 240w on the flats (relative to 240w climbs, both measured with a PowerTap G3 power meter) being due to the adrenaline that going faster on the flats produces (that's not produced on the climbs), as well as the advantage gained by the cooling effect of going faster on the flats.

Carbonfiberboy 

Beta-blocker? That or a similar pharmaceutical would explain the low and varying HR at substantial effort. If so, your performance is even more amazing. Muscles need oxygen.