Power on incline vs flat / false-flat? Power meter noob content

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Catagory6
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by Catagory6

i have an 8.5 mile climb at about an average of 3.2% grade, with a max of 7.7% for a very short stretch.
there are a number of sections that level out to about 1.5%
i've noticed that my power drops by 40 - 70 watts when i crest the "steeper" sections (yeah i know, 4% isn't steep. that's why its in quotes), and hit the flatter sections. while perceived exertion remains constant.
but if i'm riding a flat route, or mostly flat, i don't have a problem holding higher watt numbers, closer to my 4% incline numbers.

does this sound normal?

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ms6073
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by ms6073

Catagory6 wrote:
Fri Nov 26, 2021 5:51 pm
but if i'm riding a flat route, or mostly flat, i don't have a problem holding higher watt numbers, closer to my 4% incline numbers.
Sounds normal. Remmber that when riding on relatively falt roads with little or no headwind, then you are aided by inertia which contributes to momentum such that only small changes in torque are required to maintain speed. Contrast that to a steady climb where inertia is no longer providing much if any beneft and you get
more of what could be thought of as an ebb and flow effect in terms of the pressure you apply to the pedals to maintain momentum. As the power output wains even a few watts, your momentum slows and now you have to generate apply enough force to accelerate back to and maintain the previous speed.
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TobinHatesYou
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by TobinHatesYou

Everything said above plus your pedaling mechanics change with changes in flywheel momentum. At 20mph, your power phases are shorter than at 10mph or 5mph. Your muscle recruitment is going to be different. Anyone who has primarily done one of flat TTing or steep climbs won't be optimized for the other.

Catagory6
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by Catagory6

thanks for the replies
sounds like what you're describing is more an effect on speed.
seems like power output would be relatively consistent regardless of the road being level or inclined.

TobinHatesYou
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by TobinHatesYou

Speed affects your biomechanics. Biomechanics affect your power.

tjvirden
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by tjvirden

Catagory6 wrote:
Fri Nov 26, 2021 5:51 pm
i have an 8.5 mile climb at about an average of 3.2% grade, with a max of 7.7% for a very short stretch.
there are a number of sections that level out to about 1.5%
i've noticed that my power drops by 40 - 70 watts when i crest the "steeper" sections (yeah i know, 4% isn't steep. that's why its in quotes), and hit the flatter sections. while perceived exertion remains constant.
but if i'm riding a flat route, or mostly flat, i don't have a problem holding higher watt numbers, closer to my 4% incline numbers.

does this sound normal?
Yes, it's normal.
I'm not convinced by some of the explanation offered though; some good bits, some misleading in my view.

The force on the pedals (and thus torque about the crank spindle) varies dramatically as the cranks rotate, irrespective of gradient - this is always the case, regardless of other factors. As the gradient increases, what changes is the "duty cycle" ; the force on the pedals is distributed through a larger proportion of the rotation, so the force pulse is smoothed to the extent that it is still bio-mechanically "efficient" to do so. This is what every cyclist does without thinking, in order to reduce the tendency of the bike+rider to decelerate/accelerate when riding uphill. However, the OP is referring to the transition between gradients.

Muscle recruitment varies substantially between riding on the flat and uphill [and of course the variation in-between], even when comparing similar positions on the bike (seated), because of the change in "duty cycle". It's that change in muscle recruitment coupled with the need for gear/cadence changes, as one transitions between gradients, that makes a steady power harder to attain. The opposite effect to cresting a rise occurs when transitioning to a steeper gradient - power tends to increase by default, at least momentarily.

Although I've never done any I guess that crit racing helps one become better adapted to coping with gradient changes; all that accelerating out of corners produces a similar effect.

bikeboy1tr
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by bikeboy1tr

I see many ppl do their FTP testing on gradients as it appears they will get a higher number providing you have a 20min climb that you can do it on a regular basis. I am not sure I totally agree with this as I dont think it represents a true test for all around abilities.
I dont have much in my area for hills or at least not 20min worth but when the temps are cooler in the spring I have done tests with a tailwind as its easier to breathe the cold air when its not a huge headwind. Perhaps thats not a true representation of a good test either but it seems to be close for me.
I know when doing tests in rolling terrain you really have to be on the gas immediately when cresting a hill or the pwr numbers drop significantly which affects the average in the end.
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TobinHatesYou
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by TobinHatesYou

bikeboy1tr wrote:
Tue Nov 30, 2021 2:51 am
I see many ppl do their FTP testing on gradients as it appears they will get a higher number providing you have a 20min climb that you can do it on a regular basis. I am not sure I totally agree with this as I dont think it represents a true test for all around abilities.
I dont have much in my area for hills or at least not 20min worth but when the temps are cooler in the spring I have done tests with a tailwind as its easier to breathe the cold air when its not a huge headwind. Perhaps thats not a true representation of a good test either but it seems to be close for me.
I know when doing tests in rolling terrain you really have to be on the gas immediately when cresting a hill or the pwr numbers drop significantly which affects the average in the end.

The constant acceleration from gravity helps most people keep the power down, at least for a time. It's very hard for me to get in the mindset of maintaining, for example, 300W on a flattish road with gentle dips/bumps.

But in 2020 I spent almost the entire year on Zwift, with my Trainer Difficulty at 0% (no resistance changes at all, high flywheel speed.) I adapted to that kind of feedback in the pedals. I became very, very good at maintaining high aerobic power at high speeds while my ability to climb in the real world suffered slightly.

mrlobber
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by mrlobber

TobinHatesYou wrote:
Tue Nov 30, 2021 2:58 am
But in 2020 I spent almost the entire year on Zwift, with my Trainer Difficulty at 0% (no resistance changes at all, high flywheel speed.) I adapted to that kind of feedback in the pedals. I became very, very good at maintaining high aerobic power at high speeds while my ability to climb in the real world suffered slightly.
I hate the way trainer resistance changes feel in Zwift, so I always use crank/pedal PMs there, with the trainer unpaired from Zwift & set at constant resistance; plus the trainer always reads 8-10% lower than any of my crank PMs even after numerous factory recalibrations.

What I've found (might be highly individual) that this has helped for me to become really good at producing high (for me) aerobic power within a fairly narrow cadence range for a long time (helps in Zwift racing), however, IRL (flat/slightly rolling) racing with constant accelerations / decelerations I'm struggling much more, with my legs usually trying to adopt notably higher cadences to compensate for the lack of torque ability (and feeling dead much sooner as a result). Prolonged climbing in aerobic power range still feels good.
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bikeboy1tr
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by bikeboy1tr

TobinHatesYou wrote:
Tue Nov 30, 2021 2:58 am



The constant acceleration from gravity helps most people keep the power down, at least for a time. It's very hard for me to get in the mindset of maintaining, for example, 300W on a flattish road with gentle dips/bumps.


I find it does take way more focus and concentration to keep that big effort going steady on the flats so I usually just have my Percent power and elasped time on my screen and think about it in 4 quarters of 5 min each. The focus becomes counting minutes for five at a time. When doing tests in the rollers its a boat load of shifting to stay with the effort you want so that occupies my mind almost more than the 5 min quarters.
viewtopic.php?f=10&t=154188
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