Different perceived effort levels for the same power output

BugsBunny
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Different perceived effort levels for the same power output

Postby BugsBunny » Tue Sep 11, 2018 3:48 pm

I've noticed that for the same power output, I can get different perceived effort levels.

The most obvious example for me is:

200w on a flat road, I'm spinning around 95-100RPM, I find I can get into a rhythm and can hold this power longer than...
200w on a climb, I'm spinning usually a lower cadence, say 85RPM, but the effort to sustain this power/duration seems more difficult.

On the flats, I find I can "turn over" the cranks more easily. Is it because the arc where I'm putting power to the cranks is "wider" on climbs than on the flats?

Anyone else have this perception or have ideas as to why this might be the case?

Bugs

human909
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Re: Different perceived effort levels for the same power output

Postby human909 » Tue Sep 11, 2018 4:08 pm

BugsBunny wrote:Anyone else have this perception or have ideas as to why this might be the case?

-Lower cadence (lower cadence puts higher loads on your muscles, also too high/low cadence can mean lower efficiency)
-More difficult body position on steep slopes.

Jmuzz
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Re: Different perceived effort levels for the same power output

Postby Jmuzz » Tue Sep 11, 2018 4:12 pm

You are supplying more torque at the lower rpm, pushing harder on the pedal.
To compare you really need to do the exact same rpm, which gearing converts into the same torque and power.

But yeah there will be differences in acceleration and deceleration which will change the resistance curve, in the right headwind they could be equal.

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trailgumby
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Re: Different perceived effort levels for the same power output

Postby trailgumby » Tue Sep 11, 2018 6:44 pm

On my last FTP test I found I could comfortably sustain higher power output by spinning faster in an easier gear. The reason is you're not pushing as close to your strength limits. There are a whole bunch of physiological factors that spring from that.

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g-boaf
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Re: Different perceived effort levels for the same power output

Postby g-boaf » Tue Sep 11, 2018 7:21 pm

BugsBunny wrote:I've noticed that for the same power output, I can get different perceived effort levels.

The most obvious example for me is:

200w on a flat road, I'm spinning around 95-100RPM, I find I can get into a rhythm and can hold this power longer than...
200w on a climb, I'm spinning usually a lower cadence, say 85RPM, but the effort to sustain this power/duration seems more difficult.

On the flats, I find I can "turn over" the cranks more easily. Is it because the arc where I'm putting power to the cranks is "wider" on climbs than on the flats?

Anyone else have this perception or have ideas as to why this might be the case?

Bugs


That's because you are using your muscle strength, so your legs are probably getting sore/tired. The better is to stay at a more comfortable cadence (say 90rpm or better) and spin. It's sometimes called "staying on top of the gear".

You will also want to be getting out of the saddle sometimes on those climbs, that will help you a lot.

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Alex Simmons/RST
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Re: Different perceived effort levels for the same power output

Postby Alex Simmons/RST » Wed Sep 12, 2018 6:05 am

Even when climbing we are no where near our strength limits. The forces involved with strength are still an order of magnitude away.

Most people experience it the other way round, they find going up an incline feels easier at same power than maintaining it on the flat, and seems even harder when attempting to maintain the same power on a slight decline. Usually this is expressed as people tending to put out more power when climbing than when on the flat and they need to concentrate more on flat terrain to sustain the power.

I was pretty neutral in that the perception of effort (after several minutes) would even out when working at/near threshold power no matter the gradient (unless velocity was so high or so low I ran out of gears).

Then there are those who experience different perceived exertion level when riding at the same power on an indoor trainer v outdoors.

When climbing steeper inclines, the manner of muscle recruitment is a little different as the crank inertial load varies and the nature of the resistance forces changes from overcoming air resistance being dominant (higher velocity, higher CIL, velocity changes are less) to overcoming gravity being dominant (lower velocity, lower CIL while velocity variance is higher), which provides for a different neuromuscular experience for each individual. The feedback/response to changes in pedal effort is more immediate on a climb than on the flat.

With good bike fit and plenty of training usually these differences can be minimised such that sustaining the same power and effort level is possible.

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Alex Simmons/RST
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Re: Different perceived effort levels for the same power output

Postby Alex Simmons/RST » Wed Sep 12, 2018 6:13 am

Of course there is one other factor - the power measurement device itself may report differently in different scenarios.

For some a significant lowering of CIL when climbing can result in power measurement error of several percent, due to a factor similar to the error introduced through use of non-circular chainrings.

And if the meter is unilateral, then keep in mind power balance varies with pedal velocity, power output, position on the bike, crank inertial load, fatigue etc etc, and so actual and reported power will diverge by differing levels.

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MichaelB
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Re: Different perceived effort levels for the same power output

Postby MichaelB » Wed Sep 12, 2018 8:48 am

Alex Simmons/RST wrote: ...Most people experience it the other way round, they find going up an incline feels easier at same power than maintaining it on the flat, and seems even harder when attempting to maintain the same power on a slight decline. Usually this is expressed as people tending to put out more power when climbing than when on the flat and they need to concentrate more on flat terrain to sustain the power.

....


I'm one of 'those' :)

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Re: Different perceived effort levels for the same power output

Postby vosadrian » Wed Sep 12, 2018 10:44 am

Sounds to me like the cadence is the difference. Power is proportional to torque multiplied by RPM. If you want to maintain the same power, and you go to a 10% higher cadence, the torque has to go down by 10% (which means pushing down 10% less force on pedals as torque is proportional to force times crank radius). Typically I have read and found myself that at higher cadence, the legs feel better, but the cardio gets more of a workout as opposed to lower cadence at same output.

I typically find I mix it up when I am on an effort. At the same speed on a flat road, I will change a couple of gears either way to change cadence. This can ease the legs but the HR goes up. For me it is more about managing my position on the bike. My back cops it when I grind at a lower cadence in the drops compared to spinning, but when I spin my HR and breath rate tends to go up. Of course on a flat road, being aero is a factor so that can dictate body position. On a climb I can sit more upright, but often the cadence is dictated by how steep the climb is and my minimum gearing.

I tend to find my sustainable power is similar for flat and climbing. Downhills is difficult to maintain power just because it is hard to get enough resistance to push against.
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familyguy
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Re: Different perceived effort levels for the same power output

Postby familyguy » Wed Sep 12, 2018 10:52 am

trailgumby wrote:On my last FTP test I found I could comfortably sustain higher power output by spinning faster in an easier gear. The reason is you're not pushing as close to your strength limits. There are a whole bunch of physiological factors that spring from that.


Cadence is king, for me personally. I often find myself sitting in the small ring doing 95RPM while the others are all in the big ring doing 80RPM. If I try to match their cadence and gearing I blow up real fast.

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