# Power Vs Strength



## bmxhacksaw (Mar 26, 2008)

For some reason I'm having a hard time wrapping my head around the difference between power and strength. 

Is this correct?

All things being equal if two guys are riding side by side and going the same speed but one is spinning higher RPM in a lower gear is he producing more power than the other guy?


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## pretender (Sep 18, 2007)

bmxhacksaw said:


> All things being equal if two guys are riding side by side and going the same speed but one is spinning higher RPM in a lower gear is he producing more power than the other guy?


Incorrect. If all things are equal (i.e. weight, rolling resistance, wind resistance, etc), then they are producing exactly the same power.

Power = Force x Velocity. One guy is applying power to the pedals via less force but greater velocity than the other guy. But the fact that they are going the same speed means they are applying the same power to the pedals.


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## Undecided (Apr 2, 2007)

bmxhacksaw said:


> For some reason I'm having a hard time wrapping my head around the difference between power and strength.
> 
> Is this correct?
> 
> All things being equal if two guys are riding side by side and going the same speed but one is spinning higher RPM in a lower gear is he producing more power than the other guy?


No, they're making the same power. That's why they're going the same speed (assuming, as you did, that all other things are equal).

Does it help to say that, from the combustion world, torque is how much strength an engine makes, while horsepower is how much power it makes? 

Your two guys---one could apply a lot of torque to slowly spin a big gear, and the other could use much less torque to spin a little gear more quickly, but if all else is equal and they're going the same speed, they must be making the same power. If the masher applies even more torque, his cadence will increase and his bike will accelerate because he must be making more power.


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## dwgranda (Sep 8, 2009)

Ignoring drivetrain inefficiency between different cadences, if weight and aerodynamics are the same and they are going the same speed they should be producing the same power.

I think of strength vs power more like this. You have 500lbs that needs to be raised 1 ft. The fastest way one guy can do it is by lifting 500lbs all at once and it takes him 10 seconds. Another guy can't even lift 500 pounds once, but he can lift 100lbs 5 times in 9 seconds. The second guy is more powerful than the first.


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## Ventruck (Mar 9, 2009)

I'm somewhat perplexed as bmxhacksaw. I assume momentum has a role mashing in heavier gears. My legs (notably muscles) can wear more when spinning a lower gear, with the same given rolling speed.

So sometimes I don't know if heavy gear workouts really count for anything if momentum does indeed null the resistance. If I'm spinning such gears, I'm probably reducing the workout into a shorter sprint.


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## Poncharelli (May 7, 2006)

Power = Torque*RPM*k (where k is a conversion factor)

OR

Power = Torque * RPM (let's leave off the k for simplicity).


Rider 1: Power = 3 * 100rpm = 300W
Rider 2: Power = 3.75 * 80rpm = 300W

One rider is putting 100rpm and the other 80 rpm, but they are putting out the same exact power, but with different torques (3 vs. 3.75). With everything else equal, they will go the same speed. 


Just forget about the "strength" term. It confuses things.


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## morkm (Nov 12, 2002)

Another way to look at it.......Cadence means NOTHING to POWER. POWER is POWER (STRENGTH * VELOCITY). Slower velocity (slower cadence) but more Strength means equal power to higher velocity (higher cadence) with less Strength.

That's why POWER is the ultimate in training aids. Nothing else matters to POWER but POWER. All else being equal, the person putting out more POWER is going faster.

In the REAL world, though, we have wind and we have gravity. No great solution for the wind, other than be more aero. ONLY solution for gravity is LESS WEIGHT, which is why POWER to WEIGHT ratio is so important in cycling. As soon as there is an uphill, no matter how steep or how long, the heavier cyclist requires more POWER than the lighter cyclist. At a certain point, the amount of POWER required by the heavier cyclist will push him/her into the red zone/burning matches/anaerobic/whatever you call it. He/She with the greater POWER to WEIGHT ratio has a major advantage.

So, in cycling, work on increasing POWER and decreasing WEIGHT. That's why many cyclists are tiny. Those who are not tiny are tall and skinny. Very few (Think Cancellara/Boonen) have large lower bodies and tiny upper bodies. Lots of folks like to think all pros have huge legs. Not true. They often have powerful muscles with limited bulk, the definition of High POWER to low WEIGHT.

Please, please, please remember, cadence had NOTHING to do with POWER. Different people produce higher power at different cadences. MY 105-110rpm power is much greater than MY 75-80rpm power. That's ME. Another rider may be the exact opposite. The idea of low cadence "work" does not necessarily mean more POWER....it just means low cadence. Low cadence MIGHT translate into lower heartrate, but again, if POWER is the ultimate measure of a cyclist (combined with weight), the overall goal must be increased POWER and decreased WEIGHT. 

MORE POWER and LESS WEIGHT. In MY opinion that's what training is all about.

Then, of course, there is drafting and strategy, which fortunately means that just because my power to weight might not be the bestest, if I'm cleaver and my POWER to WEIGHT is close enough to the others, I have a chance.......


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## tommyrhodes (Aug 19, 2009)

I'm with you hacksaw. And reading this has left me far more confused....


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## ZoSoSwiM (Mar 7, 2008)

Last night on the trainer I was doing some easy stuff spinning at 180 watts.. I shifted up a gear and increased my cadence from 90 to 100 and my watts stayed the same. My heart rate never changed. 5 minutes at both 90 and 100 rpm.


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## dwgranda (Sep 8, 2009)

ZoSoSwiM said:


> Last night on the trainer I was doing some easy stuff spinning at 180 watts.. I shifted up a gear and increased my cadence from 90 to 100 and my watts stayed the same. My heart rate never changed. 5 minutes at both 90 and 100 rpm.


What point are you trying to make? Sounds like you're saying that heart rate stays the same at the same power irrespective of cadence. Lots of data to show this isn't true generally. Maybe at 180 watts you were at such a low level that it didn't stress your system enough. Not sure how that relates to power vs strenth though.


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## ZoSoSwiM (Mar 7, 2008)

I was meaning to point out that the power was the same for different cadences and gearing. 

I know I fall apart at lower cadences and my heart rate climbs. We all make our power differently. I spin quickly.. others don't.


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## asgelle (Apr 21, 2003)

morkm said:


> POWER is POWER (STRENGTH * VELOCITY).


Don't confuse force with strength (maximum force or tension generated by a muscle or muscle group).


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## bmxhacksaw (Mar 26, 2008)

I guess the velocity is what tripped me up. I always thought of velocity as the speed of the bike but when I thought about how power meters actually work (the strain gauges and all) then velocity is obviously the speed of the cranks (cadence).

So the next question is what's the best way to increase one's power output (I'm working on the lowering the weight part)?


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## stevesbike (Jun 3, 2002)

bmxhacksaw said:


> I guess the velocity is what tripped me up. I always thought of velocity as the speed of the bike but when I thought about how power meters actually work (the strain gauges and all) then velocity is obviously the speed of the cranks (cadence).
> 
> So the next question is what's the best way to increase one's power output (I'm working on the lowering the weight part)?


asking how to increase power output is pretty vague - there's threshold power, maximal power (sprinting), 5 min average power, etc, all of which are addressed in training 101 books, blogs, and threads....


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## Creakyknees (Sep 21, 2003)

bmxhacksaw said:


> So the next question is what's the best way to increase one's power output (I'm working on the lowering the weight part)?


intervals, duh.


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## bmxhacksaw (Mar 26, 2008)

Creakyknees said:


> intervals, duh.


That's what I figerred.


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## spade2you (May 12, 2009)

stevesbike said:


> asking how to increase power output is pretty vague - there's threshold power, maximal power (sprinting), 5 min average power, etc, all of which are addressed in training 101 books, blogs, and threads....


Actually, a study I recently read said that there are more like 202 blogs, books, and threads, none of which will be discredited by a study coming out next week....I promise. :idea:


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## PissedOffCil (Jan 3, 2008)

Creakyknees said:


> intervals, duh.


How vague. If he does 30 second high RPM at 50% FTP it won't help him increase his FTP much, yet it's an interval...

Suggesting intervals is like suggesting that he "just rides", sure it'll work but is it optimal?


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## bmxhacksaw (Mar 26, 2008)

PissedOffCil said:


> How vague. If he does 30 second high RPM at 50% FTP it won't help him increase his FTP much, yet it's an interval...
> 
> Suggesting intervals is like suggesting that he "just rides", sure it'll work but is it optimal?


I think the Creakmeister knows that I know that you know that I know what he means.


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## PissedOffCil (Jan 3, 2008)

bmxhacksaw said:


> I think the Creakmeister knows that I know that you know that I know what he means.


Given you don't understand the relation between cadence and power, I wouldn't assume too much.


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## bmxhacksaw (Mar 26, 2008)

Yeah, but I have 5841 posts.


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## nayr497 (Nov 8, 2008)

Ah ha ha, awesome bmx. 

This thread has left me more confused. I'm heading out for a ride


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## sdeeer (Aug 12, 2008)

Just a generic reminder about power to weight. Typically the higher the power to weight, the better.

BUT...dieting too hard, leading to lack of recovery typicaly leads to a loss of power and weight. 

Make sure you are not just chasing an arbritray number on the scale. And most poeple can not stay at "race weight" very long if it is a true minimum without risking overtraining.


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## tbgtbg (Mar 13, 2009)

*That's easy...*



bmxhacksaw said:


> So the next question is what's the best way to increase one's power output (I'm working on the lowering the weight part)?


PEDs...


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## Alex_Simmons/RST (Jan 12, 2008)

*Power *is the rate of doing work, or the rate of energy transfer. Work = energy.

e.g. to get up a steep hill, two riders of same mass (and other things equal) require the same total energy expenditure to get to the top, even though one might take less time than the other. IOW they both have done the same amount of work to get up the climb. However the one that takes less time did so at a higher power output (the rate of doing the same amount of work was higher).

*Strength *is the maximal force generation capacity of a muscle or group of muscles. By definition, maximal force can only be applied at zero velocity.

On a bicycle, the forces we apply to the pedals are significantly sub-maximal. We never approach our strength in cycling. The only time we get close to applying such forces are in the opening pedal stroke of a track or BMX standing start.

At regular cycling powers, the forces are quite low, such that what determines our abilities is being able to sustainably and frequently repeat the very low forces on the pedals - which is dictated by our aerobic metabolism, not our strength.

As an example, the average pedal force applied by both legs at 300 watts at 90rpm is about the equivalent down force force applied by an 18.6kg (41lb) mass.


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## swuzzlebubble (Aug 4, 2008)

Is being no good in headwinds relative to other aspects/peers more a function of lacking power or endurance?


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## Alex_Simmons/RST (Jan 12, 2008)

swuzzlebubble said:


> Is being no good in headwinds relative to other aspects/peers more a function of lacking power or endurance?


It means your power to aerodynamic drag ratio for the duration of interest is lower than theirs.


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## MonkeyClaw (Feb 3, 2012)

Alex_Simmons/RST said:


> It means your power to aerodynamic drag ratio for the duration of interest is lower than theirs.


This is also true for TTing, where power-to-weight is less important than power-to-CdA. Power-to-weight is good for climbing and accelerations, but is not the be-all, end-all of cycling.


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## iheartbenben (Mar 18, 2011)

The problem with applying physics to what you are feeling on the bike is they have nothing to do with physiological differences of the muscle system and fatigue perception.


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## JMRR1 (Apr 8, 2009)

swuzzlebubble said:


> Is being no good in headwinds relative to other aspects/peers more a function of lacking power or endurance?


Also, do not underestimate the psychological effect that COULD be part of this... If you constantly tell yourself that you are no good in headwinds you will probably not be able to push yourself as hard as others can.in the same headwind.


JMRR1


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## crawl4uball (Mar 7, 2012)

power all day


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