Quoted post said:Originally Posted by An old Guy [IMG]/img/forum/go_quote.gif[/IMG]
It is all about the force.
You think it is about power output. There is an easy test. Put your bike in its 53/11 and without shifting ride up a modest hill. (Modest hill is 5-6% for 3000' of elevation.) Even I have the power to get up the hill. I bet you lack the force.
No it is NOT all about force.
Your boundary case example just points out the reason bikes have gearing and the need to select gearing appropriate for the terrain and conditions. Sure you could likely stand up and place your full body weight on John Howard's land speed record bike with it's double jackshaft gearing and roughly 350 gear inches and the bike might not roll from a standstill. And if that's how you're gearing then yep you've got a problem.
Using your logic above you could just as easily show that setting up a bike with a 20 tooth chainring, perhaps a 39 tooth rear cog, and 20 inch wheels 'proves' that riding hills is 'cadence limited' as you spin out those 10 gear inches up that same sustained 5% climb. Both cases are absurd boundary cases and neither proves or establishes anything any more than stalling a manual transmission car while trying to start from a standstill on a steep grade in fifth gear proves that the car's engine can't produce enough torque for normal driving in appropriate gears. You've simply geared improperly for the conditions and loaded the engine outside its power band.
You claim to ride with a power meter. If so then simply inspect the torque data for the steepest hills you climb in the gearing you actually use while climbing. It's simple to take that torque data and convert it into force per pedal stroke and very easy to see that the force you apply is a small fraction of your body weight which you presumably can move uphill while climbing stairs or on an uphill hike easily enough as long as you don't try to climb those stairs or that hillside too fast. So what happens when you do try to climb that hillside too fast (on the bike or on foot), you run into your sustainable power limits or your ability to convert fuels and oxygen into muscular power. It's not the force as you can easily manage the same or higher force if you slow down and proceed at a slower pace, the issue is energy per unit time which is the definition of power.
Take the body weight stair climb / hiking test as a limit. IOW, assume that a person can repeatedly lift their body weight on one leg at a time repeatedly as long as they do so slowly. Anyone that has climbed a few flights of stairs or gone for an uphill hike can do this or much more. But take that as the limit so say a 150 pound human can repeatedly lift 150 pounds given time to do so.
Then assume that person rides with 170mm cranks and does so at 70 rpm on a moderate climb. At that very conservative limit of 150 pounds repeatable peak force that rider can generate a peak pedaling torque of ~114 newton meters. Using the published pedaling force curves from studies like Coyle's 1991 study a rider's average effective pedaling torque is approximately half of their peak torque per pedaling cycle or in this case ~57 newton meters average torque per cycle.
Fifty seven newton meters of torque at 70 rpm generates ~418 watts or 6.13 watts per kilogram of body weight for that 150 pound rider. That's world class power and right up there with the best professional cyclists. At 90 rpm it works out to ~535 watts or 7.88 w/kg which is off the charts for FTP and very high for even a handful of minutes.
But very few riders outside of the pros can actually sustain 6 w/kg even though based on the very conservative stair case or hill walking test they have plenty of repeatable force at their disposal because hill climbing speed is limited not by force but by sustainable power and that is a metabolic energy delivery and utilization issue, not a force or strength issue.
BTW, that example above used a 150 pound rider but it does not matter as the exact same analysis applies to any weight since the limiting repeatable force was taken as their body weight based on the hill walking or stair climbing criteria. IOW for any rider that can walk slowly up a hill and lift their body weight while doing so their limit on sustainable power based on proven repeatable force generation is ~ 6.1 w/kg at 70 rpm or ~7.9 w/kg at 90 rpm. Realistic repeatable force based limits are no doubt higher as most hikers can wear a substantial pack on their back and still walk uphill for hours on end if they pace appropriately so body weight represents a very conservative lower limit on repeatable force.
If you don't trust the math then simply inspect power files, the data is there and it's not hard to see that force requirements for sustained efforts are always a fraction of the rider's body weight yet we know that healthy individuals can repeatedly lift that body weight while walking so it's not hard to connect the dots.
Bottom line, if you can walk up a flight of stairs and lift your own body weight repeatedly or go for a day of hiking at a slow pace and repeatedly lift your body weight then you have more than enough repeatable force at your disposal to ride at world class power levels. Yet few riders actually do ride at world class power levels demonstrating that the limiter is not force.
-Dave
