Cyclologist

Fellow bikeforumers, I emplore your experience and understanding in answering these few questions

1.) Assuming a constant power output, do you go a constant speed as long as you are using a corresponding cadence and gearing?

2.) Assuming a constant high power output, does time to fatigue depend on choice of cadence and gearing?

3.) If choosing an optimal gear is key to maintaining a certain high power output, is the general understanding to shoot for a gearing that allows for the fastest cadence at that power or speed?

Duke of Kent

1) Technically yes. The only place this is possible is an indoor velodrome with temperature regulation, however.

2) It shouldn't from a mechanical perspective, but it does, based on your personal physiology. Some people are better off at 90rpms, some are better off at 110rpms. Many people think they're Lance and try to spin that high of a cadence, and end up robbing themselves of power. Most of these people would be faster at 95 or lower than they are at 105-110.

3) Choosing an optimal gearing is reflective of choosing an optimal cadence and pedaling the gear that lets me do so, and not vice versa, in my opinion. I want to get in the gear that lets me pound out my 90rpms at 320w. Whether that's a 54x11 or a 39x23 makes no difference.

VosBike

1) if no outside factors (wind, gradient, etc) are changing, then a constant power output equals a constant speed.

2) Cadence can affect time to fatigue at a given power output. Research is not entirely clear, but the general belief is that high cadences (above 80 or so) spare your muscles while lower cadences (approaching 60) spare your aerobic system.
Most peoples muscles are the limiting factor in fatigue, so higher cadences are generally advisable.

3)If you know, say, that you have an epic hill to climb that you're going to get up at 8 MPH, don't bring your 39x21. It's generally a good idea to have the gearing you'll need to spin a decent (not neccicarily ideal) cadence up all climbs.

BetweenRides

I would add to what Duke sez on point #2: High cadence tends to tax the cardio system more - IOW your heart rate tends to rise as your cadence does. Corresponding to that (in general), higher cadence is less taxing on the leg muscles. So it (cadence) depends on what you want to fatigue - You can often extend the period to fatigue by varying cadence/gearing and keeping the power output constant. Think of doing a long constant grade climb - as one's leg muscles start to fatigue, gear down and spin at a higher cadence to give the legs a break.


*** VosBike - you beat me to it....

Cyclologist

Thanks for the reponses.

Makes perfect sense considering bike fit and thus muscle groups and muscle composition are the other variables I neglected to consider.

This is just the sort of generalization I knew existed, but was uncertain of and just about what I was looking for.

So, if spinning at a lower cadence spares the aerobic system, then it must tax the anaerobic system. Wouldn't taxing your anaerobic system be less advantageous? Or, does alternating between the two allow each to recover? In what way does the aerobic system need to recover? What is a good ratio of balance between them?

Absolutely true from my experience. Judging by the decrease in my speed at the top of the hill, a break is just what my legs need!