Functional Threshold estimate...

[root]

Unfortunately, I don't have a "real" power meter on my road bike, but I have an indoor stationary bike (from Vision fitness), that can measure power output , but it can't record it. One of the training programs it has is the constant watts, that allows you to dial in the desired watts and the bike then adjusts the resistance so that your power output is always dialed in value. Another limitation is that the maximum power you can do with constant watts program is only 250 Watts (even though the max power the bike can measure is 700 Watts in other programs).

So, I wanted to measure my FTP by doing the constant watts program at 250 Watts for 21 min. It was freaking hard, because you can not coast for even half a second, the bike increases resistance immediately. So I'm wondering, is this method any good at all, because percieved exertion is way harder than doing a real time trial, where you can ease off for 3 - 5 seconds when you have to?

Another observation, my cadence averaged 110 RPM, which seems high for a TT effort (but I find it easier that way).

 

[Ergoman]

Unfortunately, I don't have a "real" power meter on my road bike, but I have an indoor stationary bike (from Vision fitness), that can measure power output , but it can't record it.

I'm not familiar with your particular stationary bike, but based on experience with others I would guess that the power information that you're getting isn't too accurate. I wouldn't rely on it as a device to determine your real world FTP.

OTOH, a stationary bike can be pretty consistent, and if you always use it as the standard reference for your performance it can be a useful training tool. Knowing consistent and repeatable numbers is the key to sucessful training, absolute accuracy is of lesser importance. After all, FTP is just a number that represents effort. If you can represent that effort with another number, so long as it's consistent, what's the difference?

 

[daveryanwyoming]

...So I'm wondering, is this method any good at all, because percieved exertion is way harder than doing a real time trial...

As Ergoman said, the indoor bike may or may not be accurate, but it is probably repeatable which is more important anyway. Either way, a lot of folks struggle to produce the same power indoors as they typically produce when training outside. Good cooling in the form of a big fan can help as can practice especially for trainers with small flywheels and their low moment of inertia. Some of it's psychological since it's just not very much fun or very interesting to ride in place for an hour or more at a stretch.

...Another observation, my cadence averaged 110 RPM, which seems high for a TT effort (but I find it easier that way)...

That's real typical for ergometers that hold constant power over a range of cadences. The force requirements decrease with increased cadence which of course is just the opposite of riding a real bike outdoors since real bikes don't hold constant power all by themselves. I find my intervals on ergs tend to higher cadences than I often use outdoors. Funny thing though, my long intervals outdoors often average 90 rpm or so but my time trials usually average100 to 110 rpm just like the erg workouts. So maybe the erg is a better representation of my time trial efforts after all.

-Dave

 

[sogood]

I am in the same boat and train similarly, especially for wet days. The constant power offered is consistent with the goals of power training. Fortunately, our community's stationary bike can dial up to 320W, so there's room to grow for me but no ideas as to how accurate the wattage readings are. As long as there are improvements over time, who cares?

 

[postal_bag]

Unfortunately, I don't have a "real" power meter on my road bike, but I have an indoor stationary bike (from Vision fitness), that can measure power output , but it can't record it. One of the training programs it has is the constant watts, that allows you to dial in the desired watts and the bike then adjusts the resistance so that your power output is always dialed in value. Another limitation is that the maximum power you can do with constant watts program is only 250 Watts (even though the max power the bike can measure is 700 Watts in other programs).

So, I wanted to measure my FTP by doing the constant watts program at 250 Watts for 21 min. It was freaking hard, because you can not coast for even half a second, the bike increases resistance immediately. So I'm wondering, is this method any good at all, because percieved exertion is way harder than doing a real time trial, where you can ease off for 3 - 5 seconds when you have to?

Another observation, my cadence averaged 110 RPM, which seems high for a TT effort (but I find it easier that way).

I trained for 18 months on a Lifecycle stationary bike (9100 series?), before getting my Powertap. I did map tests, FT tests, vo2 max, threshold intevals. The bikes in our gym go up to 500 w. I always used the ergo mode, however I believe that the calorie expenditure was simply based on 276 w = 1000 kcal/hr. If this is the case with your bike, maybe you can use one of the other programs which measure up to 700 w.

I would have to say that it was pretty accurate, although not pleasant to ride with the magnetic resitance and non-adjustable postition. I think that the more upright position put a lot more strain on the fronts of my quads, so I would always ride a cadence of 100+ rpms to lessen the load.