RapDaddyo said:
Has anybody tested this with a PT or SRM? How accurate is their power estimate? Does this estimate assume the unit is warmed up?
Again, has anybody tested this unit against a PT or SRM?
Precisely why I am interested. Not for myself because I have a PT SL. But, for others who don't have a PM and can't afford one yet.
I don't have a PT or SRM, so I can't provide any hard data for that. Maybe someone else who has access to a Kurt Kinetic and a real power meter can run some detailed tests.
I just thought the Kurt Kinetic trainer especially with the extra power readout would fit the niche you were trying to fill for someone who couldn't afford a power meter. Especially if they were alread looking to get a trainer to ride indoors - incremental cost is not much (~350 for Kurt Kinetic w/ power readout vs. 200-300 for cheaper fluid trainers with no power readout option.)
I think consistency (precision) is more important that absolute accuracy as you have alluded to. Absolute accuracy is only important if you want to compare your numbers to others. As long as whatever power measurement device is consistent from workout to workout -you should be able to do a FT test and design a structured program of appropriate intervals.
It is important to note that the power curve (which is used by the power computer) is strictly a function of rotational speed of the trainer's flywheel.
The manufacturer hooked up an electric motor and ran a series of tests recording the actual power required to spin the trainer at various constant speeds and then fit a curve through the data points to get the formula.
This should be pretty accurate for constant power intervals i.e. 2x20 @ 200W, since you usually try to hold pretty steady cadence.
You should try to eliminate as many variables as possible - use the same bike with the same tires inflated to the same pressure, tightening the trainers wheel against the bike's tire with the same number of turns, etc.
The Kinetic's power computer only knows how much power it takes to spin it at a certain rpm. It is not a direct measurment using strain guages as used by high end power meters.
The Kinetic power meter would report the same power output from two bikes as long as the speed maintained was identical - high end road bike with 700x23 tires inflated to 130psi vs. Pee Wee Herman bike with 2" knobby mountain bike tires inflated to 40psi. The road bike would actually take less power to turn the same speed.
Of course as long as you always rode your Pee Wee Herman bike, you could still design a structured program with it...
I think the only unknown variable is how much the resistance changes a function of fluid temperature. Supposedly whatever fluid they use does not change viscosity much over the normal operating tempurature of the unit.
I think most people would do a 5-10 min warmup anyway which should raise the temp and reduce this effect somewhat.
I still think this would be more accurate than RPE or heartrate and maybe a good solution for some people.