The clever guys at Trainerroad have taken a large amount of indoor trainers and mapped the power curve against speed. Anyone with a speed sensor and a turbo trainer now has the ability to train indoors using 'power'. The accuracy of the power reading is not entirely perfect however, providing you ensure you use the same equipment and have tire pressures and resistance the same every time, they consider it to be highly repeatable (much the same as an actual power meter). The only limitation is being unable to provide power feedback outdoors and during races.
Since getting a power meter at the end of last year, I have wondered how my virtual power recorded in March 2015 compared to actual power... Well today I finally found out.
Sticking the speed sensor back on the bike I rode at the same speed I completed my first FTP test (19.3mph). The power required at this speed is 265W. As this was an 8 min FTP test, you multiply that by .9 to get your FTP. This works out to be 238.5W.
The virtual power measured this at 218W.
Unfortunately this doesn't work in my favour! Had the actual power been lower than the virtual power it would have meant greater gains since last year.
Saying that, it's not a million miles away from the actual power with an acuracy of 91%. Given that you can get 5% differences between power meter manufacturers this is pretty dam good!
Obviously this only applies to the acuracy of the power curve for my trainer (Cycleops fluid 2). Other trainers may not be as accurate, especially if they haven't mapped the power curve and you're just using a basic map.
The results do confirm my progression in the last 12 months though...
238W (70kg = 3.4W/kg) - 04 March 2015
257W (69kg = 3.72W/kg) - 27 November 2015
287W (66.7kg = 4.3W/kg) - 30 December 2015
In less that 12 months I have managed to increase my FTP by 49W and added nearly 1W/kg to my power to weight ratio. I'm well chuffed with that!
I'm thinking of substituting a workout with another FTP test sometime in the next few weeks. I have a feeling I can break the 300W barrier.
Maybe once I have recovered from the Tour of Sufferlandria!
Cool stuff Russ, I was really curious as to how it would compare. Do you know how Stravas power guesstimates fair for accuracy?
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