22nd March Powertap v Lifefitness Comparison - results

The results of the tests are summarised on graph above mapping HR against Watts. Powertap is blue, Lifefitness green, dark lines the first session on each, light lines the second.

Observations:

• The shapes of the graphs are clearly pretty similar. The Lifefitness ones seem to be smoother than the Powertap which is consistent with me having to "hunt" the desired watts on the latter, while simply dialling it in on the Lifefitness


• At lower watts (100-178) the Lifefitness HR is slightly below the Powertap. Speculating this may be because the Lifefitness is recumbent. At the 2 higher values (219, 261) the difference is less. In fact for this range the first sessions on Powertap and Lifefitness are almost exactly the same as the graph below for just sessions 1 and 2 shows pretty well.
  

• Strangely session 3, the second Lifefitness session had a HR line less than the first.
• The second Powertap session showed the highest HRs. This may have been because it was after 90 minutes of exercise, also not helped by having the highest variation in watts during each ramp due to me being daft and looking to see what gear I was in (so having to pedal harder to get average up)

Overall on the basis of this first test it looks as if the Lifefitness power is comparable to "real" power as on a bike. I will do a couple more tests to check (in the interests of science but also a good reason to train indoors when the weather is rubbish). Plan to do:

• Same sessions as above but do Lifefitness first and last with Powertap in between.
• Same sessions as above but all on same bike. Expect some variations between each session as happened above but will be interested to see how wide these are. Also interesting to see if the slightly strange result in session 3 (second Lifefitness) repeats and heart rate actually decreases with time.
• Similar sessions to above but with longer time in each interval (time/enthusiasm permitting)
• Carry out some higher power workouts. Problem here is that heartrate can lag power so becomes less useful as a comparison tool. Also difficult to carry out comparable sessions on same day as fatigue is more likely to affect results. But will try nonetheless and see what results follow.