Today I tackled Low Saddle, a 1h45m ride that includes a single 1h33m ‘interval’ at a steady power output. My completed ride is shown in the diagram below. The top of the blue shape represents the power target that TrainerRoad wanted me to hit, the yellow line is my measured power output and the red line is my heart rate.
Once I finish a ride it gets automatically uploaded to Strava, which provides further analysis. A ride like Low Saddle is perfect for illustrating the issue. In the charts below you can see that my power output stays roughly the same throughout the ride whereas my ‘speed’ drifts from 25km/h to 29km/h and my cadence from 95rpm to 105rpm. This is a massive difference that I can really feel over the course of a ride. I’m glad it isn’t my mind playing tricks on me.
The SB20 trainer has a power meter on each crank. I’m not sure whether the problem is that:
- The measured power output from the power meters falls off during a ride, forcing me to push harder to keep the same measured power output, or
- The resistance on the trainer eases up over the course of the ride, meaning that I need to turn the cranks faster to maintain the same power output.
Does anyone know if there is something I can do to find out?