Keep this in mind (it was posted awhile back)
I just recently started using a PT.
This is recovery ride (trainer, same resistance, 60'). I notice that after about 5 minutes I sustain a stable power, but the recorded speed drops steadily until about 30' when it becomes stable. I have seen the same pattern 3 times.
The questions is: at the same power output, with the same resistance, why would the speed drop ?
Answer by WR:
It's not the same resistance. The trainer is turning all of the energy from your tire into heat, sound, and air motion. The heat inside the resistance unit is probably causing parts to expand, which will increase the resistance.
Edit: In the graph, blue is speed (sensor in the rear wheel, obviously) yellow is power. Red is HR.