Originally Posted by
Phantoj
On my trainer (KK Road Machine), trainer miles are a little bit harder than road miles. But that's not the reason I think running a speedometer is a good idea.
Trainer speed is related to power. For some trainers (like mine) that relationship is known well enough that you can "train with power" if you know your trainer speed.
If you have a good trainer (like mine) where resistance is not greatly affected by temperature, trainer speed will give a more reliable measure of effort than heart rate. HR is affected by heat (a real problem indoors), dehydration, even cadence.
I have a Road Machine and use it for this purpose, although I tend to factor in cadence and HR. So if I want to practice "hill repeats," I'll pick as speed (i.e., power) and gearing/cadence to hit the right zone. The nice thing is that work outs can easily be compared week to week.
Temp is pretty constant in my basement, although a fan is a must to limit HR variability.