greenfrog,

Hi! I've been using heart rate monitors when on my bike trainer in the house. I've been trying to keep the HR below about 140. I found that high heart rate was giving me severe headaches, as does abdominal workout, so I started with 120 bpm and slowly increased it every few days till I found my current limit, or threshold, then kept all workouts below that limit.

I can currently cycle at about 140~145 bpm. The heart rate monitor was a better tool to rely on than gut feeling or RPE. Rate of perceived exertion or RPE is what some endurance athletes can use to gauge their effort, but for me, I prefer using the HR monitor, less change for errors.

I tried to go above my limit a week ago and had a feisty headache. ggrrrr.

Good luck

Mike