Heart rate or power for FTP on trainer
I have started using a KK pro trainer and last week I did a FTP test (2x20). I had an average power of 200 watts according to the power curves for the Kurt, and an average heart rate of 175. I am 47 years old btw. 2 days later, I get back on the trainer and target 85% of my 200 watts of power, which should put me in the 170 watt range. However, I was struggling to keep 135 watts and my heart rate for the (1x20) was 177. So I guess I had not fully recovered from the initial FTP test 2 days earlier. But, should I target 85% of my FTP heart rate, or 85% of the Kurt power curves. I know that a lot of outside factors can influence my heart rate, but because of that, isn't that a more accurate determiner of exertion or stress? I could do my training at 85% of my heart rate, but not 85% of my power. What are your thoughts?