I want to figure out how to rate my intensity level for the stationary bike. Everything I read just gives low, moderate & high, which is great but how do I determine that? I think I'm working out at a moderate intensity but isn't there a mathematical way to determine that? For example today I rode for 4.58 miles in 20 mins. Is there a way to use that information to determine what level I was working out? I've search everywhere but I can't seem to find an answer. Help! Please and Thank You! 
I should have mentioned this....I can't use heart rate as an indicator because of a drug that I'm on that lowers my heart rate.

I should have mentioned this....I can't use heart rate as an indicator because of a drug that I'm on that lowers my heart rate.
