i got my HRM and found out that my heart rate on a 6mph run for 2.5 miles was 175-185. i was totally shocked because of the high heart rate for relatively low speed of my running. I am 23 yrs old and wonder what is are some good guidelines for increasing aerobic capicity and general health. Should i be running at 60-80% of max or maybe 50-70% i dont know, any advice is appreciated. Should I train differently on my bike that I do on the treadmill.