I am a physically active amateur runner, Male, Age 38, 5'7", 66 kg. I use a Heart rate monitor while running. My average Max heart rate is 200 bpm. When I start jogging after warming up, my heart rate jumps from 90 bpm to 150-160 bpm, (i.e. 75-80% of HR Max) after merely 1 minute, although I am jogging very slowly, just barely faster than walking. After 10-15 minutes, my heart rate has already reached 85%, although I am still going very slow indeed.
I am following a training programme for running a half-marathon after 3 months, which prescribes different heart-rate intensities of training on each day of the week, viz. 60-70%, 70-80% and 80-85%. However, I find that I am reaching 85% on every session, however slowly I run. Could you give me a clue what's wrong?