I am a triathlete and runner and recently had a stress test done on my heart. Heart is healthy, but I have a question on my max heart rate. I max heart rate was recorded as 180bpm. On a 10k I did last week I reached a maximum heart rate of 188bpm. My average heart rate for the 10k in 47 minutes was 175bpm.
Yesterday, I did an all out 1.5 mile run after doing push-ups and sit-ups. But I only hit a maximum heart rate of 180 and average heart rate was 171. Why is my heart rate low when I do my first sprints in a workout or do a short race, but on a longer race or longer workout I can increase my heart rate? I would think that being a short distance I should be able to hold 183-185 for only about 9 minutes if my maximum heart rate in a 10 was 188bpm. I was just curious if this is normal for heart rate to be lagging at the beginning of exercise or due to lack of warm-up.