At 58 and reasonably fit with a resting heart rate of 55-60 bpm, I was disturbed recently that my Garmin HRM records shows short periods of 5-12 minutes at 200+ bpm on my road bike after 25km after an hour and then again on a short 2.5km run after the bike. The distance and pace is not so unusual for me. I was training for an Olympic-distance triathlon and completed one such event last month in 2:45 (35+75+50) where my max HR was 161.
Normally, I max about 160-170 on a fast short run (4:20-4:30 pace) and 140-150 on the bike (30-40kph). So, when I see 241 on the bike and then 215 on a short run, I am almost surprised that I am alive to tell the tale.
In the past, I might have put this down to my HRM being too sensitive and picking up a double beat. However, the bpm rate increase on the bike is consistent with my putting in more effort to catch up a group of cyclists I had been expecting to meet. On the run, my first fast 1km at 4:30 pace was normal at 155 bpm but after easing off for 2 minutes, I kicked in again at 4:20 pace and my heart rate rose rapidly to 200 within a minute and remained high even after I eased off after a minute when I was finding it tough.
So, perhaps I should avoid sudden changes in pace, especially after not recovering in between. Needless to say that I should check with my doctor. Meanwhile, I will set a heart rate alert on my Garmin 920 watch if over 165 bpm.