I’m a 49 year old runner, having started running about 18 months ago and working up to about 20 miles a week. I’ve run four 1/2 marathons in the last several months, so have considered myself reasonably accomplished for a late bloomer to running. I keep contending with an issue where I have pretty intense heart rate spikes at almost random times in my runs. So, today, I was aiming for a 10 miler and actually had it in mind around mile 7 that I was feeling quite good and may try to see if I could hit 13. My heart was bout 155 around that point, which is a little high for my age .. I wish it could be lower, but seemed manageable. Then at mile 7.5 .. my heart rate jumped almost instantaneously to about 175 from 155 or 160. I can physically feel this happening and then check my watch. When this happens, I have seemingly no ability to get it to calm back down into a 155 rate or so. Whether I slow down or even walk for a spell, when I “trip” this event .. it seems like my run is over. I wish I could post a picture in here of my heart spike from my watch because you would see it looks like a cliff .. straight up. I haven’t been able to find any explanation for this and am concerned if it is indicative of any more serious issue. I’m hoping it’s somehow more common than I think and maybe even some ways to train through????