I have been following a marathon training program from BPN that sends workouts to my Garmin 265. Many/most of the workouts are heart rate based so you can see how the accuracy of the sensor would be important. I've been getting very low readings when wearing the watch normally (normal position, not excessively tight or loose). For example, 3 days ago I ran 16 miles with elevation mixed in, and in the last mile my watch is telling me my HR was below 120 bpm. I know this was not accurate and I played around with tightness and pushing the watch higher up above my wrist, still with inaccurate results. Fast forward to yesterday's workout: 7 miles at easy/aerobic pace - zone 3 (between 124 and 142bpm) for me. Somewhere around mile 5 or 6 I'm getting low readings again (sub 120). This time I flipped the watch around my wrist so the sensor is on the bottom (watch face facing in to the body), and the sensor is right on the veiny part of the wrist. Immediately the reading on the Garmin jumps 20 bpm to 139 and stayed in a range of about +/-8bpm for the remainder of the workout. Is this the fix? Just wearing the watch on the inside wrist instead of outside? For context I never had this issue with my Forerunner 245M, which I used for 2 years before upgrading to the 265. Please advise if there is a different solve for this issue, I know I'm not the only one.
