I'm sure there are folks here who are well-versed on the meanings of heartrate as it relates to training and effort. I'd like to hear from you! Here's why. My heartrate has been coming down, down, down over the past couple of months. While I am sure some of that decrease is due to conditioning, I feel that some of it also may relate to fatigue? I say that because I used to average 138 or so on long rides with peaks close to 160 (over an hour) and 145 and above on runs with peaks mid 160's (more than 2.5 miles). Now, on the bike, I average 118 with peaks around 145 (even when climbing), and the run is now 138 - 140. I can push it up to 155 on runs, but I can't sustain that for long. I can't peak anywhere near 160. On the bike, I can barely get up to 150 on peaks, and that's when I'm doing some steep climbs - and I feel like crap! Is this expected/normal? Here's my specifics - female, 5'4", 134 pounds, over 50 (umm, really close to 60!).