context: I'm a washed-up former elite high school runner who attempted to compete at the D1 level for a bit before stepping away from competitive running due to chronic injury and mental health issues. After 5 years of sporadic jogging I began doing speed workouts/higher mileage again this past summer, largely due to COVID-induced boredom and anxiety. I managed to run a 1:32:17 half marathon after 12 weeks of training using a plan I got from Runner's World, and have now moved on to the more advanced version of that training plan (
.) I'm now on my second attempt at week six of this plan, or my 7th week total (I repeated the week 6 workouts for a second week in a row after being unable to complete the 10 mile time trial due time constraints last week.)
I'm here because I ran a big 10 mile PR this past Sunday, and I am worried it's not legit– I felt SO good and seemingly improved so much in the span of three weeks. I ran 1:07:14 (which was closer to 6:47 grade adjusted pace because the first four miles had about 250 feet of downhill). Just three weeks ago I struggled to run that same pace during a 10k time trial on the track (42:10). How is it possible that I just ran that same pace for ten miles and didn't feel like I was pushing until the last two or three?
I am mainly doubtful because I have occasionally noticed that my Garmin Forerunner 45 overestimates how fast I'm going, most notably when I run laps around the track near my house. On that track, I have noticed that my watch consistently says I'm going about 11 seconds per mile faster than I really am. I've suspected that this inaccuracy is due to GPS not pinging enough on the track's frequent curves, and have hoped/assumed that it doesn't apply to my other runs. But I can't know for sure, because when I'm not on the track, I don't know the exact distance I'm running.
I guess what I'm asking is: should I feel proud and excited about this seeming breakthrough, or should I feel skeptical? The route I ran had occasional gentle curves for the first 4 miles and was totally flat for the next six– would that mitigate GPS inaccuracy like the kind I've noticed on the track? Is it perhaps time to get a new, more accurate watch? If so, I'd definitely take recommendations/suggestions.