When I first got my 310XT (last week) I assumed my maximum heart rate was 170 (220-age) and set that in the watch. I have done a few runs now and my heart rate as got to 185 (and I wasn't pushing all that hard) so obviously 170 is too low.
I updated my user profile in Garmin Training Center with 185 (as good a number as I have at the moment) and downloaded that to the watch. Garmin Connect still reports my "% of Max" with respect to 170 rather than 185.
Where do I change it?
Edit: D'oh. I didn't look carefully enough. Settings->Training Zones.