Sadly, in my experience with exactly that type of crash, the lost data has been missing completely beyond a few dodgy looking timestamps (always right back to the time it was last turned off). The various online repair tools don't seem to work either - although I gather the guys here.. https://forums.garmin.com/showthread.php?36743-Fit-File-Corrupt-can-you-repair-it .. sometimes have some success in finding bits and pieces that can be used...
Sadly, in my experience with exactly that type of crash, the lost data has been missing completely beyond a few dodgy looking timestamps (always right back to the time it was last turned off). The various online repair tools don't seem to work either - although I gather the guys here.. https://forums.garmin.com/showthread.php?36743-Fit-File-Corrupt-can-you-repair-it .. sometimes have some success in finding bits and pieces that can be used...