How close to a race should you test your zones. Have an upcoming marathon and I tested my zones in week 15 using talk test (had lasted tested them 6 weeks prior) and my threshold pace jumped from 8:10 to 7:19, I began training with new zones and immediately started noticing some pains and so I scaled back to a threshold pace of 7:40 out of fear of injuring myself so close to my race. Race is on November 21st (10days) struggling to determine if I should retest zones so close to race, race at a pace dictated by the zones I achieved or the ones I have been training in? My Garmin is currently predicting a 3:30:49 race not sure if that is actually reasonable.
Is this your first marathon? If it is, is it also your first race of any distance? If not, use past races as a baseline for your goal-setting. This article fleshes out how to do that and provides other guidelines for setting an appropriate pace goal: