Coaches Cathy Duffy and Andy DuBois explain how to judge whether your training is making you fitter for ultras. They contrast general health fitness with ultra-specific fitness, review common lab metrics (VO2max, threshold) and highlight the missing pieces—durability, volume, downhill conditioning, nutrition, pacing and mental experience. They give practical tips: understand how watches and training-load scores work (and why tapering can lower a fitness number), use long runs, time trials and subjective recovery measures to track progress, and trust experience and race-specific testing to close the gap between training and race day.