How can you tell if your training is improving your fitness for an ultra?

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.