The Physiology of Endurance Running Podcast · Dan Nash and Owain Zerilli

The Science of Trail & Ultra Running - with Dr Simon de Waal

·1 hr 34 min·5 clips

Three classic endurance markers explained only about 50% of trail running performance.

1. The Physiology of Endurance Running Podcast episode centers on the science of trail and ultra running with Dr Simon de Waal. 2. Simon de Waal is a lecturer and researcher at the University of Gloucestershire, formerly Stellenbosch University, and the hosts note that he knows the physiological demands of trail running well. 3. The episode asks what trail-running performance can be explained by classic endurance measures and what those measures miss. 4. Simon says trail running is “really, really complicated” because it is less predictable than a flat marathon and harder to model. 5. The first research step was a systematic review of trail-running physiology, which found very little published evidence at the time. 6. That review showed the classic trio of VO2 max, lactate threshold, and running economy explained only about 50% of trail-running performance. 7. Simon notes that most of the studies were on short trail races at marathon distance or shorter. 8. He also points out that only one study in the review covered an ultra-distance setting, a 65K mountain race. 9. The available studies mainly used flat treadmill protocols even though trail racing involves climbs, descents, and uneven terrain. 10. Simon says velocity at VO2 max performed as the strongest independent correlate in the trail-running literature. 11. He explains that velocity at VO2 max matters because it blends VO2 max with economy underneath that ceiling. 12. He links that idea to the broader endurance model associated with Michael Joyner and to regression work on marathon prediction. 13. Simon then discusses Andy Jones’ 2024 “fourth dimension” idea, which focuses on physiological resilience or durability. 14. He says endurance variables change as fatigue progresses, especially in events lasting 24 hours or more. 15. The PhD next moved to a title focused on developing a submaximal test to predict ultra trail marathon performance. 16. Simon and his collaborators decided to keep the test physiological and steady-state rather than making it overly contrived. 17. A pacing analysis of the Ultra Trail Cape Town 100K showed progressively slower pace and large positive splits as the race wore on. 18. Simon segmented the course into uphill, downhill, and undulating sections using Strava data. 19. The analysis showed uphill performance had the strongest relationship with overall race time, which pushed the work toward uphill treadmill testing. 20. The method then used Strava grade-adjusted pace and Alberto Minetti’s 2002 gradient equation to choose test speeds at 5%, 10%, and 25% grades.

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