The Next Move The In-Depth Science of HYROX: What Exercise Physiology Tells Us About Performance - Gommaar D’Hulst (#17)
Jan 19, 2026
Gommaar D’Hulst, an exercise physiologist at ETH Zurich and founder of the WOD Science channel, dives into the fascinating world of HYROX and CrossFit. He discusses key differences in their demands, emphasizing HYROX's endurance focus and the impact of muscle fiber types on performance. Gommaar shares insights from elite athletes’ lab testing, explaining how fatigue affects running economy and the importance of threshold training. He also touches on nutrition strategies, anaerobic power, and the future of functional training metrics, making this a must-listen for fitness enthusiasts!
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Fatigue Worsens Running Economy
- Fatiguing strength-style movements (deadlifts, lunges) raise VO2 for the same running speed afterward, showing running economy degrades.
- Muscle oxygenation drops after fatigue, hinting at reduced local oxygen extraction and biomechanical breakdown.
Beyond VO2: Fatigue Resistance Matters
- VO2 and lactate threshold matter but don't fully predict HYROX outcomes; fatigue-resistance across stations predicts performance.
- HYROX athletes excel when they resist efficiency loss from repeated functional contractions, not just by raw aerobic capacity.
Don't Rely On Heart Rate During Stations
- Use heart rate for continuous efforts like running, but avoid relying on it during functional stations.
- Track pace, station times, and movement power instead of heart rate for HYROX pacing decisions.
