Ultras are the fastest-growing race format in China’s running scene. In 2015, fewer than 50 ultra events existed nationwide; by 2024, over 400. UTMB (Ultra-Trail du Mont-Blanc, 168km), Western States 100, and Hardrock 100 are globally recognized ultra temples, attracting top Chinese runners (athletes like Liu Yichen have achieved strong results in UTMB series races).
## Ultramarathon Exercise Physiology Foundations
**The central role of aerobic capacity**: ultras are completed almost entirely within aerobic capacity range (pace usually well below lactate threshold); VO₂max (maximum oxygen uptake) and running economy (oxygen cost at equal speed) are the primary physiological determinants of ultra performance. Unlike shorter events, ultra race times typically exceed 12 hours — aerobic base importance far outweighs anaerobic power.
**Muscle damage and recovery**: extensive muscle microtrauma (DOMS — delayed onset muscle soreness) accumulates during ultras, especially on descents. In 100-mile events, athletes must sustain continuous movement for 36-48 hours under severe fatigue. Eccentric muscle training (downhill running, weighted squat negatives) is the core training tool for pre-adapting to ultra muscle damage.
**Gastrointestinal (GI) challenges**: the primary non-traumatic DNF cause in ultras is digestive tract problems (nausea, vomiting, stomach cramps). During prolonged exercise, blood shifts from the digestive system to muscles, reducing intestinal motility and digestive capacity. Practicing “eating while running” during training and building individualized nutrition plans are essential ultra preparation.
## Nutrition Strategy
**Energy intake**: carbohydrate intake during ultras recommended at approximately 60-90g/hour (gut-trained athletes can tolerate 120g/hour of mixed carbohydrates); solid food (rice, mashed potato, banana) becomes more important than gels in longer events.
**Sodium supplementation**: prolonged sweating causes sodium loss; hyponatremia (low blood sodium) is a significant cause of ultra medical incidents — supplement electrolyte salt tablets rather than drinking plain water only.
See [Trail Running Training System](https://sunqi.org/trail-running-training-en/) and [UTMB official website](https://utmb.world/).
