The final miles of a marathon can crush even well-trained runners. A pace that once felt smooth and controlled suddenly feels almost impossible to hold onto. Your breathing rate picks up, your heart rate climbs, your legs get heavy, and every step demands more. But that late-race fade is not just a matter of mental toughness. You can actually train your body to hold up better when the race gets hard. Researchers are paying more attention to this factor—the ability to maintain performance through the later miles of a marathon—often known as physiological resilience or durability . While marathoners tend to focus on metrics like VO2 max, lactate threshold, and running economy, those numbers usually don’t tell the full story, especially when it comes to running for hours.…