Dr. Iñigo San Millán, a former competitive cyclist and assistant professor at the University of Colorado School of Medicine, started exploring the idea that mitochondrial function could be key to peak performance almost three decades ago. He has applied his findings to the training routines of professional athletes, including two-time Tour de France winner Tadej Pogačar. “Mitochondria are stimulated by exercise,” he says. “I wanted to see if that stimulation varied depending on intensity.”