Descending feels easy aerobically, but each step triggers muscle-damaging eccentric contractions in the quadriceps and lower legs, says Greg Wells, Ph.D., an exercise physiologist at the University of Toronto and the author of Superbodies: Peak Performance Secrets from the World's Best Athletes. On level ground, these muscles shorten as they fire; on declines, they elongate while under tension as they work to control your speed. This creates more micro-tears in each fiber, which stimulates muscle growth but leaves you fatigued and sore. That's one reason the Boston Marathon, with its four-mile downhill opening stretch, is such a hard course.
RR - thank you for a cracking race report. Well done on what sounded like a tough one. Hope you are having some down time today before the flight back. Could you post a picture of your medal so we can all drool ?