The Muscular Overuse Syndrome in Long-Distance Runners

In brief: Indicators of muscular injury from overtraining were studied in 12 male runners during a road race held over 20 days. Dally mileage averaged 17.3 miles per day, twice their regular training distance. Most of the runners reported persistent mild-to-moderate thigh muscle soreness or stiffness. Serum creatine kinase (CK), an enzymatic marker of muscle tissue injury, was elevated on mornings after running but returned to normal values when the runners rested for two days after day 10. Thigh circumference became significantly reduced during the race, suggesting that the unaccustomed high running mileage also produced thigh muscle atrophy.