Time pattern of exercise-induced changes in type I collagen turnover afterprolonged endurance exercise in humans

Type I collagen is known to adapt to physical activity, and biomarkers of c ollagen turnover indicate that synthesis can be influenced by a single inte nse exercise bout, but the exact time pattern of these latter changes are l argely undescribed. In the present study, 17 healthy young males had their plasma concentrations of the carboxyterminal propeptide of type I procollag en (PICP), a marker of collagen formation, and the immunoactive carboboxyte rminal cross-linked telopeptide (ICTP), a marker of collagen resorption, me asured before and immediately postexercise, as well as 1, 2, 3, 4, 5, and 6 days after completion of a marathon run (42 km). Serum concentrations of c reatine kinase (S-CK) were measured as an indicator of muscular breakdown i n response to the exercise bout. After a transient decrease in collagen for mation immediately after exercise (plasma PICP concentration: 176 +/- 17 mu g/liter to 156 +/- 9 mu g/liter)(P < 0.05), concentrations rose in the day s following the marathon, peaked 72 hours after exercise (197 +/- 8 mu g/li ter)(P < 0.05 versus basal), and returned to basal values similar to those 5 days postexercise (170 +/- 10 mu g/liter). Apart from a short increase im mediately after exercise, collagen resorption did not change from basal lev els throughout the remaining period (P > 0.05). Muscle breakdown was elevat ed during the days following the exercise and peaked 24 hours after the exe rcise (S-CK concentration: 3133 +/- 579 U/liter). The findings in the prese nt study indicate that type I collagen synthesis is accelerated in response to prolonged strenuous exercise, reaching a peak after 3 days and returnin g to preexercising levels 5 days after the completion of a marathon run.