Damage to Liver and Skeletal Muscles in Marathon Runners During a 100 km Run With Regard to Age and Running Speed. A Polish group examined at a 100 km pathway whether there is a damage to liver and muscle, whether any damage depends on age or running speed and whether it would be possible in this case to determine the optimal running speed to have no damage. It showed that it came to an increase in liver values, with this increase in the recreational phase still went on.There was also an increase in LDH, CK and CRP.The biggest difference in the rise of these parameters was after 75 km and after 24 hours a recreational phase.
The authors concluded that age is an important variable in terms of damage by a 100 km running. You can read the work below https://pubmed.ncbi.nlm.nih.gov/25964813/