Fibre-type-specific and Mitochondrial Biomarkers of Muscle Damage after Mountain Races

Consequences of running mountain races on muscle damage were investigated by analysing serum muscle enzymes and fibre-type-specific sarcomere proteins. We studied 10 trained amateur and 6 highly trained runners who ran a 35km and 55km mountain trail race (MTR), respectively. Levels of creatine kinase (CK), CK-MB isoform (CK-MB), sarcomeric mitochondrial CK (sMtCK), transaminases (AST and ALT), cardiac troponin I (cTnI) and fast (FM) and slow myosin (SM) isoforms, were assessed before, 1h, 24h and 48h after the beginning of MTR. Significant SM increases were found at 24h in the 55km group. Levels of CK, CK-MB, AST and cTnI were significantly elevated in both groups following MTR, but in the 55km group they tended to stabilize in at 48h. Using pooled data, time-independent serum peaks of SM and CK-MB were significantly correlated. Moreover, concentration of sMtCK was significantly elevated at 1 and 24h after the race in the 35km group. Although training volume could confer protection on the mitochondria, the increase in serum CK-MB and SM in the 55km group might be related to damage to the contractile apparatus type I fibres. Competing in long-distance MTRs might be related to deeper type I muscle fibre damage, even in highly trained individuals