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To investigate changes after a mountain ultramarathon (MUM) in the serum concentration of fast (FM) and slow (SM) myosin isoforms, which are fiber-type-specific sarcomere proteins. The changes were compared against creatine kinase (CK), a widely used fiber-sarcolemma-damage biomarker, and cardiac troponin I (cTnI), a widely used cardiac biomarker.


Observational comparison of response in a single group of 8 endurance-trained amateur athletes. Time-related changes in serum levels of CK, cTnI, SM, and FM from competitors were analyzed before, 1 h after the MUM, and 24 and 48 h after the start of the MUM by 1-way ANOVA for repeated measures or Friedman and Wilcoxon tests. Pearson correlation coefficient was employed to examine associations between variables.


While SM was significantly (P = .009) increased in serum 24 h after the beginning of the MUM, FM and cTnI did not change significantly. Serum CK activity peak was observed 1 h after the MUM (P = .002). Moreover, serum peaks of CK and SM were highly correlated (r = .884, P = .004).


Since there is evidence of muscle damage after prolonged mountain running, the increase in SM serum concentration after a MUM could be indirect evidence of slow- (type I) fiber-specific sarcomere disruptions.

Carmona, Irurtia, and Cadefau are with the National Inst of Physical Education of Catalonia, Barcelona, Spain. Roca is with the University of Girona, Girona, Spain. Guerrero and Cussó are with the Dept of Physiological Sciences I, University of Barcelona, Barcelona, Spain. Nescolarde is with the Polytechnic University of Catalonia, Barcelona, Spain. Brotons is with the Catalan Sports Council, Government of Catalonia, Barcelona, Spain. Bedini is with the Hospital Clinic, Barcelona, Spain.

Address author correspondence to Joan Cadefau at jcadefau@gencat.cat.