The early response to eccentric exercise in human skeletal muscle
Stephan Klossner, Christoph Däpp, Silvia Schmutz, Michael Vogt, Hans Hoppeler, Martin Flück
Department of Anatomy, University of Berne
Background: Delayed onset muscle soreness (DOMS) is a common consequence of muscle damage as it occurs with downhill walking and leads to prolonged reduction in muscle force. Eccentric contractions, where an activated muscle is lengthened, have been argued to represent the major component of such damage as they augment the mechanical stress to skeletal muscle fibers.
Methods: 6 healthy, untrained volunteers performed a single bout of 15 minutes duration on an eccentric ergometer. Muscle force and blood parameters were measured before eccentric exercise and during recovery. Fine needle biopsies were taken from the m. vastus lateralis during the first 24 hours of recovery from the eccentric exercise bout. Total RNA was isolated and subjected to transcript profiling using a custom-designed, low-density cDNA micorarray.
Results: Muscle strength was reduced immediately after the eccentric bout but recovered within 4 days. After exercise a moderate 2-fold increased serum level of creatine kinase, the marker of muscle damage, was noted. Microarray analysis indicates transcriptional down regulation of most of the gene transcripts with recovery within 24 hours. Interestingly, also the molecular marker of muscle injury, Tenascin-C, showed decreased mRNA levels, which returned to control values after 24 hours. The early response genes c-jun, ubiquitin-c and myf 6 are the only ones to be up regultated right after the exercise.
Conclusions: Overloading of skeletal muscle via a single bout of eccentric ergometer exercise causes rapid downregulation of the mRNA pool in human skeletal muscle.
