Original Article

European Journal of Applied Physiology

, Volume 89, Issue 2, pp 202-208

Functional and biochemical properties of chronically stimulated human skeletal muscle

  • Martin NuhrAffiliated withUniversitätsklinik für Physikalische Medizin und Rehabilitation, AKH WienDepartment of Physical Medicine and Rehabilitation, General Hospital of Vienna Email author 
  • , Richard CrevennaAffiliated withDepartment of Physical Medicine and Rehabilitation, General Hospital of Vienna
  • , Bärbel GohlschAffiliated withDepartment of Biology, University of Konstanz
  • , Christian BittnerAffiliated withDepartment of Physical Medicine and Rehabilitation, General Hospital of Vienna
  • , Johannes PleinerAffiliated withDepartment of Physical Medicine and Rehabilitation, General Hospital of Vienna
  • , Günther WiesingerAffiliated withDepartment of Physical Medicine and Rehabilitation, General Hospital of Vienna
  • , Veronika Fialka-MoserAffiliated withDepartment of Physical Medicine and Rehabilitation, General Hospital of Vienna
  • , Michael QuittanAffiliated withDepartment of Physical Medicine and Rehabilitation, General Hospital of Vienna
  • , Dirk PetteAffiliated withDepartment of Biology, University of Konstanz

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Abstract

The present study was undertaken to investigate in a randomized controlled trial the effects of chronic (10 weeks, 4 h per day, 7 days per week) low-frequency (15 Hz) stimulation (CLFS) of the knee extensor and hamstring muscles of both legs in healthy volunteers via surface electrodes. A control group (n=10) underwent the same treatment (sham stimulation) as the CLFS-treated group (n=10), except that stimulation intensity was kept at a level which did not evoke contractions. Biopsy samples were taken before the onset and after cessation of stimulation from the right vastus lateralis muscle of all subjects. The biopsy samples were analyzed for changes in myosin heavy chain (MHC) isoforms and activities of citrate synthase (CS) and glyceraldehyde phosphate dehydrogenase (GAPDH) as markers of aerobic-oxidative and anaerobic pathways of energy metabolism, respectively. In addition, functional properties, i.e., oxygen consumption (V̇O2) and work capacity, were assessed. Sham stimulation did not affect the functional properties and had no detectable effect on MHC isoform and enzyme activity patterns. Conversely, CLFS induced changes in the MHC isoform pattern in the fast-to-slow direction with a ~20% decrease in the relative concentration of MHCIId/x (from 28% to 22%) and a ~10% increase in the relative concentration of MHCI (from 30% to 34%). In addition, CLFS led to a ~9% increase in the activity of CS concomitant with a ~7% decrease in the activity of GAPDH. This increase in aerobic-oxidative capacity was accompanied by improved work capacity and V̇O2 at the anaerobic threshold by 26% and 20%, respectively.

Keywords

Anaerobic threshold Chronic low-frequency stimulation Citrate synthase Fast-to-slow transition Glyceraldehyde phosphate dehydrogenase Myosin heavy chain isoforms