title: Effects of a single bout of isometric neuromuscular electrical stimulation on rat gastrocnemius muscle: a combined functional, biochemical and MRI investigation.
abstract: While muscle damage resulting from electrically-induced muscle isometric contractions has been reported in humans, animal studies have failed to illustrate similar deleterious effects and it remains to be determined whether these conflicting results are related to differences regarding experimental procedures or to species. We have investigated in vivo, in rat gastrocnemius muscles, using experimental conditions as close as possible to those used in humans (i.e., muscle length, number of contractions, stimulated muscle), the effects of a single bout of neuromuscular electrical stimulation (NMES). Maximal tetanic force was measured before, immediately after and 1h and 1, 2, 3, 7 and 14 days after NMES. Magnetic resonance imaging measurements, including volume of gastrocnemius muscles and proton transverse relaxation time (T(2)) were performed at baseline and 3, 7, and 14 days after the NMES session. Control animals did not perform any exercise and measurements were recorded at the same time points. For both groups, blood creatine kinase (CK) activity was measured within the first 3 days that followed the initial evaluation. Maximal tetanic force decreased immediately after NMES whereas measurements performed 1h and the days afterwards were similar to the baseline values. CK activity, muscle volume and T(2) values were similar throughout the experimental protocol between the two groups. Under carefully controlled experimental conditions, isometric NMES per se did not induce muscle damage in rat gastrocnemius muscles on the contrary to what has been repeatedly reported in humans. Further experiments would then be warranted in order to clearly delineate these differences and to better understand the physiological events associated with muscle damage resulting from NMES-induced isometric contractions.
authors.affiliation: Centre de Résonance Magnétique Biologique et Médicale, UMR CNRS 6612, Université de la Méditerranée, Faculté de Médecine de Marseille, Marseille, France. julien.gondin@univmed.fr
authors.forename: Julien
authors.initials: J
authors.lastname: Gondin
authors.forename: Benoît
authors.initials: B
authors.lastname: Giannesini
authors.forename: Christophe
authors.initials: C
authors.lastname: Vilmen
authors.forename: Yann
authors.initials: Y
authors.lastname: Le Fur
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Cozzone
authors.forename: David
authors.initials: D
authors.lastname: Bendahan
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods*; D007537:Isometric Contraction / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar