title: Wide-pulse-high-frequency neuromuscular stimulation of triceps surae induces greater muscle fatigue compared with conventional stimulation.
abstract: We compared the extent and origin of muscle fatigue induced by short-pulse-low-frequency [conventional (CONV)] and wide-pulse-high-frequency (WPHF) neuromuscular electrical stimulation. We expected CONV contractions to mainly originate from depolarization of axonal terminal branches (spatially determined muscle fiber recruitment) and WPHF contractions to be partly produced via a central pathway (motor unit recruitment according to size principle). Greater neuromuscular fatigue was, therefore, expected following CONV compared with WPHF. Fourteen healthy subjects underwent 20 WPHF (1 ms-100 Hz) and CONV (50 μs-25 Hz) evoked isometric triceps surae contractions (work/rest periods 20:40 s) at an initial target of 10% of maximal voluntary contraction (MVC) force. Force-time integral of the 20 evoked contractions (FTI) was used as main index of muscle fatigue; MVC force loss was also quantified. Central and peripheral fatigue were assessed by voluntary activation level and paired stimulation amplitudes, respectively. FTI in WPHF was significantly lower than in CONV (21,717 ± 11,541 vs. 37,958 ± 9,898 N·s P<0,001). The reductions in MVC force (WPHF: -7.0 ± 2.7%; CONV: -6.2 ± 2.5%; P < 0.01) and paired stimulation amplitude (WPHF: -8.0 ± 4.0%; CONV: -7.4 ± 6.1%; P < 0.001) were similar between conditions, whereas no change was observed for voluntary activation level (P > 0.05). Overall, our results showed a different motor unit recruitment pattern between the two neuromuscular electrical stimulation modalities with a lower FTI indicating greater muscle fatigue for WPHF, possibly limiting the presumed benefits for rehabilitation programs.
authors.affiliation: Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland; Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland; Institute of Movement Sciences and Sports Medicine, University of Geneva, Geneva, Switzerland;
authors.forename: Daria
authors.initials: D
authors.lastname: Neyroud
authors.affiliation: Institute of Movement Sciences and Sports Medicine, University of Geneva, Geneva, Switzerland;
authors.forename: David
authors.initials: D
authors.lastname: Dodd
authors.affiliation: Aix Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France; and.
authors.forename: Julien
authors.initials: J
authors.lastname: Gondin
authors.affiliation: Neuromuscular Research Laboratory, Schulthess Clinic, Zurich, Switzerland.
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Maffiuletti
authors.affiliation: Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland; Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland; Institute of Movement Sciences and Sports Medicine, University of Geneva, Geneva, Switzerland;
authors.forename: Bengt
authors.initials: B
authors.lastname: Kayser
authors.affiliation: Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland; Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland; nicolas.place@unil.ch.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Place
mesh_terms: D000328:Adult; D000843:Ankle Joint; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D011999:Recruitment, Neurophysiological / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: neuromuscular electrical stimulation; peripheral fatigue; pulse duration; stimulation frequency