title: Responders to Wide-Pulse, High-Frequency Neuromuscular Electrical Stimulation Show Reduced Metabolic Demand: A 31P-MRS Study in Humans.
abstract: Conventional (CONV) neuromuscular electrical stimulation (NMES) (i.e., short pulse duration, low frequencies) induces a higher energetic response as compared to voluntary contractions (VOL). In contrast, wide-pulse, high-frequency (WPHF) NMES might elicit--at least in some subjects (i.e., responders)--a different motor unit recruitment compared to CONV that resembles the physiological muscle activation pattern of VOL. We therefore hypothesized that for these responder subjects, the metabolic demand of WPHF would be lower than CONV and comparable to VOL. 18 healthy subjects performed isometric plantar flexions at 10% of their maximal voluntary contraction force for CONV (25 Hz, 0.05 ms), WPHF (100 Hz, 1 ms) and VOL protocols. For each protocol, force time integral (FTI) was quantified and subjects were classified as responders and non-responders to WPHF based on k-means clustering analysis. Furthermore, a fatigue index based on FTI loss at the end of each protocol compared with the beginning of the protocol was calculated. Phosphocreatine depletion (ΔPCr) was assessed using 31P magnetic resonance spectroscopy. Responders developed four times higher FTI's during WPHF (99 ± 37 × 10(3) N.s) than non-responders (26 ± 12 × 10(3) N.s). For both responders and non-responders, CONV was metabolically more demanding than VOL when ΔPCr was expressed relative to the FTI. Only for the responder group, the ∆PCr/FTI ratio of WPHF (0.74 ± 0.19 M/N.s) was significantly lower compared to CONV (1.48 ± 0.46 M/N.s) but similar to VOL (0.65 ± 0.21 M/N.s). Moreover, the fatigue index was not different between WPHF (-16%) and CONV (-25%) for the responders. WPHF could therefore be considered as the less demanding NMES modality--at least in this subgroup of subjects--by possibly exhibiting a muscle activation pattern similar to VOL contractions.
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wegrzyk
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Fouré
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Le Fur
authors.affiliation: Human Performance Lab, Schulthess Clinic, Zurich, Switzerland.
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Maffiuletti
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Vilmen
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.|APHM, Hôpital Sainte-Marguerite, Service de Rhumatologie, Pôle Appareil Locomoteur, Marseille, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Guye
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.|APHM, Hôpital Sainte-Marguerite, Service de Rhumatologie, Pôle Appareil Locomoteur, Marseille, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Mattei
authors.affiliation: ISSUL, Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.|Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Place
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.
authors.forename: David
authors.initials: D
authors.lastname: Bendahan
authors.affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Gondin
mesh_terms: D000328:Adult; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008279:Magnetic Resonance Imaging; D008297:Male; D018763:Muscle Fatigue; D010725:Phosphocreatine / Q000032:analysis*; D055815:Young Adult
chemical_list: D010725:Phosphocreatine