title: Human muscle energetics during voluntary and electrically induced isometric contractions as measured by 31P NMR spectroscopy.
abstract: Electrical stimulation (ES) and voluntary contraction (VC) were compared in the quadriceps muscle of ten male volunteers. In both modes, a workload corresponding to 20% of maximal voluntary contraction was applied during 64 isometric contraction (5.5 s)-relaxation (5.5 s) cycles. The protocols were performed in a 1.5 T whole-body magnet. The Pi/PCr ratio and the intracellular pH (pHi) were monitored by 31P NMR spectroscopy during baseline, exercise and recovery periods, in a superficial region of the vastus medialis. During baseline, the Pi/PCr ratio (0.12 vs. 0.10) and the pHi (7.01 vs. 7.00) were comparable in both conditions. During exercise, the Pi/PCr ratio was higher (0.36 vs. 0.14) and the pHi was lower (6.85 vs. 7.07) during ES than during VC. For the same external work production, these results reflect a different metabolic solicitation in the ES quadriceps than in the VC ones.
authors.affiliation: Physical Medicine Department, University Hospital, Liège, Belgium. mvanderthommen@ulg.ac.be
authors.forename: M
authors.initials: M
authors.lastname: Vanderthommen
authors.forename: R
authors.initials: R
authors.lastname: Gilles
authors.forename: P
authors.initials: P
authors.lastname: Carlier
authors.forename: F
authors.initials: F
authors.lastname: Ciancabilla
authors.forename: O
authors.initials: O
authors.lastname: Zahlan
authors.forename: F
authors.initials: F
authors.lastname: Sluse
authors.forename: J M
authors.initials: JM
authors.lastname: Crielaard
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D010759:Phosphorus Isotopes
chemical_list: D010759:Phosphorus Isotopes