title: Metabolic costs of force generation for constant-frequency and catchlike-inducing electrical stimulation in human tibialis anterior muscle.
abstract: Metabolic costs of force generation were compared for constant-frequency and catchlike-inducing electrical stimulation. Repetitive catchlike-inducing trains consisted of 2 interpulse intervals (IPIs) at 12.5 ms, 1 IPI at 25 ms, and 5 IPIs at 50 ms. Constant-frequency trains consisted of 8 IPIs at 37.5 ms. One train was delivered to the peroneal nerve every 2.5 s for 36 times under ischemic conditions. Anaerobic adenosine triphosphate (ATP) turnover was determined using 31-phosphorus magnetic resonance spectroscopy (P-MRS) of the human tibialis anterior muscle. Compared with constant-frequency trains, catchlike-inducing trains produced a faster force generation and were more effective in maintaining the force--time integral as well as peak force. However, ATP costs of force generation were similar for the catchlike-inducing and constant-frequency stimulation (6.7 plus/minus 1.1 and 6.6 plus/minus 1.0 micromol ATP/kg wet weight/Ncenter dots, respectively, P = 0.601). This suggests that the positive effects of catchlike-inducing stimulation on force maintenance are mediated by potentiated Ca(2+) release from the sarcoplasmic reticulum rather than by lower metabolic costs of muscle force generation. Our findings also suggest that catchlike-inducing stimulation produces larger forces in fatigued muscle than constant-frequency trains and thus may be beneficial for muscle training or rehabilitation when muscle loading needs to be maintained in repetitive contractions.
authors.affiliation: NMR Center, Department of Medical Biochemistry and Genetics A, Panum Institute, University of Copenhagen, Blegdamsveg 3, DK-2200 Copenhagen N, Denmark. aivaras@imbg.ku.dk
authors.forename: Aivaras
authors.initials: A
authors.lastname: Ratkevicius
authors.forename: Bjørn
authors.initials: B
authors.lastname: Quistorff
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000378:metabolism*; D010543:Peroneal Nerve / Q000502:physiology; D010725:Phosphocreatine / Q000378:metabolism; D010759:Phosphorus Isotopes
chemical_list: D010759:Phosphorus Isotopes; D010725:Phosphocreatine; D000255:Adenosine Triphosphate