title: Extra-torque of human tibialis anterior during electrical stimulation with linearly varying frequency and amplitude trains.
abstract: This work aimed to characterise the whole human muscle input/output law during electrical stimulation with triangular varying frequency and amplitude trains through combined analysis of torque, mechanomyogram (MMG) and electromyogram (EMG). The tibialis anterior (TA) of ten subjects (age 23-35 years) was investigated during static contraction obtained through neuromuscular electrical stimulation. After potentiation, TA underwent two 15s stimulation patterns: (a) frequency triangle (FT): 2 > 35 > 2 Hz at Vmax (amplitude providing full motor unit recruitment); (b) amplitude triangle (AT): Vmin > Vmax > Vmin (Vmin providing TA least mechanical response) at 35 Hz. 2 > 35 Hz or Vmin > Vmax as well as 35 > 2 Hz or Vmax > Vmin were defined as up-going ramp (UGR) and down-going ramp (DGR), respectively. TA torque, MMG and EMG were detected by a load cell, an optical laser distance sensor and a probe with two silver bar electrodes, respectively. For both FT and AT, only the two mechanical signals resulted always larger in DGR than in UGR, during AT extra-torque and extra-MMG were present even in the first 1/3 of the amplitude range where EMG data presented no significant differences between DGR and UGR. Our data suggest that extra-torque and extra-displacement are evident for both FT and AT, being mainly attributed to an intrinsic muscle property.
authors.affiliation: Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa, 11, 25123 Brescia, Italy; Laboratory of Neuromuscular Rehabilitation (LaRiN), University of Brescia - Institute "Casa di Cura Domus Salutis", Institute "Domus Salutis", Via Lazzaretto, 3, 25123 Brescia, Italy. Electronic address: orizio@unibs.it.
authors.forename: C
authors.initials: C
authors.lastname: Orizio
authors.forename: J
authors.initials: J
authors.lastname: Celichowski
authors.forename: F
authors.initials: F
authors.lastname: Toscani
authors.forename: C
authors.initials: C
authors.lastname: Calabretto
authors.forename: L
authors.initials: L
authors.lastname: Bissolotti
authors.forename: M
authors.initials: M
authors.lastname: Gobbo
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000843:Ankle Joint / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods*; D004566:Electrodes; D004576:Electromyography / Q000379:methods; D005528:Foot / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D011999:Recruitment, Neurophysiological / Q000502:physiology; D019415:Torque; D055815:Young Adult
keywords: Electromyogram; Mechanomyogram; Muscle extra-force; Neuromuscular electrical stimulation; Torque