title: Evoked EMG versus muscle torque during fatiguing functional electrical stimulation-evoked muscle contractions and short-term recovery in individuals with spinal cord injury.
abstract: This study investigated whether the relationship between muscle torque and m-waves remained constant after short recovery periods, between repeated intervals of isometric muscle contractions induced by functional electrical stimulation (FES). Eight subjects with spinal cord injury (SCI) were recruited for the study. All subjects had their quadriceps muscles group stimulated during three sessions of isometric contractions separated by 5 min of recovery. The evoked-electromyographic (eEMG) signals, as well as the produced torque, were synchronously acquired during the contractions and during short FES bursts applied during the recovery intervals. All analysed m-wave variables changed progressively throughout the three contractions, even though the same muscle torque was generated. The peak to peak amplitude (PtpA), and the m-wave area (Area) were significantly increased, while the time between the stimulus artefact and the positive peak (PosT) were substantially reduced when the muscles became fatigued. In addition, all m-wave variables recovered faster and to a greater extent than did torque after the recovery intervals. We concluded that rapid recovery intervals between FES-evoked exercise sessions can radically interfere in the use of m-waves as a proxy for torque estimation in individuals with SCI. This needs to be further investigated, in addition to seeking a better understanding of the mechanisms of muscle fatigue and recovery.
authors.affiliation: Clinical Exercise and Rehabilitation Unit, Exercise Health and Performance, Faculty of Health Sciences, University of Sydney, Lidcombe, 2006 NSW, Australia. ehestigoni@yahoo.com.br.
authors.forename: Eduardo H
authors.initials: EH
authors.lastname: Estigoni
authors.affiliation: Clinical Exercise and Rehabilitation Unit, Exercise Health and Performance, Faculty of Health Sciences, University of Sydney, Lidcombe, 2006 NSW, Australia. che.fornusek@sydney.edu.au.
authors.forename: Che
authors.initials: C
authors.lastname: Fornusek
authors.affiliation: Clinical Exercise and Rehabilitation Unit, Exercise Health and Performance, Faculty of Health Sciences, University of Sydney, Lidcombe, 2006 NSW, Australia. azah.hamzaid@um.edu.my.
authors.forename: Nur Azah
authors.initials: NA
authors.lastname: Hamzaid
authors.affiliation: Clinical Exercise and Rehabilitation Unit, Exercise Health and Performance, Faculty of Health Sciences, University of Sydney, Lidcombe, 2006 NSW, Australia. nazirah@um.edu.my.
authors.forename: Nazirah
authors.initials: N
authors.lastname: Hasnan
authors.affiliation: Clinical Exercise and Rehabilitation Unit, Exercise Health and Performance, Faculty of Health Sciences, University of Sydney, Lidcombe, 2006 NSW, Australia. richard.smith@sydney.edu.au.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Smith
authors.affiliation: Clinical Exercise and Rehabilitation Unit, Exercise Health and Performance, Faculty of Health Sciences, University of Sydney, Lidcombe, 2006 NSW, Australia. glen.davis@sydney.edu.au.
authors.forename: Glen M
authors.initials: GM
authors.lastname: Davis
mesh_terms: D000465:Algorithms; D004599:Electric Stimulation Therapy / Q000379:methods*; D004576:Electromyography / Q000379:methods*; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue; D053580:Muscle Strength; D020127:Recovery of Function; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013119:Spinal Cord Injuries / Q000503:physiopathology* / Q000534:rehabilitation; D019415:Torque