title: Phase- and Workload-Dependent Changes in Corticospinal Excitability to the Biceps and Triceps Brachii during Arm Cycling.
abstract: This is the first study to examine corticospinal excitability (CSE) to antagonistic muscle groups during arm cycling. Transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of the corticospinal tract were used to assess changes in supraspinal and spinal excitability, respectively. TMS induced motor evoked potentials (MEPs) and TMES induced cervicomedullary evoked potentials (CMEPs) were recorded from the biceps and triceps brachii at two positions, mid-elbow flexion and extension, while cycling at 5% and 15% of peak power output. While phase-dependent modulation of MEP and CMEP amplitudes occurred in the biceps brachii, there was no difference between flexion and extension for MEP amplitudes in the triceps brachii and CMEP amplitudes were higher during flexion than extension. Furthermore, MEP amplitudes in both biceps and triceps brachii increased with increased workload. CMEP amplitudes increased with higher workloads in the triceps brachii, but not biceps brachii, though the pattern of change in CMEPs was similar to MEPs. Differences between changes in CSE between the biceps and triceps brachii suggest that these antagonistic muscles may be under different neural control during arm cycling. Putative mechanisms are discussed.
authors.affiliation: School of Human Kinetics and Recreation Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada. g37ajds@mun.ca.
authors.forename: Alyssa-Joy
authors.initials: AJ
authors.lastname: Spence
authors.affiliation: School of Human Kinetics and Recreation Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada. lynsey.alcock@gmail.com.
authors.forename: Lynsey R
authors.initials: LR
authors.lastname: Alcock
authors.affiliation: School of Human Kinetics and Recreation Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada. ejl006@mun.ca.
authors.forename: Evan J
authors.initials: EJ
authors.lastname: Lockyer
authors.affiliation: School of Human Kinetics and Recreation Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada. dbutton@mun.ca.|Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada. dbutton@mun.ca.
authors.forename: Duane C
authors.initials: DC
authors.lastname: Button
authors.affiliation: School of Human Kinetics and Recreation Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada. kevin.power@mun.ca.|Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada. kevin.power@mun.ca.
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Power
keywords: CMEP; MEP; central pattern generator; cervicomedullary evoked potentials; cortical; motoneurone; motor evoked potential; muscle; transcranial; transmastoid