Corticomotor excitability of wrist flexor and extensor muscles during active and passive movement.
The excitability of the corticospinal projection to upper and lower limbs is constantly modulated during voluntary and passive movement; however a direct comparison during a comparable movement has not been reported. In the present study we used transcranial magnetic stimulation (TMS) to compare corticomotor excitability to the extensor and flexor carpi radialis (ECR/FCR) muscles of the forearm during voluntary rhythmic wrist movement (through 45 degrees of range), during a matched (for range and rhythm) passive movement of the wrist, and while the wrist was stationary (in mid-range). TMS was delivered when the wrist was in the neutral position. With passive and active movement, and for both FCR and ECR, corticomotor excitability was reduced during lengthening relative to shortening phases of movement. With active movement, this pattern was maintained and superimposed on an overall increase in excitability to both muscles that was greater for the ECR. The results favor a common pattern of excitability changes shared by extensor and flexor muscles as they undergo lengthening and shortening, which may be mediated by afferent input during both passive and active movement. This is combined with an overall increase in excitability associated with active movement that is greater for extensor muscles perhaps due to differences in the strength of the corticomotor projection to these muscles.
School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Western Australia, Australia.
Lilian
L
Chye
Ken
K
Nosaka
Lynda
L
Murray
Dylan
D
Edwards
Gary
G
Thickbroom
D000328:Adult; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation*; D011712:Pyramidal Tracts / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014953:Wrist / Q000294:innervation*; D055815:Young Adult