Reorganization of multidigit physiological tremors after repetitive contractions of a single finger.
In light of the interplay among physiological finger tremors, this study was undertaken to investigate the transfer effect of fatigue on coordinative strategies of multiple fingers. Fourteen volunteers performed prolonged position tracking with a loaded middle finger while measures of neuromuscular function, including electromyographic activities of the extensor digitorum (ED)/flexor digitorum superficialis (FDS) and physiological tremors of the index, middle, ring, and little fingers, were monitored. The subjects exhibited inferior tracking congruence and an increase in ED activity at the end of the tracking. Fatigue spread was manifested in a remarkable increase in tremor across fingers, in association with enhanced involuntary tremor coupling among fingers that was topologically organized in relation to the distance of the digits from the middle finger. Principal component analysis suggested that an enhanced 8- to 12-Hz central rhythm contributed primarily to the tremor restructure following fatigue spread. The observed tremor reorganization validated the hypothesis that the effect of fatigue was not limited to the instructed finger and that fatigue functionally decreased independence of the digits. The spreading of fatigue weakens neural inputs that diverge to motor units acting on various digits because of fatigue-related enhancement of common drive at the supraspinal level.
Hwang
Ing-Shiou
IS
1Department of Physical Therapy and 2Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan. ishwang@mail.ncku.edu.tw
Yang
Zong-Ru
ZR
Huang
Chien-Ting
CT
Guo
Mei-Chun
MC
D000328:Adult; D004576:Electromyography; D005260:Female; D005385:Fingers / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D025341:Principal Component Analysis; D011999:Recruitment, Neurophysiological / Q000502:physiology*; D014202:Tremor; D055815:Young Adult