Analysis of proximal and distal muscle activity during handwriting tasks.
OBJECTIVE
In this study we sought to describe upper-extremity proximal and distal muscle activity in typically developing children during a handwriting task and to explore the relationship between muscle activity and speed and quality of writing.


METHODS
We evaluated 35 third- and fourth-grade Israeli children using the Alef-Alef Ktav Yad Hebrew Handwriting Test. Simultaneously, we recorded the participants' upper trapezius and thumb muscle activity by surface electromyography. Using the coefficient of variation (standard deviation divided by mean amplitude) as a measure of variability within each muscle, we analyzed differences in muscle activity variability within and between muscles.


RESULTS
The proximal muscle displayed significantly less variability than the distal muscles. Decreased variability in proximal muscle activity was associated with decreased variability in distal muscle activity, and decreased variability in the distal muscles was significantly associated with faster speed of writing.


CONCLUSIONS
The lower amount of variability exhibited in the proximal muscle compared with the distal muscles seems to indicate that the proximal muscle functions as a stabilizer during a handwriting task. In addition, decreased variability in both proximal and distal muscle activity appears to be more economical and is related to faster writing speed. Knowledge of the type of proximal and distal muscle activity used during handwriting can help occupational therapists plan treatment for children with handwriting disabilities.
Naider-Steinhart
Shoshana
S
Rehabilitation Department, Alyn Children's Hospital, P.O.B. 9117, Olswanger Street, Kiryat Yovel, Jerusalem, 91090 Israel. Naider73@zahav.net.il
Katz-Leurer
Michal
M
D002648:Child; D004576:Electromyography; D005260:Female; D006236:Handwriting; D006801:Humans; D007557:Israel; D008297:Male; D009043:Motor Activity; D009132:Muscles / Q000502:physiology*; D010372:Pediatrics