Female high school students’ computer and smartphone usage time is increasing. Computer work and the use of smartphones can cause diseases in the neck and shoulders, and there are studies to prevent them, but there is no study on the relationship between the clothing worn and muscle activity.
The purpose of this study is to identify the muscle activity of the neck and shoulders and to provide the basic data for the development of the school uniform shirt pattern to reduce muscle activities.
Surface electromyography (SEMG) of cervical erector spinae (CES), upper trapezius (UT), anterior deltoid (AD), and posterior deltoid (PD) were measured during computer typing, smartphone use and handwriting with five subjects in two different sized school uniform shirts from two brands. The measured SEMG data were normalized by %RVC and the following conclusions were obtained:
First, in all types of shirts, CES showed the highest muscle activity among four muscles during all types of work. In A_91, CES had significantly higher muscle activity in handwriting than smartphone use. In B_88, CES had significantly higher muscle activity in handwriting than computer typing and smartphone use. In all shirt types, UT had significantly higher muscle activity in Computer typing than smartphone use and writing. In A_88, B_88 and B_91, AD had significantly higher muscle activity in computer typing. In all shirt types, PD had significantly higher muscle activity in the order of handwriting, computer typing, and smartphone use.
Second, in A_88, UT was significantly higher in late stage than early stage during computer typing. In A_91 and B_91, PD was significantly higher in early stage than late stage during computer typing. In A_91, UT was significantly higher in late stage than early stage during smartphone use. In B_88, CES was significantly higher in late stage than early stage during smartphone use. In B_91, AD was significantly higher in late stage than early stage during handwriting.
Third, in AD, B_88 and B_91 was significantly higher than A_91 during computer typing. In UT, B_88 and B_91 was significantly higher than A_91 during smartpone use. In all types of muscle was not show any significant differece during handwriting.
Fourth, in accordance with the brand of a same sized shirt, the muscle activities of CES, AD and PD during handwriting in the smaller shirt and that of AD during typing and CES and UT during smartphone use in the larger shirt were significantly higher in brand A than in brand B.
Fifth, according to the shirt size of a same brand, the muscle activity of CES, AD, and PD during smartphone use was significantly high in the smaller shirt only in brand A.
Sixth, the muscle activity of the neck and shoulder in three kinds of work was influenced by the neck circumference, biacromial breadth, back intersyce length, chest circumference and upper arm circumference of the uniform shirt. When typing on a computer, it was found to be effective to reduce muscle activity by giving sufficient ease to biacromial breadth, back intersyce length and bust circumference. When smartphone use, it was found to be effective to reduce muscle activity by giving sufficient ease to neck circumference, biacromial breadth and back intersyce length. When handwriting, it was found to be effective to reduce muscle activity by giving sufficient ease to neck circumference, biacromial breadth, back intersyce length, bust circumference, sleeve cap height 1/2, upper arm circumference and armscyle circumference.