The relationship between smartphone use and musculoskeletal discomfort was related to the duration of
ancillary function use. The duration of time spent talking on the phone was a predictor of upper back
discomfort [8]. So, the current study was to investigate the effect of smartphone duration use on pain of the
upper back and scapular muscles strength (lower trapezius, rhomboids major and rhomboids minor) in normal
subjects.
MATERIALS AND METHODS
The current study was carried out in the outpatient clinic of the faculty of physical therapy on internship
students and fresh post graduates in educational staff, Cairo University from November 2018 to May 2020. To
investigate the effect of smartphone duration use on pain of the upper back and scapular muscles strength
(lower trapezius, rhomboids major and rhomboids minor) in normal subjects.
Cross sectional observational study
Eighty normal subjects from both genders with right hand dominance were enrolled in this study. Subjects
were divided based on daily duration use of smartphone into two groups: Group A, who used smartphone less
than 4 hours daily; Group B who used smartphone more than 4 hours daily. The subjects participated in the
current study after approval of Ethical Committee of the faculty of physical therapy, Cairo University with
number (P.T.REC/012/002137), and all subjects provided written inform consent. All subjects were normal
referred with right hand dominance from both genders; subjects were included in this study if they had at least
6 months experience in using touch-screen smartphones and their age ranging from 20 to 30 years. Subjects
were excluded from the study if they had any pain or limitation (dysfunction) at neck and shoulder, who have
physical difficulties in using smartphones while sitting and standing were recruited? Any congenital
abnormalities in either the cervical or the lumbar spine, previous history of severe surgical procedures, any
history of upper extremity injury within the past year, visual problems, dizziness and vertigo, any deformity in
the upper extremities or spine, neurological or systemic disorders and if they had taken any sedative drug or
alcohol within the past 48 hours [9-10].
Initially, subjects were screened against inclusion and exclusion criteria, eligible subjects were informed
about the aim of the study and all testing procedures. Then, they were asked to participate in the study, if
agreed an informed consent was signed. Basic demographic information as well as questions regarding the
average smartphone screen size and the average daily smartphone use was collected from information sheet.
Subjects were assessed once time. During this session, the participant was assessed by analogue baseline
pull and push dynamometer from a standardized prone position to assess strength of scapular muscles [11]. Two
non-resistive training trials was provide for each muscle group to demonstrate to the subjects the positions and
specific muscle group contraction that would have the resistance applied to avoid interference of exercise or
training effect. Three measurements of each muscle group were recorded using this technique, to ensure
maximal isometric strength and to minimize muscle fatigue.
Each subject was instructed to rate the current level of pain by placing a mark across the horizontal VAS
line. The distance in millimeters from the lower limit was measured using a ruler [12]. Calibration of the pull
and push dynamometer was performed prior to use according to the manufacturer guidelines. According to
Kendall MMT testing parameters (break test) [11], the subject applies a maximal force that is resisted by the
examiner. The “breaking force” is the amount of force required to overcome a maximal effort muscle
contraction in order to move the shoulder girdle (ST) joint from the initial starting position.
Two major Scapula-humeral muscle groups were test unilaterally (right dominant side then left non
dominant side) with the Push-Pull hydraulic type hand held Dynamometer (200 N or 20 kg), The procedure used
to measure scapular muscle strength was adapted from a previous study that reported good between day intra
rater reliability for scapular dynamometer strength measurements (ICCs 0.75 to 0.97) [13].
Scapular adduction and depression and also scapular adduction and downward rotation both measured in
prone position with head turned to opposite side and therapist stabilize the contra lateral scapula. Three
maximum voluntary contractions (MVCs) for the dominant side will be record. The investigator instructed the
subject to push into the dynamometer with their maximum effort, holding for 5 second duration. Subjects were
instructed to slowly build up their force production to their maximum force before the end of the 5 seconds. The
maximum voluntary contractions were recorded by the assessor. An attempt was made to isolate the following
muscles.
Citation: Mohamed MS, Elkeblawy MM, Amin DI. Effect of smartphone duration use on scapular muscles strength in normal subjects. J Life Sci Biomed, 2020;
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