Abstract
Adverse health problem of smartphone use has been gradually increased. Prevention of this problem
is essential and urgent. The purpose of this study was to compare the differences of pain and muscle
activity at neck, shoulder, upper back and arm regions after smartphone use for 20 minutes among 3
positions (on the lap level, on the chest level and on the table). Twenty-four asymptomatic females aged
18-25 years old were recruited. The subjects were assigned to use smartphone in random order of 3 positions.
Location and severity of pain were measured by using body pain chart and visual analog scale
(VAS), respectively. Electromyography (EMG) was used to measure muscle activity of cervical erector
spinae (CES), upper trapezius (UT), middle trapezius (MT) and biceps brachii (BB) muscles. The results
showed that 1) After 20 minutes of smartphone use, pain increased significantly (p-value<0.05). 2) Pain
was found apparently, mostly in neck region; participants reported pain in 60 of 72 times, particularly in
the lap position. 3) Pain increased obviously in all positions; however, pain scale did not show any significant
difference among 3 positions. 4) EMG of CES increased up to 50% of maximum voluntary contraction
(MVC), but there was no significant difference of EMG of CES, UT, and MT among 3 positions. In summary,
smartphone use longer than 20 minutes could lead to muscular pain, particularly neck pain. CES
worked increasingly up to 50% of MVC. Therefore, we would recommend that to prevent the risk of
musculoskeletal problems, smartphone users should avoid using this IT device continually 20 minutes,
especially on the lap.
