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Electrophysiological studies of upper trapezius and abductor pollicis brevis muscles during smartphone usage with different dominant hands in adolescent age: A pre-experimental study

Rana N Hussien*, Amira M El Tohamy, Mohamed H Rashad, Walaa Abd El-Hahiem Abd El Nabie

Background: Smartphone has been increasingly used many times daily. Unfortunately, its excessive usage is associated with different musculoskeletal disorders through affecting muscles function of the upper limbs. Objectives: The aim of this study was to evaluate electrical muscle activity of upper trapezius and abductor pollicis brevis muscles in relation to dominant hand type while using a smartphone. Methods: A one group experimental study was conducted on healthy one-hundred and fifty children with age 12 – 14 years from both sexes. The electrical activities of their right and left upper trapezius and abductor pollicis brevis muscles were recorded by electromyography at 6 time points; 0, 10, 15, 20, 25, and 30 minutes while using the smartphones. Results: The results showed that the majority of children had a right dominant hand (82%). After starting smartphone use, electrical activity of the right and left upper trapezius and abductor pollicis brevis muscles declined significantly at each time point (p-value < 0.05). This reduction was significantly influenced by increased body mass index for the right and left muscles, left dominant hand for the right muscles, and right dominant hand for the left muscles. Moreover, abductor pollicis brevis muscles were more affected than upper trapezius muscles indicated by time to maximum reduction in the electrical activity (10 versus 15 minutes) and partial eta-squared. The partial eta squared for the effect of time interacted with dominant hand type is 3.2% and 5.6% for the right and left trapezius muscles compared to 12.5 % and 36.4% for the right and left abductor pollicis brevis muscles, respectively. Conclusion: Reduction in muscle activity is an adverse effect from smartphone excessive use; optimal usage time should be established to guide its use, especially among children.