Myoelectric Signs of Sustained Muscular Activity During Smartphone Texting

The aim of the present study was to analyze the upper trapezius activity, and its relationship with muscular discomfort perceived, during prolonged smartphone texting. Seventeen healthy young subjects participated in the experiment; they were asked to use their own smartphone for texting (10 min), maintaining two different postures, sitting and standing. The muscular activity of the right and left upper trapezius was recorded, and the CR10 BorgScale was administered after each experimental section. To normalize the EMG signals, the maximum voluntary contraction was acquired at the beginning of the experiment. The median, the 10th percentile (P10) and the range (difference between 90th and 10th) of EMG RMS, the relative rest time (RRT), the correlation between P10 and RRT and between P10 and CR10 scale were calculated. The results showed no statistical difference between the postures, and the body side. The value of RMS parameters was around the 2% of MVC, showing a constant muscular activity throughout the experimental section. A significant negative correlation between P10 and RRT suggested that the subjects with greater P10 showed a lower rest period; moreover, the significant positive correlation between P10 and CR10 Borg scale, for both postures, suggested that the subjects with high P10 values perceived greater discomfort in neck and cervical zone. The results support the hypothesis that the prolonged use of smartphone for texting influences the upper trapezius activity and it is strictly linked with the absence of a period of muscular recovery, and with the perception of muscular discomfort: that may be a potential risk factor to develop neck pain and musculoskeletal cervical disorders.