Effects of Tablet Tilt Angle on Hand and Wrist Muscle Activation During Digital Handwriting: A Cross-Sectional Electromyographic Study in University Students

Background: Prolonged tablet use for digital handwriting is increasingly common in educational settings, yet optimal ergonomic positioning remains unclear. This exploratory, cross-sectional study examined how tablet tilt angle affects hand and wrist muscle activation patterns during digital handwriting. Methods: This cross-sectional study recruited fifteen healthy university students (age 22.3 ± 2.2 years) who completed standardized writing tasks at three tablet tilt angles (0°, 20°, 60°). Surface electromyography recorded activation from four muscles responsible for the dynamic tripod grip: abductor pollicis brevis (APB), flexor pollicis longus (FPL), flexor digitorum superficialis (FDS), and extensor carpi ulnaris (ECU). Results: Significant differences in muscle activation were observed across angles (p < 0.05) for three muscles. APB activation was higher at 0° (18.68 ± 11.88% MVIC) and 20° (18.72 ± 12.13% MVIC) than at 60° (14.67 ± 10.38% MVIC), while FDS use decreased from 0° (10.98 ± 4.80% MVIC) to 60° (6.43 ± 3.14% MVIC). Conversely, ECU use increased from 0° (11.76 ± 6.96% MVIC) to 60° (16.15 ± 8.02% MVIC). FPL showed no significant differences. Conclusions: Tablet tilt angle substantially affects neuromuscular activation patterns during digital handwriting. In healthy young adults, these findings may help inform preventive ergonomic strategies for prolonged tablet handwriting; however, direct clinical extrapolation requires validation in clinical and more diverse populations.