Introduction: mobile Devices (MDs), such as smartphones, are becoming increasingly important in people’s lives, and they use them for entertainment, to study or to work. Consequently, pathologies that were once associated with labor have been increasingly associated with these everyday activities, affecting a large number of people. Materials and Methods: A descriptive study about the most common clinical findings and the main affected muscles in repetitive movements, according to a literature review. Results: typing in MDs requires a new way of using the musculoskeletal system, and it mainly involves the thumb. Circular movements of the thumb don’taffect the muscles in the area, but the flexion-extension movements of the thumb cause muscle fatigue more quickly than the abduction-adduction ones. The most damaging postures are associated with typing on the lower right keys among right-handed people, because flexion-extension is the main movement used in this action, causing injuries especially in the abdutor pollicis longus of the thumb. Normally, these injuries are characterized by tendonitis or tenosynovitis, which, in this context, are repetitive-motion injuries (RMIs). De Quervain tenosynovitis and carpal tunnel syndrome, though also resulting from other situations, may as well be caused or worsened by the frequent use of MDs. Conclusion: therefore, the rational use of these devices is recommended, taking pauses and stretching during use, and also suspending or reducing the use when the first symptoms appear. [ABSTRACT FROM AUTHOR]