Vibration; Adverse Effect

This study investigates the acute effects of smartphone-delivered local vibration on hand sensorimotor performance in healthy young adults. Using a custom-developed iPhone application, three vibration frequencies (80 Hz, 150 Hz, and 220 Hz) are applied to the dominant hand in a randomized crossover design with a minimum 48-hour washout between sessions. The primary aim is to evaluate frequency-dependent dose-response effects on hand grip strength. Secondary aims include assessment of two-point discrimination (tactile spatial acuity), pressure pain threshold, and hand reaction time before and immediately after each vibration condition. The study seeks to generate evidence on optimal application parameters for smartphone vibration as an accessible and portable local vibration source in clinical and educational settings.