Acute Effects of Smartphone-Delivered Local Vibration on Hand Sensorimotor Performance (SmartVib)

Acute Effects of Smartphone-Delivered Local Vibration at Three Frequencies on Hand Grip Strength, Two-Point Discrimination, Pressure Pain Threshold, and Reaction Time in Healthy Young Adults: A Randomized Crossover Study

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Healthy Volunteers; Vibration; Adverse Effect
• Intervention / Treatment: Device: Smartphone Local Vibration at 80 Hz; Device: Smartphone Local Vibration at 150 Hz; Device: Smartphone Local Vibration at 220 Hz

Detailed Description

BACKGROUND:

Local vibration (LV) has been investigated in physiotherapy and rehabilitation for modulating muscle activation, performance, and pain perception. Neurophysiological effects are mediated through tonic vibration reflex and enhanced sensory afferent input. LV offers a more targeted and portable approach compared to whole-body vibration (WBV). Short-duration LV applications have been shown to produce acute changes in muscle strength, tactile perception, reaction time, and pain threshold.

The hand region, with its high mechanoreceptor density and extensive cortical representation, provides a sensitive model for mechanical stimulation. Smartphones, through programmable haptic motors, can generate controlled vibration outputs and have been used in rehabilitation for vibrotactile feedback applications. However, studies combining assessment of grip strength, two-point discrimination, pressure pain threshold, and reaction time following mobile phone vibration on the hand are limited.

The frequency range (80-220 Hz) was selected to cover the optimal sensitivity band of Pacinian corpuscles (approximately 100-300 Hz), with 80 Hz being commonly used in LV literature. Three frequency levels (80, 150, 220 Hz) systematically represent the lower, middle, and upper portions of the range to explore a potential dose-response relationship.

STUDY DESIGN:

Randomized crossover design with three conditions (80 Hz, 150 Hz, 220 Hz). Each participant completes all three frequency conditions in separate sessions on different days. A minimum 48-hour washout period is maintained between sessions, and sessions are conducted at the same time of day. Application order is determined by counterbalanced randomization across the 6 possible sequences (3! = 6).

Measurement order (grip strength, PPT, 2PD, reaction time) is randomized for each participant at the first session and maintained consistently across all pre-tests, post-tests, and all three sessions. All measurements are performed by the same assessor. Post-vibration measurements are completed within 3-5 minutes. Total measurement time (excluding vibration) does not exceed 10 minutes per session.

VIBRATION PROTOCOL:

Vibration is delivered via a custom iPhone application using the device haptic motor. Each session applies one frequency condition. Stimulation consists of 5 repetitions of 45 seconds vibration + 15 seconds rest (total approximately 5 minutes).

Participant positioning: seated with back support, shoulder neutral, elbow approximately 90 degrees flexion, forearm supported on table in neutral position, wrist relaxed (0-20 degrees extension). The phone is held naturally in the dominant hand palm. Participants are instructed not to consciously squeeze or contract during application. Phone orientation and contact surface are kept consistent across repetitions and sessions.

OUTCOME MEASUREMENTS:

1. Hand Grip Strength: Jamar hydraulic dynamometer with ASHT-recommended positioning. Three trials with 15-30 seconds rest between trials; mean of three trials used. Additional measurement taken if variation exceeds 10%.
2. Pressure Pain Threshold (PPT): Pressure algometer on dominant hand thenar eminence, probe approximately 1 cm2, application rate approximately 1 kg/s. Three trials with 30 seconds rest; mean value used.
3. Two-Point Discrimination (2PD): Baseline Two-Point Discriminator on dominant hand third finger distal pulp, eyes closed. Smallest distance correctly identified in at least 2 of 3 trials recorded as threshold (mm).
4. Nelson Hand Reaction Time Test: Visual stimulus-motor response measured via ruler drop method. Three practice trials followed by 5 valid trials; best and worst values excluded, mean of remaining three used. Reaction time calculated using free-fall formula.

SAMPLE SIZE:

Based on Amiez et al. (2024), with conservatively reduced effect size (partial eta-squared approximately 0.10, Cohen f = 0.33), one-way repeated measures ANOVA power analysis (3 conditions, alpha = 0.05, power = 0.80, rho = 0.50) yielded a minimum of 18 completers. Target enrollment is 20 to account for potential dropouts.

STATISTICAL ANALYSIS:

Descriptive statistics. Primary analysis: two-way repeated measures ANOVA (3 frequencies x 2 time points) for each outcome variable. Post-hoc pairwise comparisons with Bonferroni correction. Effect sizes (partial eta-squared). Carry-over effects assessed. Non-parametric alternatives if assumptions are violated. Significance level: p less than 0.05.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Ali Omer Acar; Phone Number: +905378262790; Email: aliomer.acar@acibadem.edu.tr

Study Locations

• Turkey (Türkiye)
  • Istanbul, Turkey (Türkiye)
    • Acibadem Mehmet Ali Aydinlar University, Department of Physiotherapy and Rehabilitation
    • Contact: Ali Omer Acar; Phone Number: +905378262790; Email: aliomer.acar@acibadem.edu.tr
    • Principal Investigator: Ali Omer Acar

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy university students aged 18-25 years
• Willing to participate and provide written informed consent
• Able to attend three separate measurement sessions

Exclusion Criteria:

• Surgical intervention on the hand or wrist within the past 6 months
• Serious upper extremity injury or trauma within the past 6 months
• Diagnosis of carpal tunnel syndrome or peripheral nerve entrapment
• Numbness, paresthesia, or sensory impairment in the hand or wrist
• History of neurological disease (e.g., stroke, multiple sclerosis, peripheral neuropathy)
• Active pain, infection, open wound, or dermatological condition at the measurement site
• Reported hypersensitivity or intolerance to vibration
• Pregnancy

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: 80 Hz Local Vibration; Smartphone-delivered local vibration at 80 Hz applied to the dominant hand. Stimulation protocol: 5 repetitions of 45 seconds vibration + 15 seconds rest (total approximately 5 minutes). Represents the lower end of the tested frequency range.	Device: Smartphone Local Vibration at 80 Hz; Local vibration delivered via a custom-developed iPhone application using the device haptic motor at 80 Hz. Participant seated with back support, shoulder neutral, elbow 90 degrees flexion, forearm neutral on table support, wrist relaxed. Phone held naturally in dominant hand palm. Five repetitions of 45 seconds vibration + 15 seconds rest. Participants instructed not to consciously squeeze during application.
Experimental: 150 Hz Local Vibration; Smartphone-delivered local vibration at 150 Hz applied to the dominant hand. Stimulation protocol: 5 repetitions of 45 seconds vibration + 15 seconds rest (total approximately 5 minutes). Represents the middle of the tested frequency range.	Device: Smartphone Local Vibration at 150 Hz; Local vibration delivered via a custom-developed iPhone application using the device haptic motor at 150 Hz. Same positioning and protocol as 80 Hz condition. Five repetitions of 45 seconds vibration + 15 seconds rest.
Experimental: 220 Hz Local Vibration; Smartphone-delivered local vibration at 220 Hz applied to the dominant hand. Stimulation protocol: 5 repetitions of 45 seconds vibration + 15 seconds rest (total approximately 5 minutes). Represents the upper end of the tested frequency range.	Device: Smartphone Local Vibration at 220 Hz; Local vibration delivered via a custom-developed iPhone application using the device haptic motor at 220 Hz. Same positioning and protocol as 80 Hz condition. Five repetitions of 45 seconds vibration + 15 seconds rest.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Hand Grip Strength	Hand grip strength measured with Jamar hydraulic dynamometer (kg) using ASHT-recommended positioning. Three trials per measurement; mean of three trials used. Pre-post difference assessed at each frequency condition (80 Hz, 150 Hz, 220 Hz).	Immediately before and immediately after vibration application at each session (3 sessions, minimum 48 hours apart)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Two-Point Discrimination (2PD)	Tactile spatial acuity measured with Baseline Two-Point Discriminator on dominant hand third finger distal pulp (mm). Smallest distance correctly identified in at least 2 of 3 trials recorded as threshold. Lower values indicate better tactile discrimination.	Immediately before and immediately after vibration application at each session (3 sessions, minimum 48 hours apart)
Change in Pressure Pain Threshold (PPT)	Pressure pain threshold measured with pressure algometer on dominant hand thenar eminence (kg/cm2). Probe approximately 1 cm2, application rate approximately 1 kg/s. Mean of three trials used. Higher values indicate higher pain tolerance.	Immediately before and immediately after vibration application at each session (3 sessions, minimum 48 hours apart)
Change in Hand Reaction Time	Visual stimulus-motor response time assessed with Nelson Hand Reaction Time Test (ms). Five valid trials after 3 practice trials; best and worst excluded, mean of remaining three used. Reaction time calculated via free-fall formula. Lower values indicate faster reaction.	Immediately before and immediately after vibration application at each session (3 sessions, minimum 48 hours apart)

Collaborators and Investigators

• Sponsor: Acibadem University
• Investigators: Principal Investigator: Ali Omer Acar, Acibadem Mehmet Ali Aydinlar University, Faculty of Health Sciences, Department of Physiotherapy and Rehabilitation

Study record dates

Study Major Dates

• Study Start (Estimated): April 1, 2026
• Primary Completion (Estimated): July 1, 2026
• Study Completion (Estimated): November 1, 2026

Study Registration Dates

• First Submitted: April 3, 2026
• First Submitted That Met QC Criteria: April 3, 2026
• First Posted (Actual): April 9, 2026

Study Record Updates

• Last Update Posted (Actual): April 9, 2026
• Last Update Submitted That Met QC Criteria: April 3, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: crossover; dose-response; grip strength; pressure pain threshold; reaction time; hand function; two-point discrimination; local vibration; haptic feedback; smartphone vibration; sensorimotor performance
• Other Study ID Numbers: ACU-FTR-AOA5; 2026-06/275 (Other Identifier: ATADEK Ethics Committee Approval Number)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No