# The Impact of Cell Phone Usage on Fall Risk and Postural Control During Free-Standing
## 2 Materials and Methods  
### Participants and Measurement Protocol  
Thirty-three young, healthy individuals took part in the study, comprising 17 women and 16 men (Table 1). The inclusion criteria required participants to have no history of muscular or neurological disorders, no lower limb injuries in the past six months, right lower limb dominance (preferred leg for kicking a ball [26]), and right-handedness. The exclusion criteria included balance impairments, treatment with medications affecting the nervous system, and the dominance of the left lower or upper limb for writing.  
This study was approved by the University Institutional Review Board (Reference No. SKE01-15/2023) and conducted following the ethical guidelines of the Declaration of Helsinki. All participants were fully informed about the study's objectives and procedures before participation.  
The study involved a total of six trials conducted across two distinct platforms, with three trials performed under static conditions and three under dynamic conditions. The static trials were conducted using an AMTI AccuSway force platform (Advanced Mechanical Technology Inc., Watertown, MA, USA) paired with Balance Clinic 2.02.01 software, sampling data at 100 Hz. Dynamic trials were performed on the Biodex Balance System SD (BBS) platform (Biodex Medical Systems, Shirley, NY, USA), which features a circular platform capable of moving freely along both the AP and ML axes. During testing, the BBS platform operated in Fall Risk Test (FRT) mode, for which the level of stability progressively decreased from level 6 (high instability) to level 2 (low instability).  
Each trial, under both static and dynamic conditions, lasted 20 s and followed the same sequence: (1) the baseline trial (EO)--standing with both feet, with the hands resting along  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Group** & **Age [Years]** & **Body Mass [kg]** & **Body Height [cm]** \\ \hline Females (\(n\) = 17) & 22.76 \(\pm\) 1.2 & 61.94 \(\pm\) 7.59 & 166.71 \(\pm\) 5.10 \\ Males (\(n\) = 16) & 22.13 \(\pm\) 1.71 & 77.63 \(\pm\) 9.23 & 181.31 \(\pm\) 4.38 \\ All (\(n\) = 33) & 22.45 \(\pm\) 1.48 & 69.55 \(\pm\) 11.49 & 173.79 \(\pm\) 8.82 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Characteristics of the participants (mean \(\pm\) SD).  
the trunk and the eyes open while looking straight ahead; (2) the visual distraction trial with passive phone use (EP)--standing with both feet while holding a phone and looking at its turned-off screen; and (3) the cognitive-motor dual-task trial (SMS), which involved participants standing with both feet on the ground while holding a phone and typing a text message. The text messages used for this task were typical of real-life scenarios, such as informing someone that the participant would be late for an appointment due to circumstances like traffic. Examples included messages like \"Sorry, I'm going to be late, there's a terrible traffic jam in the city\" or \"Mum, I'm going to be late. I'll be there in 20 min.\" During the study, the lab environment did not maintain conditions of silence, allowing participants to engage in the task in a more natural, less controlled manner. Participants could hold the phone however they preferred, and the research team recorded whether they used one or both hands. The method of holding the phone was not specified, reflecting real-world flexibility.