## 2 Materials and Methods
### Procedure  
The study was approved by the Research Ethics Committee of the University of the Peloponnese (5365/11-03-2024) and it was conducted in accordance with the Declaration of Helsinki. Data collection was carried out by the authors in a specific room of the community senior center. Only the first authors and each participant were present in the room. Each participant came at a scheduled day and time. The order in which the participants\({}^{\prime}\) data were collected was as follows:  
1. Collection of demographic data characteristics. Muscle strength was evaluated with the 30-CST test, dynamic balance using the FSST test, and balance confidence using the ABC scale.
2. Performing the TUG test (simple activity): Each participant sat in a straight-backed chair, about 46 cm high, with their back touching the back of the chair. On the authors\({}^{\prime}\) 'Go\({}^{\prime}\) command, the participant stood up, walked straight at a normal walking pace towards the cone (placed 3 m from the chair), walked around the cone (on either side) and returned to the chair at the same walking pace, where she was seated. The time to complete the test was recorded until the subject came into contact with the chair.
3. The simultaneous execution of TUG and cognitive tasks (DT activities) as represented in [PERSON]'s study ([PERSON], 2018). In all participants, the following DT tests were performed in random order ([PERSON], 2018): 1. Mental calculation (working memory): Participants performed backward counting by threes from a randomly chosen three-digit number while simultaneously executing the TUG test (TUGMC). 2. Memory (memory recall): Participants were asked to memorize a seven-item shopping list after reading it for 15 s while seated. Then, when the DT was conducted, they tried to recall as many products from the list as possible while performing the TUG test (TUGME). This task was never given as the first task, even though the cognitive tasks were randomized. This approach was used to confirm that each participant retainedthe information for a significant period before recalling it, rather than just verbalizing the items immediately after reading them.
3. Verbal fluency: Participants needed to generate as many words as they could starting with the letter \"L\" while simultaneously performing the TUG test (TUGVF).
4. Reaction time: Participants were asked to respond verbally to an auditory stimulus while they were performing the TUG test (TUGRE). Throughout the TUG, they heard the word \"book\" as a prerecorded auditory stimulus of the same intensity and at a random rate, to which they responded as quickly as possible by uttering the word \"top\". The intensity and tempo of the word signal was the same for all participants.  
For the calculation of motor performance during the TUG as simple activity (SA) and the TUGMC, TUGME, TUGVF, and TUGRE activities, the time taken to complete the tests (measured in seconds) was noted. Higher values correspond to worse motor performance. In addition, the dual-task costs (DTC) were calculated as the difference between the DT and the simple activity on TUG test performance (in seconds), normalized with the simple activity performance and expressed as a percentage based on the equation:  
\[\text{DTC (\%)}=-\text{ (SA performance}-\text{DT performance)}/\text{(DT performance)}\times 100 \tag{1}\]  
A negative value signifies a decline in performance (i.e., dual-task cost) relative to the performance of the single-task activity (TUG) [27].