## 4 Discussion
### Comparisons of Motor Performance between the DT and TUG Tests
The findings of this study align with those of previous studies where mental number subtraction [30] and recitation of alternating letters of the alphabet [31] generally compromised gait performance in older people. A greater DTC was reported in gait during the reverse counting test compared to gait during the alternating letter recitation test [32]. According to the theories of capacity sharing [33] and bottleneck [34], attempting to execute two tasks at once can alter performance on either or both tasks due to limited attentional resources. Our findings confirmed the aforementioned theories as we observed that increased difficulty in the counting task led to higher competition for attentional resources, resulting in a more significant impact on TUG performance. Most likely, the mental calculation task utilized more of the same cortical networks as the gait task compared to the verbal fluency task, which resulted in a greater reduction in TUG performance. The assessment of the elderly living independently in the community in DT activities involving a motor and a cognitive task aims to better understand their daily mobility, since walking and general activities of daily living are often carried out simultaneously with one or more motor or cognitive tasks. The tests used in this study typically assess gait with two tasks, and each of them involves a specific cognitive process. Although there are not many studies comparing all four different cognitive-motor tests of DT in an elderly sample, the results of the present study are similar to those of [PERSON] et al. [35]. In particular, [PERSON] et al. [35] compared the same cognitive-motor DT tests in a sample of 20 elderly men and women and found the same results, i.e., that the mental counting and verbal fluency tests showed the greatest change in motor performance compared to the simple motor task. The motor task involved an 8-m gait test in a straight line for 30 s at a normal pace on an electronic treadmill, where it was possible to record the DTC of gait speed. As reported by [PERSON] et al. 's systematic review [36], healthy community-dwelling older adults with an average gait speed exceeding 1.0 m/s experience a significant reduction in gait speed when a secondary cognitive task is added. The use of similar equipment (electronic treadmill) by [PERSON] et al. [35] offers significant advantages in terms of recording the spatiotemporal aspects of gait, and contributes to a more reliable assessment of motor performance. But other previous studies [3; 37] used 3D-motion analysis instrumentation in order to assess the spontaneous walking of the subject during dual-task execution. However, the often high cost of this equipment combined with the increased dimensional space required for effective gait assessment makes this protocol difficult to implement. In this study, the TUG test was the motor task utilized in the DT tests to record changes in motor performance. It is an easy and quick test that partially simulates everyday life conditions, as it includes multiple \"motor stages\", such as lifting from a chair, walking, and turning, without requiring expensive equipment and a large dimensional space. Previous studies have assessed older adults' performance on the TUG by adding a cognitive task, like counting backward by threes [19], counting backwards from 100 [20], or answering continuous simple subtraction questions [8]. In all of the DT tests, a decline in motor performance was noted compared to the simple TUG test. Despite the aforementioned advantages of the TUG test, examining motor performance of the elderly in cognitive-motor DT tests that include different cognitive tests and comparing them utilizing the TUG has not been investigated. [PERSON] & [PERSON] [21] examined the motor performance of men and women while performing different DT tests using the TUG along with the same cognitive tasks in the current study and came to the same results. The verbal fluency test affected the spatial and temporal measures of the participants' gaits more than the reaction test.