Aerobic Fitness in Multiple Sclerosis: The Relationship Between Balance and Sensory Dual-Tasking

Participants' aerobic fitness, walking endurance, and functional exercise capacity will be assessed using the 6DKYT. Participants are asked to walk for 6 minutes at their own determined maximum safe pace in a 30-meter straight corridor, and the total distance covered is recorded in meters.

To assess participants' baseline walking performance and speed, the Z25AYT, a subtest of the universal Multiple Sclerosis Functional Composite Battery, will be administered. Participants will be asked to walk a distance of 25 steps (approximately 7.62 meters) as quickly and safely as possible, and the elapsed time will be measured with a stopwatch and recorded in seconds.

• Proprioceptive Task: The goal is to restrict/modify the proprioceptive inputs from the participant's support surface. For this purpose, the participant is asked to stand on an unstable surface (BOSU ball) to examine the effect of uncertainty in deep sensory inputs on static postural control.
• Vestibular Task: The participant's proprioceptive inputs are stabilized by having them stand on a hard, stable surface. The role of the vestibular system in balance is assessed by having the participant stand while making rhythmic head movements (accompanied by a metronome). Thus, by manipulating the inputs from the vestibular apparatus, the stability of static balance, excluding visual and somatosensory inputs, is measured.

• Vestibular Task (GKST + Head Movement): During the standard GKST, participants will be asked to perform rhythmic head movements to the accompaniment of a metronome to assess the effect of the vestibular system on mobility.
• Proprioceptive Task (GKST + Soft Surface): To manipulate ground proprioception, the standard GKST protocol will be repeated on a soft foam surface of a specific density instead of a hard surface. This method will record walking stability and task completion time under conditions where proprioceptive feedback is limited.

Participants' objective balance and fall risk will be measured using the BDI (Brain Stability Inventory). The scale consists of 14 different functional balance tasks, including sitting, standing, reaching, and turning, and is evaluated on a scale of 0-56 points. Lower scores indicate an increased risk of falls.

The 16-item Fall Fear and Balance Confidence Scale (FDSS) will be administered to assess fall fear and balance confidence during daily living activities. The FDSS consists of 16 items scored between 0 and 100. Each item asks the individual to rate their confidence in their ability to maintain their balance without falling during a specific activity, on a scale of 0 (not confident at all) to 100 (completely confident). The total score is calculated by taking the arithmetic mean of all items, resulting in a value between 0 and 100. A higher total score indicates that the individual has high balance confidence and reduced fall fear during daily living activities.

To assess the impact of fatigue on physical, cognitive, and psychosocial functions, a 21-item fatigue risk assessment scale will be used. The fatigue risk assessment scale consists of 21 items that inquire about fatigue experiences over the past four weeks. Each item evaluates the impact of fatigue on daily life using a Likert-type scale ranging from 0 (never) to 4 (always). The total score obtainable from the scale ranges from 0 to 84. An increase in the total score indicates a greater negative impact of fatigue on the patient's physical, cognitive, and psychosocial functions, and a greater impact on quality of life.