Assessment of Perceptive Accuracy for Motor Performance in Persons With Multiple Sclerosis

For all work packages, the following information will be recorded from all participants in the first day: demographic data and PROMs of physical activity level [Godin Leisure-Time Exercise questionnaire], sleep quality [Pittsburgh Sleep Quality Index], self-efficacy [General and MS-specific Self-Efficacy scales], affectivity [Positive and Negative Affect Schedule], anxiety and depression [Hospital Anxiety and Depression Scale], habitual symptoms and fatigue [Checklist for Symptoms in Daily life, Brief Pain Inventory, Fatigue Scale for Motor and Cognitive Functions and Modified Fatigue Impact Scale], body and mobility perception [Multidimensional Assessment of Interoceptive Awareness (MAIA-2), Interoceptive Sensitivity and Attention Questionnaire (ISAQ), Postural Awareness Scale (PAS), Multiple Sclerosis Walking Scales, Falls Efficacy Scale] are recorded via secured digital surveys (CASTOR© Electronic Data Capture system). Symbol Digit Modalities Test (SDMT) for processing speed; Brief Visuospatial Memory Test (BVMT) for memory skills; Dual Joint Position Test (DJPT) for proprioception Timed 25-Foot Walk test (T25FW) for maximal walking speed; Test for the Sensory Interaction of Balance (for postural control; 6-Minutes Walking Test (6MWT, walking as far but safe during 6') and 30 seconds Chair Stand Test (30CST, completing as many STSs in 30 seconds) for specific walking and STS performance. IMUs are applied (APDM©, see below) and subjective state fatigue is measured before and after motor performance tasks using a Visual Analogue Scale (VAS, scoring from 0 to 10).

Work package 1a -Protocol: Participants will be familiarized with task-specific perceptual reporting methods. Standardized instructions are formulated in a neutral way to not bias participants' attention toward their symptoms. They will be instructed to report the time-points of perceived changes ("as soon as you perceive it"), either positive or negative, in quantitative or qualitative aspects of their motor performance: the speed or the smoothness of their self-motion. It is explained to the participants as 'a movement that happens in a continual fashion, without any interruptions'. To collect reports we designed a light portable haptic device fitting in the hand (shaped in a similar fashion as the Jamar hand-dynamometer®) and connected via Bluetooth® to a peak-detection Matlab© algorithm. Reports were given by a squeeze. To remove the signal noise produced by involuntary hand-grip forces, the threshold sensitivity of the sensor (i.e., minimum to save a report) will be set at 25% of the maximal hand-grip strength of the participant.

The first task involves a 6MWT at maximal walking speed in silence (eg. no information on time-on-test or verbal encouragements), while instructed to perceive fluctuations in either speed either smoothness (2 walking sessions, counterbalanced order) fluctuations and, as soon as they perceive a performance change, squeeze the sensor in the handheld device. The second task consists on repeated STS transitions: participants perform STSs at a fixed pace (one every ten seconds for six minutes), each one attempting to maximize speed, from a chair with normalized seat-height (lower leg length). Participants will use the handheld force sensor to indicate when variations are perceived during the task, comparing speed/smoothness (2 STS sessions, counterbalanced order) of consecutive STS transitions. Motor performance in the 2 tasks will be recorded with wearable sensors: 6 APDM© inertial motion units (2 over the dorsal part of the feet, 2 on the lower legs, 1 anterior to the sternum and 1 posterior to the fourth lumbar vertebra). The recordings allow for an objective comparison between reported and actual performance variations. Fatigue perception will be assessed before and after each session using the VAS. A brief interview will follow, asking participants to rate their confidence for having been accurate in detecting performance variations (on a scale from to 100) and to describe their own strategy: the sensory cues they relied on, for their reports.

-Work package 1b. "Imposed motor performance" WP1b assesses perceptive awareness for externally-imposed motor performance variations. After assessing perceptive sensitivity for performance variations in self-paced scenarios, we now focus on the quantification of subjects' perceptive accuracy using a real-time verbal reporting approach. Like in WP1a, we will use 2 tasks, walking and STS, with order counterbalanced at group level.

Protocol Walking task - Treadmill Participants will familiarize during a 10-minute supervised treadmill session with the moving belt, safety bars, and general usability. To determine a personalized speed range, participants will start walking at 50% of their maximal walking speed, calculated in their 6MWT overground performance as the highest 15-second moving average. They need to confirm if that is their comfortable treadmill walking speed. If not, adjustments will be made. Participants will see a vertical visual scale in front of them to indicate perceived variations: verbal descriptors will indicate walking speed, with 0% representing comfort and +100% representing maximal walking speed. Afterwards, they will be instructed to adapt their gait to continuous belt acceleration toward their maximal walking speed. This is as familiarization with their personalized range of speed: they will be informed about every 10th step on the VAS (0-100), experiencing how it feels to walk at those speed levels.