Biomedical Engineering - Motor System Rehabilitation

Notes from Lab Activities

Laboratory

Laboratories of Motor System Rehabilit ation , Biomedical Engineering PoliMi A.Y.202 5-26 IND EX 4. MSR THROUGH FUNCTION RESTORATION ................................ ................................ ....... 1 LAB 1 – NEUROMUSCULAR ELECTRICAL STIMULATION ................................ .................... 1 INTRODUCTION ................................ ................................ ................................ ......................... 1 Stimulation parameters ................................ ................................ ................................ ................ 1 Non -invasive electrical stimulation ................................ ................................ ............................... 1 SET -UP ................................ ................................ ................................ ................................ ........ 1 LAB 2 – FES CYCLING AND CYBATHLON EXPERIENCE ................................ ...................... 2 LAB 3 – INCLUSIVE MULTIPLAYER EXERGAMES ................................ ................................ . 2 ACCESSIBILITY ................................ ................................ ................................ .......................... 2 ITERATIVE CO -DESIGN ................................ ................................ ................................ ............. 2 Stakeholders ................................ ................................ ................................ ................................ 2 Specifications ................................ ................................ ................................ ............................... 3 Devices ................................ ................................ ................................ ................................ ........ 3 GAME ................................ ................................ ................................ ................................ .......... 3 Minigames ................................ ................................ ................................ ................................ .... 3 Facilitators ................................ ................................ ................................ ................................ .... 4 ASPOC ................................ ................................ ................................ ................................ ........ 4 HANDWRITING ANALYSIS IN REHABILITATION – THE SMART INK PEN ............................ 5 STATE OF THE ART ................................ ................................ ................................ ................... 5 Clinical need ................................ ................................ ................................ ................................ 5 Requirements ................................ ................................ ................................ ............................... 5 Design ................................ ................................ ................................ ................................ .......... 5 DEVELOPMENT ................................ ................................ ................................ .......................... 5 Electronic design ................................ ................................ ................................ .......................... 5 Feature extraction ................................ ................................ ................................ ........................ 6 VALIDATION ................................ ................................ ................................ ................................ 6 Parkinson’s disease ................................ ................................ ................................ ..................... 6 Mild Cognitive Impairment ................................ ................................ ................................ ............ 7 Laboratories of Motor System Rehabilit ation , Biomedical Engineering PoliMi A.Y.202 5-26 1 4 . MSR THROUGH FUNCTION RESTORATION 25/03/2026 LAB 1 – NEUROMUSCULAR ELECTRICAL STIMULATION INTRODUCTION Stimulation parameters Stimulation parameters define the behavior of electrical stimulation and the response of neuromuscular tissue. • Current Amplitude (A) [mA]: excites the nerve , different activation thresholds exist ; • Pulse Width (PW) [μs]: defines the charge delivered per pulse ; • Voltage (V) : supports current delivery ; • Stimulation Frequency (f = 1/T) [Hz]: regulates the force of muscle contraction ; • Stimulus Shape : helps minimize potential tissue damage. Non -invasive electrical stimulation Different types of non -invasive electrical stimulation can be identified, each targeting specific physiological mechanisms. 1. Conventional Transcutaneous Electrical Nerve Stimulation (TENS) : only afferent fibers are elicited. It is used for pain relief through the gate control mechanism. 2. Sensory Afferent Electrical Stimulation (SAES) : only afferent fibers are elicited, producing a reflex response in the muscle. Typical parameters are: a. Current amplitude: ≈120% of sensory threshold ; b. Pulse Width: 500 –1000 μs ; c. Frequency: low frequency (5 –10 Hz) with short bursts of high frequency (≈100 Hz) . 3. Neuro -Muscular Electrical Stimulation (NMES) : both afferent and efferent fibers are elicited, producing a muscle contraction. Typical parameters are: a. Current amplitude: 10 –150 mA, producing visible contraction b. Pulse Width: 200 –500 μs c. Frequency: 20 –50 Hz For the current amplitude, different thresholds can be identified: a. Sensory threshold: when the patient first perceives the stimulation ; b. Motor threshold: when a visible or palpable contraction occurs ; c. Maximum threshold: beyond which the subject cannot tolerate further increases in current . 4. Functional Electrical Stimulation (FES) : this occurs when NMES is used to induce a functional movement. In this case, a functional threshold is defined as the minimum stimulation level required to produce the desired movement. SET -UP The experimental set -up is composed of: • Robotic test -bench , including: Laboratories of Motor System Rehabilit ation , Biomedical Engineering PoliMi A. Y.2025 -26 2 o Sensojoint BLDC motor (Sensodrive GmbH) ; o Torque sensor ; o Encoder . • EMG acquisition system , for example TMSI SAGA ; • Stimulator , used to deliver electrical stimulation . 01/04/2026 LAB 2 – FES CYCLING AND CYBATHLON EXPERIENCE …see slides on Webeep … 15/04/2026 LAB 3 – INCLUSIVE MULTIPLAYER EXERGAMES Children with disabilities often find it difficult to interact with others, especially in physical education contexts; as a result, they are frequently excluded from group activities. The aim is therefore to provide children with disabilities with enjoyable and inclusive group experiences through serious games that are designed to be fun, accessible, and collaborative. ACCESSIBILITY Accessibility is required in several contexts, for example at school. However, there are several barriers: • Lack of funding ; • Lack of training ; • Standard activities are often inaccessible . These issues are particularly evident in Physical Education classes. Exergames can help alleviate some of these critical issues and should be co -designed with experts. ITERATIVE CO -DESIGN By iterative co -design , we mean involving stakeholders in the design and development process. Stakeholders • Collaboration with clinicians from the Child Neurology and Psychiatry unit, ASST Lecco : o Game play definition ; o Methods for using the input devices ; o Accessibility specifications . • Collaboration with ASPOC ( Associazione per lo Sviluppo del POtenziale Cognitivo ) in Lecco: o Two groups of 18 -40 years old ; o Accessibility of the games . • Collaboration with primary school Santo Stefano in Lecco for t eachers’ feedback . Laboratories of Motor System Rehabilit ation , Biomedical Engineering PoliMi A.Y.202 5-26 3 Specifications The game must be: • Multiplayer ; • Cooperative ; • Multiple inputs . The design process starts from clinical requirements and then moves to technical requirements. Devices There are five main devices used in the system: • Cosmo switch buttons , used for press -based movements ; • Tablet , used for the touchscreen and, more importantly, for the gyroscope to detect rotations ; • Leap Motion Controller , used for hand tracking ; • Homing system (TechnoBody device), used for full -body tracking ; • VR headset , used for immersive virtual reality . GAME Minigames The game is developed in Unity and includes four mini -games: 1. Kitchen : a group decision -making task based on a voting system ; 2. Runner : a running game with predictable stimuli, visible from a distance ; 3. Igloo : similar to Runner but with appearing stimuli, used to assess reaction times ; 4. Volcano : based on collaboration and suggestion mechanics . Laboratories of Motor System Rehabilit ation , Biomedical Engineering PoliMi A. Y.2025 -26 4 Facilitators Within the games, different facilitators are implemented to support the specific impairments of the children. ASPOC ASPOC is Associazione per lo Sviluppo del Potenziale Cognitivo in Lecco. Through testing, the following research questions were addressed: 1. Is it possible to create a positive experience for heterogeneous groups of people with intellectual disabilities? 2. Can carefully selected devices and facilitators reduce the gaps between individuals with different disabilities? Laboratories of Motor System Rehabilit ation , Biomedical Engineering PoliMi A.Y.202 5-26 5 05/05/2026 HANDWRITING ANALYSIS IN REHABILITATION – THE SMART INK PEN STATE OF THE ART Clinical need Rationale Handwriting is a fundamental daily activity in the real world. Its analysis is highly relevant in clinical settings because it involves fine motricity and reflects meaningful functional health. Furthermore, handwriting engages multiple neurological and physiological domains: • Motor Control; • Cognition (specifically planning and attention); • Sensorimotor Integration. Consequently, handwriting analysis holds significant value in rehabilitation by tracking recovery over time, enabling personalized therapy, and supporting clinical decision -making. It is considered a non -invasive, ecologically valid biomarker that links cl inical assessment to real -world function. Objective The primary goal is to study handwriting as a biomarker for the early detection of neurodegenerative disorders, such as: • Essential Tremor (ET) ; • Mild Cognitive Impairment (MCI) ; • Parkinson’s Disease (PD) ; • Alzheimer’s Disease (AD) . Requirements The main technical requirement is the extraction of temporal kinematic signals from handwriting. The system must be designed for both supervised use (for collecting clinical data) and unsupervised use (outside of formal clinical assessments), specifically optimized for ecological settings. Design The technical requirements for the device include: • A rechargeable system designed for intuitive user interaction ; • Miniaturized sensors enabling accurate, high -resolution signal acquisition, including an Inertial Measurement Unit (IMU) and a Pressure sensor ; • Integrated Bluetooth Low Energy (BLE) for low -power wireless communication. DEVELOPMENT Electronic design Laboratories of Motor System Rehabilit ation , Biomedical Engineering PoliMi A. Y.2025 -26 6 Feature extraction A series of features are extracted from the use of the pen during writing tasks: • Time domain : Used to understand cognitive or neurological impairment ; • Force domain ; • Kinematic oscillations domain ; • Smoothness domain : Used to understand impairments in motor centers ; • Frequency domain : Considered the most important domain for handwriting analysis. Essential tremor Essential Tremor is an action tremor caused by cerebello –thalamo –cortical dysfunction, producing rhythmic, stereotyped oscillations in the hands. To treat this condition, Focused Ultrasound (FUS) can be utilized: • A non -invasive, MR -guided treatment ; • Targets the Vim nucleus of the thalamus ; • Disrupts pathological oscillations, leading to tremor reduction. While clinicians can evaluate handwriting qualitatively, instrumented analysis provides objective and reproducible quantification. This enables precise measurement of tremor characteristics and treatment effects, such as observing changes in angular veloci ty or force signals pre - and post - FUS. Parkinsonian tremor Parkinson’s Disease is a neurodegenerative disorder caused by dopamine loss in the basal ganglia. It is characterized by: • Bradykinesia (slowness of movement); • Rigidity; • Rest tremor (typically ~4 –7 Hz). Typical handwriting alterations in PD include micrographia (a progressive reduction in letter size), reduced speed and fluidity, irregular stroke timing and possible superimposed tremor oscillations. A key diagnostic tool is the Archimedes’ Spiral , which is useful for evaluating how tremor impacts voluntary functional activities. Patients must follow the spiral without lifting the pen from the paper. This test involves the entire kinematic chain of the upper limb: • Central part of the spiral: Involves more distal joints ; • External part of the spiral: Activates proximal joints. VALIDATION Parkinson ’s disease A validation study was conducted with the following participants: • 29 PD patients: o Mean age 72.9 ± 7.6 years; o UPDRS motor score 26.6 (± 10.3)/56; o Acquired during "ON" treatment. • 29 age -matched healthy controls (HC). The results showed significant moderate correlations: • Increased tremor indicators in tremor -dominant patients (correlating with high values in Jankovic, Schiess, and Kang scales, and UPDRS III resting tremor scores). • Reduced smoothness indicators for tremor -dominant and severe patients (high Hoehn and Yahr and UPDRS III scores). Pen indicators revealed aspects of the disease not captured by standard clinical scales. Using a Catboost Model with "Leave -one -out" validation: • 100% (29/29) of PD patients were correctly classified ; Laboratories of Motor System Rehabilit ation , Biomedical Engineering PoliMi A.Y.202 5-26 7 • 3/29 HC were misclassified as PD. In unsupervised contexts, AI models can also be applied. Tests using free -text exercises were attempted; while results can be highly affected by the lack of constraints, the validation performance remained good considering the non -standardized tasks and th e novel acquisition approach. Mild Cognitive Impairment The study involved 45 subjects (30F/15M) with a mean age of 79.3 ± 5.3, 10 (5) years of education, and a mean MMSE score of 27 (4). Participants performed three tasks: 1. Free text: Writing freely ; 2. List creation: Writing a shopping list ; 3. PnP (Word/Non -word test) : 15 words total (7 regular, 3 irregular, 5 non -words). Observations from this experiment included: • More significant correlations and higher correlation values (> |0.4|) for block letters compared to cursive ; • Higher "time in air" reflects increased cognitive demand (thinking) ; • Higher number of pauses reflects hesitations during the tasks. Specifically, in the PnP test: • Irregular words posed the greatest challenge in the temporal domain for both cursive and block letters, resulting in worse temporal parameters. • Non -words rely solely on the segmental pathway and seem to be less impaired in MCI. • Irregular words rely on the lexical pathway (considering spelling), making them more cognitively demanding. Applying Machine Learning (ML) to these tests yielded good performance, especially considering the reduced sample size, the non -standardized tasks, and the new data acquisition approach.