Evaluation of wearable E-Tattoo sensors for measuring muscle activity.

At each appointment in the Spasticity Clinic, participants will be assessed as indicated below. The first appointment will be a baseline session, with a follow up session at the second appointment 6 weeks later. Spasticity in the relevant muscle(s) will be measured using the Modified Ashworth Scale (MAS). This test is part of the standard assessment conducted by rehabilitation consultants in the Spasticity Clinic. At the first and follow-up appointments in the Spasticity Clinic, the E-Tattoo electrodes will be applied by the physiotherapist to the skin overlying the spastic muscles and their antagonists. In the upper limb these will be the biceps (elbow flexor) and triceps (elbow extensor) muscles; in the lower limb, these will be the gastrocnemius, soleus (plantarflexors) and tibialis anterior (dorsiflexor) muscles. The electrodes will be worn for the duration of the Clinic appointment and during the relevant functional tests, and then removed before the participant leaves the Clinic. Raw sEMG signals will be collected via a myRIO data acquisition system (National Instruments, Texas, US) at a sampling rate of 2000Hz. The data will be transferred to a computer for further processing. This includes signal processing, data segmentation, feature extraction, and classification, followed by pattern recognition to analyse muscle activity. The signal will be filtered using a bandpass filter between 20Hz and 450Hz. Additionally, a band-stop filter in the range of 49-51 Hz will be used to mitigate electrical and power frequency noise. The functional tests will take approximately 30 minutes to complete. Lower limb tasks: While wearing the sEMG electrodes, participants with lower limb spasticity will be assessed on the following tasks: • Walking. Participants will wear research-grade APDM inertial sensors (APDM Inc. Portland OR) attached by straps to their sternum, sacrum and limbs and will walk a minimum of 100 metres along a corridor near the Clinic, using their usual gait aid, if required, to obtain spatiotemporal measures and kinematics of gait. Participants will be asked to walk without an ankle-foot orthosis if they normally wear one. Signals from the accelerometer on the sternum will be used to derive non-linear measures of gait, including the local divergence exponent (LDE), a measure of gait stability which has been shown by our group to be a much more sensitive measure of walking disability than traditional spatiotemporal measures. • Timed Up and Go (TUG) test Participants will be asked to stand up from sitting on a chair, walk 3 metres, turn around, and walk back to sit on the chair. The task will be timed using a stopwatch. • 5 times Sit-to-Stand (5xSTS): Participants will be asked to complete five consecutive sit-to-stand movements from a seated position. The task will be timed using a stopwatch. Upper limb tasks: While wearing the sEMG electrodes, participants with upper limb spasticity will be assessed on the following tasks: • Upper limb coordination task. Participants will have their arm fully supported on a table with their forearm resting on a sheepskin pad, with an accelerometer attached to the wrist. They will be asked to bend and straighten their elbow at a self-selected speed and also as fast as they can. • 9-hole peg test (9HPT). The 9HPT is a brief, timed, standardised, quantitative test of finger dexterity. Participants will pick up pegs one by one from the container and place them in the empty holes in a board. • Moving cones. Participants will be asked to grasp a cone from the table in front of them and move it forward as far as possible on the table. They will then return the cone to the starting position, and repeat this task another nine times. The test will be timed. A semi-structured interview will be conducted with each participant immediately after each assessment timepoint to obtain information about their perceptions about the integrated E-Tattoo system. The interview will take 20 minutes.