Background and rationale:

Surface electromyography (EMG) is a non-invasive method to measure muscle activity, among others in people after a stroke during gait analysis. Measurement quality is strongly influenced by electrode placement. However, the commonly used SENIAM guidelines do not take individual variations in muscle morphology into account, which can lead to inaccurate measurements. In previous research demonstrated that the standard placement on the triceps surae (medial and lateral gastrocnemius and soleus) was suboptimal at the group level and sometimes even problematic at the individual level. Therefore, new placement guidelines (EPICA guidelines, Electrode Placement for Individual Calf Anatomy) were developed, which are currently being tested in healthy individuals.

Method:

In this project aims to validate these newly developed guidelines in people after a stroke who exhibit atrophy of their calf muscles. For each participant, electrode positions on the hemiplegic side will be determined according to our guidelines while the participant is lying prone. Circular stickers will be used instead of actual EMG electrodes and will be placed according to the EPICA guidelines as well as according to the SENIAM guidelines. Subsequently, the muscle borders of the triceps surae will be identified on the participant's leg using 2D ultrasound. Afterwards, the distance between the electrodes and the surrounding muscle borders will be measured to map electrode placement on the muscle in order to validate the guidelines.

In the second part of this study, 3D ultrasound recordings will be made of the soleus, medial gastrocnemius, and lateral gastrocnemius with the electrodes (stickers) on these muscles, so that during image processing, electrode positions can be visualized relative to the entire muscle, including along the depth axis. In addition, participants who can safely walk without an ankle-foot orthosis will be asked to walk a maximum of five times ten meters. Additionally, an ultrasound probe will be attached to the leg to investigate how the electrode position relates to the muscle-tendon junction during movement. Subsequently, actual electrodes will also be placed to record muscle activity during walking and heel raises.

Furthermore, all participants will be asked to do a heel raise to activate the calf muscles. As such, the quality of the EMG signals will be evaluated. Other measurements will included: Fugl-Meyer Assessment of the lower limb, measure passive ankle range of motion with a goniometer, and measure lower leg length with a tape measure. These will be used as descriptive parameters of our study population.

Patients will be asked on a voluntary basis to participate in a second, short measurement approximately two weeks after the first session. During this measurement, electrode placement will again be performed according to the EPICA guidelines. 3D ultrasound will again be used to calculate the distances between the electrodes and the muscle borders. This second measurement is necessary to investigate the test-retest reliability of the EPICA guidelines in people after a stroke.

Inclusion Criteria:

• Adult individuals who have experienced a stroke (CVA or cerebrovascular accident).
• Have no other neurological disorder.
• Are able to lie in the prone position for approximately one and a half hours.
• Are able to walk without shoes for the walking component (only applicable to participants who will perform walking). The use of an assistive device such as a walking stick (or similar) is permitted.

Exclusion Criteria:

• Presence of other neurological or orthopedic conditions that may influence the measurements and results (e.g., Parkinson's disease, peripheral neuropathy of the lower limbs, severe ankle osteoarthritis limiting range of motion, etc.).
• Having undergone a surgical intervention on the hemiparetic lower leg (e.g., ankle joint arthrodesis, etc.).
• Severe cognitive impairments that prevent understanding participation in the study (assessed using the AbilityQ).

Persons after stroke.