Features Of Surface Electromyographic Signal Of Shoulder And Elbow Muscles On Upper Limb Hemiplegia In Patients With Chronic Stroke

Objective: To study the features of surface electromyography (sEMG) signal change related muscles when stroke patients perform shoulder and elbow maximum isometric contraction (MIC) movement tasks; then put forward computational formula of co-synergy ratio (CSR) on the shoulder and elbow, and calculate intermuscular coherence of shoulder and elbow, providing effective means for limb assessment of stroke patients with hemiplegia,discussing the feasible central mechanism of upper limb abnormal muscle synergies of stroke patients with hemiplegia, giving a basis for guiding rehabilitation.Methods: Sixteen hemiplegic patients with chronic stroke and nine healthy men with matched age, height and weight were selected in this study. Firstly, Used Alcohol Prep Pad to remove grease from the subjects’limb skin, then the bipolar surface electromyography,along with the direction of muscle fiber, was pasted on the muscle belly of pectoralis major,the muscle belly of anterior, intermediate and posterior deltoids, the muscle belly of biceps brachii, triceps brachii and brachioradialis, respectively. Secondly, participants sat in a chair which the back is fixed, the trunk was restrained to the back of chair with belts crossing the chest and abdomen. Participants’ arm was placed in the instrument for measuring force of upper extremity of hemiplegic, keeping the shoulder at 75° abduction, 40° flexion and the elbow at 90° flexion angle, fastening distal upper arm and wrist. The subjects’ hand was approximately aligned with the median sagittal plane of the subject himself, keeping the palm in a neutral position. Thirdly, recorded the force value and the surface electromyogram signal of corresponding muscles when participants were required to carry out shoulder abduction (SABD), shoulder adduction (SADD), elbow flexion (EF) and elbow extension(EE) with maximum voluntary contraction. Finally, compared the difference of power between patients and the healthy controls under different action tasks; then calculated corresponding muscles’integrated electromyogram (iEMG) and root mean square (RMS),co-synergy ratio (CSR) and intermuscular coherence of shoulder and elbow using MATLAB(Math Works, Inc.; Natick, Ma, Usa), compared the differences of the above indicators between patients and health people.Results: 1. Force value comparison: Compared with the healthy people, sixteen stroke patients, strength decreased obviously under different action tasks: the shoulder abductor muscles-strength declined 32.36%, the shoulder adductor muscles-strength declined 42.36%,and the elbow flexor and extensor muscles-strength declined 41.09% and35.52%,respectively; this is to say the ability of power output of stroke patients was impaired significantly, and the distal muscles-strength was being more serious impaired than the proximal muscle, flexor was being severely damaged than extensor. The degree of muscles-strength reduction coincided with manual muscle test ( MMT). 2. Integrated electromyogram(iEMG) and root mean square (RMS) comparison: the active and passive muscles’ iEMG and RMS of stroke patients were less than healthy people. 3.Co-synergy ratio comparison:When making shoulder abduction tasks, though the patients’ CSR of triceps brachii was significantly larger than healthy people. The patients’ CSR of biceps brachii was significantly larger than healthy people when making shoulder adduction tasks, and there are statistically significant. The patients’ CSR of pectoralis major and deltoid was significantly larger than healthy people when making elbow flexion tasks and there are statistically significant. While, when making elbow extension tasks, the patients’ CSR of passive muscles was larger than healthy people, there was no statistical difference between the two groups.4.Coherence comparison: The intermuscular coherence of shoulder and elbow of patients was significantly less than healthy people in the beta and gamma when making shoulder abduction tasks; and the coherence between the EMG of the elbow flexor and shoulder abductor for elbow flexion tasks was lower in patients compared with the health in the beta and gamma. While the coherence between the EMG of the elbow and shoulder for shoulder adduction tasks and elbow extension tasks was no statistical difference between the two groups.Conclusions: 1. Stroke patients’ strength was found to be significantly lower than healthy people under different action tasks, we can use the instrument for measuring force of upper extremity of hemiplegic to evaluate upper limb’s muscle strength of stroke patients.2. We found that the active and passive muscles’iEMG and RMS of stroke patients were less than healthy people under different action tasks, and the results of sEMG was consistent with the force value, simple in computing, so sEMG could be used to evaluate neuromuscular functional status of stroke patients. 3. The concept of CSR was proposed, CSR can be used to quantitatively describe abnormal synergy of stroke patients, that means the use of CSR to evaluate abnormal synergy of stroke patients was feasible. 4. The intermuscular coherence maybe reflected the interruption of information flow in the corticospinal pathway, which may be the main cause of abnormal muscle coupling after stroke.