An integrated computer-based system to study neuromuscular disorders of the upper limb

A multi-channel computer-based clinical instrument was developed to simultaneously acquire, process, display, quantify and correlate electromyographic (EMG) activity, resistive torque, range of motion (ROM), and pain levels in the upper limbs of humans. Each channel consisted of a time and frequency domain block, a torque and angle measurement block, an experiment number counter block and a data storage and retrieval block. The data in each channel was used to display and quantify: raw EMG, rectified EMG, smoothed rectified EMG, root-mean-squared EMG, fast Fourier transformed (FFT) EMG, and normalized power spectrum density (NPSD) of EMG. Torque and angle signals representing elbow extension measured by a KIN-COM© dynamometer, as well as rectangular pulses generated by a battery-operated pain marker switch were interfaced to the system and presented in one integrated display. Calibration and weight compensation were implemented by developing a special interface between the system and the dynamometer. The system was used to carry out a study in ten subjects. Three males and seven females, in the age range 41-72 years (56±10) with no history of neurological or upper quarter neuromusculoskeletal injury volunteered for the study. The study consisted of two major testing protocols. The first was an objective passive movement protocol to measure range of motion (ROM) and evoked resistive torque during elbow extension. The second was an electromyographic (EMG) protocol to record the EMG of 10 shoulder and arm muscles during the controlled passive elbow extension as the last component of upper limb tension test (ULTT). The occurrence of pain onset and pain tolerance limit during the experimental task were indicated by the subject operating the pain switch. The study showed that there was increased level of EMG activity prior to pain onset (P<0.05). There was also clear evidence that elevated perception of pain and elevated levels of resistive torque (P<0.05) were positively correlated with the EMG activity in the muscles responsible for antalgic posture of the upper limb (P<0.05).