ABSTRACT
A myoelectric protocol to objectively discriminate between test subjects based on trunk muscular performance differences (endurance) was investigated in a group of 11 healthy volunteers and ten industrial patients undergoing functional restoration for chronic disabling spinal disorders. The subjects performed a standardized exercise protocol, holding their upper torso unsupported for successive fixed-time trials while electromyographic (EMG) signals were recorded from erector spinae. A Fast Fourier Transform allowed calculation of the initial mean power frequency (MPF) for each trial. Isokinetic extensor trunk strength was independently measured at each session for comparison with myoelectric signal analysis. The investigation revealed significant differences in group statistics between patients in early rehabilitation and their subsequent tests, as well as between their initial test and the normal subject scores. However, test sensitivity for identifying patients with "low endurance" is questionable. There was no significant correlation between EMG initial MPF measures and isokinetic extensor trunk strength measures, even though all patients showed isokinetic improvement. Data suggest that the protocol used and myoelectric power spectrum temporal shifts may have some value for identification of individual subjects with endurance limitations (or fatigue resistance) in patients of this type. However, lack of a "gold standard" for comparison presents difficulties in documenting the value and validity with respect to endurance. The test may be of value to measure relative loads.
Subject(s)
Muscle Contraction , Muscles/physiology , Physical Endurance , Spinal Diseases/physiopathology , Adult , Electromyography , Exercise , Female , Humans , Male , Spinal Diseases/rehabilitationABSTRACT
A prototype isokinetic torso rotation unit and an EMG signal processing system were utilized to obtain preliminary information on torso rotation. In Study 1, range-of-motion was found to be surprisingly uniform between low-back pain patients and normal subjects, although there was a significant strength variation between them at all isokinetic speeds tested. Both female patients and normal females showed approximately 70%-75% of the strength (torque/body weight) levels relative to their male counterparts. The decrement in trunk strength at high speeds was proportional for both patients and controls and was not nearly as dramatic as the decrement seen in the sagittal plane. In Studies 2 and 3, anatomic relationships evaluated by EMG testing of obliques and erector spinae showed that the contralateral abdominal obliques were the most consistent muscles providing a significant torsional moment to the spine.