Manifestation of morphofunctional specificity of muscles in spectral evaluations of the surface electromyogram

Abstract

Relatively few theoretical and applied studies have been carried out using spectrum analysis of electromyograms (EMGs) in comparison with electroencephalograms. The essence of the method is measurement of frequency and energy response characteristics of the relevant forms of bioelectrical activity: spectral density of power G ( ω ) (power spectrum), effective band (width) of the spectrum, maximum G ( ω ) and the corresponding frequency, and mean and square mean G ( ω ) per unit frequency [1]. The most widespread method of calculating G ( ω ) is fast Fourier transform of a fragment of a bioelectrical activity record stored in the memory of a digital EMG system with numerical and/or graphic presentation of the final result. A special emphasis is made on the role of morphological, functional, and biophysical factors (fatigue; testing muscular effort; type of muscular contraction; sizes of muscles, muscular fibers, and motor units; type and size of electrodes; methods of recording the bioelectrical activity; etc.) that influence the values and reproducibility of EMG spectral characteristics [2-10].Some authors have reported specific features of EMG power spectra of various muscles, which, in their opinion, must be allowed for in diagnosis of neuromuscular diseases [11,12].Our purpose was to clarify the features of spectral characteristics of the surface EMG of different muscles of upper and lower limbs as dependent on the degree of cortical influences on segmental motoneuron pools. METHODSWe examined ten healthy subjects (five men and five women) at an age of 21-28 ( 24.0 ± 2.1 ) years and 19 patients at an age of 11-30 ( 20.4 ± 1.4 ) years. The patients were tested during follow-up at the Laboratory of Movement Physiology and Neurophysiology (Ilizarov Research Center for Restorative Traumatology and Orthopedics) 4.9 ± 1.3 years after surgical correction of asymmetry in the length of the lower limbs after Ilizarov (congenital anomaly, 12 patients; consequence of hematogenous osteomyelitis, 6; of osteoarticular tuberculosis, 1). Their limbs were lengthened by 5-12 ( 7.3 ± 0.6 ) cm in the thigh and 3-10 ( 5.3 ± 0.6 ) cm in the shin. The thigh was lengthened in nine patients, the shin in six, and both the thigh and shin in four. The examination employed a BASIS-2381 bioelectrical activity analyzer (O.T.E. Biomedica, Italy). The following muscles were examined in the healthy subjects: m. deltoideus (the middle portion), m. biceps br. ( c.l. ), m. triceps br. ( c.l. ), m. extensor dig., m. flexor carpi rad. , m. gluteus max., m. rectus fem., m. biceps fem., m. tibialis ant., m. gastrocnemius ( c.l. ), m. extensor dig. br. , m. flexor dig. brev. , m. thenar , and m. hypothenar (on the left and right). In the patients, we examined the muscles of the lengthened segments of the leg ( m. rectus fem. and m. biceps fem. in the thigh; m. tibialis ant. and m. gastrocnemius c.l. in the shin). Surface bioelectrical activity of the tested muscles was recorded bipolarly (electrode length, 8 mm; interelectrode distance, 10 mm) with ...

Muscle spindles in elongation of the extremity: Proprioceptive conflict or activity deficit?

“…An alternative viewpoint is based on the fact that muscle effort of a preset level remains difficult for orthopedic patients even in delayed periods after elongation of the lower limbs by distraction osteosynthesis [4]. This suggests that long-term dosed distraction of the limb tissues during correction of its length largely involves the proprioceptor system of the muscles.…”