Electromyographic Assessment of Functional Symmetry of Paraspinal Muscles during Static Exercises in Adolescents with Idiopathic Scoliosis

Background. The question of how to correct and rehabilitate scoliosis remains one of the most difficult problems of orthopaedics. Controversies continue to arise regarding various types of both symmetric and asymmetric scoliosis-specific therapeutic exercises.Objective. The aim of the present paper was to conduct an electromyographic assessment of functional symmetry of paraspinal muscles during symmetric and asymmetric exercises in adolescents with idiopathic scoliosis.Materials and Methods. The study was conducted in a group of 82 girls, mean age 12.4 ± 2.3 years with single- or double-major-idiopathic scoliosis, Cobb angle 24 ± 9.4°. The functional biopotentials during isometric work of paraspinal muscles in “at rest” position and during two symmetric and four asymmetric exercises were measured with the use of the Muscle Tester ME 6000 electromyograph.Results. In general, asymmetric exercises were characterised by larger differences in bioelectrical activity of paraspinal muscles, in comparison with symmetric exercises, both in the groups of patients with single-curve and double-curve scoliosis.Conclusion. During symmetric and asymmetric exercises, muscle tension patterns differed significantly in both groups, in comparison with the examination at rest, in most cases generating positive corrective patterns. Asymmetric exercises generated divergent muscle tension patterns on the convex and concave sides of the deformity.

Energy cost and fatigue during intermittent electrical stimulation of human skeletal muscle

Force generation and ATP utilization under anaerobic conditions were studied in the quadriceps femoris muscle of six volunteers. Electrical stimulation (20 Hz) was used to produce contractions with a duration of 0.8 s in one leg and contractions with a duration of 3.2 s in the other leg. The two procedures were designed to give the same total contraction time of 51 s and used the same number of stimulation pulses. Muscle biopsies were taken at rest and after 22 and 51 s of work and analyzed for ATP, phosphocreatine, and glucolytic intermediates. The results were compared with previous studies on continuous and intermittent stimulation. Fatigue developed significantly faster with contractions of short duration, and the energy cost was higher. Since force at the end of stimulation had a negative correlation to ATP utilization, there is no indication that the energy resources limit force generation. By comparison of stimulations producing the same amount of isometric work but with a different number of contractions, we estimate that the energy cost for activation and relaxation of a 1-s contraction is approximately 37% of the total ATP consumption.

EMG Power Spectrum Analysis to Assess Muscle Fatigue under Isometric Endurance Work

A research experimental study was conducted to make use of EMG power spectrum shift to assess the local muscle fatigue induced by isometric work. Sixteen male volunteer subjects participated in the study. The results indicate that the shift in mean power frequency (MPF) and the time constant of the straight line relationship between in (MPF) and elapsed time are reliable objective measures of local muscular fatigue.

Epitrochlearis muscle. I. Mechanical performance, energetics, and fiber composition

An in vitro rat muscle preparation is described that can contract at rates of 12–240 twitches/min. Maximum dF/dt paralleled maximum twitch tension, their ratio being constant at approximately 8 ms for contraction rates of 12-120 twitches/min. Time to peak tension was 8–13 ms, time to peak dF/dt 5–8 ms, and half-relaxation time 4 ms. These parameters were unaffected by rate of contraction or duration of isometric work. Differential ATPase staining demonstrated that 60–65% of the fibers were fast-twitch white, 20% fast-twitch red, and 15% slow-twitch red. The preponderance of fast-twitch fibers correlated with the observed mechanical performance of the muscle. Muscles contracting for 60 min at rates up to 48 twitches/min maintained total adenine nucleotide content (ATP, ADP, AMP) at near resting levels. At higher twitch rates (72–240 twitches/min), total adenine nucleotide content decreased 40%, reflecting exclusively a fall in ATP in the presence of adequate phosphocreatine stores. Adequate oxygenation was reflected by lactate-to-pyruvate ratios in the range of 11–15 at all rates of contraction.