A musculotendon model of the fatigue profiles of paralyzed quadriceps muscle under FES
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Abstract:
A musculotendon model of the quadriceps muscle of the activated leg of a paraplegic patient incorporating fatigue was developed. The right quadriceps of a paraplegic patient who was engaged in a functional electrical stimulation (FES) training program was used for the measurements. The muscle studied was considered trained, both relating to strength and fatigue resistance. Extended stimulation was applied with an adjustable electrical stimulator, providing monophasic rectangular pulse trains with a frequency of 20 Hz, pulse width of 0.2 ms, and an intensity of up to 220 mA. The intensity used corresponded to the intensity required for the tested patient to stand up. This intensity was selected to deliberately encourage fatigue, and the result was a gradual and steady decay of the muscle force due to fatigue. The model was able to predict the decaying force during continuous electrical stimulation, as well as to indicate the muscle parameters which yield the best fit between the model prediction and the previously obtained experimental force profiles.< Keywords:
Functional electrical stimulation
Muscle Fatigue
Tension (geology)
Quadriceps muscle
Muscle fatigue has been studied in various fields. As it accompanied the change of its mechanical characteristics, we had studied the relation between muscle fatigue and its biomechanical characteristics (visco-elasticities) by using biomechanical impedances in case of the isometric contraction with continuous load. It was confirmed, as a result, that the condition of muscle fatigue was estimated from its visco-elasticities. In this study, we adopted the isometric contraction with intermittent load to examine how the rest time affected muscle fatigue. Three sets of 5 minutes 15% MVC (Maximum Voluntary Contraction) load were applied with 1 or 4 minutes interval on an antebrachial flexor muscle. The advancement and the recovery of muscle fatigue were observed in both loaded and unloaded situation. Longer rest decreased the fatiguing speed and caused an obvious recovery. Visco-elasticities were less sensitive to muscle fatigue at its early stage than MFs, which were calculated from surface EMGs.
Muscle Fatigue
Rest (music)
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Quadriceps muscle
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Effects of intermittent one leg isometric fatigue on maximal isometric force, force production, relaxation and blood lactate were studied using 29 male students as subjects. The relative changes of variables during fatigue and recovery were intercorrelated together with muscle structure variables, which were determined using needle biopsy technique. Maximal force decreased, force production and relaxation became slower and muscle lactate increased during fatigue. Change of maximal force, force production and lactate during fatigue as well as recovery of maximal force and lactate after fatigue were correlated significantly to muscle fiber distribution. Fatiguability of the force‐time characteristics was therefore influenced by the differences in the metabolic profiles of the individual muscle fibers. However, ability to relax the muscle quickly was not observed to be dependent on muscle structure. This suggests that different fatigue mechanisms might be present in relaxation than in force production.
Muscle Fatigue
Muscular fatigue
Muscle relaxation
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Objective To investigate the effect of muscle fatigue on linear and nonlinear dynamics of sEMG from biceps brachii during maximal voluntary isometric contractions.Method Ten young volunteers subjects performed non-fatiguing isometric contractions with four load levels and fatiguing maximal voluntary isometric contractions.Linear and nonlinear analysis were used to examine the sEMG signals and the changes of sEMG signals when MVC decreased to levels of 80% MVC,70% MVC,60%MVC and 50%MVC compared with the signals of sEMG during non-fatiguing contractions.Result Statistical analyses revealed that AEMG and %DET were significantly higher at fatigue states than those at non fatigue states,while MPF and C(n)were significantly lower than those at non fatigue states.With the development of muscle fatigue,MPF and %DET significantly decreased during maximal effort,while AEMG and %DET stayed stable.The interaction of load level and fatigue state for AEMG,MPF and C(n)were significant.Conclusion MPF and C(n)significantly decrease during maximal voluntary isometric contractions.sEMG dynamics between fatigue state and non-fatigue state is significantly different.
Muscle Fatigue
Turnover
Biceps brachii muscle
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The extent to which the normal fatigue compensatory mechanisms are disturbed in partially denervated muscles was investigated in human patients. Surface EMG, as well as motor unit electrical and mechanical activity, were analyzed from the partially denervated first interosseous muscle, during fatiguing isometric submaximal contraction. The EMG power and frequency changes which reveal the local fatigue process of healthy muscle have not been systematically found. Motor unit firing rate changes were rather normal and twitch contraction time did not increase during the fatiguing exercise. Differences between normal and partially denervated muscles could be explain by the occurrence of a central fatigue process more or less important in neurogenic lesions.
Motor unit
Muscle Fatigue
Motor Unit Recruitment
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Muscle contractions of upper limbs induced by functional electrical stimulation (FES) is a widely used rehabilitation method for stroke patients. However, FES tends to result in rapid muscle fatigue, which greatly limits activities such as FES-assisted rehabilitation exercises. In order to minimize the effect of muscle fatigue, an intelligent Muscle Fatigue Status (MFS) and an Function Impairment Level (FIL) controlled micro-stimulator are proposed. The stimulation parameters of the FES are updated according to the FIL of stroke patients initially. During the break of stimulation, mean frequency (MNF) and median frequency (MDF) are exacted from an electromyography (EMG) signal, which is directly detected from the stimulated muscle of stroke patients. The MFS that can be generated from MNF and MDF is used to control the operation mode of micro-stimulator. This implantable micro-stimulator will be designed and fabricated using system on chip technology.
Functional electrical stimulation
Muscle Fatigue
Stroke
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Changes in Quadriceps Femoris Muscle Strength Using Isometric Exercise Versus Electrical Stimulation
Reports in the literature appear to support the effectiveness of electrical stimulation as a means of increasing strength in normal muscles. The objective of this study was to measure and compare quadriceps muscle torque, isometrically and isokinetically, in three groups: 1) control group subjects (N = 9) did not alter their daily activities for 5 weeks, 2) isometric exercise group subjects (N = 10) exercised their quadriceps femoris muscle using maximum voluntary isometric exercises 3 times per week for 5 weeks, and 3) electrical stimulation group subjects (N = 10) who had 10 quadriceps femoris muscle contractions produced by electrical stimulation, 3 times per week for 5 weeks. No strength changes were noted in the control group; ANOVA revealed significant strength increases (P < 0.05) for both the electrical stimulation and isometric exercise groups. J Orthop Sports Phys Ther 1987;8(11):537-541.
Quadriceps femoris muscle
Electrical muscle stimulation
Quadriceps muscle
Functional electrical stimulation
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Summary. In isometric contractions, the type II fibres of animal muscle may have a greater specific strength than the type I fibres. This paper reports two retrospective analyses of the influence of fibre‐type composition on the ratio of the voluntary isometric strength of the quadriceps to its cross‐sectional area at mid‐thigh. In 15 normal quadriceps, the ratio of the muscle's strength to its cross‐sectional area was weakly correlated with the percentage contribution of type II fibres to a biopsy from the lateral mass of the muscle (r = 0·55, P<0·05). Linear regression suggested that type II fibres might have about three times the specific strength of type I fibres. Measurements of the atrophied quadriceps of 11 patients with unilateral knee injury/immobilization were standardized by comparison with the contralateral muscles. Strength/cross‐sectional area was again correlated with the percentage area as type II fibres (r = 0·62, P<0·05). The data suggested that type II fibres might have about twice the specific strength of type I fibres. Despite the wide confidence limits of each of the analyses, they agree that, in isometric contractions, the type II fibres of the human quadriceps seem stronger, for their cross‐sectional area, than the type I fibres.
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Quadriceps muscle
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Three subjects performed five successive isometric contractions to fatigue; the tension in any one experiment was constant at tensions varying from 20 to 80% of the maximal voluntary contraction (MVC). The interval between contractions was held constant at 11 min. Muscle biopsy specimens were obtained at the start of the experiment, after the first, fourth, and fifth, and before the second and fifth of the successive contractions. The concentrations of ATP, CP, glycogen, and lactate were measured in each sample of muscle. Changes in ATP and glycogen were insufficient to be held accountable for the development of isometric fatigue. Changes in CP and lactate were large after fatigue at intermediate tensions, but those of CP were considered unlikely to be responsible for the fatigue. At tensions of 30–50% MVC the increase in lactate could be responsible for fatigue either directly or by indirect changes in pH; at higher and lower tensions the possibility that lactate is directly implicated in the development of fatigue seems remote.
Muscle Fatigue
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