A Non-Linear Control Method to Compensate for Muscle Fatigue during Neuromuscular Electrical Stimulation
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Abstract:
Neuromuscular electrical stimulation (NMES) is a promising technique to artificially activate muscles as a means to potentially restore the capability to perform functional tasks in persons with neurological disorders. A pervasive problem with NMES is that overstimulation of the muscle (among other factors) leads to rapid muscle fatigue, which limits the use of clinical and commercial NMES systems. The objective of this paper is to develop an NMES controller that incorporates the effects of muscle fatigue during NMES-induced non-isometric contraction of the human quadriceps femoris muscle. Our previous work that used the RISE class of nonlinear controllers cannot accommodate fatigue and muscle activation dynamics. A totally new control design approach and associated stability proof is required to derive a new class of NMES control design that accounts for muscle fatigue dynamics and a first order activation dynamics, in addition to the second order musculoskeletal dynamics. Motivated from a control method for robotic systems in a strict-feedback form, a backstepping based nonlinear NMES controller was designed to accommodate for the additional muscle activation dynamics. Further, experimentally identified estimates of the fatigue and activation dynamics were incorporated in the control design. The developed controller uses a neural network-based estimate of the musculoskeletal dynamics and error due to fatigue estimation. A globally uniformly ultimately bounded stability is proven the new controller that accounts for an uncertain nonlinear muscle model and bounded nonlinear disturbances (e.g., spasticity, changing load dynamics). The developed controller was validated through experiments on the left and right legs of 3 able-bodied subjects and was compared with a proportional-derivative (PD) controller and a PD augmented with a neural network. The statistical analysis showed improved control performance compared to the PD controller.Keywords:
Muscle Fatigue
Functional electrical stimulation
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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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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Canine tracheal smooth muscle was used as an in vitro model of smooth muscle in intrapulmonary airways to determine whether active tension curves derived from isometric and isotonic muscles are similar, and thus resemble striated muscle in this respect. Isometric, isotonic after-loaded, and isotonic free-loaded contractions elicited at different lengths and loads, were analysed. The data demonstrate that length–tension (L–T) diagrams are different in these various types of contractions for electrically and carbachol driven tracheal smooth muscles strips. In general, at any given length active tension is less in isotonic and free-loaded modes of contraction as compared with isometric. We conclude that the ability to actively develop tension at a given length in airway smooth muscle depends on the mode of contraction.
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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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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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For individuals that suffer from paraplegia activities of daily life are greatly inhibited. With over 5,000 new cases of paraplegia each year in the United States alone there is a clear need to develop technologies to restore lower extremity function to these individuals. One method that has shown promise for restoring functional movement to paralyzed limbs is the use of functional electrical stimulation (FES), which is the application of electrical stimulation to produce a muscle contraction and create a functional movement. This technique has been shown to be able to restore numerous motor functions in persons with disability; however, the application of the electrical stimulation can cause rapid muscle fatigue, limiting the duration that these devices may be used. As an alternative some research has developed fully actuated orthoses to restore motor function via electric motors. These devices have been shown to be capable of achieving greater walking durations than FES systems; however, these systems can be significantly larger and heavier. To develop smaller and more efficient systems some research has explored hybrid neuroprostheses that use both FES and electric motors. However, these hybrid systems present new research challenges.
In this dissertation novel control methods to compensate/inhibit muscle fatigue in neuroprosthetic and hybrid neuroprosthetic devices are developed. Some of these methods seek to compensate for the effects of fatigue by using fatigue dynamics in the control development or by minimizing the amount of stimulation used to produce a desired movement. Other control methods presented here seek to inhibit the effects of muscle fatigue by adding an electric motor as additional actuation. These control methods use either switching or cooperative control of FES and an electric motor to achieve longer durations of use than systems that strictly use FES. Finally, the necessity for the continued study of hybrid gait restoration systems is facilitated through simulations of walking with a hybrid neuroprosthesis. The results of these simulations demonstrate the potential for hybrid neuroprosthesis gait restoration devices to be more efficient and achieve greater walking durations than systems that use strictly FES or strictly electric motors.
Functional electrical stimulation
Muscle Fatigue
Limiting
Functional movement
Neuroprosthetics
Paraplegia
Motor Control
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