A Review of Non-Invasive Techniques to Detect and Predict Localised Muscle Fatigue

Muscle fatigue is an established area of research and various types of muscle fatigue have been investigated in order to fully understand the condition. This paper gives an overview of the various non-invasive techniques available for use in automated fatigue detection, such as mechanomyography, electromyography, near-infrared spectroscopy and ultrasound for both isometric and non-isometric contractions. Various signal analysis methods are compared by illustrating their applicability in real-time settings. This paper will be of interest to researchers who wish to select the most appropriate methodology for research on muscle fatigue detection or prediction, or for the development of devices that can be used in, e.g., sports scenarios to improve performance or prevent injury. To date, research on localised muscle fatigue focuses mainly on the clinical side. There is very little research carried out on the implementation of detecting/predicting fatigue using an autonomous system, although recent research on automating the process of localised muscle fatigue detection/prediction shows promising results

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes. This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications

Investigation of localized muscle fatigue

Muscle fatigue is a condition where the ability of the muscle to contract and produce force is reduced. Generally the result of prolonged, relatively strong muscle activity, localized muscle fatigue (LMF) occurs when a muscle or a group of muscles has reduced ability to contract and produce force despite neural stimulation. The causes of physical fatigue include poor workplace practices and lack of regular physical exercise. Signs of fatigue include reduced motivation, blurred vision, increased reflex time and poor concentration – all elements in fatigue-related accidents. Muscle fatigue is a leading cause of workplace and transport-related accidents, as well as work-related musculoskeletal disorders. This thesis reports on an experimental study conducted to determine the effects of LMF on the physiological signals produced during voluntary isometric and cyclic muscle contraction. Surface electromyography (SEMG) was considered relevant for this research because it is the most practical and non-invasive technique for recording such physiological signals. Time and frequency domain responses were extracted from recorded signals and analysed. Statistical analysis on extracted data was carried out using analysis of variance (ANOVA) and non parametric (sign-test) analysis. Sign-test analysis shows a statistically significant change in root-mean-square (RMS) amplitude both before and after the onset of fatigue during cyclic contraction but no statistically significant change in median frequency (MDF). But for isometric contraction the results of sign-test show that there is a statistically significant change in both MDF and RMS before and after the onset of fatigue. Similarly, ANOVA results suggest that for isometric contraction there is a statistically significant change in both MDF and RMS before and after the onset of fatigue. In addition, there is a statistically significant change in RMS amplitude before and after the onset of fatigue during cyclic contraction but no statistically significant change in MDF. The results clearly demonstrate that while SEMG analysis is appropriate for muscular fatigue detection, the use of MDF alone does not provide a reliable and valid measure for LMF detection in real world applications where most tasks require a combination of both isometric and cyclic contractions

Computational Intelligence in Electromyography Analysis

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG may be used clinically for the diagnosis of neuromuscular problems and for assessing biomechanical and motor control deficits and other functional disorders. Furthermore, it can be used as a control signal for interfacing with orthotic and/or prosthetic devices or other rehabilitation assists. This book presents an updated overview of signal processing applications and recent developments in EMG from a number of diverse aspects and various applications in clinical and experimental research. It will provide readers with a detailed introduction to EMG signal processing techniques and applications, while presenting several new results and explanation of existing algorithms. This book is organized into 18 chapters, covering the current theoretical and practical approaches of EMG research

Evaluation of performance fatigability through surface EMG in health and muscle disease: state of the art

In literature, it is commonly reported that the progress of performance fatigability may be indirectly assessed through the changes in the features of the surface electromyogram (sEMG) signal. In particular, during isometric constant force contractions, changes in the sEMG signal are caused by several physiological factors, such as a decay in muscle fibers conduction velocity (CV), an increase of the degree of synchronization between the firing times of simultaneously active motor units (MUs), by the central nervous system, and a reduction of the recruitment threshold and a modulation of MUs firing rate. Amplitude and spectral parameters may be used to characterize the global contributions to performance fatigability, such as MU control properties and fiber membrane properties, or central and peripheral factors, respectively. In addition, being CV a physiological parameter, its estimation is of marked interest to the study of fatigue both in physiological and in presence of neuromuscular diseases