Extrapolation of time series of EMG power spectrum parameters in isometric endurance tests of trunk extensor muscles

The aim of the present study was to test the viability of using short isometric contractions of trunk extensor muscles to perform an assessment of their endurance capacity. To this aim two types of analysis were performed. First, electromyographic (EMG) mean power frequency (MPF) slopes with respect to time as estimated over shorter fixed periods were compared to slopes estimated over the full contraction period of a contraction sustained until the endurance time. Second, the relationship between MPF slope estimates as estimated over various periods and the endurance time of the muscle group was evaluated. Five subjects performed three isometric trunk endurance tests at 25%, 50% and 75% of their maximum voluntary contraction (MVC), respectively. EMG signals of the left and right multifidus, iliocostalis and longissimus muscles were continuously recorded and spectral parameters were calculated. The MPF appeared to decrease consistently during all endurance tests. The extrapolation from a MPF time series of half the estimated contraction period to the time series of the complete contraction period gave reasonable results at all force levels, when data from several electrode locations were incorporated in a single slope estimate (mean or steepst slope). The accuracy of the prediction of trunk extensor endurance on the basis of these parameters describing the MPF time series over half the estimated contraction period was satisfactory. Endurance time predictions from yet shorter periods were unreliable

Motor control retraining exercises for shoulder impingement: effects on function, muscle activation, and biomechanics in young adults

Objective: Evidence for effective management of shoulder impingement is limited. The present study aimed to quantify the clinical, neurophysiological, and biomechanical effects of a scapular motor control retraining for young individuals with shoulder impingement signs.Method: Sixteen adults with shoulder impingement signs (mean age 22 ? 1.6 years) underwent the intervention and 16 healthy participants (24.8 ? 3.1years) provided reference data. Shoulder function and pain were assessed using the Shoulder Pain and Disability Index (SPADI) and other questionnaires. Electromyography (EMG) and 3 dimensional motion analysis was used to record muscle activation and kinematic data during arm elevation to 90? and lowering in 3 planes. Patients were assessed pre and post a 10-week motor control based intervention, utilizing scapular orientation retraining.Results: Pre-intervention, patients reported pain and reduced function compared to the healthy participants (SPADI in patients 20 ? 9.2; healthy 0 ? 0). Post intervention, the SPADI scores reduced significantly (P < .001) by a mean of 10 points (?4). EMG showed delayed onset and early termination of serratus anterior and lower trapezius muscle activity pre-intervention, which improved significantly post-intervention (P < .05). Pre intervention, patients exhibited on average 4.6-7.4? less posterior tilt, which was significantly lower in 2 arm elevation planes (P < .05) than healthy participants. Postintervention, upward rotation and posterior tilt increased significantly (P <.05) during 2 arm movements, approaching the healthy values.Conclusion: A 10-week motor control intervention for shoulder impingement increased function and reduced pain. Recovery mechanisms were indicated by changes in muscle recruitment andscapular kinematics. The efficacy of the intervention requires further examined in a randomizedcontrol trial

Electromyographic analyses of the erector spinae muscles during golf swings using four different clubs

The purpose of this study was to compare the electromyography (EMG) patterns of the thoracic and lumbar regions of the erector spinae (ES) muscle during the golf swing whilst using four different golf clubs. Fifteen right-handed male golfers performed a total of twenty swings in random order using the driver, 4-iron, 7-iron and pitching-wedge. Surface EMG was recorded from the lead and trail sides of the thoracic and lumbar regions of the ES muscle (T8, L1 and L5 lateral to the spinous-process). Three-dimensional high-speed video analysis was used to identify the backswing, forward swing, acceleration, early and late follow-through phases of the golf swing. No significant differences in muscle-activation levels from the lead and trail sides of the thoracic and lumbar regions of the ES muscle were displayed between the driver, 4-iron, 7-iron and pitching-wedge (P > 0.05). The highest mean thoracic and lumbar ES muscle-activation levels were displayed in the forward swing (67–99% MVC) and acceleration (83–106% MVC) phases of the swing for all clubs tested. The findings from this study show that there were no significant statistical differences between the driver, 4-iron, 7-iron and pitching-wedge when examining muscle activity from the thoracic and lumbar regions of the ES muscle

A wireless body sensor network for clinical assessment of the flexion-relaxation phenomenon

none5noAn accurate clinical assessment of the flexion-relaxation phenomenon on back muscles requires objective tools for the analysis of surface electromyography signals correlated with the real movement performed by the subject during the flexion-relaxation test. This paper deepens the evaluation of the flexion-relaxation phenomenon using a wireless body sensor network consisting of sEMG sensors in association with a wearable device that integrates accelerometer, gyroscope, and magnetometer. The raw data collected from the sensors during the flexion relaxation test are processed by an algorithm able to identify the phases of which the test is composed, provide an evaluation of the myoelectric activity and automatically detect the phenomenon presence/absence. The developed algorithm was used to process the data collected in an acquisition campaign conducted to evaluate the flexion-relaxation phenomenon on back muscles of subjects with and without Low Back Pain. The results have shown that the proposed method is significant for myoelectric silence detection and for clinical assessment of electromyography activity patterns.openPaoletti M.; Belli A.; Palma L.; Vallasciani M.; Pierleoni P.Paoletti, M.; Belli, A.; Palma, L.; Vallasciani, M.; Pierleoni, P

The effects of cervical muscle fatigue on balance - A study with elite amateur rugby league players

Neck muscle fatigue has been shown to alter an individual’s balance in a similar way to that reported in subjects suffering from neck pain or subjects that have suffered a neck injury. The main purpose of the present study was to quantify the effects of neck fatigue on neck muscle electromyography (EMG) activity, balance, perceived fatigue and perceived stability. Forty four elite amateur rugby league players resisted with their neck muscles approximately 35% maximum voluntary isometric contraction (MVIC) force for 15 minutes in eight different directions. Sway velocity and surface electromyography were measured. Questionnaires were used to record perceived effort and stability. Repeated measures ANOVA showed that after 15 minutes isometric contraction, significant changes were seen in sway velocity, perceived sway and EMG median frequency. There were no differences in perceived efforts. The changes in sway velocity and median frequency were more pronounced after extension and right and left posterior oblique contractions but there was no significant difference in sway velocity after contraction in the right lateral flexion, right anterior oblique and left anterior oblique direction of contraction. All the subjects showed oriented whole-body leaning in the plane of the contraction. The experiment produced significantly altered and perceived altered balance in this group of physically fit individuals. The results may contribute to our understanding of normal functional capacities of athletes and will provide a basis for further investigation in healthy non-athletes and participants that have suffered neck injuries. This may ultimately help develop accurate and valid rehabilitation outcome measures

Optimizing physical and psychosocial assessment in patients with non-specific chronic low back pain

NS-LBP is defined as pain and discomfort, localized below the costal margin and above the inferior gluteal folds, with or without referred leg pain, that is not attributable to a recognizable, known specific pathology. NS-CLBP involves NS-LBP persisting for at least 12 weeks. In the civilian as well as in the military population NS-CLBP is a common problem with an important impact on the patient’s functioning and on the society. Previous research demonstrated that NS-CLBP is not only caused by physical factors, but the psychosocial factors also play an important role in the onset and perpetuation of NS-CLBP. It is commonly accepted that these patients should be assessed biopsychosocialy. The planetary model is therefore an adequate coat rack in the management of NS-CLBP. To ensure a good outcome, it is primordial to tailor the therapy in function of the patient’s needs. This is only possible after a detailed physical and psychosocial assessment of the patient. Different tools and concepts were proposed to sustain this assessment, but some pitfalls exist. The aim of this doctoral dissertation was to optimize some aspects of the assessment of patients with NS-CLBP, to objectify the patient’s complaints and the associated influencing factors. The project was subdivided in three parts. In the first part trunk muscle recruitment patterns were investigated with sEMG. Literature often described altered trunk recruitment patterns in patients with NS-CLBP. Trunk muscle recruitment patterns were analyzed in terms of ratios of deep stabilizing muscle groups to global torque producing muscles. In Chapter 1 de influence of velocity of isokinetic movement on trunk muscle recruitment patterns was investigated. Fifty-three healthy subjects (26 men and 27 women) performed flexion-extension movements on a Cybex isokinetic dynamometer at different velocities (30°/s, 60°/s, 90°/s, 120°/s). The activity of two deep stabilizing muscle groups (m. obliquus internus abdominis (IO) and the lumbar m. multifidus (LMF)) and two superficial torque producing muscles (m. obliquus externus abdominis (EO) and the m. iliocostalis lumborum pars thoracis (ICLT)) were recorded simultaneously. The relative muscle activity as well the ratios LMF/ICLT and IO/EO were analyzed. Results demonstrated that the relative muscle activity of the different back muscles decreased with increasing velocity, but the LMF was less influenced by velocity than the ICLT, resulting in an increased ratio LMF/ICLT at high velocity. This study did not demonstrate an influence of velocity on the abdominal muscle groups. In Chapter 2 the same ratios were analyzed during 6 sensorimotor control exercises. Sixty-three healthy men and 36 patients with NS-CLBP participated in this study. All patients demonstrated a flexion-related MCI. Based on the trunk muscle recruitment patterns during the 6 exercises a statistical model was developed to discriminate between patients and healthy subjects. This part of the project led to the adjustment of several physical tests of the clinical pathway for NS-CLB at the MHQA. Chapter 1 underlined the importance of the use of different velocities in isokinetic evaluation and treatment of these patients. Chapter 2 provided evidence that trunk muscle recruitment patterns can be measured objectively in patients with flexion-related MCI. This is not only relevant in the clinical practice, but also in research as on objective variable in for example studies investigating the influence of therapy. The second part of the project focused on the improvement of psychosocial evaluation in patients with NS-CLBP. The aim was to optimize the use of self-report questionnaires. Therefore cross-cultural adaptation to Dutch and French was performed for the following questionnaires (Chapter 3): TSK, PHQ-15, QBPDI, OMPQ and the MPIpart1. Based on these and other questionnaires (PCS, DRAM, HADS, SF-36) a battery of self-report questionnaires was developed and long-term test-retest reliability was investigated. Test-retest reliability was analyzed on 48 French-speaking and 43 Dutch-speaking patients with NS-CLBP. Results indicated that scores on most of the questionnaires remained stable over time (> 1 month), except for the SF-36. In Chapter 4, the clinical interpretation of the scores on the questionnaires was facilitated by determining cut-off scores for screening questionnaires (TSK, PHQ-15, OMPQ) on198 patients with NS-CLBP, as well as determining MCIC for evaluative questionnaires (TSK, QBPDI, OMPQ, MPIpart1, SF-36) on 70 patients with NS-CLBP. This part of the study allowed the use of these questionnaires in a French and Dutch-speaking population. Although some waiting time exists between the moment the questionnaire is filled in and the start of the therapy, the clinician may be confident that the scores of the questionnaire are stable over a long period of time (> 1 month), if the patient’s status remains stable. The cut-off scores and the MCIC led to an easy interpretation of the scores and the change in scores. These results are also important in further research. Results of the questionnaires could for example be used as outcome variable in the evaluation of different therapies. The third part of this doctoral project underlined the link between psychosocial and physical evaluation, in the line of existing literature. Chapter 5 gave on example of this. Research was done on the influence of psychosocial factors on performance during two endurance tests for the abdominal and back muscles. Three hundred thirty two patients with NS-CLBP filled in a series of questionnaires. Then they effectuated the Biering-Sorensen back muscle endurance tests (B-S test) and an abdominal endurance test. Simultaneously the muscle activity of the LMF and the ICLT during the B-S test and the IO and the EO during the abdominal endurance test were recorded by sEMG. The time to exhaustion was also recorded. Based on the intrinsic muscle fatigue (normalized slope) the predicted time to exhaustion was calculated for both tests separately. By comparing the real time to exhaustion by the predicted time patients were divided in a performance and an underperformance group. Questionnaire results were compared for both groups. Regression analyses were performed to examine the predictive value of the questionnaires on the time to exhaustion. Results demonstrated that for the B-S test scores on the physical subscales of the SF-36 were lower in the underperformance groups. A higher BMI and low scores on the SF-36PF were significant predictors of low performance on the B-S test (R²=0.10). Concerning the abdominal endurance test, the group patients with low performance had significantly higher scores on the DRAMMZDI and the PCS, and lower scores on the SF-36. A higher BMI and lower scores on the SF-36MCS were significant predictors of lower scores on this test (R³=0.04). The results demonstrated that both tests were influenced differently. The B-S test seemed more influenced by physical factors and the abdominal endurance test were influenced by mental components. Why this difference exists is not clear, but this demonstrates again that in the interpretations of physical tests, psychosocial influences should be considered. Psychosocial influences are not equal for each physical test; therefore a complete psychosocial evaluation is needed. The overall aim of this doctoral dissertation was to contribute to the assessment of NS-CLBP, by improving the use of some instruments and tools. The results of these studies are not only interesting for the clinical practice, but are also useful in further research

Applications of EMG in Clinical and Sports Medicine

This second of two volumes on EMG (Electromyography) covers a wide range of clinical applications, as a complement to the methods discussed in volume 1. Topics range from gait and vibration analysis, through posture and falls prevention, to biofeedback in the treatment of neurologic swallowing impairment. The volume includes sections on back care, sports and performance medicine, gynecology/urology and orofacial function. Authors describe the procedures for their experimental studies with detailed and clear illustrations and references to the literature. The limitations of SEMG measures and methods for careful analysis are discussed. This broad compilation of articles discussing the use of EMG in both clinical and research applications demonstrates the utility of the method as a tool in a wide variety of disciplines and clinical fields

Application of Advanced Biomechanical Methods in Studying Low Back Pain – Recent Development in Estimation of Lower Back Loads and Large-Array Surface Electromyography and Findings

Low back pain (LBP) is a major public health problem and the leading disabling musculoskeletal disorder globally. A number of biomechanical methods using kinematic, kinetic and/or neuromuscular approaches have been used to study LBP. In this narrative review, we report recent developments in two biomechanical methods: estimation of lower back loads and large-array surface electromyography (LA-SEMG) and the findings associated with LBP. The ability to estimate lower back loads is very important for the prevention and the management of work-related low back injuries based on the mechanical loading model as one category of LBP classification. The methods used for estimation of lower back loads vary from simple rigid link-segment models to sophisticated, optimization-based finite element models. In general, reviewed reports of differences in mechanical loads experienced in lower back tissues between patients with LBP and asymptomatic individuals are not consistent. Such lack of consistency is primarily due to differences in activities under which lower back mechanical loads were investigated as well as heterogeneity of patient populations. The ability to examine trunk neuromuscular behavior is particularly relevant to the motor control model, another category of LBP classification. LA-SEMG not only is noninvasive but also provides spatial resolution within and across muscle groups. Studies using LA-SEMG showed that healthy individuals exhibit highly organized, symmetric back muscle activity patterns, suggesting an orderly recruitment of muscle fibers. In contrast, back muscle activity patterns in LBP patients are asymmetric or multifocal, suggesting lack of orderly muscle recruitment. LA-SEMG was also shown capable of capturing unique back muscle response to manual therapy. In conclusion, estimation of low back load and LA-SEMG techniques demonstrated promising potentials for understanding LBP and treatment effects. Future studies are warranted to fully establish clinical validity of these two biomechanical methods