The potential use of spectral electromyographic fatigue as a screening and outcome monitoring tool of sarcopenic back muscle alterations

Background: To examine whether or not median frequency surface electromyographic (MF-EMG) back muscle fatigue monitoring would be able to identify alterations in back muscle function in elderly muscles, if a protocol was used that allowed optimum standardization of the processes underlying electromyographic fatigue, and whether these tests were reliable from day to day. Methods: A total of 42 older (21 females; 67 (±10.5) years old) and 44 younger persons (19 females; 33 (±10) years) performed maximum isometric back extensions which were followed by one 30 s lasting 80% submaximum extension. Participants were seated on a dynamometer with their trunks 30° anteflexed, and they repeated all tests after 1-2 days and 6 weeks. SEMG was recorded bilaterally from the L1 (iliocostalis lumborum), L2 (longissimus), and L5 (multifidus) recording sites. Outcome variables included maximum back extension torque, initial MF-EMG (IMF-EMG), MF-EMG slope declines, and individual MF-EMG muscular imbalance scores. Two-factorial ANOVAs served to examine the age and gender-specific effects, and models from Generalizability Theory (G-Theory) were used for assessing retest-reliability. Results: Maximum back extension moment was non-significantly smaller in elders. IMF-EMG was overall higher in elders, with significant differences at the L5 recordings sites. In the elderly, MF-EMG fatigue declines were significantly smaller in L5, in the recording with the most negative slope, or if the slope of all electrodes was considered. Retest reliability was unanimous in young and older persons. ICC-type measurements from G-Theory of both the IMF and the fatigue slopes ranged from 0.7 to 0.85. Absolute SEM values were found clinically acceptable for the IMF-EMG, but relatively high for the fatigue slope declines. Conclusions: The MF-EMG fatigue method is able to elucidate alterations of aging back muscles. This method, thus, might be suggested as a potential biomarker to objectively identify persons at risk for sarcopenia. Considering the clinical relevance of the IMF-EMG relative to the MF-EMG slope declines, spectral EMG may also be used as an outcome monitoring tool in elderly populations

Age and gender related neuromuscular pattern during trunk flexion-extension in chronic low back pain patients

Background: The root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from standing has repeatedly been recommended to objectively assess muscle function in chronic low back pain patients. However, literature addressing older patients is sparse. This cross sectional study sought to examine differences in neuromuscular activation between age groups (>60 versus 40-60 versus <40 years) and sexes during a standardized trunk flexion-extension task. Methods: A total of 216 patients (62 older, 84 middle-aged, 70 younger) performed maximum trunk extensions followed by trunk flexion extension testing thereby holding static positions at standing, half, and full trunk flexion. The lumbar extensor muscle activity and 3d-accelerometric signals intended to monitor hip and trunk position angles were recorded from the L5 (multifidus) and T4 (semispinalis thoracis) levels. Permutation ANOVA with bootstrapped confidence intervals were performed to examine for age and gender related differences. Ridge-regressions investigated the impact of physical-functional and psychological variables to the half flexion relaxation ratio (i.e. muscle activity at the half divided by that in maximum flexion position). Results: Maximum back extension torque was slightly but significantly higher in youngest compared to oldest patients if male and females were pooled. Normalized RMS-SEMG revealed highest lumbar extensor muscle activity at standing in the oldest and the female groups. Patients over 60 years showed lowest activity changes from standing to half (increments) and from half to the maximum flexion position (decrements) leading to a significantly lower half flexion relaxation ratio compared to the youngest patients. These oldest patients demonstrated the highest hip and lowest lumbothoracic changes of position angles. Females had higher regional hip and gross trunk ranges of movement compared to males. Lumbothoracic flexion and the muscle activity at standing had a significant impact on the half flexion relaxation ratio. Conclusions: The neuromuscular activation pattern and the kinematics in this trunk flexion-extension task involving static half flexion position changed according to age and sex. The test has a good potential to discriminate between impaired and unimpaired neuromuscular regulation of back extensors in cLBP patients, thereby allowing the design of more individualized exercise programs. Electronic supplementary material The online version of this article (doi:10.1186/s12984-016-0121-1) contains supplementary material, which is available to authorized users

Evidence based medicine in physical medicine and rehabilitation (English version)

In the last twenty years the term “Evidence Based Medicine (EBM)” has spread into all areas of medicine and is often used for decision-making in the medical and public health sector. It is also used to verify the significance and/or the effectiveness of different therapies. The definition of EBM is to use the physician’s individual expertise, the patient’s needs and the best external evidence for each individual patient. Today, however, the term EBM is often wrongly used as a synonym for best “external evidence”. This leads not only to a misuse of evidence based medicine but suggests a fundamental misunderstanding of the model which was created by Gordon Guyatt, David Sackett and Archibald Cochrane. This problem becomes even greater the more social insurance institutions, public healthcare providers and politicians use external evidence alone as a main guideline for financing therapies in physical medicine and general rehabilitation without taking into account the physician’s expertise and the patient’s needs.The wrong interpretation of EBM can lead to the following problems: well established clinical therapies are either questioned or not granted and are therefore withheld from patients (for example physical pain management). Absence of evidence for individual therapy methods does not prove their ineffectiveness! In this short statement the significance of EBM in physical medicine and general rehabilitation will be analysed and discussed

The Back Muscle Surface Electromyography-Based Fatigue Index: A Digital Biomarker of Human Neuromuscular Aging?

As part of our quest for digital biomarkers of neuromuscular aging, and encouraged by recent findings in healthy volunteers, this study investigated if the instantaneous median frequency (IMDF) derived from back muscle surface electromyographic (SEMG) data monitored during cyclic back extensions could reliably differentiate between younger and older individuals with cLBP. A total of 243 persons with cLBP participated in three experimental sessions: at baseline, one to two days after the first session, and then again approximately six weeks later. During each session, the study participants performed a series of three isometric maximal voluntary contractions (MVC) of back extensors using a dynamometer. These were followed by an isometric back extension at 80% MVC, and&mdash;after a break&mdash;25 slow cyclic back extensions at 50% MVC. SEMG data were recorded bilaterally at L5 (multifidus), L2 (longissimus dorsi), and L1 (iliocostalis lumborum). Linear mixed-effects models found the IMDF-SEMG time-course changes more rapidly in younger than in older individuals, and more prominently in male participants. The absolute and relative reliabilities of the SEMG time&ndash;frequency representations were well compared between older and younger participants. The results indicated an overall good relative reliability, but variable absolute reliability levels. IMDF-SEMG estimates derived from cyclic back extensions proved to be successful in reliably detecting differences in back muscle function in younger vs. older persons with cLBP. These findings encourage further research, with a focus on assessing whether an IMDF-SEMG-based index could be utilized as a tool to achieve the preclinical detection of back muscle aging, and possibly predict the development of back muscle sarcopenia

Overactivity in chronic pain, the role of pain related endurance and neuromuscular activity - an interdisciplinary, narrative review

Objectives: Decades of research have convincingly shown, that fear of pain and pain-related avoidance behavior are important precursors of disability in daily life. Physical underuse as a consequence of avoidance, however, cannot not be blamed for chronic disability in all patients, a contrasting behavior, pain-related dysfunctional endurance in a task and overactivity, have to be considered. Currently there is a need to better understand psychological determinants of overactivity, dysfunctional endurance and neuro-biomechanical consequences. Methods: Narrative review. Results: The first part of this review elucidates research on self-reported overactivity, showing associations with higher levels of pain and disability, especially in spinal load positions, e.g. lifting, bending or spending too long in specific positions. In addition, measures of habitual endurance-related pain responses, based on the avoidance-endurance model, related to objective assessments of physical activity and again, especially in positions known to cause high spinal load (part two). The final part reveals findings from neuromuscular research on motor control indicating the possibility that in particular overactivity and dysfunctional endurance may result in a number of dysfunctional adaptations with repetitive strain injuries of muscles, ligaments and vertebral segments as precursors of pain. Discussion: This narrative review brings together different research lines on overactivity, pain-related endurance and supposed neuromuscular consequences. Clinicians should distinguish between patients who rest and escape from pain at low levels of pain -but high levels of fear of pain - and those who predominantly persist in activities despite severely increasing pain until a break will be enforced by intolerable pain levels