Shoulder and forearm oxygenation and myoelectric activity in patients with work-related muscle pain and healthy subjects

Frailty influences the vascular responsiveness of elderly individuals with chronic heart failure

INTRODUCTION

Frailty is highly prevalent in heart failure (HF) patients. HF is associated with oxidative stress and chronic inflammation, which impair oxygen use by skeletal muscles. Little is known about the influence of frailty on vascular responsiveness and tissue oxygenation.

OBJECTIVE

Analyze the influence of frailty on vascular responsiveness and muscle oxygenation in elderly individuals with and without HF.

METHODS

Individuals aged ≥60 years, with or without HF, were evaluated for frailty (phenotype). Near-infrared spectroscopy (NIRS) was used to assess muscle oxygenation at rest (oxygen saturation - StO₂ and deoxyhemoglobin) and during handgrip exercise (minimum StO₂ and maximum deoxyhemoglobin), and oxygenation variables.

STATISTICAL ANALYSIS

Results were grouped according to the frailty phenotype: non-frail, pre-frail, and frail. Shapiro-Wilk test was used to assess normality. Data were compared using a two-way analysis of variance (ANOVA). Bonferroni post hoc test was applied to determine the influence of frailty or HF on NIRS variables. SPSS software was used in the analyses; p < 0.05 was considered significant.

RESULTS

55 elderly participants (61.8% female; 70.4 ± 7.2 years old; 28 HF patients) participated in the study. 32.7% (n = 18) were classified as non-frail, 43.3% (n = 24) as pre-frail, and 23.6% (n = 13) as frail. The analysis of vascular responsiveness (n = 52) identified an influence (p < 0.05) of frailty on the reperfusion rate (slope 2 and ∆StO₂ of nadir-peak) and desaturation during occlusion (area under the curve of StO₂) in HF patients. There was no influence of frailty or HF on muscle oxygenation at rest and during exercise (n = 54; p > 0.05).

CONCLUSION

The coexistence of frailty and HF seems to impair vascular responsiveness, as frail elderly participants with HF presented lower reperfusion rates and higher desaturation levels during the arterial occlusion test. However, the presence of frailty or HF alone had no influence on muscle oxygenation at rest or during exercise.

NIRS-EMG for Clinical Applications: A Systematic Review

In this review, we present an overview of the applications and computed parameters of electromyography (EMG) and near-infrared spectroscopy (NIRS) methods on patients in clinical practice. The eligible studies were those where both techniques were combined in order to assess muscle characteristics from the electrical and hemodynamic points of view. With this aim, a comprehensive screening of the literature based on related keywords in the most-used scientific data bases allowed us to identify 17 papers which met the research criteria. We also present a brief overview of the devices designed specifically for muscular applications with EMG and NIRS sensors (a total of eight papers). A critical analysis of the results of the review suggests that the combined use of EMG and NIRS on muscle has been only partially exploited for assessment and evaluation in clinical practice and, thus, this field shows promises for future developments.

Comparing two methods to record maximal voluntary contractions and different electrode positions in recordings of forearm extensor muscle activity: Refining risk assessments for work-related wrist disorders

BACKGROUND:

Wrist disorders are common in force demanding industrial repetitive work. Visual assessment of force demands have a low reliability, instead surface electromyography (EMG) may be used as part of a risk assessment for work-related wrist disorders. For normalization of EMG recordings, a power grip (hand grip) is often used as maximal voluntary contraction (MVC) of the forearm extensor muscles. However, the test-retest reproducibility is poor and EMG amplitudes exceeding 100% have occasionally been recorded during work. An alternative MVC is resisted wrist extension, which may be more reliable.

OBJECTIVE:

To compare hand grip and resisted wrist extension MVCs, in terms of amplitude and reproducibility, and to examine the effect of electrode positioning.

METHODS:

Twelve subjects participated. EMG from right forearm extensors, from four electrode pairs, was recorded during MVCs, on three separate occasions.

RESULTS:

The group mean EMG amplitudes for resisted wrist extension were 1.2–1.7 times greater than those for hand grip. Resisted wrist extension showed better reproducibility than hand grip.

CONCLUSIONS:

The results indicate that the use of resisted wrist extension is a more accurate measurement of maximal effort of wrist extensor contractions than using hand grip and should increase the precision in EMG recordings from forearm extensor muscles, which in turn will increase the quality of risk assessments that are based on these.

Normalization of the trapezius sEMG signal - a reliability study on women with and without neck-shoulder pain

Objective

To evaluate within- and between-days reliability of two normalization methods of surface electromyography (sEMG) recordings of the trapezius muscle.

Methods

Nineteen women were allocated into 2 groups (healthy and with neck-shoulder pain). The sEMG was recorded in two sessions with 7 days in between sessions. The four portions of the trapezius muscle (the clavicular and acromial fibers of the upper trapezius, the middle and the lower trapezius) were evaluated during maximal and submaximal isometric voluntary contractions. The within- and between-days reliability of both maximal and submaximal contractions were assessed through Intraclass Correlation Coefficient (ICC_(2,1) was used for within-day analyses of both maximal and submaximal contractions, and for between-days analyses of maximal contractions while ICC_(2,3) was used for between-days analyses of submaximal contractions), Coefficient of Variation, Standard Error of Measurement, and Bland–Altman analysis.

Results

In general, submaximal contractions presented higher within-day reliability, with higher ICC values (e.g., middle trapezius – mean of 0.97), smaller Coefficient of Variation and Standard Error of Measurement ranges compared to maximal contractions (ICC values, e.g. for middle trapezius – mean of 0.94) in both groups. The same pattern was observed for between-days analyses, with submaximal contractions presenting higher ICC values (e.g., middle trapezius – mean of 0.84), smaller Coefficient of Variation and Standard Error of Measurement ranges than maximal contractions (ICC values, e.g. for middle trapezius – mean of 0.73) in both groups.

Conclusion

Submaximal contractions are recommended for normalization procedures of trapezius sEMG, in both subjects with neck-shoulder pain and healthy individuals.

Muscle pain induced by static contraction in rats is modulated by peripheral inflammatory mechanisms

Muscle pain is an important health issue and frequently related to static force exertion. The aim of this study is to evaluate whether peripheral inflammatory mechanisms are involved with static contraction-induced muscle pain in rats. To this end, we developed a model of muscle pain induced by static contraction performed by applying electrical pulses through electrodes inserted into muscle. We also evaluated the involvement of neutrophil migration, bradykinin, sympathetic amines and prostanoids. A single session of sustained static contraction of gastrocnemius muscle induced acute mechanical muscle hyperalgesia without affecting locomotor activity and with no evidence of structural damage in muscle tissue. Static contraction increased levels of creatine kinase but not lactate dehydrogenase, and induced neutrophil migration. Dexamethasone (glucocorticoid anti-inflammatory agent), DALBK (bradykinin B1 antagonist), Atenolol (β1 adrenoceptor antagonist), ICI 118,551 (β2 adrenoceptor antagonist), indomethacin (cyclooxygenase inhibitor), and fucoidan (non-specific selectin inhibitor) all reduced static contraction-induced muscle hyperalgesia; however, the bradykinin B2 antagonist, bradyzide, did not have an effect on static contraction-induced muscle hyperalgesia. Furthermore, an increased hyperalgesic response was observed when the selective bradykinin B1 agonist des-Arg⁹-bradykinin was injected into the previously stimulated muscle. Together, these findings demonstrate that static contraction induced mechanical muscle hyperalgesia in gastrocnemius muscle of rats is modulated through peripheral inflammatory mechanisms that are dependent on neutrophil migration, bradykinin, sympathetic amines and prostanoids. Considering the clinical relevance of muscle pain, we propose the present model of static contraction-induced mechanical muscle hyperalgesia as a useful tool for the study of mechanisms underlying static contraction-induced muscle pain.

Analysis of scapular muscle EMG activity in patients with idiopathic neck pain: a systematic review

It is proposed that altered scapular muscle function can contribute to abnormal loading of the cervical spine. However, it is not clear if patients with idiopathic neck pain show altered activity of the scapular muscles. The aim of this paper was to systematically review the literature regarding the differences or similarities in scapular muscle activity, measured by electromyography ( = EMG), between patients with chronic idiopathic neck pain compared to pain-free controls. Case-control (neck pain/healthy) studies investigating scapular muscle EMG activity (amplitude, timing and fatigue parameters) were searched in Pubmed and Web of Science. 25 articles were included in the systematic review. During rest and activities below shoulder height, no clear differences in mean Upper Trapezius ( = UT) EMG activity exist between patients with idiopathic neck pain and a healthy control group. During overhead activities, no conclusion for scapular EMG amplitude can be drawn as a large variation of results were reported. Adaptation strategies during overhead tasks are not the same between studies. Only one study investigated timing of the scapular muscles and found a delayed onset and shorter duration of the SA during elevation in patients with idiopathic neck pain. For scapular muscle fatigue, no definite conclusions can be made as a wide variation and conflicting results are reported. Further high quality EMG research on scapular muscles (broader than the UT) is necessary to understand/draw conclusions on how scapular muscles react in the presence of idiopathic neck pain.

Comparative metabolomics of muscle interstitium fluid in human trapezius myalgia: an in vivo microdialysis study

Purpose

The mechanisms behind trapezius myalgia are unclear. Many hypotheses have been presented suggesting an altered metabolism in the muscle. Here, muscle microdialysate from healthy and myalgic muscle is analysed using metabolomics. Metabolomics analyse a vast number of metabolites, enabling a comprehensive explorative screening of the cellular processes in the muscle.

Methods

Microdialysate samples were obtained from the shoulder muscle of healthy and myalgic subjects that performed a work and stress test. Samples from the baseline period and from the recovery period were analysed using gas chromatography—mass spectrometry (GC–MS) together with multivariate analysis to detect differences in extracellular content of metabolites between groups. Systematic differences in metabolites between groups were identified using multivariate analysis and orthogonal partial least square discriminate analysis (OPLS-DA). A complementary Mann–Whitney U test of group difference in individual metabolites was also performed.

Results

A large number of metabolites were detected and identified in this screening study. At baseline, no systematic differences between groups were observed according to the OPLS-DA. However, two metabolites, l-leucine and pyroglutamic acid, were significantly more abundant in the myalgic muscle compared to the healthy muscle. In the recovery period, systematic difference in metabolites between the groups was observed according to the OPLS-DA. The groups differed in amino acids, fatty acids and carbohydrates. Myristic acid and putrescine were significantly more abundant and beta-d-glucopyranose was significantly less abundant in the myalgic muscle.

Conclusion

This study provides important information regarding the metabolite content, thereby presenting new clues regarding the pathophysiology of the myalgic muscle.

Oxygenation and hemodynamics do not underlie early muscle fatigue for patients with work-related muscle pain

Patients suffering from work-related muscle pain (WRMP) fatigue earlier during exercise than healthy controls. Inadequate oxygen consumption and/or inadequate blood supply can influence the ability of the muscles to withstand fatigue. However, it remains unknown if oxygenation and hemodynamics are associated with early fatigue in muscles of WRMP patients. In the present study we applied near-infrared spectroscopy (NIRS) on the extensor carpi radialis (ECR) and trapezius (TD) muscles of patients with WRMP (n = 18) and healthy controls (n = 17). Our objective was to determine if there were group differences in endurance times for a low-level contraction of 15% maximal voluntary contraction (MVC) – sustained for 12–13 min, and to see if these differences were associated with differences in muscle oxygenation and hemodynamics. At baseline, oxygen saturation (StO₂%) was similar between groups for the ECR, but StO₂% was significantly lower for TD for the WRMP patients (76%) compared to controls (85%) (P<0.01). Also, baseline ECR blood flow was similar in the two groups. For both muscles there were a larger number of patients, compared to controls, that did not maintain the 15% MVC for the allotted time. Consequently, the endurance times were significantly shorter for the WRMP patients than controls (medians, ECR: 347 s vs. 582 s; TD: 430 s vs. 723 s respectively). Responses in StO₂% during the contractions were not significantly different between groups for either muscle, i.e. no apparent difference in oxygen consumption. Overall, we interpret our findings to indicate that the early fatigue for our WRMP patients was not associated with muscle oxygenation and hemodynamics.