Muscle oxygenation and glycolysis in females with trapezius myalgia during stress and repetitive work using microdialysis and NIRS. Eur J Appl Physiol
ABSTRACT The aim of this investigation was to study female workers active in the labour market for differences between those with trapezius myalgia (MYA) and without (CON) during repetitive pegboard (PEG) and stress (STR) tasks regarding (1) relative muscle load, (2) trapezius muscle blood flow, (3) metabolite accumulation, (4) oxygenation, and (5) pain development. Among 812 female employees (age 30-60 years) at 7 companies with high prevalence of neck/shoulder complaints, clinical examination identified 43 MYA and 19 CON. At rest, during PEG, and STR the trapezius muscle was measured using (1) EMG and MMG, (2) microdialysis, and (3) NIRS. Further, subjective pain ratings were scored (VAS). EMGrms in %MVE (Maximal Voluntary EMG-activity), was significantly higher among MYA than CON during PEG (11.74 +/- 9.09 vs. 7.42 +/- 5.56%MVE) and STR (5.47 +/- 5.00 vs. 3.28 +/- 1.94%MVE). MANOVA showed a group and time effect regarding data from the microdialysis: for MYA versus CON group differences demonstrated lower muscle blood flow and higher lactate and pyruvate concentrations. Potassium and glucose only showed time effects. NIRS showed similar initial decreases in oxygenation with PEG in both groups, but only in CON a significant increase back to baseline during PEG. VAS score at rest was highest among MYA and increased during PEG, but not for CON. The results showed significant differences between CON and MYA regarding muscle metabolism at rest and with PEG and STR. Higher relative muscle load during PEG and STR, insufficient muscle blood flow and oxygenation may account for the higher lactate, pyruvate and pain responses among MYA versus CON.
- SourceAvailable from: Tessy Luger
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- "The design of the experimental task was based on previous laboratory studies (Sundelin 1993; Henning et al. 1997; Sjörs et al. 2009; Sjøgaard et al. 2010), which simulated low-intensity assembly work using a Pegboard (Purdue Pegboard Model 32020; Lafayette Instrument Company, Lafayette, IN, USA; Figure 1). We applied two types of task variation in a work-rest ratio of 55:5 min. "
ABSTRACT: Work-related musculoskeletal disorders are increasing due to industrialisation of work processes. Task variation has been suggested as potential intervention. The objectives of this study were to investigate, first, the influence of task variation on electromyographic (EMG) manifestations of shoulder muscle fatigue and discomfort; second, noticeable postural shoulder changes over time; third, if the association between task variation and EMG might be biased by postural changes. Outcome parameters were recorded using multichannel EMG, Optotrak and the Borg scale. Fourteen participants performed a one-hour repetitive Pegboard task in one continuous and two interrupted conditions with rest and a pick-and-place task, respectively. Manifestations of shoulder muscle fatigue and discomfort feelings were observed throughout the conditions but these were not significantly influenced by task variation. After correction for joint angles, the relation between task variation and EMG was significantly biased but significant effects of task variation remained absent. Practitioner Summary: Comparing a one-hour continuous, repetitive Pegboard task with two interrupted conditions revealed no significant influences of task variation. We did observe that the relation between task variation and EMG was biased by posture and therefore advise taking account for posture when investigating manifestations of muscle fatigue in assembly tasks.Ergonomics 06/2015; DOI:10.1080/00140139.2015.1043356 · 1.56 Impact Factor
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- "The majority of studies concerning chronic trapezius myalgia have reported increases in the metabolites lactate and pyruvate. Often-suggested explanations for the higher concentration of lactate are insufficient oxygen supply and anaerobic conditions, but there is not a consistent picture with respect to blood flow in this pain condition or in chronic widespread pain/FMS using microdialysis or other techniques.22,89,94,103,128–130 Reduction in tissue oxygenation in FMS131 and in chronic trapezius myalgia132 may result in higher pyruvate and higher lactate concentrations, due to a shift toward an anaerobic state. "
ABSTRACT: Chronic musculoskeletal pain conditions are multifaceted, and approximately 20% of the adult population lives with severe chronic pain, with a higher prevalence in women and in lower income groups. Chronic pain is influenced by and interacts with physical, emotional, psychological, and social factors, and a biopsychosocial framework is increasingly applied in clinical practice. However, there is still a lack of assessment procedures based on the activated neurobiological pain mechanisms (ie, the biological part of the biopsychosocial model of pain), which may be a necessary step for further optimizing outcomes after treatments for patients with chronic pain. It has been suggested that chronic pain conditions are mainly driven by alterations in the central nervous system with little or no peripheral stimuli or nociception. In contrast, other authors argue that such central alterations are driven by peripheral alterations and nociceptive input. Microdialysis is an in vivo method for studying local tissue alterations and allows for sampling of substances in the interstitium of the muscle, where nociceptor free nerve endings are found close to the muscle fibers. The extracellular matrix plays a key role in physiologic functions of cells, including the primary afferent nociceptor. The present review mainly concerns the results of microdialysis studies and how they can contribute to the understanding of activated peripheral nociceptive and pain mechanisms in humans with chronic pain. The primary aim was to review molecular studies using microdialysis for the investigation of human chronic muscle pain, ie, chronic masticatory muscle pain, chronic trapezius myalgia, chronic whiplash-associated disorders, and chronic widespread pain/fibromyalgia syndrome. Several studies clearly showed elevated levels of serotonin, glutamate, lactate, and pyruvate in localized chronic myalgias and may be potential biomarkers. These results indicate that peripheral muscle alterations are parts of the activated pain mechanisms in common chronic pain conditions. Muscle alterations have been reported in fibromyalgia syndrome and chronic widespread pain, but more studies are needed before definite conclusions can be drawn. For other substances, results are inconclusive across studies and patient groups.Journal of Pain Research 06/2014; 2014:7:313 - 326. DOI:10.2147/JPR.S59144
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- "The study design, recruitment of participants, randomization of 48 women, and main results have been described in detail previously  . In the present case-control study, 42 women with trapezius myalgia (MYA, mean ± SD: 44 ± 8 yrs, 165 ± 6 cm, 72 ± 15 kg, and days with neck pain during previous year 219 ± 19 days) and 20 women comparable with regard to job-type, age, weight, and height but without neck muscle complications (CON, mean ± SD: 45 ± 9 yrs, 167 ± 6 cm, 70 ± 11 kg, and days with neck pain during previous year 5 ± 6 days) participated. "
ABSTRACT: Aim: This study investigates consequences of chronic neck pain on muscle function and the rehabilitating effects of contrasting interventions. Methods: Women with trapezius myalgia (MYA, n = 42) and healthy controls (CON, n = 20) participated in a case-control study. Subsequently MYA were randomized to 10 weeks of specific strength training (SST, n = 18), general fitness training (GFT, n = 16), or a reference group without physical training (REF, n = 8). Participants performed tests of 100 consecutive cycles of 2 s isometric maximal voluntary contractions (MVC) of shoulder elevation followed by 2 s relaxation at baseline and 10-week follow-up. Results: In the case-control study, peak force, rate of force development, and rate of force relaxation as well as EMG amplitude were lower in MYA than CON throughout all 100 MVC. Muscle fiber capillarization was not significantly different between MYA and CON. In the intervention study, SST improved all force parameters significantly more than the two other groups, to levels comparable to that of CON. This was seen along with muscle fiber hypertrophy and increased capillarization. Conclusion: Women with trapezius myalgia have lower strength capacity during repetitive MVC of the trapezius muscle than healthy controls. High-intensity strength training effectively improves strength capacity during repetitive MVC of the painful trapezius muscle.02/2014; 2014:187324. DOI:10.1155/2014/187324