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 · 1.61 Impact Factor
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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
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- "Exclusion criteria for both groups were as follows: history of severe shoulder–neck pathology/trauma, orthopaedic surgery, documented life-threatening diseases, cardiovascular diseases, rheumatoid arthritis, generalized pain, adverse psycho-social conditions or pregnancy, and positive clinical tests for cervical radiculopathy (i.e., Spurling A test, Neck Distraction test, Involved Cervical Rotation test (less than 60°) (Wainner et al., 2003). The inclusion and exclusion criteria were identified by a detailed interview and a self-reported questionnaire, validated in previous studies (Andersen et al., 2008; Sandsjo et al., 2006; Sjogaard et al., 2010), as well as a clinical examination of the upper limb and neck performed by a physiotherapist. A total of 69 subjects volunteered to participate. "
ABSTRACT: Neuromuscular control of the scapular muscles is important in the etiology of shoulder pain. Electromyographical (EMG) biofeedback in healthy people has been shown to support a selective activation of the lower compartment of the trapezius muscle, specifically. The aim of the present paper was to investigate whether patients with Subacromial Impingement Syndrome (SIS) were able to selectively activate the individual compartments within the trapezius muscle, with and without EMG biofeedback to the same extent as healthy controls (No-SIS). Fifteen SIS and 15 No-SIS participated in the study. Sessions with and without visual biofeedback were conducted. Surface EMG was recorded from four compartments of the trapezius muscle. Selective activation was defined as activation above 12% with other muscle parts below 1.5% or activation ratio at or above 95% of the total activation. Without biofeedback significantly fewer SIS subjects than No-SIS achieved selective activation (p=0.02-0.03). The findings of the study show that without biofeedback No-SIS had a superior scapular muscle control. However, when provided with visual EMG feedback the SIS group performed equally well as the No-SIS group. This indicated that individuals with SIS may benefit from biofeedback training to gain control of the neuromuscular function of the scapular muscle.Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 10/2013; DOI:10.1016/j.jelekin.2013.09.008 · 1.73 Impact Factor