| 1. |
- Elcadi, Guilherme H., et al.
(författare)
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A Strong Correlation Between Dorsolateral Prefrontal Cortex And Vastus Lateralis Activity During Running To Fatigue
- 2016
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Ingår i: Medicine and science in sports and exercise. - : Ovid Technologies (Wolters Kluwer Health). - 0195-9131 .- 1530-0315. ; 48:5, s. 854-854
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue is a phenomenon of pronounced importance in sports. Recently, there is strong evidence of interplay between the prefrontal cortex and motor output during fatiguing contractions. The dorsolateral prefrontal cortex (DLPC) due to its large involvement in cognitive and motor activities is believed to be involved but this requires physiological clarification. AIM: We investigated the relationship between DLPC activity - responses in oxyhemoglobin (HbO2) and total hemoglobin (HbT) measured by near-infrared spectroscopy (NIRS), and the vastus lateralis muscle (VL) activity - quantified as root-mean-square (RMS) of the EMG signal, during a fatigue protocol.METHODS: Four male runners (32±12 yrs) with probes for NIRS over the DLPC and EMG over the VL performed a track running test at a constant speed to fatigue (exhaustion). The running speed was individually determined as the average speed of a 1200-m time trial performed ~3 days prior to testing. For NIRS changes in μmole/L of HbO2 and HbT were computed. The VL EMG-RMS of the contraction of each step was normalized as a percent of a submaximal reference contraction (%RMS), thus removing the non-activity between steps. Data of 10s epochs at 20, 40, 60, 80 and 100% of time for each lap were averaged for analyses. Regression analyses performed with HbO2 and with HbT as dependent variables and %RMS as the independent variable.RESULTS: Over time there was an increase in HbO2 and HbT in the DLPC, and in VL-%RMS. Both HbO2 and HbT correlated strongly with EMG-RMS during running to fatigue (see figures below); p<0.001 for both.CONCLUSION: The strong relationship between DLPC and VL activities during running to fatigue suggests the involvement of the DLPC in the central processing of fatigue.
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| 2. |
- Barkstedt, Vanda, et al.
(författare)
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Sophämtares fysiska och psykosociala arbetsbelastning
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Arbetet som sophämtare inkluderar manuell hantering som hämtning och hantering av hushållsavfall i kärl och säckar. Det finns tidigare studier som visat att arbetet kan vara tungt med en hög helkroppsbelastning. Tungt arbete förknippas ofta med besvär i rörelseorganen. Psykologiska påfrestningar i arbetet kan också bidra till besvärsuppkomst.Biltrafikens arbetsgivarförbund och Svenska Transportarbetareförbundet tog gemensamt initiativ till det här projektet ”Sophämtarnas arbetsmiljö - allas ansvar”. Projektet har utförts av Transportfackens Yrkes- och Arbetsmiljönämnd (TYA) i samarbete med Karolinska Institutet (KI) och Centrum för belastningsskadeforskning (CBF) vid Högskolan i Gävle. I den här delen av projektet var syftet att kartlägga branschens förekomst av arbetsrelaterade besvär och undersöka den fysiska och psykosociala arbetsbelastningen hos sophämtare vid arbete med insamling av hushållsavfall.Samtliga Sveriges sophämtare som arbetar med insamling av hushållsavfall, knappt 2000, erbjöds att fylla i ett omfattande frågeformulär avseende arbete och hälsa. Sextiosex procent svarade. Inom projektetet genomfördes också heldagsmätningar av puls och arbetsställningar för rygg och armar på 56 sophämtare som arbetade med baklastande sopbil. På 12 sophämtare som arbetade med sidlastande sopbil genomfördes dessutom mätningar av muskelbelastning i skulder- och underarmsmuskulatur under en hel arbetsdag. I samband med heldagsmätningarna observerades sophämtarnas arbete av en observatör från en efterföljande bil, eller via en personburen videokamera. För att få fram ytterligare information om belastning på skuldror, rygg och knän genomfördes även biomekaniska fältexperiment där sophämtare fick utföra typiska arbetssituationer samtidigt som förekommande skjut- och drag-krafter registrerades.Enligt enkätundersökningen ansåg 17 procent av sophämtarna att deras fysiska arbetsförmåga var låg, vilket är samma procentandel som tidigare har registrerats hos flygplanslastare, men något bättre än vad man brukar se bland män med kort utbildningstid.Det var vanligare med kroppsliga besvär bland sophämtare än generellt i befolkningen. Andelen med besvär för olika kroppsdelar som skuldror (60 procent), ländrygg (62 procent), nacke (49 procent), händer/handleder (44 procent), motsvarade situationen för flygplanslastare; det fanns dock en skillnad för knän, där 52 procent av sophämtarna hade besvär mot 44 procent av flyglastarna.Sophämtarnas psykosociala arbetsbelastning liknade i stort den hos flygplanslastare, och motsvarar generellt förhållandena i den arbetande befolkningen. I genomsnitt rapporterar sophämtarna även samma upplevda stöd ifrån ledningen som andra yrkesgrupper, men sophämtare på arbetsställen med särskilt lågt stöd ifrån ledningen rapporterade fler olyckstillfällen, hade högre förekomst av kroppsliga besvär och lägre arbetsförmåga än sophämtare på arbetsställen med högt stöd. Mycket talande var att många fler, 27 procent skattade låg psykisk arbetsförmåga av dem på arbetsställen med generellt lågt upplevt stöd från ledningen jämfört med 8 procent av dem på arbetsställen med högt stöd.Det var vanligare med olycksfallstillbud bland de som angav ett ständigt högt arbetstempo, vilka återfanns både bland de som svarade att de, 64 procent av sophämtarna, som fick och bland de som inte fick gå hem tidigare om de var klara med dagens uppgifter.Fyrtiofyra procent av sophämtarna svarade att de en eller flera gånger hade råkat ut för olycksfall som lett till sjukskrivning. Halkolyckor var klart vanligast. Bland de som rapporterade ett ständigt högt arbetstempo var det vanligare med olyckor.De 41 kvinnor som ingick i enkätstudien rapporterade generellt högre upplevd fysisk och psykosocial belastning, samt sämre hälsa och arbetsförmåga än sina manliga kollegor.Heldagsmätningarna visade att baklastarnas genomsnittliga arbetstid utanför depån var drygt 6½ timma, varav 43 procent utgjordes av bilkörning. Pulsmätningarna visade, liksom enkäterna, att hämtning från flerbostadhus var mera belastande än hämtning i villaområden och på landsbygden. Pulsen var stundtals hög, men i genomsnitt var den för de flesta sophämtare acceptabel enligt internationella rekommendationer.De biomekaniska analyserna visade att krafterna vid dragning av sopkärl ibland var höga, speciellt på snöunderlag, men de föreföll inte att innebära några tydliga risker för ländryggen enligt amerikanska rekommendationer för acceptabla nivåer. Det finns dock forskning som indikerar att upprepad exponering för höga dragkrafter kan innebära risk för skulderbesvär. Att hoppa eller att gå framlänges ned från styrhytt var förknippat med knäbesvär, och kan enligt de biomekaniska analyserna även ge höga ländryggsbelastningar.Mot bakgrund av dessa resultat kan några rekommendationer/frågeställningar i syfte att förbättra arbetsmiljön vara följande:Kan man öka stödet från ledningen? Ledarskaps- och arbetsmiljöutbildning för första linjens chefer? Strategi vid chefsrekrytering?Kan man påverka sophämtarna att inte arbeta i ett ”onödigt” högt tempo, om det egentligen inte är bråttom?Kan man se till att det finns tid (eller om det redan finns tid, att få sophämtarna att använda denna tid) att arbeta i ett rimligt tempo, och kanske hjälpas åt vid hantering av mycket tunga kärl?Kan man få alla att ta sig ner från hytten på "rätt sätt"? Kan man i större utsträckning använda sopbilar med låga insteg?
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| 3. |
- Domkin, Dmitry, et al.
(författare)
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Ciliary muscle contraction force and trapezius muscle activity during manual tracking of a moving visual target
- 2016
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Ingår i: Journal of Electromyography and Kinesiology. - : Elsevier BV. - 1050-6411 .- 1873-5711. ; 28, s. 193-198
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have shown an association of visual demands during near work and increased activity of the trapezius muscle. Those studies were conducted under stationary postural conditions with fixed gaze and artificial visual load. The present study investigated the relationship between ciliary muscle contraction force and trapezius muscle activity across individuals during performance of a natural dynamic motor task under free gaze conditions. Participants (N = 11) tracked a moving visual target with a digital pen on a computer screen. Tracking performance, eye refraction and trapezius muscle activity were continuously measured. Ciliary muscle contraction force was computed from eye accommodative response. There was a significant Pearson correlation between ciliary muscle contraction force and trapezius muscle activity on the tracking side (0.78, p < 0.01) and passive side (0.64, p < 0.05). The study supports the hypothesis that high visual demands, leading to an increased ciliary muscle contraction during continuous eye–hand coordination, may increase trapezius muscle tension and thus contribute to the development of musculoskeletal complaints in the neck–shoulder area. Further experimental studies are required to clarify whether the relationship is valid within each individual or may represent a general personal trait, when individuals with higher eye accommodative response tend to have higher trapezius muscle activity.
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| 4. |
- Domkin, Dmitry, et al.
(författare)
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Effect of ciliary-muscle contraction force on trapezius muscle activity during computer mouse work
- 2019
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Ingår i: European Journal of Applied Physiology. - : SPRINGER. - 1439-6319 .- 1439-6327. ; 119:2, s. 389-397
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Tidskriftsartikel (refereegranskat)abstract
- The present study aimed to identify whether or not an increase in ciliary-muscle contraction force, when the eye-lens is adjusted for viewing at a near distance, results in an increase in trapezius muscle activity, while performing a natural work task. Twelve participants, ranging in age from 21 to 32years, performed a computer-mouse work task during free gaze conditions. A moving visual target was tracked with a computer mouse on a screen placed at two different distances from the eyes, 25cm and 50cm. Tracking performance, eye accommodation, and bilateral trapezius muscle activity were measured continuously. Ciliary-muscle contraction force was computed according to a formula which takes into account the age-dependent, non-linear relationship between the contraction force of the ciliary muscle and the produced level of eye accommodation. Generalized estimating equations analyses were performed. On the dominant hand side and for the nearest screen distance, there was a significant effect of ciliary-muscle contraction force on the trapezius muscle activity (p<0.001). No other effects were significant (p>0.05). The results support the hypothesis that high visual demands, during computer mouse work, increase ciliary muscle contraction force and contribute to a raise of the sustained level of trapezius muscle activity. The current study specifically clarifies the validity of the relationship between ciliary-muscle contraction force and trapezius muscle activity and demonstrates that this relationship is not due to a general personality trait. We conclude that a high level of ciliary muscle contraction force can contribute to a development of musculoskeletal complaints in the neck-shoulder area.
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| 5. |
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| 6. |
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| 7. |
- Elcadi, Guilherme H.
(författare)
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Near infrared spectroscopy for assessing oxygenation and hemodynamics in the upper extremities of healthy subjects and patients with work-related muscle pain
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The prevalence of work-related muscle pain (WRMP) is large in the general population in the industrialized world. Despite significant advances over recent years in some research areas, the mechanisms of why WRMP occurs and the pathophysiological mechanisms behind the disorders are still unclear. One suggested explanation is that WRMP is caused initially by a limitation of the local muscle circulation and oxidative metabolism. There is a lack of objective methods to gauge the development and diagnosis of WRMP. Near infrared spectroscopy (NIRS) is a non-invasive technique that allows for determinations of oxygenation and blood flow. The purpose of this thesis was to evaluate NIRS (1) as a method for measuring muscle oxygenation and hemodynamics for the extensor carpi radialis (ECR) and trapezius descendens muscles (TD), and (2) to investigate whether variables measured by NIRS differed between patients diagnosed with WRMP and healthy subjects. Several variables of NIRS were produced and investigated. These included muscle oxygenation (StO2%), changes during contractions (∆StO2%) and StO2% recovery (Rslope), total hemoglobin (HbT) as an indication of blood volume and its changes during contractions (∆HbT). In addition, for the ECR, by applying an upper arm venous occlusion (VO) HbTslope increase as a surrogate of blood flow, and for both VO and arterial occlusion (AO) HHbslope increase (i.e. deoxyhemoglobin slope) as a surrogate of oxygen consumption were variables of interest. A first objective was to determine how StO2% and HbT responded to various contraction forces and how it related to muscle activation measured by electromyography (EMG). For both muscles isometric contractions of 10, 30, 50 and 70% of maximal voluntary contraction (MVC) were maintained for 20 s each by healthy males and females; additionally a 10% MVC contraction was sustained for 5 min. For the different contraction levels, predictable relationships were seen between ∆StO2% and force, and between ∆StO2% and EMG RMS amplitude. The general trend was a decrease in ∆StO2% with increasing force and increasing EMG. Females showed a tendency for a higher oxygen use (i.e., drop in StO2%) for the ECR over force levels than males and a higher RMS% MVC for the TD. For the 10% MVC contraction sustained for 5 min gender specific changes over time for HbT and RMS for the ECR, and for StO2% for the TD muscle were seen. A second objective was to determine the day-to-day reliability of NIRS variables for the ECR and TD muscles at group level (Pooled data) and at gender level (males and females). Measurements were performed on two occasions separated by 4-6 days and intraclass correlation coefficients (ICC) and limits of agreement (LOA) were determined as reliability and reproducibility indicators, respectively. Variables tested were ∆StO2% during submaximal isometric contractions of 10, 30, 50 and 70% MVC and StO2% recovery (Rslope) after contractions and after AO. For the ECR, HbTslope as an indication of blood flow (using VO) and HHbslope as a surrogate of oxygen consumption for both VO and AO were computed. For ∆StO2% for the ECR the highest ICC was at 30% MVC for both the pooled data and at gender level. For the TD ICCs were comparably high for 30, 50, 70 % MVC (for both muscles the ∆StO2% at 10% MVC showed the lowest ICC). Further, females showed a higher ICC than males for contraction levels of 50 and 70% MVC. For both muscles, LOA for ∆StO2% was lowest at 10% and highest at 50 and 70% MVC. For the ECR Rslope ICCs were high for all contraction levels, but was lower for AO; LOA was lowest at 70% MVC. For the TD, Rslope ICCs were also high for all contraction levels and LOA was lowest at 30 % MVC. ICC for HbTslope was the lowest of all variables tested. For HHbslope ICC was higher for AO than for VO, and LOA was lower for AO. A third objective was to determine if there were differences between healthy subjects and patients diagnosed with WRMP in ∆StO2% and ∆HbT responses during varying submaximal contractions (10, 30, 50 and 70% MVC), and StO2% recovery (Rslope) immediately after contractions and AO. Additional variables tested in the ECR at rest were HHbslope to indicate oxygen consumption (using AO) and HbTslope as an indication of blood flow. There were no differences between groups in ∆StO2% and ∆HbT variables during the contractions or Rslope in the recovery after contractions or AO. Furthermore, HbTslope was not different between groups However, oxygen consumption for the ECR and StO2% for the TD at rest were significantly greater for healthy subjects compared to patients. A fourth objective was to determine if there were differences in StO2% and HbT between healthy subjects and WRMP patients during a 12 min sustained contraction of 15 % MVC. In addition, the protocol included a recovery period of 30 min. Prior to contraction, as well as during the recovery period, HbTslope as a surrogate of blood flow was determined for the ECR. Neither the ECR nor the TD exhibited significant differences between groups for StO2% and HbT during the contraction. For the TD patients showed a lower StO2% value at rest and throughout the contraction than healthy subjects. For the ECR HbT during the sustained contraction the general trend was an initial decrease with gradual increase throughout the contraction for both groups. For HbTslope no differences were seen between patients and healthy subjects before the sustained contraction and during the recovery period for both muscles.NIRS is deemed a suitable technique for assessing physiological measurements of the upper extremity, including for day-to-day testing.NIRS was not able to distinguish between the patients with WRMP and controls. A concern in the thesis is the characteristics of the patient group in being equally active in recreational sports, actively working, and similar in muscle strength as controls. Thus, applying NIRS for studying a more severe patient group could yield different results.
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| 8. |
- Elcadi, Guilherme H., 1966-, et al.
(författare)
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Oxygenation and Hemodynamics Do Not Underlie Early Muscle Fatigue for Patients with Work-Related Muscle Pain
- 2014
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Ingår i: PLOS ONE. - : PLOS (Public library of science). - 1932-6203. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- 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 (StO(2)%) 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 StO(2)% 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.
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| 9. |
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| 10. |
- Elcadi, Guilherme H., 1966-, et al.
(författare)
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Shoulder and forearm oxygenation and myoelectric activity in patients with work related muscle pain and healthy subjects
- 2013
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Ingår i: European Journal of Applied Physiology. - New York : Springer. - 1439-6319 .- 1439-6327. ; 113:5, s. 1103-1115
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Tidskriftsartikel (refereegranskat)abstract
- We tested hypotheses of (i) reduced oxygen usage, oxygen recovery, blood flow and oxygen consumption; and (ii) increased muscle activity for patients diagnosed with work related muscle pain in comparison to healthy controls. Oxygenation was measured with near infrared spectroscopy (NIRS), and muscle activity with EMG for the extensor carpi radialis (ECR) and trapezius descendens (TD) muscles. Eighteen patients with diffuse neck-shoulder-arm pain and seventeen controls (matched in age and sex) were equipped with NIRS and EMG probes. After determining an individual’s maximum voluntary contraction (MVC) force, short term (20 sec) isometric contractions for the ECR and TD of 10%, 30%, 50% and 70% MVC generated ∆StO2% and StO2% recovery (Rslope) from NIRS, and RMS%max from EMG signals. In addition, upper arm venous (VO) and arterial (AO) occlusions generated slopes of total hemoglobin (HbTslope) and deoxyhemoglobin (HHbslope) for the resting ECR as surrogates of blood flow and oxygen consumption, respectively. Mixed Model analyses, t-tests, and Mann-Whitney test were used to assess differences between groups. There was no significant difference in MVC between groups for either muscle. Also, ∆StO2%, Rslope for either muscle, and ECR-HbTslope were not different between groups, thus our hypotheses of reduced oxygen use, recovery, and blood flow for patients were not confirmed. However, patients had a significantly lower ECR-HHbslope confirming our hypothesis of reduced consumption. Further, there was no difference in RMS%max during contractions meaning that the hypothesis of increased activity for patients was not confirmed. When taking into account the number of NIRS variables studied, differences we found between our patient group and healthy controls (i.e. in forearm oxygen consumption and shoulder oxygen saturation level) may be considered modest. Overall our findings may have been impacted by the fact that our patients and controls were similar in muscle strength, which is in contrast to previous studies.
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