| 1. |
- Jahangir, Sana, et al.
(författare)
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Sensitivity of simulated knee joint mechanics to selected human and bovine fibril-reinforced poroelastic material properties
- 2023
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Ingår i: Journal of Biomechanics. - 0021-9290. ; 160
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Tidskriftsartikel (refereegranskat)abstract
- Fibril-reinforced poroviscoelastic material models are considered state-of-the-art in modeling articular cartilage biomechanics. Yet, cartilage material parameters are often based on bovine tissue properties in computational knee joint models, although bovine properties are distinctly different from those of humans. Thus, we aimed to investigate how cartilage mechanical responses are affected in the knee joint model during walking when fibril-reinforced poroviscoelastic properties of cartilage are based on human data instead of bovine. We constructed a finite element knee joint model in which tibial and femoral cartilages were modeled as fibril-reinforced poroviscoelastic material using either human or bovine data. Joint loading was based on subject-specific gait data. The resulting mechanical responses of knee cartilage were compared between the knee joint models with human or bovine fibril-reinforced poroviscoelastic cartilage properties. Furthermore, we conducted a sensitivity analysis to determine which fibril-reinforced poroviscoelastic material parameters have the greatest impact on cartilage mechanical responses in the knee joint during walking. In general, bovine cartilage properties yielded greater maximum principal stresses and fluid pressures (both up to 30%) when compared to the human cartilage properties during the loading response in both femoral and tibial cartilage sites. Cartilage mechanical responses were very sensitive to the collagen fibril-related material parameter variations during walking while they were unresponsive to proteoglycan matrix or fluid flow-related material parameter variations. Taken together, human cartilage material properties should be accounted for when the goal is to compare absolute mechanical responses of knee joint cartilage as bovine material parameters lead to substantially different cartilage mechanical responses.
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| 2. |
- Meyland, Jacob, et al.
(författare)
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Sex differences in muscular load among house painters performing identical work tasks
- 2014
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 114:9, s. 1901-1911
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Tidskriftsartikel (refereegranskat)abstract
- The present study aimed to estimate possible differences in upper body muscular load between male and female house painters performing identical work tasks. Sex-related differences in muscular load may help explain why women, in general, have more musculoskeletal complaints than men. In a laboratory setting, 16 male and 16 female house painters performed nine standardised work tasks common to house painters. Unilateral electromyography (EMG) recordings were obtained from the supraspinatus muscle by intramuscular electrodes and from the trapezius, extensor and flexor carpi radialis muscles by surface electrodes. Relative muscular loads in %EMG(max) as well as exerted force in Newton, based on ramp calibrations, were assessed. Sex differences were tested using a mixed model approach. Women worked at about 50 % higher relative muscular loads than men in the supraspinatus and forearm muscles at all percentiles and in all tasks. Women exerted about 30 % less force in the trapezius muscle at the 50th percentile. Female house painters had a higher relative muscular load than their male colleagues without exerting more force. The effects of a higher relative muscular load accumulated over years of work may in part explain why musculoskeletal complaints in the upper body occur more frequently among women than men.
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| 3. |
- Péter, Annamária, et al.
(författare)
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Effect of footwear on intramuscular EMG activity of plantar flexor muscles in walking.
- 2020
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Ingår i: Journal of Electromyography & Kinesiology. - : Elsevier. - 1050-6411 .- 1873-5711. ; 55
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Tidskriftsartikel (refereegranskat)abstract
- One of the purposes of footwear is to assist locomotion, but some footwear types seem to restrict natural foot motion, which may affect the contribution of ankle plantar flexor muscles to propulsion. This study examined the effects of different footwear conditions on the activity of ankle plantar flexors during walking. Ten healthy habitually shod individuals walked overground in shoes, barefoot and in flip-flops while fine-wire electromyography (EMG) activity was recorded from flexor hallucis longus (FHL), soleus (SOL), and medial and lateral gastrocnemius (MG and LG) muscles. EMG signals were peak-normalised and analysed in the stance phase using Statistical Parametric Mapping (SPM). We found highly individual EMG patterns. Although walking with shoes required higher muscle activity for propulsion than walking barefoot or with flip-flops in most participants, this did not result in statistically significant differences in EMG amplitude between footwear conditions in any muscle (p > 0.05). Time to peak activity showed the lowest coefficient of variation in shod walking (3.5, 7.0, 8.0 and 3.4 for FHL, SOL, MG and LG, respectively). Future studies should clarify the sources and consequences of individual EMG responses to different footwear.
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| 4. |
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| 5. |
- Pingel, Jessica, et al.
(författare)
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Injection of high dose botulinum-toxin A leads to impaired skeletal muscle function and damage of the fibrilar and non-fibrilar structures
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Botulinum-toxin A (BoNT/A) is used for a wide range of conditions. Intramuscular administration of BoNT/A inhibits the release of acetylcholine at the neuromuscular junction from presynaptic motor neurons causing muscle-paralysis. The aim of the present study was to investigate the effect of high dose intramuscular BoNT/A injections (6 UI = 60 pg) on muscle tissue. The gait pattern of the rats was significantly affected 3 weeks after BoNT/A injection. The ankle joint rotated externally, the rats became flat footed, and the stride length decreased after BoNT/A injection. Additionally, there was clear evidence of microstructural changes on the tissue level by as evidenced by 3D imaging of the muscles by Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM). Both the fibrillar and the non-fibrillar tissues were affected. The volume fraction of fibrillary tissue was reduced significantly and the non-fibrillar tissue increased. This was accompanied by a loss of the linear structure of the muscle tissue. Furthermore, gene expression analysis showed a significant upregulation of COL1A1, MMP-2, TGF-b1, IL-6, MHCIIA and MHCIIx in the BoNT/A injected leg, while MHVIIB was significantly downregulated. In conclusion: The present study reveals that high dose intramuscular BoNT/A injections cause microstructural damage of the muscle tissue, which contributes to impaired gait.
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