| 1. |
- Barnekow-Bergkvist, Margareta, et al.
(författare)
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Prediction of development of fatigue during a simulated ambulance work task from physical performance tests.
- 2004
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Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 47:11, s. 1238-1250
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Tidskriftsartikel (refereegranskat)abstract
- The aims of this study were (1) to identify which physical performance tests could best explain the development of fatigue during a simulated ambulance work task, (2) to investigate the effect of height and weight and (3) to investigate in what respects these findings differ between female and male ambulance personnel. Forty-eight male and 17 female ambulance personnel completed a test battery assessing cardio-respiratory capacity, muscular strength and endurance, and co-ordination. The subjects also completed a simulated ambulance work task -- carrying a loaded stretcher. The work task was evaluated by development of fatigue. Univariate and multiple regression analyses were used to investigate to what extent the tests in the test battery were able to explain the variance of developed fatigue. The explained variance was higher for female than for male ambulance personnel (time > 70% of HRpeak: R2 = 0.75 vs 0.10, accumulated lactate: R2 = 0.62 vs 0.42, perceived exertion: R2 = 0.75 vs 0.10). Significant predictors in the models were VO2max, isometric back endurance, one-leg rising, isokinetic knee flexion and shoulder extension strength. Height, but not weight, could further explain the variance. The high physical strain during carrying the loaded stretcher implies the importance of investigating whether improved performance, matching the occupational demands, could decrease the development of fatigue during strenuous tasks.
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| 2. |
- Björklund, Martin, 1961-
(författare)
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Effects of repetitive work on proprioception and of stretching on sensory mechanisms : implications for work-related neuromuscular disorders
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aims of the thesis were (i) to investigate the impact of repetitive low-intensity work exposure on proprioception and (ii) to examine effects of muscle stretching (especially sensory effects and effects on muscle nociception) and to relate its application to the prevention, alleviation and/or treatment of work-related neuromuscular disorders. The effects of low-intensity repetitive work on the shoulder proprioception were tested in healthy subjects. The effect of working time on the retention of subjective fatigue and their relation to changes in proprioception, and the immediate effect of stretching on shoulder proprioception were investigated. A new method to test the stretchability of the rectus femoris muscle was investigated for reliability and validity and used to assess the effects of a two-week stretching regimen on range of motion and on subjective stretch sensation. Finally, the interactions between innocuous muscle stretch and nociceptive chemical stimulation on discharge behavior of nociceptive dorsal horn neurons in the feline spinal cord were explored. The main findings were as follows: 1) The repetitive low-intensity work to fatigue diminished the shoulder proprioception; the working time as well as the retention of subjective fatigue were partly related to the extent of changed proprioception. 2) There was no effect of acute muscle stretching on the proprioception. 3) The new method for testing muscle stretchability proved valid and reliable. A two-week stretching regimen increased the tolerance to stretch torque, but the range of motion remained unchanged. 4) Half of the nociceptive dorsal horn neurons that responded to close arterial injections of bradykinin were modulated by muscle stretching applied directly after the injections. Altogether, the results give credence to the hypothesis of an involvement of sensory information distortion due to repetitive low-intensity work exposure in the development of work-related neuromuscular disorders. Increased tolerance to stretch torque may be an important mechanism in explaining improvements following stretch treatment. The spinal interactions between innocuous stretch and nociceptive muscle afferent inputs indicate a possible mechanism involved in stretching-induced pain alleviation.
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| 3. |
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| 4. |
- Björklund, Martin, et al.
(författare)
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Muscle stretch-induced modulation of noxiously activated dorsal horn neurons of feline spinal cord.
- 2004
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Ingår i: Neuroscience research. - : Elsevier BV. - 0168-0102 .- 1872-8111. ; 48:2, s. 175-184
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Tidskriftsartikel (refereegranskat)abstract
- The present work was designed to check for the possibility of interactions between mechanical innocuous and chemically induced noxious muscle afferent inputs on discharge behavior of nociceptive superficial dorsal horn neurons (SDHNs) of the spinal cord in decerebrated cats. The innocuous and noxious stimuli were applied separately and in combination, so that the effects of the innocuous stimulus on nociceptive processing could be evaluated. The innocuous stimulus consisted of ramp-and-hold stretches of the gastrocnemius muscles, whereas the noxious stimulus consisted of i.a. injections of bradykinin (BK; 0.5-1 ml, 50 microg/ml) into the arterial circulation of same muscles. Only neurons up to approximately 1mm depth and those that responded to noxious pinch of the gastrocnemius muscles were selected for further analysis. The activity of 16 dorsal horn neurons was recorded extracellularly with high-impedance glass microelectrodes, out of which seven responded to stretch, while 12 neurons responded to bradykinin injections. The bradykinin injections induced three types of responses: excitatory, inhibitory and mixed. The majority of the neurons that showed excitatory and mixed responses to bradykinin were also influenced by stretches applied directly after the bradykinin injection. In these neurons, the stretch usually counteracted the bradykinin-induced response, i.e. shortening and reducing bradykinin-induced excitation and re-exciting the cells after bradykinin-induced inhibition. The mechanism of the stretch modulation is proposed to reside in a segmental spinal control of the nociceptive transmission.
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| 5. |
- Björklund, Martin, et al.
(författare)
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Sensory adaptation after a 2-week stretching regimen of the rectus femoris muscle
- 2001
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Ingår i: Archives of Physical Medicine and Rehabilitation. - : Elsevier BV. - 0003-9993 .- 1532-821X. ; 82:9, s. 1245-1250
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To study the effects of a muscle stretching regimen for the rectus femoris muscle on subjective stretch sensation and range of motion (ROM). DESIGN: A 2 x 2 crossover design comprising 2 treatments and 2 intervention periods. SETTING: A military base in Sweden. PARTICIPANTS: A volunteer sample of 29 male military conscripts divided into 2 groups, with each group subjected to both experimental and control treatments at different time periods. INTERVENTION: Two weeks of supervised stretching (4 times/wk) of the rectus femoris muscle (experimental treatment) and the calf muscles (control treatment). MAIN OUTCOME MEASURES: Subjective rating of the stretch sensation for the anterior aspect of the thigh determined on a category ratio scale. Passive knee flexion ROM determined on each test with the same applied torque, specific for each subject. RESULTS: An additive analysis of variance revealed that the stretch sensation after the experimental treatment was decreased, compared with the control treatment (p <.01). The knee flexion, however, remained the same regardless of the treatment. CONCLUSION: Sensory adaptation seems to be an important mechanistic factor in the effect stretching has on ROM changes. The lack of change in knee flexion suggests that the stretching, as performed in this study, did not influence stiffness of the rectus femoris muscle. Sensory adaptation may also be an underlying mechanism in the alleviating effect of stretching when applied to tired, tender, and painful muscles.
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| 6. |
- Daerga, Laila, et al.
(författare)
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Work-related musculoskeletal pain among reindeer herding Sami in Sweden : a pilot study on causes and prevention
- 2004
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Ingår i: International Journal of Circumpolar Health. - 1239-9736 .- 2242-3982. ; 63 Suppl 2, s. 343-348
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To investigate the prevalence and to identify causes of musculoskeletal pain (MSP) among reindeer herding Sami, and to evaluate the impact on the MSP symptoms elicited by an intervention-pre- vention programme (lP programme). Study Design. A prospective cohort study in which alterations in MSP symptoms were documented over a two-year period. Methods. Data were collected from 51 rein- deer herders (26 men, 25 w omen) before and af ter a two-year lP programme. Information on MSP cha- racteristics (affected body regions, pain duration and pain intensity) and exposure to a number of phy- sical and psychosocial risk factors were collected as part of comprehensive health examinations. Cli- nical examinations and interviews complemented self-reported data collected through questionnaires. Results. MSP symptoms were prevalent, both among w omen and men. High exposure to physical risk factors, to a large extent related to extensive use of snowmobiles and motorcycles, was the main cau- se of MSP among men, while psychosocial risk factors were suggested to be more important among wo- men. About one-third of the reindeer herders reported fewer MSP symptoms as a resull of the lP programme. Conclusions. This pilot study suggests that it is possible to reduce the number and the se- verity of the MSP symptoms among reindeer herders by implementing suitably tailored intervention- prevention measures.
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| 7. |
- Domkin, Dmitry, et al.
(författare)
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Structure of joint variability in bimanual pointing tasks
- 2002
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 143, s. 11-23
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Tidskriftsartikel (refereegranskat)abstract
- Changes in the structure of motor variability during practicing a bimanual pointing task were investigated using the framework of the uncontrolled manifold (UCM) hypothesis. The subjects performed fast and accurate planar movements with both arms, one moving the pointer and the other moving the target. The UCM hypothesis predicts that joint kinematic variability will be structured to selectively stabilize important task variables. This prediction was tested with respect to selective stabilization of the trajectory of the endpoint of each arm (unimanual control hypotheses) and with respect to selective stabilization of the timecourse of the vectorial distance between the target and the pointer tip (bimanual control hypothesis). Components of joint position variance not affecting and affecting a mean value of a selected variable were computed at each 10% of normalized movement time. The ratio of these two components ( R(V)) served as a quantitative index of selective stabilization. Both unimanual control hypotheses and the bimanual control hypothesis were supported both prior to and after practice. However, the R(V) values for the bimanual control hypothesis were significantly higher than for either of the unimanual control hypothesis, suggesting that the bimanual synergy was not simply a simultaneous execution of two unimanual synergies. After practice, an improvement in both movement speed and accuracy was accompanied by counterintuitive changes in the structure of kinematic variability. Components of joint position variance affecting and not affecting a mean value of a selected variable decreased, but there was a significantly larger drop in the latter when applied on each of the three selected task variables corresponding to the three control hypotheses. We conclude that the UCM hypothesis allows quantitative assessment of the degree of stabilization of selected performance variables and provides information on changes in the structure of a multijoint synergy that may not be reflected in its overall performance.
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| 8. |
- Edin-Liljegren, A, et al.
(författare)
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Risk factors for cardiovascular diseases among Swedish Sami : a controlled cohort study
- 2004
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Ingår i: International Journal of Circumpolar Health. - 1239-9736 .- 2242-3982. ; 63:Suppl 2, s. 292-297
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To investigate the occurrence of clinical, psychosocial and behavioural risk factors for cardiovascular diseases (CVD) among reindeer herding (RS) and non-reindeer herding Sami (NRS). STUDY DESIGN: A retrospective cohort study, comparing risk factors behind CVD between Sami and non-Sami, RS and NRS, and Sami men and women. METHODS: A cohort of 611 Swedish Sami (276 men and 335 women) was constructed from national population registers. A twice as large control cohort of non-Sami was created, matched by age, gender and area of residence. Information on risk factors was obtained from a database containing clinical and psychosocial-behavioural data from a regional CVD preventive programme for the period 1990-2001. RESULTS: The Sami and the non-Sami showed similar risk factor patterns. The main differences were related to working conditions and lifestyle factors of the RS. The RS men had lower blood pressure, were more physically active and had higher job demand and decision latitude. The RS women showed more negative scores on the indices of the job strain model. CONCLUSIONS: Previously reported differences in CVD mortality between Sami and non-Sami, and Sami men and women, can only partly be explained by different exposure to the psychosocial and behaviour risk factors investigated in this study.
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| 9. |
- Eriksson, Per-Olof, et al.
(författare)
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Deranged jaw-neck motor control in whiplash-associated disorders
- 2004
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Ingår i: European Journal of Oral Sciences. - : Wiley. - 0909-8836 .- 1600-0722. ; 112:1, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- Recent findings of simultaneous and well coordinated head-neck movements during single as well as rhythmic jaw opening-closing tasks has led to the conclusion that 'functional jaw movements' are the result of activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital and cervical spine joints. It can therefore be assumed that disease or injury to any of these joint systems would disturb natural jaw function. To test this hypothesis, amplitudes, temporal coordination, and spatiotemporal consistency of concomitant mandibular and head-neck movements during single maximal jaw opening-closing tasks were analysed in 25 individuals suffering from whiplash-associated disorders (WAD) using optoelectronic movement recording technique. In addition, the relative durations for which the head position was equal to, leading ahead of, or lagging behind the mandibular position during the entire jaw opening-closing cycle were determined. Compared with healthy individuals, the WAD group showed smaller amplitudes, and changed temporal coordination between mandibular and head-neck movements. No divergence from healthy individuals was found for the spatiotemporal consistency or for the analysis during the entire jaw opening-closing cycle. These findings in the WAD group of a 'faulty', but yet consistent, jaw-neck behavior may reflect a basic importance of linked control of the jaw and neck sensory-motor systems. In conclusion, the present results suggest that neck injury is associated with deranged control of mandibular and head-neck movements during jaw opening-closing tasks, and therefore might compromise natural jaw function.
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| 10. |
- Hassler, Sven, et al.
(författare)
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Fatal accidents and suicide among reindeer-herding Sami in Sweden
- 2004
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Ingår i: International Journal of Circumpolar Health. - 1239-9736 .- 2242-3982. ; 63 Suppl 2, s. 384-388
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Over the last decades, reindeer-herding management has experienced drarnatic changes, e.g. increased motorization and socio-econornic pressure. The airn of the present study was to investigate whether these changes have increased the risk of fatal, work-related accidents and suicide between 1961 and 2000. Study design and methods. A c oh ort containing 7,482 members of reindeer-herding Sami families was extracted from national population registers. Information on fatal accidents and suicide was obtained from the Swedish Causes of Death Register, and compared to the expected number of deaths in a dernographica11y matched control population of non-Sami. Results. The ffiale reindeer her- ding Sami showed a significantly increased risk of dying from accidents such as vehicle accidents and poisoning. No significant increased risk of suicide was observed. A comparison between the periods of 1961-1980 and 1981- 2000 showed non-significant differences in risk, although a trend towards incre- ased risks was observed for most types of external causes of death except suicide. Conclusions. It is suggested that the increased socio-econornic pressure and the extensive use of terrain vehicles have increased the risk for fatal accidents arnong Swedish reindeer herders, and that commercial reindeer ma- nagement is one of the most dangerous occupations in Sweden
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