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 (StO₂%) 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 StO₂% 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.

Prolonged computer use, especially if fatigue ensues, is associated with visual and musculoskeletal symptoms. The aim was to determine the time-course of perceived fatigue in the wrist, forearm, shoulder and eyes during a 60-min mouse task (painting rectangles), and whether object size and/or mouse use demands were of influence. Also, we investigated performance (number of rectangles painted), and whether perceived fatigue was paralleled by local muscle fatigue or tissue oxygenation. Ten women performed the task for three conditions (crossover design). At condition 1, rectangles were 45 × 25 mm, square paint cursor size 1.3 × 1.3 mm, and mousepointer movement ratio 1:26. At condition 2, the same cursor size and mousepointer movement ratio was used, but rectangles were smaller. At condition 3, the smaller rectangles were used, but the cursor size was also smaller and mousepointer movement ratio was 1:8. The results showed increased self-reported fatigue over time, with the observed increase greater for the eyes, but no change in physiological responses. Condition 2 resulted in higher performance and increased eye fatigue. Perceived fatigue in the muscles or physiological responses did not differ between conditions. In conclusion, computer work tasks imposing high visual and motor demands, and with high performance, seemed to have an influence on eye fatigue. 

The aim of the study was to evaluate the effects of individually prescribed physical exercise programmes on development of fatigue during the carrying of a loaded stretcher up and down the stairs. Nineteen ambulance personnel performed the training for 1 year. Testing occurred before and after 1 year of the training. Both the training group (n = 19) and the control group (n = 15) were assessed for physical capacity and lactate concentration in blood and ratings of perceived exertion during carrying a stretcher on the stairs. When comparisons were made between those who had been training three times/week for 1 year and the control group, lactate concentration was significantly decreased. In conclusion, markers of fatigue during stretcher carrying can be reduced by the use of individually prescribed physical exercise programmes.

Objectives: The aim of the present study was to assess physiological and subjective stress markers during a 24-h ambulance work shift and during the next two work-free days, and relate these parameters to self-reported health complaints. Methods: Twenty-six ambulance personnel were followed during a 24-h work shift and during the next two work-free days with electrocardiogram, cortisol assessments and diary notes. The ambulance personnel also performed tests of autonomic reactivity before and at the end of the work shift. The subjects were categorized into two groups according to their number of health complaints. Results: In general, stress markers did not show differences between the work shift and leisure time. However, a modest deviation in heart rate variability pattern and higher morning cortisol values during work in comparison with work-free days were observed in personnel with many health complaints. Conclusions: Subjective and physiological characteristics of ambulance personnel did not indicate distinctive stress during the 24-h work shift. Relationships between frequent health complaints and specific work-related factors require further prospective studies.

Although musculoskeletal disorders (MSDs) and other health cornplaints are an occupational problem for ambulance personnel, there is a lack ofknowJedge regarding work-related factors associated with MSDs and other health cornplaints. The overall aim ofthis thesis was to investigate the relationships between occupational demands, individual characteristics and health-related outcornes among ambulance personnel.

A random sarnple of 234 female and 953 male ambulance personnel participated in a national questionnaire suTVey on work-related factors, and musculoskeletal and other health cornplaints. Physical demands was associated with activity limitation due to neck-shoulder and low-back complaints among the female personnel. Among the male personnel, physical demands was associated with low-back cornplaints and activity limitation due to low-back cornplaints. Psychological demands was significantly associated with neck-shoulder complaints, sleeping problerns, headache and stomach syrnptorns among both female and male ambulance personnel. Worry about work conditions was associated with musculoskeletal disorders and sleeping problerns, headache and stomach symptoms.

A local sample of 26 ambulance personnel was followed during a 24-hour work shift and for the next two work-free days. Subjective stress- and energy levels, and cortisol levels were measured at regular inteTYals, and heart rate was registered continuously by electrocardiogram (ECG). Autonomic reactivity to standardized tests before (pre-work) and at the end of the work shift (post-work) was also investigated. For the whole group, baseline values of heart rate were higher pre-work than post-work, but autonomic reactivity did not differ. lncreased reactivity to the mental test, modest deviation in heart rate variability (HRV) pattem during the Jate night hours at work and higher moming cortisol values during work than during leisure time were obseTVed in personnel with many health cornplaints, but not among their co-workers without or with few complaints. Ambulance personnel with many health complaints also reported higher psychological demands and tended to be more worried about work conditions.

Heart rate (HR), lactate level (LL) and perceived exertion (RPE) were investigated in 17 female and 48 male ambulance personnel during a simulated standardized work task "carry a loaded stretcher". The ambulance personnel had to carry the loaded stretcher (920 N) up and down three tlights of stairs twice. The high physiological strain (HR, LL, RPE) for the male, and near or at maximal strain for the female ambulance personnel, implied the importance to identify what kind of physical capacity is most important for ambulance personnel. Therefore, the explained variance of developed fatigue by tests of cardiorespiratory capacity, muscular strength and endurance, and coordination was investigated. The results showed that VO2max and isometric back endurance were important predictors for development of fatigue when carrying a loaded stretcher .

The influence of body size on the relationships between maximal strength and functional performance was investigated in a methodological study. The results confirm that the assessment ofphysical performance could be confounded by the body weight. Therefore, the models for explaining development of fatigue when carrying the loaded stretcher were adjusted for height and weight. lncluding height in the models significantly increased the exp1ained variance of accumulated lactate among female, but not among male personnel. Lactate levels were higher among short cornpared to tall female personnel. Weight had no effect on any of the models.

In conclusion, the national suTVey showed that self-reported physical demands was a risk factor of having MSDs, and that self-reported psychological demands and worry about work were important risk factors of having MSDs and other health complaints. Stress monitoring of ambulance personnel during work and leisure time showed that physiological and subjective stress markers did not show any differences between the 24-hour ambulance work shift and leisure time afterwards. However, ambulance personnel with many health cornplaints had certain physiological changes during the work shift in cornparison with the next two work-free days. The physiological and subjective responses during carrying a loaded stretcher, especially among the female ambulance personnel, showed that female and male ambulance personnel could be exposed to intemal exposures at different levels when performing the same work task. A better understanding of the relationships between occupational demands and health-related ou tcomes require further studies on age- and gender matched groups in long-term perspective studies.

This cross-sectional study on a random sample of 1,500 ambulance personnel investigated the relationships between self-reported work-related physical and psychosocial factors, worry about work conditions, and musculoskeletal disorders among female and male ambulance personnel. Three different outcomes, complaints, activity limitation, and sick leave, for the neck-shoulder and low-back region, respectively, were chosen. Among the female personnel, physical demands was significantly associated with activity limitation in the neck-shoulder (OR 4.13) and low-back region (OR 2.17), and psychological demands with neck-shoulder (OR 2.37) and low-back (OR 2.28) complaints. Among the male personnel, physical demands was significantly associated with low-back complaints (OR 1.41) and activity limitation (OR 1.62). Psychological demands and lack of social support were significantly associated with neck-shoulder complaints (OR 1.86 and OR 1.58, respectively) and activity limitation (OR 3.46 and OR 1.71) as well as activity limitation due to low-back complaints (OR 2.22 and OR 1.63). Worry about work conditions was independently associated with activity limitation due to low-back complaints among the female (OR 5.28), and to both neck-shoulder and low-back complaints (OR 1.79 and OR 2.04, respectively) and activity limitation (OR 2.32 and OR 1.95) among the male personnel. In conclusion, the association patterns between physical and psychological demands and MSDs suggest opportunities for intervention.

This study aimed at investigating the relationships between work-related psychosocial factors, worry about work conditions and health complaints (sleeping problems, headache and stomach symptoms) among female and male ambulance personnel. Out of 4000 ambulance personnel in Sweden, 1500 (300 female and 1200 male personnel) were randomly selected. They answered a questionnaire including items on self-reported health complaints, individual characteristics, work-related psychological demands, decision latitude, social support and worry about work conditions. Twenty-five per cent of the female and 20% of the male ambulance personnel reported two or more health complaints sometimes or often. According to the demand-control-support questionnaire, ambulance personnel reported a generally positive psychosocial work environment, although psychological demands were associated with sleeping problems, headache and stomach symptoms among both female and male ambulance personnel. Another factor that was significantly associated with health complaints among both genders was worry about work conditions. When worry about work conditions was added to the regression models, this variable took over the role from psychological demands as a predictor for health complaints among the female ambulance personnel. The prevalence of sleeping problems, headache and stomach symptoms were significantly associated with psychological demands among both female and male ambulance personnel. Notably, worry about work conditions seems to be an important risk factor for health complaints. This suggests that worry about work conditions should not be neglected when considering risk factors among ambulance personnel.

The role of body size has often been neglected in routine tests of muscle strength and movement performance. The aim of the present study was to test the hypothesis that different types of functional movement performance require different normalisations in order to assess muscle strength. Twenty-one right-handed male university students were tested on the following functional movement tasks: vertical jump, standing soccer ball kick, seated medicine ball throw and standing maximal isometric lift. Isokinetic strength of active muscle \, groups was also recorded. The performance of the vertical jump and standing s9ccer ball kick demonstrated stronger relationship with the strength of active muscles normalised for body size, while the performance of the s~ated medicine ball throw and standing maximal

Iisometric lift demonstrated stronger relationship with the non- normalised strength.

It was concluded that the ability of performing functional movements based on overcoming gravitational and/or inertial resistance of subject's own body (such as keeping certain body postures, or various body movements) should be assessed by the tested muscle strength normalised for body size, while the functional performance based on muscle action performed against external objects (e.g. manual material handling, or lifting heavy objects) should be assessed by the non-normalised muscle strength. The obtained f"mdings proved to be in line with our recently proposed classification of muscle strength and functional movement tests based on the role of body size in the re~orded performance.