Examining the factorial structure, measurement invariance and convergent and discriminant validity of a novel self-report measure of work ability: work ability--personal radar.

For identification of groups and domains for work ability promotion, brief self-report measure, work ability - personal radar (WA-PR), based on the 'the house of work ability' model is presented and psychometrically evaluated in the structural equation framework using data from technological sector (N = 3754). The house model had acceptable fit to the data. In addition, factor loadings in the model were invariant across groups, demonstrating metric invariance of the WA-PR. Scalar invariance of WA-PR was fully demonstrated across men and women, and partially demonstrated across age and employee groups. Comparisons between groups revealed lower levels of health and functional capacity, but higher levels of four other WA-PR dimensions in older employees. In addition, all house structures showed convergence with alternative work ability measures. WA-PR demonstrated potential for effective measurement of multiple work ability dimensions from employees' perspective. It provides means for efficient location of relevant domains and focus groups for work ability promotion. PRACTITIONER SUMMARY: A novel approach to multidimensional work ability measurement was developed to tackle the challenges of work ability promotion. The properties of the instrument were psychometrically evaluated in structural equation modelling framework. Instrument demonstrated potential for locating relevant domains and focus groups for work ability promotions at workplaces and organisations.

A quasi-experimental study of the effects of the Erggi action model of musculoskeletal symptoms and VDU working conditions among university staff.

PURPOSE: The aim of this study was to investigate musculoskeletal symptoms and working conditions of university workers with and without contact with an Erggi action model. METHODS: A quasi-experimental and longitudinal field study design examined effects of the Erggi action model with 3 types of questionnaires filled by 1000 university workers. The statistical analyses used logistic regression. RESULTS: Subjects who had contact with the Erggi action model had a higher probability of weekly musculoskeletal symptoms impairing their work, perceived more possibilities to influence their musculoskeletal symptoms and had lower risk for sick leave compared to those without contact with the Erggi action model. CONCLUSIONS: The Erggi action model increases the probability of influencing workers' musculoskeletal symptoms, decreases the number of sick leave and increases awareness of musculoskeletal symptoms and working conditions.

A new heart rate variability-based method for the estimation of oxygen consumption without individual laboratory calibration: application example on postal workers.

Traditionally, the estimation of oxygen consumption (VO2) at work using heart rate (HR) has required the determination of individual HR/VO2 calibration curves in a separate exercise test in a laboratory (VO2-TRAD). Recently, a new neural network-, and heart rate variability-based method has been developed (Firstbeat PRO heartbeat analysis software) for the estimation of VO2 without individual calibration (VO2-HRV). In the present study, the VO2-values by the VO2-HRV were compared with the values by VO2-TRAD in 22 postal workers. Within individuals the correlation between the two methods was high (range 0.80-0.99). The VO2-TRAD gave higher values of VO2 compared to VO2-HRV (19%) especially during low physical activity work when non-metabolic factors may increase HR. When assessed in different HR categories, the smallest difference (11%), and highest correlations (range 0.83-0.99) in VO2 between the methods were observed at higher HR levels. The results indicate that the VO2-HRV is a potentially useful method to estimate VO2 in the field without laboratory calibration.

Associations between work ability, health-related quality of life, physical activity and fitness among middle-aged men.

The Work ability of ageing work force is a matter of major concern in many countries. The aim of this study was to examine the relationship between perceived work ability and health-related quality of life (HRQoL), and to investigate their associations with age, physical activity and physical fitness in middle-aged men working in blue-collar occupations. The study population consisted of 196 middle-aged (aged 40-60 years) men (construction and industrial work) attending occupationally orientated early medical rehabilitation. They were mostly healthy having only symptoms of musculoskeletal or psychological strain. Perceived work ability was assessed with the work ability index (WAI) and HRQoL with the Rand, 36-item health survey (Rand-36). Information on physical activity was obtained with a structured questionnaire. Cardiorespiratory fitness was estimated with a submaximal exercise test on a cycle-ergometer. The WAI was significantly (p<0.001) associated with the total score of Rand-36, and with all its domains. Age, physical activity and cardiorespiratory fitness were neither associated with the WAI, nor did physical activity predict any of the dimensions of Rand-36. Cardiorespiratory fitness was associated with the physical functioning dimension of the Rand-36 whilst age was positively associated with the dimensions of the energy, emotional well being and social functioning of the Rand-36. The present study on middle-aged men showed a close relationship between perceived work ability and the HRQoL. It is suggested that the promotion of work ability may have beneficial effects on quality of life.

Effect of aerobic fitness on the physiological stress responses at work.

OBJECTIVES: The aim of the present study was to examine the effects of aerobic fitness on physiological stress responses experienced by teachers during working hours. MATERIALS AND METHODS: Twenty-six healthy female and male teachers aged 33-62 years participated in the study. The ratings of perceived stress visual analogue scale (VAS), and the measurement of physiological responses (norepinephrine, epinephrine, cortisol, diastolic and systolic blood pressure, heart rate (HR), and trapezius muscle activity by electromyography (EMG), were determined. Predicted maximal oxygen uptake (VO(2)max) was measured using the submaximal bicycle ergometer test. The predicted VO(2)max was standardized for age using residuals of linear regression analyses. RESULTS: Static EMG activity, HR and VAS were associated with aerobic fitness in teachers. CONCLUSIONS: The results suggest that a higher level of aerobic fitness may reduce muscle tension, HR and perceived work stress in teachers.

Are cardiorespiratory fitness and walking performance associated with self-reported quality of life and work ability?

OBJECTIVES: In Finland, testing cardiorespiratory fitness (VO2max) is popular in health promotion programs and work ability evaluations. The most common instruments used for this purpose are the submaximal cycle ergometer test, and the 2-km walking test. However, limited data exist on the associations between VO2max and wellbeing in working age adults. The aim of the study was to evaluate how the measured (cycle ergometer) and the estimated (walking test) VO2max and walking performance are associated with health-related quality of life and work ability. MATERIALS AND METHODS: The subjects were 104 middle-aged men workers (45-55 years old), mostly from the construction and manufacturing industries. VO2max was directly measured by a maximal exercise test on a cycle ergometer. The 2-km walking test parameters were the walking time, predicted VO2max, and fitness index. Health-related quality of life was assessed with the RAND-36 questionnaire which was further divided into physical dimensions (P-RAND-36) and mental dimensions (M-RAND-36). Perceived work ability was assessed with the work ability index (WAI) in a subgroup of 51 subjects. RESULTS: The 2-km walking test parameters significantly predicted the score on P-RAND-36 (r2=0.18, p=0.001), and correlated significantly with WAI. The directly measured VO2max was not associated with P-RAND-36, M-RAND-36 or WAI. CONCLUSIONS: The inexpensive 2-km walking test may be more useful when evaluating the quality of life and work ability, compared to the more expensive direct measurement of one's cardiorespiratory fitness in a laboratory.

Responses of the autonomic nervous system during periods of perceived high and low work stress in younger and older female teachers.

The aim of this study was to examine the response of the autonomic nervous system in younger (mean age 31 yrs, n=14) and older (mean age 54 yrs, n=14) healthy female teachers during work periods of perceived high and low stress. In the younger participants, heart rate, cortisol excretion rate and psychosomatic symptoms were significantly higher during the high work stress period. The older participants experienced no decrease in their heart rate and cortisol excretion during the low stress period and they exhibited no significant decrease in blood pressure after the work in the evening during both periods. It may be concluded that the recovery from the stress in the older teachers was insufficient particularly in view of their elevated diastolic blood pressure during the low work stress period. Ergonomic and individually tailored measures in terms of work time control, specific relaxation techniques, and a part-time retirement may improve the stress management of older teachers.

Empowerment in farmers' occupational health services.

This study attempted to develop farmers' health and farmers occupational health services (FOHS) by examining the effects and feasibility of empowered farmers' teams on walk-through surveys of Finnish dairy farms. FOHS personnel of the health centre in three municipalities selected three farmer teams for the intervention group. Each team consisted of three or four couples. The selected comparison group resembled the intervention group. The number of the farms was 31 in the intervention group and 33 in the comparison group. Before and after the intervention each subject responded to questionnaires. The initial walk-through survey was carried out in 1998-1999, and the follow-up took place in 2000-2001. During the follow-up the FOHS personnel identified the changes made after the initial surveys on the farms. The farmers and FOHS personnel also underwent a thematic interview. Altogether 217 changes were made, half of them to improve ergonomics, and 87 of the 217 were extensive. The empowered farmer groups produced more changes in the work environment. The use of empowered farmer groups is feasible in walk-through surveys, and the approach can be easily learned. Empowered groups are also a challenge for FOHS personnel, and they enrich the work of these workers. The farmers want more varied measures for work-site health promotion, and, particularly, they feel that an occupational health physician should be present on walk-through surveys.

Psychophysiological stress in high school teachers.

OBJECTIVES: The aim of this study was to follow psychophysiological stress over a year with four repeated measurements in full-time employed high school teachers and to compare their results with those obtained in the part-time retired teachers, gardeners and rescue workers. MATERIALS AND METHODS: The subjects consisted of 17 (10 females, 7 males) full-time and 9 part-time employed teachers (7 females and 2 males) in three high schools, 12 female gardeners and 13 male rescue workers. The data on job conditions, well-being, and psychosomatic symptoms were obtained by a questionnaire. The perceived stress was recorded using a visual analogue scale. The neuroendocrine reactivity was assessed by determining the diurnal urine excretion of epinephrine and norepinephrine. Electromyography of the trapezius muscle was recorded during working days in all subjects and in full-time teachers on one day in the holiday season. Blood pressure and heart rate were measured in the morning and in the afternoon. RESULTS: Psychophysiological stress in the full-time employed teachers was at similar levels on all three working days in December, March and November. Recovery from psychophysiological stress of working period was observed on summer holidays. Blood pressure, static muscle tension, perceived strain, psychosomatic symptoms and epinephrine level decreased significantly during the summer holidays as compared to the working days. The full-time employed teachers reported more perceived stress and psychosomatic symptoms than the part-time retired teachers or gardeners and rescue workers. Also static muscle activity was higher in full-time teachers than in rescue workers on the working days. CONCLUSIONS: More emphasis should be given to prevent psychophysiolocigal stress among teachers as well as to develop stress coping methods, and part-time working systems to facilitate work ability of aging teachers.

Ergonomics in practice: physical workload and heat stress in Thailand.

This study consists of assessments of the thermal environment and physiological strain in tasks associated with airport, construction, and metal jobs. The number of male and female participants was 108. Environmental heat stress was evaluated with the WBGT index. Physiological strain was evaluated by the relative cardiovascular load (%CVL) based on the measurements of heart rate. Also the increase of body temperature, weight loss, and perceived discomfort were determinated. At work sites the assessments lasted for 2 to 4 hrs for each participant. The mean physiological strain exceeded the level of 30%CVL. Severe peaks (over 60% CVL) were observed in specific tasks being in agreement with perceived discomfort ratings. The increase of body temperature and weight loss in most cases remained within acceptable limits. For the most strenuous tasks, various ergonomic improvements were developed in consultation with workers and managers.

Differences in heart rate variability of female nurses between and within normal and extended work shifts.

The aim of this study was to investigate differences in heart rate variability (HRV) reflecting the function of autonomic nervous system (ANS) and psycho-physiological strain associated with normal and extended work shifts in nursing work. Complete data were available from 51 female nurses with a mean age of 40 yr, and based on two comparable 36-h HRV measurements supplemented with a questionnaire. Time-domain (meanRR, SDNN, RMSSD) and frequency-domain (LF power, HF power) parameters represented the HRV data, and were analyzed by linear mixed models. The differences between the compared work shifts were minor, revealing mainly increased sympathetic activity at the beginning of the normal work shift. The HRV parameters detected significant differences between work and leisure-time during the normal and extended work shifts in female nurses. During work shifts, an increase in sympathetic and a decrease in parasympathetic control of HRV was observed when compared to the leisure-time situation. Older subjects had overall lower HRV than younger subjects indicating increased sympathetic activation of ANS, especially during work. HRV parameters revealed significant differences between work, leisure-time and sleep of female nurses, but there were few differences between normal and extended work shifts in HRV parameters. This lack of differences between work shifts may be a consequence of the adaptation of nurses to the extended shifts or the more flexible organization of work duties possible during extended work shifts.

Effects of implementing an ergonomic work schedule on heart rate variability in shift-working nurses.

OBJECTIVES: The aim of this study was to compare the psychophysiological strain related to a conventional shift schedule and new ergonomically improved two- and three-shift schedules using heart rate variability (HRV) analysis. The specific aim was to determine whether the introduced ergonomic shift arrangement had any positive effects on the psychophysiological strain such as increased HRV or decrease in the sympathovagal balance of the autonomic nervous system (ANS). METHODS: Questionnaire data and 24-hour HRV recordings were gathered from 48 female shift-working nurses once while working the conventional shift schedule (baseline) and again after one year working an ergonomic shift schedule during the morning shift. RESULTS: Comparisons between conventional and ergonomic shift schedules (baseline and follow-up, respectively) revealed significant differences in frequency-domain parameters. Implementing an ergonomic shift schedule resulted in decreased normalized low frequency (LF) power, increased normalized high frequency (HF) power, and decreased LF/HF ratio at the beginning of the shift. Furthermore, at baseline, mean RR interval, root mean square of successive RR interval differences (RMSSD) and normalized HF power were increased at the end of the shift compared with the values at the beginning of the morning shift. In contrast, at the follow-up, LF power was increased between the end and beginning of the morning shift. CONCLUSIONS: The psychophysiological strain measured by HRV analysis was lower at the beginning of the work shift for the ergonomic shift schedules compared with the conventional schedule. This indicates that an ergonomic shift schedule may have a positive effect on the ANS recovery occurring between successive work shifts.

Factors associated with changes in perceived strain at work among fire-fighters: a 3-year follow-up study.

OBJECTIVE: The objective of this study was to investigate individual and work-related psychosocial factors associated with changes in the perceived physical and mental strain among fire-fighters. METHODS: The 3-year follow-up study, done by a questionnaire, was based on data on 632 fire-fighters. The associations were investigated mainly by logistic regression modelling. RESULTS: Accidents were associated with increased perceived physical as well as mental strain (OR 1.4-2.6). Unfair distribution of work tasks was associated with increased perceived physical strain (OR 8.5, CI 1.5-49.6). Frequent differences of opinion disturbing work (OR 2.7, CI 1.2-6.1) and lack of possibilities for career advancement (OR 4.6, CI = 1.0-22.5) were associated with perceived increased mental strain at work. CONCLUSIONS: The results suggest that measures to reduce the perceived physical and mental strain of fire-fighters should be multi-factorial. However, to determine the content of the measures needs further intervention studies.

Assessment of Physical Load at Work Sites: A Finnish-German Concept.

The aim of this article is to introduce a set of work physiology methods for the assessment of physical load at the work site and to consider (a) their relevance for different types of muscular work, and (b) their feasibility for occupational health and safety practitioners. The results of an ergonomic intervention study for the reduction of workload associated with various manual materials handling tasks were used for the evaluation of the feasibility and sensitivity of the measurements of heart rate, the Edholm and OWAS methods, and the ratings of overall and local perceived exertion. The methods proved feasible, although time consuming, and their sensitivity for the quantification of small changes in physical workload was limited. Despite these shortcomings, these methods can be used by occupational health and safety practitioners when their strategy and data collection techniques are developed further. In conclusion, there are relevant and feasible methods fora reliable work-site assessment of cardiorespiratory and postural load related to the activation of large muscle masses. On the other hand, field methods for the quantification of local static workload and repetitive type of workload with small muscle masses are scarce.

Evaluation of a step-test for assessing the cardiorespiratory capacity of workers in Thailand: a pilot study.

The aim of this pilot study was to evaluate the accuracy of a simple step-test procedure supplemented by the measurement of heart rate (HR) (STEP1) to assess the cardiorespiratory capacity i.e., maximal oxygen consumption (VO2max) of Thai workers. The subjects comprised 18 men and 17 women. Their ages varied from 19 to 20 years and all were physically active. The subjects performed three tests: a submaximal incremental cycle-ergometer (CYCLE) test supplemented by HR recordings and respiratory gas exchange, and two step-tests (STEP1 and STEP2). In the STEP1 test HR was recorded continuously. The STEP2 test included the measurements of HR and respiratory gas exchange. For the male subjects the mean difference of the estimated VO2 max values obtained from the CYCLE and STEP1 test was 15% (p < 0.05). With the female subjects the mean VO2 max values were equal when predicted according to the CYCLE and STEP1 tests. The present STEP1 test is not sufficiently accurate to predict the VO2 max of Thai men. The results of this pilot study need to be confirmed with larger samples of subjects with various backgrounds in terms of individual characteristics and occupations.

Cardiorespiratory capacity of Thai workers in different age and job categories.

The objective of this study was to assess the cardiorespiratory capacity of Thai male and female blue-collar workers in different age and occupational categories. The maximal oxygen uptake (VO2max) of 70 men and 56 women was assessed using a submaximal bicycle-ergometer test supplemented with ventilatory gas analyses. The age of the subjects varied from 16 to 55 years. They worked in construction, manual materials handling and metal jobs. For the male subjects the VO2 max ranged from 1.43 to 3.50 l/min and from 21.3 to 66.3 ml/min/kg. The corresponding values for the female subjects were 0.97-2.97 l/min and 16.2-42.4 ml/min/kg. According to the European fitness classifications the mean age related VO2max of the male and female subjects can be considered moderate or poor. When compared to the European data heart rate of the subjects was 25-30% higher at submaximal levels of oxygen uptake, confirming earlier results. The low cardiorespiratory capacity of many Thai workers may be a limiting or even risk factor in physically demanding jobs.