Associations of self estimated workloads with musculoskeletal symptoms among hospital nurses.

OBJECTIVES: To investigate the prevalence of neck, shoulder, and arm pain (NSAP) as well as low back pain (LBP) among hospital nurses, and to examine the association of work tasks and self estimated risk factors with NSAP and LBP. METHODS: A cross sectional study was carried out in a national university hospital in Japan. Full time registered nurses in the wards (n = 314) were selected for analysis. The questionnaire was composed of items on demographic conditions, severity of workloads in actual tasks, self estimated risk factors for fatigue, and musculoskeletal pain in the previous month. Rate ratios (RRs) and 95% confidence intervals (95% CIs) were calculated by the Cox's proportional hazards model to study the association of pain with variables related to work and demographic conditions. RESULTS: The prevalences of low back, shoulder, neck, and arm pain in the previous month were 54.7%, 42.8%, 31.3%, and 18.6%, respectively. The prevalence of musculoskeletal symptoms among hospital nurses was higher than in previous studies. In the Cox's models for LBP and NSAP, there were no significant associations between musculoskeletal pain and the items related to work and demographic conditions. The RRs for LBP tended to be relatively higher for "accepting emergency patients" and some actual tasks. Some items of self estimated risk factors for fatigue tended to have relatively higher RRs for LBP and NSAP. CONCLUSIONS: It was suggested that musculoskeletal pain among hospital nurses may have associations with some actual tasks and items related to work postures, work control, and work organisation. Further studies, however, are necessary, as clear evidence of this potential association was not shown in the study.

Effects of box weight, vertical location and symmetry on lifting capacities and ratings on category scale in Japanese female workers.

The aim was to clarify the effects of box weight, vertical location and symmetry on the lifting capacities and subjective burden in Japanese female workers with manual material handling tasks. Sixteen healthy females were tested. They performed 12 different lifting tasks (three heights * two weights * two symmetries). It is difficult for Japanese women to exert dynamic force in lifting a 15-kg weight from the elbow to the shoulder level. A remarkable increase was observed in heart rate and category scale with ratio properties (CR-10) on large muscle group in lifting a 15-kg weight as compared with lifting a 10-kg one. Judging from calculation of the Recommended Weight Limit using the application manual by the National Institute for Occupational Safe and Health, it was also suggested that lifting the 15-kg weight from the elbow to the shoulder level was difficult for female workers. Not only peak force, but also the average upward acceleration and peak velocity were lower in asymmetric liftings than those in symmetric liftings. CR-10 for the left back and right thigh were also higher in 90 degrees right lateral plane lifting than in the mid-sagittal plane. Thus, asymmetric lifting was supposed to impose higher stress on the back contralaterally and thigh ipsilaterally to the location of the weight.

Test-retest reliability of isometric and isoinertial testing in symmetric and asymmetric lifting.

The aim of this study was to evaluate test-retest reliability of a dynamometer in measuring lifting strength or force parameters under several combinations of ergonomic factors. Thirteen healthy participants were tested on peak force (PF), related variables and isometric strength (IS) twice, at intervals of 3 months. Correlation coefficients for all parameters in the sagittal plane were 0.60-0.85. Coefficients of variations (CVs) of methodology error for PF in the sagittal plane were 6.2-6.9%. Correlation coefficients and CVs for IS at 90 degrees to the lateral plane were 0.51-0.54 and 16.6-17.9%, respectively. In paired t-tests of the parameters under all conditions, there was a significant difference between test and retest. In the test and retest, ratings of perceived exertions for the low back and the right arm in isometric lifting were significantly higher than those in dynamic lifting. It was concluded that the test-retest reliability of dynamic forces in the dynamometer was high. The peak force in the sagittal plane was considered reliable. In isometric lifting, isometric strength in the sagittal plane seemed reliable, while that at right angles to the lateral plane was considered to be less reliable.

Epicondylitis among cooks in nursery schools.

OBJECTIVES: To investigate the prevalence and risk factors of epicondylitis among cooks in nursery schools in a cross sectional study because they are suspected to have strenuous workloads on the hands and arms. METHODS: Prevalence of epicondylitis among 209 nursery school cooks and 366 control workers aged 40-59 were studied. Both groups consisted of women workers chosen from 1299 subjects who agreed to participate from 1329 social welfare employees in a city. All workers were interviewed with a questionnaire and had a clinical examination of the tenderness to palpation of epicondyles and epicondylar pain provoked by resisted extension and flexion of the wrist. RESULTS: Nursery school cooks had a significantly higher prevalence of epicondylitis (11.5%) than the controls (2.5%). In a logistic regression model, job title of the cook was also found to have a strong association with epicondylitis (odds ratio (OR) 5.4, 95% confidence interval (95% CI) 2.4 to 11.9) after adjustment for age, body length, and body mass index. Weaker associations were also found between epicondylitis and suspected job stress or workload scores for mechanical workload and psychosocial stressors based on factor analysis. CONCLUSIONS: This study supported the hypothesis that nursery school cooks had a higher prevalence of epicondylitis than other workers with less strenuous hand and arm tasks. It was suggested that risk factors of epicondylitis would be multifactorial, including mechanical workload and psychosocial factors.

A comparative study of physical work load in Japanese and Swedish nursery school teachers.

Comparisons were made of general and local physical work loads between two groups of 58 Japanese and 15 Swedish nursery school teachers. Heart rate, number of steps, rating of perceived exertion (RPE), frequency and time expended with respect to trunk flexion, sitting/kneeling, and lifting/carrying loads of 1 kg or more were monitored during working hours. The average percentage heart rate increase in the maximal heart rate range was lower in the Japanese than in the Swedish teachers. However, all parameters of local physical work load indicating musculoskeletal stress were higher in the Japanese than in the Swedish teachers. The RPE was slightly higher in the Japanese than in the Swedish teachers. These features of general and local work load in the Japanese teachers were typically observed among the teachers in charge of very young children (0-2 years). The Japanese teachers in charge of children aged 3-5 years, on the other hand, had similar levels of both general and local work load as the Swedish teachers in charge of classes comprising children of various ages (1-5 years). The physical work load measured in the present study was not sufficient to explain the difference in the magnitude of musculoskeletal problems for nursery school teachers in the two countries, and other factors should now be examined.

Low back pain among cooks in nursery schools.

A cross-sectional questionnaire study was conducted on cooks working for nursery schools in N city in order to verify epidemiological evidence of the work-relatedness of low back pain among them. After female workers aged 30 or more were selected from a study base of 2,799 workers in social welfare facilities, low back pain prevalence of cooks (n = 240) was compared with nursery school teachers (n = 955). Age-standardized prevalence ratios (PRs) of low back pain were 1.9 (95% CI: 1.5-2.5) in cooks compared with nursery school teachers. Among cooks, relative risks of low back pain increased with the increase in the number of lunches to be prepared and decreased with the increase in the number of cooks making lunches in a logistic regression model controlling age and body length. Low back pain was also found to be associated with self-estimated job stressors/ work load by logistic regression models. Multifactorial effects from ergonomic and psychosocial factors, and individual factors on the low back were suggested. From the viewpoint of epidemiological criteria for work-relatedness, it was concluded that the work-relatedness of low back pain among cooks in nursery schools was partially supported.

Effects of asymmetric dynamic and isometric liftings on strength/force and rating of perceived exertion.

A laboratory study was undertaken to determine the postural and physical characteristics and subjective stress during dynamic lifting of a usual load (10 kg) compared with during isometric lifting. The authors also aimed to clarify the effects of asymmetric lifting on these parameters. The subjects were thirteen male college students. They were asked to lift a box weighing 10 kg. They performed sixteen different lifting tasks from the floor to a height of 71 cm, involving a combination of three independent factors: two lifting modes (isometric lifting and dynamic lifting), four lifting angles in relation to the sagittal plane (sagittal plane, right 45 degree, right 90 degree and left 90 degree planes) and two lifting postures (squat and stoop). For each lifting task, strengths or forces and ground reaction forces were measured. At the end of each task, the authors asked the subjects to rate their perceived exertion (RPE) during lifting at ten sites of the body. Angle factor had a significant effect on isometric strengths and dynamic peak forces. Isometric strengths during the maximum 3 s were highest in lifting in the right 45 degree plane, followed by that in the sagittal plane, while those in the right 90 degree and left 90 degree planes were the lowest. However, peak forces in dynamic lifting were the highest in the lifting in the sagittal plane, followed by that in the right 45 degree plane, while those in the right 90 degree and left 90 degree planes were the lowest. Postural factor had a significant effect on height at peak force, which is higher in squat lifting than in stoop lifting. RPEs for the left arm, the backs and the right whole body in isometric lifting were significantly higher than in dynamic lifting of 10 kg. There were remarkably high RPEs for the ipsilateral thigh to the box in right 90 degree and left 90 degree planes during both isometric and dynamic liftings. Locations of the resultant force consisting of three component forces on the force plate were closer to the foot on the same side as the box in asymmetric lifting. Thus, some similarities and differences were found between isometric lifting and dynamic liftings regarding the indexes of strength used in this experiment. The authors consider that the subjects used the foot nearer to the box as a fulcrum during asymmetric lifting. Dynamic measurement using the 10 kg weight is less stressful than the conventional isometric measurement. It was possible to obtain the height data at peak force and time-based changes in the force and the box location during lifting only through dynamic lifting measurement. The results provide new knowledge about the biomechanical features of dynamic lifting tasks.

Relationship of task strain and physical strength to end-of-work fatigue among nurses at social welfare facilities.

To study the relationship of task strain and physical fitness to fatigue among nurses employed at social welfare facilities, we investigated the degree of habitual end-of-work fatigue among 99 nurses (ages 20-49 years) in its relationship to both the degree of strain in various tasks and various indices of physical fitness. Results were as follows: (1) Fatigue complaint rates were nearly the same (35-38%) regardless of age. (2) Mean arm power and maximal oxygen uptake (VO2max) were significantly lower in a high degree of fatigue group than a low degree of fatigue group. (3) Four of 21 tasks elicited strain complaint rates greater than 50%: "nursing of seriously ill patients", "nursing of medical device-assisted patients", "bathing care", and "excretory/diaper changing care". (4) Significant positive correlations were noted between the degree of fatigue and the degree of strain complaint with regard to "nursing of medical device-assisted patients", "bathing care", and "excretory/diaper changing care". (5) Strain complaint rates were significantly higher in a low arm power group than a high arm power group with regard to "nursing of seriously ill patients", "nursing of medical device-assisted patients", and "excretory/diaper changing care". (6) Strain complaint rates were significantly higher in a low VO2max group than a high VO2max group with regard to "nursing of medical device-assisted patients", "bathing care", and "excretory/diaper changing care". These results suggest the need for measures to alleviate task strain and to increase arm strength and overall stamina so that nursing work does not result in excessive fatigue.

Seasonal variations of ventilatory response to hypercapnia at rest.

In order to examine the seasonal variation of CO2 sensitivity, the slope (S) of the ventilatory response to CO2 was determined in 10 healthy males throughout a year. It was found that the average value of logarithm S was significantly (p less than 0.05) higher in the September than in the annual average, though average magnitude of S was not significantly different. In addition, the average value of ventilation (VE(60] corresponding of PACO2 60 mmHg was significantly (p less than 0.05) lower in January than in September. These results indicate that the timing of the start and/or finish of training is an important factor in the effect of physical training on the S and VE(60).

[Effects of carbon dioxide inhalation prior to maximal exercise on blood lactate and physical performance].

In order to examine the effect of acute respiratory acidosis induced by CO2 inhalation prior to maximal exercise on blood lactate and physical performance, double determinations were carried out for each subject on separate days; one day, after CO2 inhalation and other day, after inhalation of room air. It was observed that in the untrained subjects the CO2 inhalation prior to maximal treadmill exercise does not affect endurance time and maximum aerobic power, whereas blood lactate during recovery was lower in CO2 breathing than that in room air. In addition, no significant difference of 200m sprint time in the athletes was noticed between CO2 and room air while blood lactate after 200m sprint running was significantly lower in the CO2 than that in room air. From these results, it was suggested that the effect of CO2 inhalation prior to maximal exercise as applied here appeared to be mediate through metabolic rather than oxygen transport mechanism, but not related to physical performance.

Effects of prolonged physical training on ventilatory response to hypercapnia.

In order to determine whether or not resting ventilatory response to hypercapnia is changed by physical training, we studied the effect of long-term physical training on the slope of ventilatory response to CO2 at rest. The subjects were 9 untrained freshmen ranging in age from 18 to 20 years. Five out of nine subjects belonged to the badminton team after entering university in April 1980, and participated in their team's training for about 3 hr per day, 3 times a week year round for about 4 years until March 1984. Maximum oxygen uptake (VO2max), maximum pulmonary ventilation (VEmax) and maximum heart rate (HR max) were determined during maximal treadmill exercise before and after training. The slope (S) of ventilatory response to carbon dioxide at rest was measured by Read's rebreathing method. VO2max increased after training in the trained subjects and mean values of VO2max which were measured in 1982, 1983, and 1984, were statistically higher than that of 1980. Similar tendency was observed in VEmax and VO2max/W. Average values and standard deviations of S before training were 1.91 +/- 0.52 liter/min/torr and were decreased gradually with increasing training period; the differences in the S value before (1980) and after training, i.e., 1982, 1983, and 1984, were all significant. Such difference could still be seen after S was recalculated as SN by using normalized ventilation for 70 kg body weight, while there were no significant differences in the S and SN between baseline and repeated studies in the untrained group. In addition, CO2 responsiveness was found to correlate negatively with maximum oxygen uptake in 4 out of the 5 trained subjects. These results suggest that in normal subjects, long-term physical training, as in the present study, decreases CO2 responsiveness at rest.

Development of a telemetry system for measuring oxygen uptake during sports activities.

A new system for continuous measurement of oxygen uptake by means of a telemeter has been developed. Oxygen uptake and pulmonary ventilation during rest and exercise were determined using a portable oxygen consumption meter (Oxylog). A small interface circuit between the Oxylog and the transmitter of a frequency modulated bio-telemeter system was designed and installed inside the Oxylog. Data from the transmitter were passed to a receiver and were fed into a microcomputer system. The microcomputer system displayed and printed out minute values of ventilation and oxygen uptake. The accuracy and reliability of the new system were checked by comparison with the traditional (Douglas bag) method. In the range less than 80 l.min-1 of ventilation and less than 2 l.min-1 of oxygen uptake, the system was not inferior to the Douglas bag method. The new system was applied for field continuous measurement of oxygen uptake during a doubles tennis game. The results of the application indicate that the telemetry system developed here is a very practical and useful way of measuring oxygen uptake during sports activities.

Effects of CO2 inhalation prior to maximal exercise on physical performance.

In the untrained subjects, inhalation of 4.5-6.0% CO2 prior to maximal treadmill exercise does not affect physical performance and maximum oxygen uptake, while blood lactate levels during recovery have a tendency to greater decrease in CO2 breathing than that in the room-air breathing. It was suggested that CO2 inhalation immediately prior to maximal exercise as applied here is not a useful tool in increasing physical performance.

The influence of body size on the ventilatory response to hypercapnia.

The slope of ventilatory response to hypercapnia at rest was determined in 77 healthy male students by means of the CO2 rebreathing method. It was found that the hypercapnic ventilatory response slope (S) was significantly lower in the lean group with BMI (body mass index) below 19 than that in the normal group, while there were no significant correlation between S and body weight or height. These results indicate that sensitivity of hypercapnia in the lean subjects differed from that of normal and overweight subjects.