Physiological effects associated with the use of respiratory protective devices. A review.

Several types of filtering (air-purifying) devices, air-line (supplied-air) apparatus, and self-contained breathing apparatus are used at work. The most important parameters of the respiratory protective devices that affect physical work capacity are additional inspiratory and expiratory breathing resistance, dead space, and weight. The main physiological effects of the respirators are alterations in breathing pattern, hypoventilation, retention of carbon dioxide, and increase in the work of breathing. The undesirable effects are accentuated during heavy physical work, maximal physical work capacity thereby being reduced.

Age and sex as determinants of the relative aerobic strain of nonmotorized mail delivery.

The relative aerobic strain (RAS) of nonmotorized mail delivery was assessed in 54 Finnish mail carriers who represented both sexes, the entire workage range and both downtown and suburban delivery districts. The mean RAS of the entire delivery time was 55% of the maximal oxygen uptake (ml/kg-min). It was higher for women than for men, and higher for suburban than for downtown delivery. The RAS tended to increase systematically with age after the age of 50. The work strain of mail carriers of over 50 years of age, especially of older women carriers in suburban areas, was concluded to be high enough to lead to possible excessive strain on the workers.

Heart rate as an estimator of oxygen consumption during manual postal delivery.

Nine young healthy postmen performed three progressive maximal exercise tests (on a bicycle ergometer and with and without a 10-kg shoulder bag on a treadmill) for which the least-squares regression equations of heart rate (HR) on oxygen consumption (VO2) were established. HR and VO2 were then measured during five modes of simulated postal delivery: on level ground by foot (F), bicycle (B), and push-cart (C) and on stairs by foot (S/F) and push-cart (S/C). The respective work HR values were inserted into the three regression equations established for HR/VO2, and VO2 was solved for. The estimated VO2 values tended to be systematically higher than the measured ones. The best regression proved to be that established for the treadmill plus mailbag; the regression coefficients between the measured and estimated VO2s were higher than 0.75, and the percentage differences between the means of the measured and estimated values were no more than 10% for F and B delivery. All the regressions yielded inaccurate estimations of VO2 for C, S/F and S/C delivery. It was concluded that HR is acceptable as an estimator of VO2 only when the test work closely resembles the muscle work in the job.

Changes in maximal cardiorespiratory capacity among aging municipal employees.

Before and after a four-year follow-up, maximal oxygen consumption (VO2max) was determined for 67 municipal employees (initial age about 51 years). The VO2max (ml.kg-1) decreased 6% among the women and increased 8% among the men, the greatest and smallest change occurring for employees doing mental and physical work, respectively. The men's increase was associated with an increase in leisure-time physical activity. Work content was not associated with the level of VO2max for either gender. After the four years the women's absolute VO2max was about 66% of the men's. There were marked changes in VO2max at the individual level, the most marked decreases being associated with the use of medication in some cases. After the four years the women's VO2max of 63% was insufficient according to current recommendations. Therefore physically demanding jobs are not generally recommended for older women.

Effects of Ergorest arm supports on muscle strain and wrist positions during the use of the mouse and keyboard in work with visual display units: a work site intervention.

The effects of Ergorest arm supports on wrist angles and musculoskeletal strain in the neck-shoulder-arm region and electrical activity in the shoulder and arm muscles were studied during typing or the use of the mouse in work with a visual display unit (VDU). Twenty-one women were randomized into 3 groups (1 arm support, 2 arm supports, and control). Measurements were carried out before and after the 6-week intervention. The wrist extension of the mouse hand, the muscle activity of the trapezius muscle, and the subjective discomfort ratings indicated that 2 arm supports were better than 1 in work with a mouse. The Ergorest arm support alleviates muscle and joint strain in VDU work when used for both arms.

Effect of heat stress on muscle blood flow during dynamic handgrip exercise.

During exercise in a hot environment, blood flow in the exercising muscles may be reduced in favour of the cutaneous circulation. The aim of our study was to examine whether an acute heat exposure (65-70 degrees C) in sauna conditions reduces the blood flow in forearm muscles during handgrip exercise in comparison to tests at thermoneutrality (25 degrees C). Nine healthy men performed dynamic handgrip exercise of the right hand by rhythmically squeezing a water-filled rubber tube at 13% (light), and at 34% (moderate) of maximal voluntary contraction. The left arm served as a control. The muscle blood flow was estimated as the difference in plethysmographic blood flow between the exercising and the control forearm. Skin blood flow was estimated by laser Doppler flowmetry in both forearms. Oesophageal temperature averaged 36.92 (SEM 0.08) degrees C at thermoneutrality, and 37.74 (SEM 0.07) degrees C (P less than 0.01) at the end of the heat stress. The corresponding values for heart rate were 58 (SEM 2) and 99 (SEM 5) beats.min-1 (P less than 0.01), respectively. At 25 degrees C, handgrip exercise increased blood flow in the exercising forearm above the control forearm by 6.0 (SEM 0.8) ml.100 ml-1.min-1 during light exercise, and by 17.9 (SEM 2.5) ml.100 ml-1.min-1 during moderate exercise. In the heat, the increases were significantly higher: 12.5 (SEM 2.2) ml.100 ml-1.min-1 at the light exercise level (P less than 0.01), and 32.2 (SEM 5.9) ml.100 ml-1.min-1 (P less than 0.05) at the moderate exercise level.(ABSTRACT TRUNCATED AT 250 WORDS)

Policemen's physical fitness in relation to the frequency of leisure-time physical exercise.

Ninety to ninety-five men (aged 27 to 46 years) from the police academy were the study subjects. Their prior habits of physical exercise, estimated aerobic capacity (VO2max), muscular performance, and thickness of subcutaneous fat were determined. The policemen were taller (181 cm vs 175 cm) and heavier (84 kg vs 74 kg) than the average 20- to 40-year-old Finnish man, and their VO2max (1 X min-1) was higher (3.41 1 X min-1 vs 2.96 1 X min-1). The frequency of prior physical exercise significantly correlated with most of the variables studied. Those policemen who did not exercise at all (n = 12) were inferior to the average 20- to 40-year-old Finnish man on all the physical fitness tests, whereas the results of the most active policemen (n = 23) were clearly higher. The results indicate that the selection of heavier and taller men for police training guarantees a certain absolute level of physical performance capacity. However, the physical activity involved in police work is insufficient to maintain a high level of physical fitness, which must be achieved through participation in regular and effective physical training.

Physical work and strain involved in manual sorting of postal parcels.

A field study was conducted to assess cardiorespiratory and musculoskeletal stress and strain and work output during manual sorting of postal parcels, and to detect the effects of parcel sorting on the maximal muscle strength and endurance. The volunteer subjects comprised 32 healthy male sorters with mean (+/- s.d.) age of 34 +/- 7 years at five different sorting sites. Each subject was studied during one evening work shift. During the shift of 391 +/- 46 min the subjects manually sorted 1173 +/- 630 parcels and walked 4.7 +/- 2.3 km with and without the load. While sorting, heart rate was 101 +/- 18 beats min-1. In the heaviest tasks the oxygen consumption was 1.2 +/- 0.41 min-1, and no elevated blood lactate concentrations were found. Work postures in which the back was bent forward averaged 24% of the time for sorting. The overall cardiorespiratory rating and local ratings of perceived exertion for arms, back, and legs did not exceed the 'somewhat strong' level during the work shift. The maximal static strength both for the right and left hand-grip muscles was, on average, 3% lower (p less than 0.05) after the work shift than before the shift. No significant differences were found in the static or dynamic endurance times for the hand-grip muscles when the results obtained after the work shift were compared to the baseline values. At sorting centres the stress and strain on the cardiorespiratory and musculoskeletal system was evaluated to remain within acceptable limits for healthy male sorters.

Anthropometric, muscle strength, and spinal mobility characteristics as predictors in the rating of acceptable loads in parcel sorting.

The rating of acceptable load (RAL) attained with a standard test (RALSt) and a wrk-simulating test (RALW) for postal parcel sorting was related to anthropometric, muscle strength, and spinal mobility characteristics of 18 male sorters. The subjects comprised a subsample of 103 experienced male sorters who carried out the RAL tests at postal sorting centres. The dynamic hand-grip endurance correlated significantly (p = 0.036) to the RALSt results. Correspondingly, there was a significant correlation (p = 0.044) between the ratio of maximal isometric strength of trunk extension to body weight and the RALW. The dynamic hand-grip endurance predicted 26% of the variation in the RALSt; in the RALW the maximal isometric strength of trunk flexion to body weight ratio predicted 24%. The subjects who rated heavier weights for RALSt tended to have a better trunk mobility. The dynamic endurance of hand-grip muscles, trunk strength, and spinal flexibility seemed to be the most powerful predictors for the psychophysically assessed 'acceptable loads' in experienced workers performing manual materials handling tasks.

Are the job demands on physical work capacity equal for young and aging firefighters?

The job demands on physical work capacity and the frequency of the firefighting and rescue tasks were rated by 156 professional firefighters (age range, 22 to 54 years) who responded to a questionnaire. Smoke-diving requiring the use of personal protective equipment was considered to demand most aerobic power. The clearing of debris with heavy manual tools, and roof work set the highest demands on muscular performance and motor coordination, respectively. During the past 5 years, 83 to 88% of the respondents had performed these tasks on average four times a year. The rating and frequency of the tasks were not significantly affected by age. The results suggest that the job demands on physical work capacity remain the same throughout the occupational career of the firefighters.

Work load and physiological responses during asbestos removal with protective clothing.

The removal of asbestos-containing building materials requires the use of dust-repelling protective clothing and a respirator. The present study was aimed at measuring physiological responses to asbestos removal in actual work situations. The subjects were eight asbestos workers. During the work, the men wore permeable or impermeable clothing along with a powered or non-powered filtering device including a full-face or half-face mask. Environmental parameters, work postures, heart rate (HR), the skin temperature at two sites and the rectal temperature were recorded every minute during work. Perceived exertion, thermal sensation, thermal comfort, and skin wetness were rated by the subjects. The ambient temperature at work sites ranged from 19 degrees to 37.5 degrees C and relative humidity, from 21% to 50%. The mean HR ranged from 101 to 141 beats min-1. The calculated (from HR measurements) average oxygen consumption (VO2) varied from 0.9 to 1.9 l min-1, which corresponded to 27%-60% of the maximal value. The peak rectal temperature and the highest mean of two measurements of skin temperature were 37.7 degrees +/- 0.3 degree C and 34.4 degrees +/- 0.9 degree C, respectively. The sweat rate varied from 162 to 583 g h-1. Poor work posture was common during asbestos removal. The arms were elevated over shoulder level for 35% of the work time. During the work the mean physiological strain was considered to be moderate, with some heavy peak loads being registered.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological strain in work with gas protective clothing at low ambient temperature.

Wearing an impermeable gas protective suit (Dräger 500 or 600) and a self-contained breathing apparatus (Dräger PA 80; total weight 27 kg (59.5 lb], seven experienced firemen and one mechanic performed simulated repair and rescue tasks in a chemical plant. The subjects' mean (+/- SD) age, height, weight and estimated maximal oxygen consumption were: 36 +/- 4 years; 181 +/- 6 cm; 83 +/- 8 kg; and 42 +/- 5 mL/min/kg, respectively. The operations took place outdoors (ambient temperature 2.0 degrees C (35.6 degrees F), wind velocity 0-4 m/s). The total work time averaged 37 minutes. During tasks of search, handling vents, and sawing and replacing bolts, the mean (+/- SE) heart rates measured by a Depex recording device were 146 +/- 2, 148 +/- 2, and 147 +/- 5 beats/min, respectively. The mean rectal temperature increased 0.8 degrees C during the whole work period. Weight loss due to sweat averaged 300 g. In conclusion, typical tasks with gas protective clothing caused marked physiological strain among subjects in average physical condition even though the thermal strain was relatively low because the weather was cool. The results emphasized the need to evaluate physical fitness during the periodic check-ups of workers who may have to use gas protective clothing.

Work ability and job demands of aging white- and blue-collar workers in 1981 and 1996.

This study compared perceived work ability and job demands in 1981 and 1996. Two samples of municipal workers were formed by matching according to location (eastern Finland), occupational status (white- and blue-collar jobs), gender (men), and age (> or = 45 years). In 1981, 50 white-collar (mean age 51 [SD 3] years) and 214 blue-collar (mean age 51 [SD 4] years) workers responded. In 1996, the corresponding numbers were 43 and 54, respectively, the mean age being 50 [SD 4] years for both groups. Perceived work ability and psychological resources changed very little from 1981 to 1996, but there seemed to be a trend towards a more positive view of future work ability. General and mental job demands, in particular, seemed to be increasing among white-collar workers. The observed differences in work ability and job demands were systematically more positive among blue-collar workers than among the white-collar workers.

Cardiorespiratory and subjective responses to prolonged arm and leg exercise in healthy young and older men.

Ten young (aged 23-30 years) and nine older (aged 54-59 years) healthy men with a similar size of limb muscle mass performed arm crank and leg cycle exercise for 30 min at relative exercise intensities of 50% and 75% of maximal oxygen uptake for the corresponding muscle group. In the tests, heart rate, blood pressure, gas exchange variables, rating of perceived exertion and blood lactate concentration were measured. The limb muscle mass was determined by anthropometric measurements. At the 75% target exercise level, four of the older men and two of the young men could not complete the arm-cranking test, and one of the older men and two of the young men could not complete the leg-cycle test. During arm-cranking the absolute exercise intensity was similar for the young and older men because of similar maximal values during arm-cranking. But during leg-cycling the absolute exercise intensity was higher for the young men than for the older men due to the difference in corresponding maximal values. During arm-cranking there were no significant differences in the physiological responses between the age groups except that a higher ventilatory response was noted among the older compared to the young men. During leg-cycling the heart rate values were higher among the young compared to the older men. But, when the heart rate values were expressed as a percentage of maximal heart rate in the corresponding maximal tests, no significant differences between the age groups were found. The results indicated that 30-min of arm or leg exercise at the same relative submaximal exercise intensity produces a similar degree of physiological strain in healthy older compared to young men. During armcranking, the young and the older men exercised at the same external intensity, indicating a similar ability to perform prolonged excercise using smaller muscle groups expressed both in absolute and relative terms.

Cardiorespiratory effects of respiratory protective devices during exercise in well-trained men.

The effects of a filtering device, an air-line breathing apparatus and a self-contained breathing apparatus ( SCBA ) on pulmonary ventilation, oxygen consumption and heart rate were studied in 12 well-trained firemen aged 21-35 years. Their average maximal oxygen consumption (VO2 max) was 64.9 ml X min-1 X kg-1. Sequential tests without and with the respirator were performed on a treadmill. The continuous test contained five components, each of which lasted 5 min: sitting at rest, walking at 20%, 40%, and 60% of the individual VO2 max, and recovery sitting. During the higher submaximal work levels and recovery, ventilation, heart rate, and oxygen consumption in particular increased more with respirators than without them. At the highest work level the increments in oxygen consumption caused by the respirators were 13%, (8.7 ml X min-1 X kg-1), 7% (4.4 ml X min-1 X kg-1), and 20% (12.7 ml X min-1 X kg-1) of VO2 max. All three respirators hampered respiration, resulting in hypoventilation. The additional effort of breathing and the weight of the apparatus (15 kg with the SCBA ) increased the subjects' cardiorespiratory strain so clearly that the need for rest periods and the individual's work capacity when the respirators are worn must be carefully considered, particularly with the SCBA .

Differences in cardiorespiratory responses during and after arm crank and cycle exercise.

The differences in cardiorespiratory responses were examined during and after intermittent progressive maximal arm-crank and cycle exercise. Arm-crank exercise was performed in a standing position using no torso restraints to maximize the amount of active skeletal muscle mass. Recovery was followed for 16 min. In the tests a variety of ventilatory gas exchange variables, heart rate, the blood pressure, and the arm venous blood lactate concentration were measured in 21 untrained healthy men aged 24-45 years. At equal submaximal external workloads for arm cranking and cycling (50 and 100 W) the respiratory frequency, tidal volume, pulmonary ventilation, oxygen uptake, carbon dioxide output, the respiratory exchange ratio, heart rate, the arm venous blood lactate concentration, and the ventilatory equivalent for oxygen were higher (P less than 0.001) during arm cranking than cycling. The maximal workload for arm cranking was 44% lower than that for cycling (155 +/- 37 vs 277 +/- 39 W, P less than 0.001) associated with significantly (P less than 0.001) lower maximal tidal volume (-20%), oxygen uptake (-22%), carbon dioxide output (-28%), systolic blood pressure (-17%) and oxygen pulse (-22%) but a higher ventilatory equivalent for carbon dioxide (+22%) and arm venous blood lactate concentration (+37%). However, these responses after arm-crank and cycle exercises behaved almost similarly during recovery. The high cardiorespiratory stress induced by arm work should be taken into account when the work stress and work-rest regimens in actual manual tasks are assessed, and when arm work is used for clinical testing, and in physiotherapy particularly for patients with heart or pulmonary diseases.

Effects of industrial respirators on breathing pattern at different work levels.

The effects of a filtering device and an air-line apparatus on breathing pattern were studied in healthy men with different physical characteristics and work capacity. The subjects comprised nine construction workers aged 35-44, and nine firemen aged 21-35. The construction workers' mean maximal oxygen consumption (VO2max) was 34.5 ml min-1 kg-1, the firemen's 66.9 ml min-1 kg-1. Breathing pattern was analyzed for its components, inspiratory time, expiratory time, breathing frequency, tidal volume, and pulmonary ventilation at rest, during two submaximal treadmill walks when the subjects' absolute work load was equal, and during recovery. Neither the filtering device nor the air-line apparatus had a significant effect on breathing pattern when compared with the control values measured twice with a low-resistance breathing valve. A significantly longer expiratory time, lower breathing frequency, and smaller pulmonary ventilation were found for the firemen with the breathing valve and the industrial respirators. The breathing pattern of the construction workers and the firemen differed, but the alterations were not induced by the use of the filtering device or the air-line apparatus when studied at aerobic work levels up to 60% VO2max.

Rating of acceptable load in manual sorting of postal parcels.

The psychophysical test, the rating of acceptable load (RAL) were used to assess acceptable weights for dynamic lifting in postal workers engaged in sorting parcels. The standard test (RALSt) and a work-simulating test (RALW) were administered to 103 volunteers: all experienced male sorters. In the RALSt, subjects selected the weight which would be acceptable for lifting in a box with handles from table to floor and back to the table once every 5 min for the working day. for the RALW, the box was without handles and the weight was chosen to be acceptable for transfer 4-6 times/min from a table to the parcel container and back to the table. Both tests were made during normal working hours at postal sorting centres. The overall means for RALSt and RALW were 16.4 kg and 9.4 kg respectively (p < 0.001): both being substantially higher than the average parcel weight of 4 kg. The RALSt and RALW tests proved to be repetitive and sensitive for differentiating the effects of load and task variable in actual manual material handling. Thus they appear to be applicable to the evaluation of manual materials handling problems.

Physical work capacity in dynamic exercise with differing muscle masses in healthy young and older men.

Ten young (aged 23-30 years) and nine older (aged 54-59 years) healthy men with similar estimated limb muscle volumes performed, in random order, three different types of ergometer exercise tests (one-arm cranking, two-arm cranking, and two-leg cycling) up to the maximal level. Values for work load (WL), peak oxygen consumption (V0(2)), peak heart rate (HR), peak ventilation (V(E)), respiratory gas exchange ratio (R), recovery blood lactate concentration [La-], and rating of perceived exertion (RPE) were compared between the age-groups in the given exercise modes. No significant age-related differences in WL, peak V0(2), peak HR, R, [La-], or RPE were found in one-arm or two-arm cranking. During one-arm cranking the mean peak V0(2) was 1.65 (SD 0.26)1*min(-1) among the young men and 1.63 (SD 0.10)l*min(-1) among the older men. Corresponding mean peak V0(2) during two-arm cranking was 2.19 (SD 0.32)1*min(-1) and 2.09 (SD 0.18)1*min(-1), respectively. During one-arm cranking peak V(E) was higher (P <0.05) among the older men compared to the young men. During two-leg cycling the young men showed higher values in WL (P <0.001), peak V0(2) (P <0.001), and peak HR (P <0.001). The mean peak V0(2) was 3.54 (SD 0.24)1*min(-1) among the young men and 3.02 (SD 0.20)1 . min(-1) among the older men. Corresponding mean peak HR was 182 (SD 5) beats*min(-1) and 170 (SD 8) beats*min(-1), respectively. During two-leg cycling, peak V(E), R, [La-], and RPE did not differ between the two age-groups. In summary, the older men with similar sizes of estimated arm and leg muscle volumes as the young men had a reduced physical work capacity in two-leg cycling. In one-arm or two-arm cranking, no significant difference in work capacity was found between the age-groups. These results indicate, that in healthy men, age, at least up to the 6th decade of life, is not necessarily associated with a decline in physical work capacity in exercises using relatively small muscle groups, in which the limiting factors are more peripheral than central.