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Biomedical subjects

R Ilmarinen

Publications and source records attributed to R Ilmarinen.

18 recordsLinked to original sources
PubMed1995

Maximal physical work performance with European standard based fire-protective clothing system and equipment in relation to individual characteristics.

Every fire fighter needs to wear fire-protective clothing and a self-contained breathing apparatus (SCBA) several times a year while carrying out various fire-fighting and rescue operations in hazardous work environments. The aim of the present study was to quantify the effects of a multilayer turnout suit designed to fulfil European standard EN 469 used over standardized (Nordic) clothing and with SCBA (total mass 25.9 kg) on maximal physical work performance, and to evaluate the relationship between individual characteristics and power output with the fire-protective clothing system and SCBA. The subjects were 12 healthy firemen aged 26-46 years. The range of their body mass, body fat and maximal oxygen consumption was 69-101 kg, 10-20% and 2.70-5.86 l.min-1, respectively. The maximal tests without (control) and with the fire-protective clothing system and SCBA were carried out on a treadmill in a thermoneutral environment. When compared to the control test, the decrease in the maximal power output in terms of maximal working time and walking speed averaged 25% (P < 0.001) varying from 18% to 34% with the fire-protective clothing system and SCBA. At maximum, no significant differences were found in pulmonary ventilation, absolute oxygen consumption, the respiratory exchange ratio, heart rate, systolic blood pressure, the rate-pressure product, mechanical efficiency, and the rating of perceived exertion between the tests with and without the fire-protective clothing system and SCBA. The reduction of the power output was related to the extra mass of the fire protective clothing and SCBA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Cold water immersion simulations using the Wissler Texas Thermal Model: validation and sensitivity analysis.

BACKGROUND: Wissler's Texas Thermal Model (TM) has been used to simulate the effects of thermal stresses on individuals under a variety of conditions. As part of a U.S. Navy effort to develop integrated protection garments, TM was modified to predict tolerance to cold water immersion (CWI) with garments with clo values less than 0.1 (15). METHODS: With these modifications, TM predictions were validated using experimental data obtained from 39 males and females during anti-exposure suit CWI assessments. Data analyses were based on changes in rectal (Tre) and various skin temperatures (Tsk). A sensitivity analysis was also performed to determine which TM parameters were most affected during simulated CWI. The condition tested was head-out immersion in 4.4 degrees C water by a 72.6 kg man (10 mm mean skinfold thickness). RESULTS: For most of the subject pool, the estimated change in Tre, chest, thigh, calf, and arm temperatures were not statistically different from experimental values. However, TM predictions were less accurate with respect to female responses. Based on thermal end points, TM predictions indicated that the following body segments were most sensitive to changes in insulation level (ordered from most to least important): chest and abdomen, leg, head, and arm. The physical parameters mean skinfold thickness, basal metabolic rate, body weight, and exercise metabolic rate had the most impact on TM predictions. CONCLUSIONS: The relative benefit of increased insulation on individual body segments was identified to aid garment design. Further, the relative importance of model physical parameters was identified so that judicious initial conditions could be selected to ensure that only garment design changes would be reflected in model predictions.

Abdomen↗
PubMed1993

Plasma atrial natriuretic factor during cold-induced diuresis.

The purpose of this study was to evaluate the possible contribution of atrial natriuretic factor (ANF) to cold-induced diuresis. Seven healthy men, dressed in shorts, were exposed to a cold environment (+12 degrees C) for 90 min, and also to a thermoneutral environment. Exposure to cold increased urine output and sodium excretion significantly but plasma ANF concentration remained unchanged. The increase in urinary potassium excretion during cold exposure was not significant (P = 0.0636) and plasma renin activity did not change either. Exposure to cold increased mean arterial pressure significantly but it did not affect heart rate. We concluded that acute exposure to the cold environment induced a diuretic response, which was a solute diuresis in its nature. Our results did not give support to the hypothesis that ANF might be involved in the renal response to cold exposure.

Adolescent↗
PubMed1992

The effect of appraisers in estimating metabolic rate with the Edholm scale.

A study was made of the appraisers' effect on the estimation of metabolic rate with the Edholm scale and a table of the ISO 7243 heat stress standard. The appraisers, five experienced and five inexperienced persons, estimated the metabolic rate of three different work tasks from videotapes. Analysis of variance indicated significant ( [Formula: see text] ) differences in the appraisers' recordings of the activities. The appraisers were grouped according to the similarity of the estimated values they gave. The groups thus contained both experienced and inexperienced appraisers, and it was not possible to classify the appraisers into experienced and inexperienced groups according to their earlier experience. The metabolic rates according to the Edholm scale were higher than according to the ISO 7243 table. The differences in metabolic rates given by the individual observers varied from 38 to 118 W/m(2). The variations in the estimation of metabolic rates were greater when the Edholm scale was used. This variation caused considerable variation also in the predicted mean vote, PMV index. It is recommended that the appraisers be selected carefully, because it is not possible to know whether a randomly selected appraiser is an 'average' or an 'extreme' appraiser without a test. Before conducting extensive field surveys where several appraisers estimate the metabolic rates, it would be useful to arrange training in order to calibrate the levels of the Edholm scale as well as ISO method among the appraisers because training clearly unified the estimation.

Journal Article↗
PubMed1991

An evaluation of heat stress indices (ISO 7243, ISO/DIS 7933) in the prediction of heat strain in unacclimated men.

The ISO 7243 heat stress standard based on the wet bulb globe temperature (WBGT) heat stress index and the analytical standard proposal ISO/DIS 7933 were evaluated in eight physically trained and eight untrained, unacclimated men during prolonged light exercise carried out while wearing industrial work clothing. The exercise tests were done in a thermoneutral (20 degrees C/40%), a warm humid (30 degrees C/80% humidity), and a hot dry (40 degrees C/20% humidity) environment. Both of the standards were effective in predicting the excessive thermal strain observed in the dry and humid heat (WBGT, 28 degrees C). In dry heat, neither of the standards took into account the higher sweating capacities of the physically trained men. The large inter-individual variability in the physiological responses to heat stress questioned the calculations of definite allowable exposure times (ISO/DIS 7933).

Acclimatization↗
PubMed1990

Responses of young and older men during prolonged exercise in dry and humid heat.

Eight young, sedentary men (aged 34 years, SD 3) and six older moderately active, unacclimated men (aged 57 years, SD 2) walked on a treadmill at 30% of their maximum oxygen consumption up to 3.5 h in a thermoneutral [dry bulb temperature (Td) 21 degrees C, relative humidity (r.h.) 43%)], a warm humid (Tdb 30 degrees C, r.h. 80%) and a hot dry (Tdb 40 degrees C, r.h. 20%) environment while wearing ordinary working clothes (0.7 clo). Their oxygen consumption, heart rate (fc), rectal (Tre) and mean skin temperature (Tsk), sweat rate (SR), and evaporative rate (ER) were measured during the tests. The ratings of thermal sensation (TS) and perceived exertion (RPE) were assessed using standard scales. In the heat stress tests, the number of experiments discontinued did not significantly differ between the two groups. The mean levels and end-exercise values of Tre, Tsk, fc, TS and RPE were not significantly different between the young and older subjects in any of the environments. In the warm humid environment, however, the Tre and RPE of the older subjects increased continuously (P less than 0.05) during the test compared to the young subjects. No significant difference between the groups was observed in SR or in ER. In the hot dry environment, however, the ER of older men increased more slowly compared to the young men. In spite of some time-related differences observed in Tre, RPE, and ER, the older subjects did not exhibit higher fc during exercise in the heat, they were not more hyperthermic and their performance times were similar to the young subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Design of functional work clothing for meat-cutters.

The aim of this study was to design new functional work clothing for meat-cutters, paying particular attention to the metabolic requirements of the work and the thermal and general working conditions in slaughterhouses. On the basis of the results of the pilot study (review of the literature, questionnaires and interviews, work analysis, physiological measurements) different types of work clothing were designed for prolonged used during normal work in meat cutting. Physical material tests and measurements of thermal insulation values (l(cl)), and the follow-up of clothing maintenance were carried out. Further modifications and evaluations of work clothing were based on the opinions of meat-cutters and on the physiological trials in slaughterhouses. The final assembly of work clothing consists of three pieces (cotton/polyester): an apron, trousers with extra insulation in the lower back, and a work coat with extra insulation in the neck and shoulders, and at the wrists. The sleeves are protected against moisture by special textile material. The thermal insulation of this new set of work clothing together with long sleeved and legged underwear is 1.3 clo and it proved to be sufficient for thermal comfort in moderate work in an air temperature of 10 degrees C.

Journal Article↗
PubMed1990

The accuracy of estimating the thermal insulation of clothing ensembles - the effect of appraisers.

The effect of the appraisers on the estimation of the thermal insulation of clothing ensembles was investigated. Nine appraisers, four experienced and five inexperienced, estimated the total thermal insulation by summing the values for individual garments. Lists of individual garments worn by workers were given during thermal comfort measurements carried out in shops and stores during one winter and summer. The beginners estimated the thermal insulation as accurately as the experienced appraisers. There were, however, great individual differences, for which three main reasons were found. Interpolation between the insulation provided by two garments was insufficient, and the insulation of these garments should be checked in more precise tables. Classification of the garments into heavy, medium and light clothing items was not adequate, and garments not listed by the workers confused the estimation given by different appraisers. The effect of error in thermal insulation on the PMV index is negligible if more than one appraiser estimates the thermal insulation and the mean of the estimates is used.

Journal Article↗
PubMed1990

Postural stability in shooters.

Ten competition shooters were tested during simulated race using the force platform technique to investigate the effect of training on postural stability. The shooters were tested at 30-min intervals during a race simulating actual race conditions. Sway velocity was calculated during 27-second periods. The postural stability was evaluated with and without competition clothing. The shooters had significantly better stability than untrained control subjects, when tested without supportive clothing. The competition clothing reduced the sway velocity further both in visual and nonvisual conditions. The Romberg quotient was higher in shooters than in normal controls, indicating that the shooters used to an increased amount proprioceptive and vestibular cues to stabilize their posture. The good postural stability of the shooters apparently results from assiduous training aimed to improve postural stability.

Adolescent↗
PubMed1987

Skin blood flow during incremental exercise in a thermoneutral and a hot dry environment.

Eight physically fit men performed two incremental bicycle ergometer tests, one in an ambient temperature of 25 degrees C and the other at 40 degrees C. Oesophageal temperature (Tes) increased continuously throughout the tests up to 38.0 and 38.3 degrees C, respectively. In both environments, forearm blood flow (plethysmography) was linearly related to Tes above the Tes threshold for vasodilation, but at the heaviest work loads this relationship was clearly attenuated and therefore indicated skin vasoconstriction, which tended to be more pronounced at 25 degrees C. During recovery at 25 degrees C, in some subjects the forearm blood flow increased above the levels observed at the end of the graded exercise in spite of a decreasing Tes. Skin blood flow, measured by laser Doppler flow meter at the shoulder, was quantitatively different but, on average, seemed to reveal the same response pattern as the forearm blood flow. In spite of the higher level of skin blood flow in the heat, blood lactate accumulation did not differ between the two environments. The present results suggest that there is competition between skin vasoconstriction and vasodilation at heavy work rates, the former having precedence in a thermoneutral environment to increase muscle perfusion. During short-term graded exercise in a hot environment, skin vasoconstriction with other circulatory adjustments seems to be able to maintain adequate muscle perfusion at heavy work levels, but probably not during maximum exercise.

Adult↗
PubMed1987

Circulatory and thermal responses of men with different training status to prolonged physical work in dry and humid heat.

Eight physically trained and eight untrained, unacclimated men walked on a treadmill at 30% of their maximum oxygen consumption up to 3.5 h in a thermoneutral [20 degrees C/40% relative humidity (RH)], a warm humid (30 degrees C/80% RH), and a hot dry (40 degrees C/20% RH) environment while wearing industrial work clothing. Their oxygen consumption, rectal and skin temperatures, sweating, cardiac output, heart rate, stroke volume, and peripheral blood pressure were measured during the tests. Thirteen of the 32 heat stress tests were prematurely stopped due to high rectal temperature, high heart rate, subjective fatigue, or heat syncope. The physiological strain, as indicated by the rectal temperature and heart rate, was not significantly different between the warm humid and hot dry environments (wet bulb globe temperature approximately 28 degrees C). The rectal temperature and heart rate responses of the physically trained and untrained subjects did not differ in any of the environments. In the heat, the heart rate was significantly higher than in the thermoneutral environment, but because of the markedly reduced stroke volume the average cardiac output was not different between the three environments. The impaired work performance in the heat seemed mainly to be related to the circulatory instability accompanying the increased cutaneous circulation.

Adult↗
PubMed1986

Aerobic and anaerobic responses to incremental exercise in a thermoneutral and a hot dry environment.

In an investigation of the effect of acute heat exposure on aerobic and anaerobic metabolism, eight unacclimated men performed two incremental bicycle ergometer tests in random order, once under thermoneutral conditions (25 degrees C) and once in a hot dry (40 degrees C) environment. Oxygen consumption (VO2) and pulmonary ventilation were measured every minute. Fingertip blood samples were taken at each work level for blood lactate (LA) determination. Compared to the results at 25 degrees C, the mean VO2 was significantly (P less than 0.01) lower during exercise at 40 degrees C. In the hot dry environment the blood lactate threshold was slightly reduced in four subjects, but neither the average peak nor the post-exercise blood LA values differed from the findings at 25 degrees C. During the exercise-heat stress, the ventilatory threshold did not change significantly. The results indicated that, during relatively short-term incremental exercise in a hot environment, almost adequate muscle metabolism can be maintained.

Adult↗
PubMed1986

Circulatory reaction to heat and cold in vibration-induced white finger with and without sympathetic blockade--an experimental study.

Central nervous, sympathetic mechanisms and local factors influencing the vascular response to cold in the finger skin were studied with plethysmographic and laser-Doppler methods in a chamber with controlled temperatures from 45 to about 5 degrees C, with and without sympathetic finger blockade. Blood flow and pressure were assessed after finger occlusion, together with finger heating and cooling, in workers with vibration-induced white finger (VWF) and in healthy persons not exposed to cold or vibration. Finger blood flow at vasodilatation, as measured by finger arterial inflow (FAI) after occlusion was smaller in the VWF group than in the reference subjects both with and without anesthesia, and capillary flux in the anesthetized finger tended to be smaller. At vasoconstriction, with or without anesthesia, the VWF subjects had lower FAI values than the referents. The studied flow and pressure variables differed considerably between the groups. The peripheral resistance of the VWF subjects was higher than that of the referents. This difference was the most pronounced after finger anesthesia. A possible pathogenetic mechanism in VWF is an increase in peripheral resistance due to a local defect in the vessels, with subsequent reduction in flow and intramural pressure.

Adult↗
PubMed1986

Vasomotor oscillation in vibration-induced white finger.

Vasomotor oscillation at different ambient temperatures, with and without anesthesia of the finger nerves, was studied in six persons with vibration-induced white finger (VWF) and in 10 referents. The power spectral density (PSD) of the Fourier transform of the laser-Doppler flowmeter signal from the finger pad vessels was analyzed. In both groups, the PSD of the vasomotor oscillation in the frequency range of 0.05-0.25 Hz was more pronounced in a cold than in a hot environment. Without finger nerve anesthesia, the oscillations of the referents were significantly greater (p less than 0.01) than those of the VWF subjects (PSD -34.4 dB and -41.6 dB, respectively). With anesthesia of the finger vasomotor nerves, the PSD was reduced in both groups. In the anesthetized finger there was no statistically significant group difference. Thus the myogenic component of the vasomotor activity was the same in the referents as in the VWF subjects. The results show that the autonomic neural influence on vasomotor oscillation in skin of the finger pad is weaker in persons with VWF. This weakness may be a sign of peripheral neuropathy, which may lead to a denervation syndrome causing hypersensitivity of the adrenoceptors to cold.

Adult↗
PubMed1981

[Studies on differences in the preventive effects of habitual physical activity in occupation versus leisure time. II. Effects of physical activity in occupation versus leisure time on physical working capacity (author's transl)].

One hundred and twenty men, aged 23--60 years and having various professions participated in studies on relationships between daily physical activity and physical performance capacity (PPC). The determination of daily physical activity at work and of the habitual leisure time activities has been described earlier (Ilmarinen et al. 1980). The determination of physical performance capacity was based on W170, W85% and on predicted VO2 max measured with continuously increasing work load on a bicycle ergometer. The W85% modification corresponds to the working capacity at a heart rate level of 85% of maximal heart rate. Workers with a combination of heavy physical work and active leisure time showed systematically the highest absolute and relative values of PPC. However, although the results indicated that the effect of work activity on PPC was not significant, the effects of leisure time activities on W85% and on VO2 max related to lean body mass were significant. It is concluded that the leisure time sport activities are more important than the physical activity at work in maintaining or increasing the PPC. Aerobic sport activities in leisure time are recommended both for persons with physically heavy and light work.

Adult↗
PubMed1980

Circadian variation of physiological functions related to physical work capacity.

The circadian variation of selected physiological functions related to physical work capacity was studied in four trained young male subjects. The twofold objective was to describe, in parametric terms, the variation of these functions and estimate the times and values of their maximum and minimum responses. Statistically significant periodic regression effects were found for the following functions: oral temperature; systolic blood pressure; heart rate at rest, during work (245 and 270 W) and after a 5-min recovery; ratings of perceived exertion; strength of hand grip; and neuromuscular coordination measured with a seesaw board balance test. The Fourier curve (sine curve) accounted for 63 % of the variation in oral temperature and from 13 to 38 % of the variation in the other significant harmonic intensities. In phase with the rhythm of oral temperature, but with larger amplitude, were systolic blood pressure, heart rate at rest and heart rate during work; roughly in phase were strength of hand grip and neuromuscular coordination. Ratings of perceived exertion and heart rate after a 5-min recovery showed a rhythm which was out of phase with the oral temperature. The number of disturbances in neuromuscular coordination was greatest at 2400 and smallest at 1200, the difference being as large as 44 %. The results suggest that the measured capacities of muscle strength and neuromuscular coordination are the lowest, that physical work is perceived as the heaviest, and recovery after work is the slowest at night. These findings appear to support the notion that performance capacity is reduced during the night.

Adult↗
PubMed1977

Effects of environmental heart on performance and some physiological responses of a man during a psychomotor task.

In climatic chamber experiments some physiological responses of a young healthy man were studied. He was able to perform a pursuitmeter task in a fairly wide range of warm climates without decrement of performance. The highly trained and heat-acclimatized subject was exposed nearly undressed to various ambient temperatures (28--55 degrees C) and air humidities (10--92%) which were combined in such a way that the conditions were tolerable up to 4 h. In 18 experiments the man was sitting quietly all the time, and in a parallel series of 19 experiments (up to 50 degrees C) he performed the pursuitmeter task during the last 2 hours of each exposure. Under equal climatic conditions work caused a slight increase in oxygen uptake corresponding to an increase in metabolic heat generation by about 70 kj/h (17kcal/h) on the average. Rectal temperature and temperature next to the eardrum were 0.1--0.2 degrees C higher at work as compared with rest. Weight loss at work exceeded weight loss at rest, the difference ocrresponding to an increase in evaporative heat loss by about 110 kj/h (26 kcal/h) which resulted in a decrease of mean skin temperature of 0.5 to 0.9 degrees C. Superelevation of heart rate due to work reached about 10 beats/min in a thermally neutral environment, but up to 30 beats/min in hot dry and warm humid surrounding, reflecting the additional effort for maintaining performance under conditions of increasing heat stress.

Acclimatization↗