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Biomedical subjects

J Smolander

Publications and source records attributed to J Smolander.

At least 37 records · Page 2Linked to original sources
PubMed1992

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)

Adult↗
PubMed1992

Thermoregulation during rest and exercise in the cold in pre- and early pubescent boys and in young men.

Eight minimally dressed pre- and early pubescent boys (age 11-12 yr) and 11 young adult men (age 19-34 yr) rested for 20 min and exercised on a cycle ergometer for 40 min at approximately 30% of their maximum oxygen consumption (VO2max) at 5 degrees C. To quantify the added increase in metabolic rate because of cold, a separate test was carried out at 21 degrees C at rest and at equal work rates as in the cold. Both groups were similar in subcutaneous fat thickness and VO2max per kilogram body weight. Rectal temperature increased slightly during the exposure to the cold, but no significant difference was observed between the boys and men. In the cold, the boys had lower skin temperatures than the adults in their extremities but not in the trunk. The boys increased their metabolic rates in the cold more than did the men. As a result, the boys maintained their core temperature as effectively as the adults. Similar age-related differences in thermoregulatory responses to cold were observed when two boys and two men with equal body sizes were compared. Our results suggest that there may be maturation-related differences in thermoregulation in the cold between children and adults.

Adult↗
PubMed1991

Individual response to physical work in the heat in relation to sweating and skin blood flow.

The aim of the present study was to examine heart rate and rectal temperature responses to dynamic exercise in a hot environment and their relationship to sweating and skin blood flow. Eight physically trained men were the study subjects. The experiments consisted of 60-min bicycle ergometer tests at intensities of 50 and 100 W in the heat (36 degrees C/30% relative humidity). During the tests, oxygen consumption, heart rate, rectal temperature, and skin temperatures on eight sites were measured. The whole-body sweat rate and evaporation rate and the rate of dripping sweat were measured by a continuous weighing technique. Skin blood flow was estimated from the changes in forearm blood flow. In all, 13 tests were done at 50 W and 10 tests were conducted at 100 W. At 50 W, a physiological steady state was attained in all tests, i.e. the rise in heart rate was less than 10 beats min-1. At 100 W, in all experiments the heart rate and rectal temperature increased continuously throughout the tests. At the end of exercise, the heart rate varied from 98 to 150 beats min-1. At 50 W work load, the heart rate and rectal temperature did not significantly correlate with any of the thermoregulatory parameters. At 100 W, the heart rate and rectal temperature correlated with the total sweat rate (r = -0.66 and -0.71, respectively; P less than 0.05), with the onset of dripping (r = 0.74 and 0.66, respectively, P less than 0.05), and with the ratio of forearm blood flow to dripping sweat rate (r = 0.83 and 0.85, respectively; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

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)

Adult↗
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↗
PubMed1991

The combined effect of the cold pressor test and isometric exercise on heart rate and blood pressure.

The purpose of this study was to determine if the cold pressor test during isometric knee extension [15% of maximal voluntary contraction (MVC)] could have an additive effect on cardiovascular responses. Systolic and diastolic blood pressures, heart rate and pressure rate product were measured in eight healthy male subjects. The subjects performed the cold pressor tests and isometric leg extensions singly and in combination. The increases of systolic and diastolic blood pressure during isometric exercise were of almost the same magnitude as those during the cold pressor test. The responses of arterial blood pressure, and heart rate to a combination of the cold pressor test and isometric knee extension were greater than for each test separately. It is suggested that this additional effect of cold immersion of one hand during isometric exercise may have been due to vasoconstriction effects in the contralateral unstressed limb. In summary, the circulatory effects of the local application of cold during static exercise at 15% MVC were additive.

Adult↗
PubMed1991

Biomechanical evaluation of heavy tool-handling in two age groups of firemen.

The biomechanical load of a rescue-clearing task (lifting a power saw from the floor up to the ceiling level) was evaluated with six older (47 +/- 5 years) and seven younger firemen (32 +/- 2 years). The mean dynamic compressive force at the L5/SI disc was 5998 N for the older subjects and 6392 N for the younger subjects. The peak torques for the back and knee extensions were about equal for the two groups of the subjects. The younger subjects had a significantly higher movement speed in the knee extension than the older subjects (89.1 +/- 25.7 vs. 35.3 +/- 11.5 degrees/s, p less than 0.001). The results showed that lifting a power saw produced a high load on the musculoskeletal system, and that the load was not influenced by age.

Adult↗
PubMed1991

Sweating and skin blood flow during exercise: effects of age and maximal oxygen uptake.

Individuals greater than or equal to 60 yr of age are more susceptible to hyperthermia than younger people. However, the mechanisms involved remain unclear. To gain further insight, we examined the heat loss responses of 7 young (24-30 yr) and 13 older (58-74 yr) men during 20 min of cycle exercise [67.5% maximal O2 uptake (VO2max)] in a warm environment (30 degrees C, 55% relative humidity). Forearm blood flow (FBF) and chest sweat rate (SR) were plotted as a function of the weighted average of mean skin and esophageal temperatures [Tes(w)] during exercise. The sensitivity and threshold for each response were defined as the slope and Tes(w) at the onset of the response, respectively. When the young sedentary men were compared with a subgroup (n = 7) of the older physically active men with similar VO2max, the SR and FBF responses of the two groups did not differ significantly. However, when the young men were compared with a subgroup of older sedentary men with a similar maximal O2 pulse, the SR and FBF sensitivities were significantly reduced by 62 and 40%, respectively. These findings suggest that during a short exercise bout either 1) there is no primary effect of aging on heat loss responses but, rather, changes are associated with the age-related decrease in VO2max or 2) the decline in heat loss responses due to aging may be masked by repeated exercise training.

Adult↗
PubMed1991

Effect of work load on cutaneous vascular response to exercise.

The purpose of the present study was to examine whether intensity of exercise affects skin blood flow response to exercise. For this purpose, six healthy men cycled, in a random order on different days, for 15 min at 50, 60, 70, 80, and 90% of their maximum oxygen consumption (VO2max) at a room temperature of 25 degrees C. At the end of exercise, esophageal temperature (Tes) averaged 37.4 +/- 0.2, 37.7 +/- 0.2, 37.9 +/- 0.2, 38.6 +/- 0.3, and 38.9 +/- 0.4 degrees C (SE) at the 50, 60, 70, 80, and 90% work loads, respectively. At the two highest work loads, no steady state was observed in Tes. Skin blood flow was estimated by measuring forearm blood flow (FBF) with strain-gauge plethysmography and by laser-Doppler flowmetry on the upper back. Both techniques showed that skin blood flow response to rising Tes was markedly reduced at the 90% work load compared with other work loads. At the end of exercise, FBF averaged 7.5 +/- 1.7, 10.7 +/- 3.1, 9.6 +/- 2.1, 11.3 +/- 2.6, and 5.4 +/- 1.3 (SE) ml.min-1.100 ml-1 (P less than 0.01) at the 50, 60, 70, 80, and 90% VO2max work loads, respectively. The corresponding values for Tes threshold for cutaneous vasodilation (FBF) were 37.42 +/- 0.16, 37.48 +/- 0.13, 37.59 +/- 0.13, 37.79 +/- 0.19, and 38.20 +/- 0.22 degrees C (P less than 0.05) at 50, 60, 70, 80, and 90% VO2max, respectively. In two subjects, no cutaneous vasodilation was observed at the 90% work load.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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↗
PubMed1989

Cardiorespiratory strain during walking in snow with boots of different weights.

In order to assess the physiological strain of different boot weights, seven male and three female subjects walked on a treadmill and a snow-field while wearing three types of boots: winter jogging boots (WJB), rubber boots (RB), and rubber safety boots (RSB), weighing (means +/- s.d.) 0.9 +/- 0.1, 1.9 +/- 0.4 and 2.5 +/- 0.2 kg, respectively During each walk the subjects wore the same clothing ensembles and moved at the same, individually determined speed. The mean (+/- s.e.) depths of the footprint impression in the snow while walking in the WJB, RB, and RSB were 26.1 +/- 1.5, 25.6 +/- 1.4 and 26.1 +/- 1.5 cm (NS), respectively. During walking on the treadmill, the means for oxygen consumption were 0.79 +/- 0.05, 0.81 +/- 0.06 and 0.83 +/- 0.04 l min-1 (NS) and in snow 2.24 +/- 0.18, 2.34 +/- 0.17 and 2.34 +/- 0.19 l min-1 (p less than 0.01) with the WJB, RB and RSB, respectively. The mean oxygen consumption levels observed during the walks averaged 23% and 65% of the subject's maximum oxygen consumption on the treadmill and in the snow-field, respectively. During the walking tests the corresponding mean heart rates were 106 +/- 4, 93 +/- 5, and 95 +/- 5 beats min-1 (p less than 0.05) on the treadmill, and 151 +/- 11, 150 +/- 11 and 151 +/- 12 beats min-1 (NS) in snow. No significant differences in ratings of perceived exertion were observed between the walking tests in snow with the three types of boots. In accordance with earlier studies, walking in snow was found to be strenuous work. In conclusion, the use of the RSB is recommended during logging work in snow, since they are known to provide greater protection than lighter boots and the increase in physiological strain experienced with RSB in this study was not appreciably greater than that with boots of lighter weight.

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

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.

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↗
PubMed1985

Cardiorespiratory strain in jobs that require respiratory protection.

Twenty-one workers in the construction, foundry, shipyard, and metal industries, and nine firemen were studied in jobs that require the regular use of various industrial respirators. The subjects' heart rates (HR) were continuously recorded during 1 to 2 workshifts or during special tasks. Their oxygen consumption (VO2) and ventilation rates were measured during main work phases. The subjects' VO2max were determined by a submaximal bicycle-ergometer test. In construction and industrial jobs, when a filtering device or an air-line apparatus was worn, the subjects' mean HR-values ranged from 66 to 132 beats min-1, which is equivalent to a relative aerobic strain of 12 to 57% VO2max. In smog-diving and repair and rescue tasks with self-contained breathing apparatus and protective clothing, the corresponding mean values were 142 to 160 beats min-1 and 54-74% VO2, respectively. The field results were compared with those measured in the laboratory with the same type of respirator. The suitability of different respirators in practical work situations was then evaluated, as were the physical qualifications required of the wearer.

Adult↗