Dose-dependent acute and sustained renal effects of the endothelin receptor antagonist avosentan in healthy subjects.

The endothelin receptor antagonist avosentan may cause fluid overload at doses of 25 and 50 mg, but the actual mechanisms of this effect are unclear. We conducted a placebo-controlled study in 23 healthy subjects to assess the renal effects of avosentan and the dose dependency of these effects. Oral avosentan was administered once daily for 8 days at doses of 0.5, 1.5, 5, and 50 mg. The drug induced a dose-dependent median increase in body weight, most pronounced at 50 mg (0.8 kg on day 8). Avosentan did not affect renal hemodynamics or plasma electrolytes. A dose-dependent median reduction in the fractional renal excretion of sodium was found (up to 8.7% at avosentan 50 mg); this reduction was paralleled by a dose-related increase in proximal sodium reabsorption. It is suggested that avosentan dose-dependently induces sodium retention by the kidney, mainly through proximal tubular effects. The potential clinical benefits of avosentan should therefore be investigated at doses of

Effects of long-term whole-body cold exposures on plasma concentrations of ACTH, beta-endorphin, cortisol, catecholamines and cytokines in healthy females.

OBJECTIVE: Cold therapy is used to relieve pain and inflammatory symptoms. The present study was designed to determine the influence of long-term regular exposure to acute cold temperature. Two types of exposure were studied: winter swimming in ice-cold water and whole-body cryotherapy. The outcome was investigated on humoral factors that may account for pain alleviation related to the exposures. MATERIAL AND METHODS: During the course of 12 weeks, 3 times a week, a group of healthy females (n = 10) was exposed to winter swimming (water 0-2 degrees C) for 20 s and another group (n = 10) to whole-body cryotherapy (air -110 degrees C) for 2 min in a special chamber. Blood specimens were drawn in weeks 1, 2, 4, 8 and 12, on a day when no cold exposure occurred (control specimens) and on a day of cold exposures (cold specimens) before the exposures (0 min), and thereafter at 5 and 35 min. RESULTS: Plasma ACTH and cortisol in weeks 4-12 on time-points 35 min were significantly lower than in week 1, probably due to habituation, suggesting that neither winter swimming nor whole-body cryotherapy stimulated the pituitary-adrenal cortex axis. Plasma epinephrine was unchanged during both experiments, but norepinephrine showed significant 2-fold to 3-fold increases each time for 12 weeks after both cold exposures. Plasma IL-1-beta, IL-6 or TNF alpha did not show any changes after cold exposure. CONCLUSIONS: The main finding was the sustained cold-induced stimulation of norepinephrine, which was remarkably similar between exposures. The frequent increase in norepinephrine might have a role in pain alleviation in whole-body cryotherapy and winter swimming.

Lung function after acute and repeated exposures to extremely cold air (-110 degrees C) during whole-body cryotherapy.

Whole-body cryotherapy (WBC) is one mode of cold therapy, during which rheumatic patients are exposed to very cold air (-110 degrees C) in minimal clothing. It is also proposed to have a bronchodilatory effect. The aim was to examine the effects of WBC on lung function in healthy humans after acute and repeated exposures. Twenty-five healthy, non-smoking subjects participated in the study. They were exposed to WBC for 2 min three times per week for 12 weeks. The peak expiratory flow rate (PEF) and forced expiratory volume in 1 s (FEV1) were measured before and after (at 2 and 30 min) the first WBC, and then similarly at 4, 8 and 12 weeks. At all time points, after 30 min of the WBC the PEF values were slightly lower compared with values before the WBC, and the reductions reached statistical significance at 1 month (5.1 +/- 1.2%), and at 3 months (3.2 +/- 1.7%). After 30 min of the first WBC, the FEV1 was significantly reduced by 2.3 +/- 0.8%, but no other changes were observed during the study. In conclusion, the WBC induced minor bronchoconstriction in healthy humans instead of proposed bronchodilatation. The WBC seems not to be harmful for lung function, but should be used with caution in susceptible individuals.

Acute and long-term effects of winter swimming and whole-body cryotherapy on plasma antioxidative capacity in healthy women.

The effects of severe cold stress on total peroxyl radical trapping antioxidant capacity of plasma (TRAP) were studied in two groups of healthy women: a whole-body cryotherapy group (WBC, n = 10) and a winter swimming group (WS, n = 10). The biovariability of TRAP values was also analysed. The WBC group was exposed to -110 degrees C for 2 min, whereas the exposure for the WS group lasted 20 s in ice-cold water. Sessions were organized three times per week for 12 weeks. Blood specimens were collected at 2, 4, 8 and 12 weeks at rest, 2 and 35 min after the cold exposures and at the corresponding times without cold exposure on a separate day. Conventional methods were used to determine TRAP values. The between-subject variation was 13.6% and the within-subject variation 6.4%. The index of individuality was 0.46, and the index of heterogeneity was 0.079. These results indicate a marked heterogeneity among subjects. During the first 4 weeks, the mean TRAP value significantly increased at 2 min after cold exposure in the WBC group, returning to baseline 35 min after the exposure. Similar changes were observed in the WS group. However, all changes due to cold were relatively mild (<5%). After 4 weeks no changes in TRAP values after the cold exposures were noticed and no long-term changes in basal TRAP values were observed. In the main, regular WBC and WS do not seem to be harmful as far as plasma antioxidative capacity is concerned.

Effect of cold exposure on older humans.

Epidemiological studies have shown excess winter mortality particularly in older age groups. A question is how much these statistics are affected by age-related physiological changes in cold thermoregulation and how much due to other factors related to aging. In experimental studies concerning age and cold stress both whole-body and local exposures have been used mostly in resting subjects with minimal clothing. Older persons, particularly men over ca. 60 years, are less able to maintain core temperature during a given cold challenge compared to younger individuals. Older persons have a reduced cutaneous thermal sensitivity, and a reduced subjective thermal perception during cooling. Thus, older people may require a more intense stimulus to perform protective actions against cold stress. Older persons' skin vasoconstrictive response to cold is diminished compared to younger persons, which seems partly related to a reduced skin vasomotor sensitivity to sympathoneuronal stimuli. The cold-induced rise in metabolic rate is attenuated in older persons, but the mechanism is unknown. Both central and peripheral components seem to be involved in the age-related changes in regulatory effector functions. Enhanced aerobic fitness may not give added protection against core cooling during cold stress in the elderly, but seems to attenuate older subjects' heightened blood pressure response to cold. Bronchial responsiveness to face cooling may increase with age. Further studies are needed to examine the age-related changes in non-thermoregulatory responses to cold (e. g. hemodynamics, cardiac function, respiration, autonomic nervous function), and the modifying effects of acute exercise and physical training.

Work ability, physical activity, and cardiorespiratory fitness: 2-year results from Project Active.

An adequate level of physical activity may maintain or promote work ability in aging workers. Project Active is a randomized trial comparing a Lifestyle physical activity program with a Structured exercise program in sedentary but healthy adults aged 35 to 60 years. Subjects in both groups received 6 months of intensive intervention followed by 18 months of active follow-up. The total number of subjects was 235, from which 80 subjects participated in the work ability assessment. Primary outcome measures were energy expenditure (kcal.kg-1.day-1), cardiorespiratory fitness (peak oxygen uptake in ml.min-1.kg-1), and the Work Ability Index. At 6 months, daily energy expenditure had increased significantly over baseline (mean +/- SD, from 33.0 +/- 0.9 to 34.4 +/- 1.8 kcal.kg-1.day-1) and was maintained over baseline at 24 months (34.0 +/- 2.5 kcal.kg-1.day-1). The significant increase in energy expenditure was observed particularly in moderate levels of activity. The average percentage of body fat was significantly higher at baseline compared with 6 months and 24 months. Peak oxygen uptake increased from baseline significantly during the first 6 months (from 29.6 +/- 5.7 to 30.6 +/- 6.3 ml.min-1.kg-1) and decreased to the baseline level (29.1 +/- 5.5 ml.min-1.kg-1) at 24 months. At baseline, the average Work Ability Index was 44.2 +/- 4.0, and it remained unchanged at 6 months (44.4 +/- 3.9) and at 24 months (44.2 +/- 3.1). In conclusion, a 2-year physical activity intervention increased daily energy expenditure, reduced body fat, and maintained peak oxygen uptake in healthy, middle-aged, sedentary subjects. The average Work Ability Index score at baseline was excellent and did not change during the 2-year physical activity interventions.

Cardiorespiratory responses to fatiguing dynamic and isometric hand-grip exercise.

In occupational work, continuous repetitive and isometric actions performed with the upper extremity primarily cause local muscle strain and musculoskeletal disorders. They may also have some adverse effects on the cardiorespiratory system, particularly, through the elevation of blood pressure. The aim of the present study was to compare peak cardiorespiratory responses to fatiguing dynamic and isometric hand-grip exercise. The subjects were 21 untrained healthy men aged 24-45 years. The dynamic hand-grip exercise (DHGE) was performed using the left hand-grip muscles at the 57 (SD 4)% level of each individual's maximal voluntary contraction (MVC) with a frequency of 51 (SD 4) grips x min(-1). The isometric hand-grip exercise (IHGE) was done using the right hand at 46 (SD 3)% of the MVC. The endurance time, ventilatory gas exchange, heart rate (HR) and blood pressure were measured during both kinds of exercise. The mean endurance times for DHGE and IHGE were different, 170 (SD 62) and 99 (SD 27) s, respectively (P < 0.001). During DHGE the mean peak values of the breathing frequency [20 (SD 6) breaths x min(-1)] and tidal volume [0.89 (SD 0.34) l] differed significantly (P < 0.01) from peak values obtained during IHGE [15 (SD 5) breaths x min(-1) and 1.14 (SD 0.32) l, respectively]. The corresponding peak oxygen consumptions, pulmonary ventilations, HR and systolic blood pressures did not differ, and were 0.51 (SD 0.06) and 0.46 (SD 0.11) l x min(-1), 17.1 (SD 3.0) and 16.7 (SD 4.7) l x min(-1), 103 (SD 18) and 102 (SD 17) beats x min(-1), and 156 (SD 17) and 161 (SD 17) mmHg, respectively. The endurance times of both DHGE and IHGE were short (< 240 s). The results indicate that the peak responses for the ventilatory gas exchange, HR and blood pressure were similar during fatiguing DHGE and IHGE, whereas the breathing patterns differed significantly between the two types of exercise. The present findings emphasize the importance of following ergonomic design principles in occupational settings which aim to reduce the output of force, particularly in tasks requiring isometric and/or one-sided repetitive muscle actions.

Physical activity, fitness and body composition of Finnish police officers: a 15-year follow-up study.

This study evaluated changes in the physical activity, fitness and body composition of 103 police officers during a 15-year follow-up. The absolute aerobic capacity was similar in 1981 and 1996, muscular performance had declined, and body weight had increased approximately 0.5 kg/year. More than half the subjects (53%) had increased their leisure-time physical activity in 1996. The correlation was significant between physical activity in 1981 and physical fitness in 1996, but weak between physical activity in 1996 and fitness in 1996. It was also significant between waist circumference and waist/hip ratio in 1996 and physical activity during the previous 5 and 15 years. No significant correlations were found between physical activity and work ability or perceived physical or mental job stress. The physical fitness of middle-aged police officers seems to be predicted strongly by physical activity in early adulthood. Therefore health and fitness promotion measures should start at that time. This, together with regular systematic training, should help to sustain work ability of middle-aged police officers.

Physiological strain during kitchen work in relation to maximal and task-specific peak values.

Six female and three male subjects from a hospital kitchen volunteered for the study. The subjects were working on a conveyor belt collecting and sorting dirty plates, glasses and cutlery for cleaning. In the study, a medical examination, a maximal clinical exercise test with a 12-lead electrocardiogram (ECG) and a maximal arm cranking test were performed in the laboratory. Further, each subject was studied for 30 min during a normal work shift in the kitchen. Oxygen uptake (VO2) and heart rate (HR) were continuously registered. During the work period, a rating of perceived exertion (RPE) was asked at the 5th, 15th and 30th minute. Physiological responses were measured by a portable system (K4) both in the laboratory and in the field. VO2 and HR measured in the field were proportioned to corresponding maximal values during cycling and to peak values during arm-cranking. The mean VO2 for the male and the female subjects during kitchen work was 0.65 +/- 0.16 l min-1. This corresponded to 24% of VO2max and to 41% of VO2peak during arm-cranking. The difference was significant (p < 0.001). Owing to a magnetic field at the conveyor belt, reliable HR values were obtained only from the female subjects. The mean HR during work among the female subjects was 101 beats min-1. It corresponded to 55% of HRmax and 67% of HRpeak during arm-cranking (p < 0.05). The present study shows that the relative work intensity is markedly higher when it is expressed relative to the corresponding muscle group's VO2peak instead of the VO2max. Similar difference was also seen in the HR response. More task-specific testing of physical capacity may provide improved evaluation of physical strain in a job.

Heart rate and blood pressure responses to isometric exercise in young and older men.

The aim of this study was to examine the isometric endurance response and the heart rate and blood pressure responses to isometric exercise in two muscle groups in ten young (age 23-29 years) and seven older (age 54-59 years) physically active men with similar estimated forearm and thigh muscle masses. Isometric contractions were held until fatigue using the finger flexor muscles (handgrip) and with the quadriceps muscle (one-legged knee extension) at 20%, 40%, and 60% of the maximal voluntary contraction (MVC). Heart rate and arterial pressure were related to the the individual's contraction times. The isometric endurance response was longer with handgrip than with one-legged knee extension, but no significant difference was observed between the age groups. The isometric endurance response averaged 542 (SEM 57), 153 (SEM 14), and 59 (SEM 5) s for the handgrip, and 276 (SEM 35), 94 (SEM 10) and 48 (SEM 5) s for the knee extension at the three MVC levels, respectively. Heart rate and blood pressure became higher during one-legged knee extension than during handgrip, and with increasing level of contraction. The older subjects had a lower heart rate and a higher blood pressure response than their younger counterparts, and the differences were more apparent at a higher force level. The results would indicate that increasing age is associated with an altered heart rate and blood pressure response to isometric exercise although it does not affect isometric endurance.

Prediction of acceptable physical work loads based on responses to prolonged arm and leg exercise.

Nine healthy men (aged 54-59 years) performed arm crank and leg cycle exercises for 30 min at relative work loads of 50 and 75% of peak oxygen uptake (VO2) for the corresponding muscle group, and for 60 min at a relative work load of 30% of peak VO2 for the corresponding muscle group. In the tests, heart rate (HR), blood pressure, gas exchange variables, rating of perceived exertion (RPE) and blood lactate were measured. At the 75% target exercise level, four subjects interrupted the arm-cranking test, and one subject interrupted the leg-cycle test. Owing to differences in peak values during arm-cranking and leg-cycling, the work load and the VO2 were higher during leg-cycling than during arm-cranking. There was no difference in HR between the work modes, but the HR increased to a greater extent during arm-cranking compared to leg-cycling at the 30% (NS) and 50% (P < 0.05) exercise levels. Similarly, the RPE increased more during arm-cranking compared to leg-cycling at each exercise level. The blood lactate concentration was higher after arm-cranking than after leg-cycling; at the 50% exercise level the difference was statistically significant. The results indicate a higher physiological strain with time during arm exercise than during leg exercise at the same muscle group-specific relative work load. The acceptable physical work load, expressed as the percentage peak VO2 for the corresponding muscle group, should thus be lower during arm exercise than during leg exercise. The RPE and the relative HR, expressed as percentage of peak HR for the corresponding muscle group, however, seem to be comparable indicators for the physiological strain during arm and leg exercise.

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.

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.

Energy expenditure and clearing snow: a comparison of shovel and snow pusher.

In order to assess the energy demands of manual clearing of snow, nine men did snow clearing work for 15 min with a shovel and a snow pusher. The depth of the snowcover was 400-600 mm representing a very heavy snowfall. Heart rate (HR), oxygen consumption (VO2), pulmonary ventilation (VE), respiratory exchange ratio (R), and rating of perceived exertion (RPE) were determined during the work tasks. HR, VE, R, and RPE were not significantly different between the shovel and snow pusher. HR averaged (+/- SD) 141 +/- 20 b min-1 with the shovel, and 142 +/- 19 beats.min-1 with the snow pusher. VO2 was 2.1 +/- 0.41.min-1 (63 +/- 12%VO2 max) in shovelling and 2.6 +/- 0.51.min-1 (75 +/- 14%VO2max) in snow pushing (p < 0.001). In conclusion manual clearing of snow in conditions representing heavy snowfalls was found to be strenuous physical work, not suitable for persons with cardiac risk factors, but which may serve as a mode of physical training in healthy adults.

Response to rest and exercise in the cold: effects of age and aerobic fitness.

The aim of this study was to determine whether age-related differences in the response to cold exposure are due to aging per se or are caused by a reduced maximal oxygen uptake (VO2max) often observed with aging. Three groups of men, 8 young adults (YA), 8 well-trained seniors (TS), and 11 untrained seniors (US), were tested on a cycle ergometer in thermoneutral (22 degrees C) and cold (5 degrees C) conditions during rest and then during exercise (approximately 50 W). In the thermoneutral conditions, 10 min of rest were followed by 10 min of exercise. After 60 min of rest, subjects entered the cold where 30 min of rest were followed by 30 min exercise. The subjects of the three groups had similar body surface area and subcutaneous fat thickness. It was found that rectal temperature (Tre) decreased during rest in the cold and continued to decrease at a higher rate during exercise in TS and US but not in YA. The mean skin temperature was similar in all the groups, except for the thigh temperature, which was lower in YA than in TS and US. Oxygen uptake (VO2) increased during cold, significantly more so at rest than during exercise. YA displayed the highest VO2 during the first 10 min of rest in the cold, whereas TS displayed the highest VO2 during exercise in the cold. Neither aging nor VO2max appeared to affect thermal comfort or cold sensation.(ABSTRACT TRUNCATED AT 250 WORDS)

Capacity for vasodilatation in the forearms of manual and office workers.

The aim of the present study was to investigate whether occupational physical work using the arms would have a local training effect on the capacity for vasodilatation in the forearm. The subjects were 13 installation workers, and 13 office workers, who were similar in age, height, and body mass. The installation workers were exposed to heavy manual tasks during most of their workshift, whereas the office workers did no heavy manual exercise. The index of forearm capacity for vasodilatation was the plethysmograph flow response after 10 min of arterial occlusion (240 mmHg, 32 kPa). Systolic and diastolic blood pressure, and skin red cell flux (laser-Doppler) were determined together with the blood flow. In both groups, the dominant arm had significantly higher circumference and volume compared to the nondominant arm, whereas handgrip strength was similar for both the arms. The manual workers had greater volumes in both arms in comparison to the office workers, but handgrip strength did not differ between groups. In both groups, the peak forearm vascular conductance was higher in the dominant arm compared to the nondominant arm. In both forearms, the manual workers exhibited significantly higher peak blood flow, and peak vascular conductance than the office workers. No significant difference in skin blood flow was seen between the groups or arms. In conclusion, the forearms of the manual workers had a greater capacity for vasodilatation compared to the office workers suggesting a local vascular training effect due to frequent exposure to heavy physical work using hands.

Physiological responses of firefighting students during simulated smoke-diving in the heat.

While wearing a self-contained breathing apparatus and fire-protective clothing, 35 healthy firefighting students aged 19-27 years performed smoke-diving (entry into a smoke-filled room) during a simulated shipboard fire. The mean (+/- SD) ambient temperature inside the simulator was 119 +/- 12 degrees C, and the task lasted 17 +/- 4 min. All subjects were fit according to their maximal oxygen consumption, which was 52.4 +/- 5.2 mL/min/kg (4.08 +/- 0.45 l/min). During the smoke-diving the average heart rate was 150 +/- 13 beats/min (79 +/- 6% of maximal heart rate attained in a cycle-ergometer test), and the peak heart rate was 180 +/- 13 beats/min (95 +/- 6% of maximal heart rate). The estimated oxygen consumption was 2.4 +/- 0.5 L/min (60 +/- 12% of maximal oxygen consumption). Neither ability to tolerate stress (as determined by the instructors) nor previous experience in smoke-diving tasks seemed to influence the heart rate or estimated oxygen consumption during experiment. Smoke-diving was physically very demanding even for the young and fit subjects, showing the importance of regular evaluation of the health and physical fitness of every firefighter who has to carry out smoke-diving tasks.

Circadian variation in peripheral blood flow in relation to core temperature at rest.

The aim of the present study was to examine the circadian variation in skin blood flow and its relationship to the rhythm of rectal temperature. Eight young men were confined to continuous bed rest for 24 h in a thermoneutral environment. Rectal temperature, oxygen consumption, and peripheral blood flow (laser-Doppler flowmetry and plethysmography) were measured at intervals of 2 h, except at 2400 hours and 0600 hours. According to the cosinor-method, the mean rectal temperature displayed a statistically significant circadian variation with a minimum at 0400 hours. A significant circadian rhythm was also observed in total finger blood flow, finger laser-Doppler flow, and forearm laser-Doppler flow, but not in total forearm blood flow and forehead laser-Doppler flow. The rhythms of rectal temperature and extremity skin blood flow were phased differently, i.e. the decrease in rectal temperature was preceded by an increase in extremity skin blood flow with an average of 4-h time difference. The results would support the idea that circadian rhythm of core temperature is, at least in part, regulated by variation in extremity skin blood flow.

Responses to whole body and finger cooling before and after an Antarctic expedition.

Eight subjects, who were indoor workers and not habitually exposed to cold, spent 53 days in Antarctica. They did mainly geological field work often requiring the use of bare hands. The effects of the expedition on responses to a whole body cold exposure test, a finger blood flow test and a cold pressor test were studied. After the expedition, during whole-body cooling the time for the onset of shivering was delayed by 36 min (P < 0.001) and forearm and thigh temperatures were 1.5 degrees C higher (P < 0.05) at the end of exposure. During local cooling of the finger with 10 degrees C perfusion, finger vascular resistance was 14.9 (SEM 6.6) mmHg.ml-1.min.100 ml (P < 0.05) lower and finger temperature 3.9 (SEM 0.8) degrees C higher (P < 0.01). However, the decrease in rectal temperature during whole-body cooling was unaltered and the response to a cold pressor test was unchanged. The data would indicate that partial acclimatization to cold had been developed. Changes in forearm temperature were correlated with the duration of cold exposure of the hands (P < 0.05) and finger vascular resistance and finger temperature were correlated with responses to cooling before the expedition (P < 0.001 and P < 0.01, respectively). Because the ambient temperature was not clearly lower in Antarctica in comparison to Finland, the reason for the changes developed seems to be the increased exposure to the outdoor climate in Antarctica.

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.