Biomedical subjects

S Rissanen

Publications and source records attributed to S Rissanen.

At least 19 recordsLinked to original sources

PubMed2006

Temperature limit values for touching cold surfaces with the fingertip.

OBJECTIVES: At the request of the European Commission and in the framework of the European Machinery Directive, research was performed in five different laboratories to develop specifications for surface temperature limit values for the short-term accidental touching of the fingertip with cold surfaces. METHODS: Data were collected in four laboratories with a total of 20 males and 20 females performing a grand total of 1655 exposures. Each touched polished blocks of aluminium, stainless steel, nylon-6 and wood using the distal phalanx of the index finger with a contact force of 1.0, 2.9 and 9.8 N, at surface temperatures from +2 to -40 degrees C for a maximum duration of 120 s. Conditions were selected in order to elicit varying rates of skin cooling upon contact. Contact temperature (TC) of the fingertip was measured over time using a T-type thermocouple. RESULTS: A database obtained from the experiments was collated and analysed to characterize fingertip contact cooling across a range of materials and surface temperatures. The database was subsequently used to develop a predictive model to describe the contact duration required for skin contact temperature to reach the physiological criteria of onset of pain (15 degrees C), onset of numbness (7 degrees C) and onset of frostbite risk (0 degrees C). CONCLUSIONS: The data reflect the strong link between the risk of skin damage and the thermal properties of the material touched. For aluminium and steel, skin temperatures of 0 degrees C occurs within 2-6 s at surface temperatures of -15 degrees C. For non-metallic surfaces, onset of numbness occurs within 15-65 s of contact at -35 degrees C and onset of cold pain occurs within 5 s of contact at -20 degrees C. The predictive model subsequently developed was a non-linear exponential expression also reflecting the effects of material thermal properties and initial temperature. This model provides information for the protection of workers against the risk of cold injury by establishing the temperature limits of cold touchable surfaces for a broad range of materials, and it is now proposed as guidance values in a new international standard.

Adolescent↗

PubMed2003

Dementia with Lewy bodies according to the consensus criteria in a general population aged 75 years or older.

OBJECTIVE: To estimate the prevalence of dementia with Lewy bodies (DLB) according to the consensus criteria in a general population aged 75 years or older. METHODS: The "Kuopio 75+ study" is a population based health survey focused on the clinical epidemiology of dementia and functional capacity among elderly subjects aged 75 years or older. On 1 January 1998, a random sample of 700 subjects was drawn from a total population born before 1 January 1923, living in the city of Kuopio, northeast Finland (n = 4518). The study subjects underwent a structured interview and clinical examination. RESULTS: 601 elderly subjects (86% of the random sample) were examined. A dementia disorder was diagnosed in 137-a prevalence of 22.8% (95% confidence interval 19.4% to 26.2%). The prevalence of DLB was 5.0% (3.2% to 6.7%), comprising 22% of all demented subjects. Probable DLB was diagnosed in 20 subjects (3.3% (1.9% to 4.8%)), and possible DLB in 10 (1.7% (0.6% to 2.7%)). The prevalence of Alzheimer's disease was 10.6% (47% of all demented subjects), of vascular dementia, 5.3% (23%), and of other types of dementing disorders, 1.8% (8%). CONCLUSIONS: In a general population aged 75 years and older, the prevalence of a disorder fulfilling the diagnostic criteria of DLB is half that of Alzheimer's disease and the same as for vascular dementia.

Aged↗

PubMed2002

Temperature limit values for gripping cold surfaces.

OBJECTIVES: At the request of the European Commission and in the framework of the European Machinery Directive, research was conducted jointly in five different laboratories to develop specifications for surface temperature limit values for the gripping and handling of cold items. METHODS: Four hundred and fourteen experiments were run where male and female subjects were invited to grip for up to 20 min cold bars of different contact coefficients, i.e. polished wood, nylon, stone, steel and aluminium. The air temperature and the bars' initial surface temperatures ranged between 0 and -30 degrees C for the various experiments. While gripping the bars, either only the hand or the whole body was exposed to cold. RESULTS: The data were used to develop a prediction formula and a graph of the surface temperature limit values in order for the skin contact temperature not to reach <15 degrees C. This duration is shown to offer a significant degree of safety with respect to the minimal surface temperature spontaneously tolerated by the subjects. CONCLUSIONS: Experiments and modelling must be pursued to extend these data to other conditions of exposure.

Adult↗

PubMed2002

Simulated parachute descent in the cold: thermal responses and manual performance.

BACKGROUND: Ejection from a fighter aircraft can expose the pilot to extreme cold and windy conditions. Knowledge of the effects of such conditions on thermal responses and performance of the pilot is scarce. HYPOTHESIS: It is expected that the temperature of bare skin and fingers may decrease to the level where health and/or performance are hampered. METHODS: Seven fighter pilots performed a simulated parachute descent (SPD) at ambient temperature (Ta) of -35 degrees C and wind velocity of 10 m x s(-1). The 8-min SPD was followed by a 60-min cold exposure (CE) at Ta of -20 degrees C. Flight garments with or without immersion suit were used. During SPD the subjects performed basic survival tasks. Rectal and skin temperatures were measured and manual performance was tested. RESULTS: Thermal responses did not significantly differ between the clothing ensembles. Mean skin temperature was 28 degrees C and 27 degrees C at the end of SPD and CE, respectively. The cheek temperature was 9 degrees C (range 3.2-13.8 degrees C) at the end of SPD. Finger skin temperature was 7 degrees C and 9 degrees C at the end of SPD and CE, respectively. The subjects could perform the defined tasks during SPD while manual performance was slightly impaired during CE. CONCLUSIONS: Subjects could tolerate the 8-min SPD and the following CE in the studied conditions without a loss of vital performance in basic survival actions. However, the risk of frostbite on the uncovered skin area as well as numbness of the fingers may jeopardize pilots' health and performance during parachuting.

Adaptation, Physiological↗

PubMed2001

Effects of whole body cooling on sensory perception and manual performance in subjects with Raynaud's phenomenon.

Patients with Raynaud's phenomenon (RP) have abnormal digital vasoconstriction in response to cold. The aim of the study was to investigate the effects of cooling on sensory perception and manual performance in healthy male subjects and subjects with RP. There were two groups of subjects with primary RP: 12 subjects fulfilled the criteria of Lewis (L) and the other 12 the more critical criteria of Maricq (M). Control group (C) consisted of 19 healthy men. Subjects were exposed to 5 degrees C for 60 min. Skin temperatures were measured. Finger dexterity, pinch strength, abduction/adduction of fingers, pressure perception threshold and vibration perception threshold were tested during the exposure every 15 min. At the beginning of the exposure the mean (S.E.) finger temperature was 2.5 (1.2) degrees C (P<0.05) lower in M than in C. Manual performance and sensory perception were impaired due to the cooling, the impairment being significantly greater in M than in C. Responses of L were between those of M and C. In a given finger temperature vibration and pressure sensibility and manual performance were lower in M and L than in C. In conclusion, cold exposure decreased sensory perception and manual performance in the subjects with RP to a lower level than in the healthy subjects. Non-thermal factors may also decrease performance in RP.

Adult↗

PubMed2000

Prediction of duration limited exposure for participants wearing chemical protective clothing in the cold.

The suitability of the IREQ (insulation required) index for predicting the thermal responses of 6 participants wearing chemical protective clothing was tested during exercise at -20 and -25 degrees C. IREQ was used to calculate duration limited exposure (DLE). Measured DLE correlated (r =0.899, p <0.001) with the predicted DLE. In exposures exceeding 40 min, however, the predicted DLE tended to be 10-20 min too short compared to the measured one. During short exposures the prediction was 5-20 min too long. The results show that IREQ overestimated the cold strain in participants wearing chemical protective clothing during cold exposures longer than 40 min. Nevertheless, predicted DLE never exceeded measured times and thus the prediction was always safe from the occupational point of view.

Adult↗

PubMed2000

Stretch- and H-reflexes of the lower leg during whole body cooling and local warming.

BACKGROUND: This study was undertaken to evaluate if possible changes in stretch- and H-reflexes could be related to the changes in the EMG activity of the cooled lower leg muscles observed during a stretch-shortening cycle exercise. METHODS: Eight subjects wearing shorts and jogging shoes were exposed once to 27 degrees C and twice to 10 degrees C for 60 min each. During the second exposure to 10 degrees C, the subject's lower legs were kept warm (10 degrees Clw) with electrical pillows. After the exposures Achilles tendon reflex (stretch reflex) was induced and the EMG activity of the triceps surae was measured. Immediately after reflex measurements the EMG activity of the triceps surae and tibialis anterior during a drop-jump (stretch-shortening cycle) was measured. After similar thermal exposures electrically induced H-reflex from the calf was measured. RESULTS: During the preactivity and stretch phases the EMG activity of the triceps surae increased after the exposure to 10 degrees C, whereas during the shortening phase it decreased. During the shortening phase cooling, on the contrary, increased the activity of tibialis surae anterior. These changes disappeared at 10 degrees Clw. At 10 degrees C the maximum EMG-amplitude of triceps surae during stretch reflex decreased (p<0.05), reflecting suppressed muscle spindle activity. Suppressed spindle activity causes the agonist to be unfacilitated and the antagonist muscle contraction to be uninhibited, which was seen in the present study as decreased agonist and increased antagonist EMG activity during the shortening phase at 10 degrees C. The Hmax/Mmax-ratio, H-reflex latency and amplitude increased at 10 degrees C (p<0.05), reflecting increased motoneuron pool excitability. This in part may explain the increased EMG activity during the preactivity and stretch phases. CONCLUSION: Cooling-induced increase in the excitability of the motoneuron pool and suppression of muscle spindle activity seem to be responsible of the EMG activity changes during the stretch-shortening cycle, consequently decreasing muscular performance.

Adult↗

PubMed1999

Muscle fatigue caused by repeated aerial combat maneuvering exercises.

BACKGROUND: Little is known about the development of in-flight muscular fatigue during repeated flights. HYPOTHESIS: This study was conducted to evaluate muscular fatigue in different upper body and neck muscles during repeated aerial combat maneuvering exercises. METHODS: Six pilots volunteered as test subjects. They performed one-to-one dog fight exercise three times (1 pilot, four times) in one day. During the flights, the pilots' electromyographic activity (EMG) was measured from the abdomen, back, neck and lateral neck. The mean muscular strain for each muscle was calculated. Before the first flight and after each flight, the maximal isometric strength of each muscle was measured. RESULTS: The results showed that maximal isometric strength between the first and last measurement decreased in the back, neck (p < 0.05) and lateral neck muscles. While the G-stress remained the same, the muscular strain during exercises increased in every muscle, but was significant only in neck and lateral neck (p < 0.05-0.01). Due to these changes, the fatigue index in the neck and lateral neck muscles was 2.0-2.1, and 1.3-1.4 (1.0 = no fatigue) in the abdomen and back muscles. CONCLUSIONS: Repeated aerial combat maneuvering exercises caused fatigue in every muscle studied. The fatigue was greater in the neck area, which may increase the risk for neck injuries, and may reduce mission effectiveness. The fighter pilots' muscular strength and endurance in the neck area are subjected to very high demands, especially if exercises are repeated several times. The recovery of the neck muscles from fatigue after repetitive exercises should receive special attention.

Abdominal Muscles↗

PubMed1998

Effects of repeated exercise/rest sessions at -10 degrees C on skin and rectal temperatures in men wearing chemical protective clothing.

The development of thermophysiological responses during four consecutive exercise/rest sessions in the cold was studied in men wearing chemical protective clothing and a face mask. Six men repeated four exercise/rest sessions during 8 h at -10 degrees C. Each session consisted of step exercise (240 W x m(-2)) for 60 min and rest for another 60 min. Rectal and skin temperatures were measured continuously and thermal sensations were obtained at 30-min intervals. Entering the cold from a warm environment and the onset of exercise resulted in a decrease in skin temperatures during the first session and the decrement in the temperatures of the extremities continued for 10-20 min during the following period of exercise. Torso skin temperature was at its lowest during the first rest period. After the first session of cold exposure the range and the level of variation in mean body temperature (Tb) followed a pattern which was repeated until the end of the experiment. However, the torso skin temperatures increased gradually until the fourth session, while the temperatures of the extremities, in contrast, tended to decrease up to the third session. In conclusion, the present results indicated that although Tb, reflecting the whole body heat balance, showed a typical pattern of change after the first session (2 h), the torso area was warming until the end of the cold exposure while the extremities continued to cool down up to the third session (6 h), obviously due to a prolonged redistribution of the circulation.

Adult↗

PubMed1998

Manual performance in cold conditions while wearing NBC clothing.

Manual performance while wearing a whole body covering NBC garment was studied at -10 degrees C. Hands were protected by thin cotton gloves, which were covered with rubber gloves. The test subjects were exposed for 40 min in one of the four conditions: standing at -10 degrees C, standing for 10 min followed by walking (5 km/h) for 30 min on a treadmill, standing while holding a solid steel bar (see section 2.2), or standing at 20 degrees C. Six different manual tasks were performed after each 40-min exposure. All tests were also performed with bare hands at 20 degrees C. Moreover, the effect of contact cooling on skin temperatures and rewarming thereafter was examined by means of gripping a steel bar (-10 degrees C) during cold exposure. During exposure to -10 degrees C conditions finger skin temperature rapidly decreased to 10.7 +/- 2.2 degrees C (mean +/- SD). Improvement of body heat balance by exercise increased finger temperatures to 19.6 +/- 9.0 degrees C. Hand temperature remained at a higher level both during rest and exercise at -10 degrees C (20.1 +/- 1.7 and 20.6 +/- 6.1 degrees C, respectively). Cold exposure deteriorated manual performance and especially those functions that are related to finger dexterity. Finger skin temperature had high correlation with screwing, peg-board and magazine loading tests (r = -0.90, r = -0.77 and r = -0.72, respectively, p < 0.01) but no relation was found with hand grip strength (r = -0.03). Manual performance was impaired in every test both by gloves and cooling. Contact cooling decreased skin temperatures on the palm side of the hand and fingers around twice as effectively in normothermic subjects and 3.9-6.5 times more effectively in cooled subjects in comparison to cooling by cold air alone. Contact cooling had no significant effect on skin temperatures on the dorsal side of the fingers. The rewarming rate after the release of the steel bar was clearly higher in the dominant hand in comparison to the non-dominant hand. In conclusion, the present results show that the thermal insulation of rubber gloves was clearly insufficient, allowing unacceptably low finger temperatures during work in the cold. However, only those tasks requiring finger dexterity were clearly adversely affected. Heat production by physical exercise was able to increase finger skin temperature and to partly restore manual performance. Handling of cold tools is especially harmful for the palm side temperature of the non-dominant hand.

Acclimatization↗

PubMed1997

Muscle performance and electromyogram activity of the lower leg muscles with different levels of cold exposure.

The purpose of this study was to evaluate the relationship between different levels of body cooling and muscle performance decrement and to study the motor co-ordination of the working agonist-antagonist muscle pair of the lower leg. Eight volunteer male subjects dropped from a 40-cm bench on to a force plate and performed a maximal rebound jump (stretch-shortening cycle). The jumps were performed after 60-min exposures to 27 degrees C, 20 degrees C, 15 degrees C and 10 degrees C. In comparison to those at 27 degrees C, all the exposures to lower temperatures decreased the flight time of the jump, average force production and take-off velocity in a dose-dependent manner. The changes in electromyogram (EMG) activity also behaved in a dose-dependent manner. During pre-activity and stretch phases the integrated EMG (iEMG) activity of the agonist muscle (triceps surae) increased due to cooling (at 10 degrees C, P < 0.05). In contrast, during the shortening phase iEMG of the agonist muscle decreased due to cooling (at 15 degrees C and 10 degrees C, P < 0.05). Moreover, the activity of the antagonist muscle (tibialis anterior) increased due to cooling (at 15 degrees C and 10 degrees C, P < 0.01). The mean power frequency of the agonist muscle during the shortening phase was shifted from 124 (SEM 12) Hz (at 27 degrees C) to 82 (SEM 7) Hz (at 10 degrees C, P < 0.01). We concluded that there was a dose-dependent response between the degree of cooling and the amount of decrease in muscle performance as well as EMG activity changes. A relatively low level of cooling was sufficient to decrease muscle performance significantly.

Adult↗

PubMed1997

Thermal responses and physiological strain in men wearing impermeable and semipermeable protective clothing in the cold.

The purpose of the present study was to examine the effects of long term cold exposure on thermal responses and physical performance in men while wearing nuclear, biological and chemical (NBC) protective clothing. Six healthy men performed 60 min work/60 min rest cycles during 8 hours at an ambient temperature of -10 degrees C. Work was performed by stepping on a 20 cm high bench 15 times.min-1. Subjects were tested while wearing two different types of NBC clothing: impermeable rubber suit (IP) or semipermeable charcoal impregnated suit (SP) with cold weather underwear layers, as well as rubber gloves, boots and a full-face mask. During the tests oxygen consumption (VO2), rectal (Tre) and skin temperatures and sweat production were measured. Rectal and skin temperatures and body heat content followed the work/rest cycles in both types of NBC clothing. T(re) averaged 37.1 +/- 0.04 and 37.3 +/- 0.1 degrees C for IP and SP (NS), respectively. On average, mean skin temperature (Tsk) was 28.6 +/- 0.2 and 29.7 +/- 0.2 degrees C for IP and SP (p < 0.01), respectively. Finger skin temperature decreased rapidly to below 10 degrees C in both ensembles during the rest periods. During work the finger rewarming rate was 0.49 +/- 0.06 and 0.70 +/- 0.02 degree C.min-1 for IP and SP (p < 0.01), respectively. Decrease in body heat storage (S) during cold exposure was smaller in SP than in IP and S was restored to the level of -0.6 +/- 0.3 and -3.0 +/- 0.6 kJ.kg-1 in SP and IP (p < 0.01), respectively, during the work. Work load, according to VO2 measurements, was 1.5 +/- 0.1 and 1.3 +/- 0.11.min-1 for IP and SP (p < 0.05), respectively. Furthermore, during rest VO2 was 30% (p < 0.001) higher in IP than in SP. In conclusion, both types of NBC protective clothing could be used for long periods in cold conditions at a moderate work load without marked whole body heat debt or heat load. However, peripheral parts of the body experienced a rapid and severe cooling during the rest periods. The semipermeable suit enabled higher body heat storage and faster rewarming of extremities during work than the impermeable suit.

Acclimatization↗

PubMed1996

Effects of leg covering in humans on muscle activity and thermal responses in a cool environment.

Thermal responses and muscle performance in humans were studied during rest and exercise in a cool environment with different clothing distributions over the legs. Nine female subjects were exposed to 5 degrees C wearing shorts (SS), trousers with long legs (LL) or trousers with one long leg and one short leg (LS: LSc covered leg, LSu uncovered leg). The subjects also wore T-shirts and long-sleeved shirts. The subjects were seated for 60 min and after this they performed light stepping exercise for a further 60 min. Rectal temperature (T(re)) and skin temperature from seven (LL, SS) or nine sites (LS) were measured continuously. Surface electromyography (EMG) from three muscles (biceps femoris, gastrocnemius and tibialis anterior) were recorded during the exercise from six subjects. Integrated EMG (iEMG) and mean power frequency (MPF) were used to describe muscle activity. The T(re) was virtually unchanged during rest in every ensemble, whereas during exercise T(re) was significantly lower in SS than in LL. Mean skin temperature (T(sk)) decreased during rest in every ensemble, being significantly lower in SS than in LL. After the rest period local T(sk) of thigh and calf were significantly lower in SS than in LL and they were also lower in LSu than in LSc. At the beginning of the exercise the iEMG of the tibialis anterior muscle in SS and LL averaged 84 (SEM 7) and 64 (SEM 3) mu V (P <0.05), respectively. Respective values for LSu and LSc were 86 (SEM 9) and 66 (SEM 6) mu V (P <0.05). The MPF of the tibialis anterior muscle was significantly higher in LL 102 (SEM 5) Hz than in SS 90 (SEM 5) Hz (P <0.05) and similarly the MPF of the gastrocnemius muscle was also higher in LL 111 (SEM 5) Hz than in SS 100 (SEM 5) Hz (P < 0.05). It was concluded that exposing bare legs to a cool environment enhanced the motor unit activity in relation to covered legs. This would suggest that wearing shorts in a cool environment may, at the beginning of exercise, result in higher (about 25 percent) EMG activity and this may reflect increased muscle strain in comparison with wearing long trousers. Our results showing a unilateral increase in EMG activity during unilateral cooling suggest that the increase of strain is restricted to the uncovered part of the limb.

Adult↗

PubMed1996

Muscle strain during aerial combat maneuvering exercise.

BACKGROUND: Little is known about the in-flight muscular strain of fighter pilots. HYPOTHESIS: The purpose of this study was to measure fighter pilots' mean and peak muscular strain during aerial combat maneuvering exercises. The results obtained were compared against existing ergonomic recommendations. METHODS: Six pilots volunteered to serve as test subjects. Their mean age (+/- SD) was 28.5 +/- 5 yr, height 181 +/- 7 cm, and weight 75 +/- 10 kg. They performed one-to-one dog-fight exercises in the morning and in the afternoon. During the flights, the pilots' electromyographic activity (EMC) was measured from the thigh, abdomen, back, and lateral neck. The mean and peak muscular strain for each muscle was calculated as the percentage of maximal voluntary contraction (%MVC). RESULTS: The results showed that the mean muscular strain was 5.2-19.8% MVC, the strain in the lateral neck being the highest. Peak muscular strain (over 50% MVC) occurred almost only during the encounters and usually in the lateral neck. Other muscles were subjected to fewer peak strain episodes; most of these occurred in the back. At least one peak strain episode exceeding 100% MVC was recorded for every muscle studied. The highest peak strain 257% MVC, was measured in the lateral neck. This peak strain episode caused an injury to the lateral neck area, and the flight mission was discontinued. CONCLUSIONS: The mean muscular strain measured in this study was rather low. However, the strain occurring in the lateral neck and the back exceeds the ergonomic recommendations for static work. Especially in the lateral neck, and to some extent in the back, peak strain occurs frequently, in a magnitude that is well above the maximal voluntary contraction; in these areas, the peak strain presents a potential risk of injury and negative health effects. The level and frequent occurrence of peak strain episodes means that fighter pilots' muscular strength and muscular endurance, especially in the neck and shoulder area, are subjected to demands clearly higher than those of the average population.

Abdomen↗

PubMed1995

Cardiorespiratory strain of a five day jogging relay.

The heart rates of 14 voluntary subjects (seven male and seven females) participating in a 5 d jogging relay were recorded. The jogging speed was controlled at 3.0 m.s-1 on average. The heart rate measurements were related to cardiorespiratory responses obtained during VO2max test on a treadmill. The mean (s.d.) VO2max values were 53(2) and 48(2) ml.kg-1.min-1 and the anaerobic threshold was 42(1) and 38(2) ml.kg-1.min-1 for male and female subjects respectively. During the relay the mean(s.d) heart rate values of male and female subjects were 150(1), and 167(3) beats.min-1 (P < 0.001), corresponding to 68(1) and 76(2)% VO2max (P < 0.01) as calculated from the individual HR/VO2 regression equations. The jogging time above anaerobic threshold heart rate level was 9(3)% for the males and 43(7)% for the females (P < 0.001) of the total jogging time. The results indicate that even in a leisure oriented jogging event, cardiorespiratory strain can be rather high and that the strain can be significantly higher for female than for male subjects. The determination of the anaerobic threshold as well as VO2max is important when quantifying the level of cardiorespiratory strain of exercise.

Adult↗

PubMed1994

Thermal responses affected by different underwear materials during light exercise and rest in cold.

The purpose of this study was to evaluate the effects of two types of underwear materials on thermophysiological responses during rest and light exercise. Two differently moisture-regaining underwear materials were tested: 100% cotton (COTTON) and 100% acrylic (ORLON). Nine female subjects participated in the experiments at an ambient temperature of -10 degrees C. The experiment comprised a 20-min of rest, a 40-min of walking exercise (6 km/h) and a 40-min of recovery. No significant differences could be found in the average values of core temperature, skin and clothing temperatures, amount of non-evaporated and evaporated sweat or subjective ratings of thermal sensations within the two different underwear ensembles. The amount of sweat accumulated into the underwear was very low (3 +/- 1g) and (5 +/- 3g) (mean +/- SE) in COTTON and ORLON, respectively. In both ensembles moisture was transferred towards outer layers of the clothing where the amount of moisture correlated significantly with the total sweat production. In a heavily sweating individual, however, the properties of COTTON underwear, such as wicking ability and high moisture regain, became apparent (accumulated sweat 71g) compared to ORLON (46g). It is concluded that the underwear materials have no significant influence on the thermophysiological responses or subjective sensations under the conditions studied, especially when the sweat rate is low. On the other hand, in individuals with a higher sweating rate the differences between materials may become evident even during light exercise.

Acrylic Resins↗

PubMed1993

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.

Adult↗

PubMed1993

Gross efficiency of muscular work during step exercise at -15 degrees C and 21 degrees C.

In an effort to assess the effect of ambient temperature on the gross efficiency (Effg) of step exercise 12 subjects performed a modified step test either at -15 degrees C or 21 degrees C ascending to three different heights (corresponding to light, moderate and heavy work), for 20 min each with a frequency of 18 steps min-1. Heart rate (HR), rectal temperature, skin temperatures and heat flux from skin were continuously measured. Oxygen consumption was measured during the last 5 min of each step height and perceptions of thermal sensation were recorded. The results indicate that, while using conventional clothing adequate in these temperatures, Effg is altered in a contradictory manner. At -15 degrees C Effg increased with increasing work load, whereas at 21 degrees C it decreased when the work load increased. The highest Effg (heavy work at -15 degrees C and light work at 21 degrees C) values are reflected as rather similar rectal temperatures. (37.4-37.7 degrees C) and identical mean skin temperatures (32.8 degrees C) as well as the same (slightly warm) thermal sensation of the legs. At -15 degrees C the lowest Effg in light work was probably due to the need to warm up the muscles. At 21 degrees C, on the contrary, the activation of heat dissipation systems was probably responsible for the lowest Effg in heavy work.

Adult↗