Comparison of argon and air as thermal insulating gases in drysuit dives during military Arctic diving equipment development tests.

INTRODUCTION: It is vital to protect divers from the cold, particularly in Arctic conditions. The insulating gas layer within the drysuit is crucial for reducing heat loss. The technical diving community has long claimed the superiority of argon over air as an insulating gas. Although argon is widely used, previous studies have shown no significant differences between the two gases. Owing to its lower heat conductivity, argon should be a better thermal insulating gas than air. METHODS: The study aimed to determine whether argon is beneficial for reducing heat loss in divers during development of military drysuit diving equipment in Arctic water temperatures. Four divers completed 14 dives, each lasting 45 minutes: seven dives used air insulation and seven used argon insulation. Rectal and eight skin temperatures were measured from which changes in calculated mean body temperature (MBT) were assessed. RESULTS: There was a significant reduction in area weighted skin temperature over time (0-45 minute) on air dives (ΔTskin = -4.16°C, SE = 0.445, P ⟨ 0.001). On argon dives the reduction was significantly smaller compared to air dives (difference between groups = 2.26°C, SE = 0.358, P ⟨ 0.001). There were no significant changes in rectal temperatures, nor was a significant difference seen between groups. CONCLUSION: Compared to air, argon may be superior as a drysuit insulating gas in Arctic water temperatures for some divers. Argon used as insulating gas can make diving safer and may diminish the risks of fatal diving accidents and occupational hazard risks in professional diving.

Cardiovascular responses to cold and submaximal exercise in patients with coronary artery disease.

Regular year-round exercise is recommended for patients with coronary artery disease (CAD). However, the combined effects of cold and moderate sustained exercise, both known to increase cardiac workload, on cardiovascular responses are not known. We tested the hypothesis that cardiac workload is increased, and evidence of ischemia would be observed during exercise in the cold in patients with CAD. Sixteen men (59.3 ± 7.0 yr, means ± SD) with stable CAD each underwent 4, 30 min exposures in a randomized order: seated rest and moderate-intensity exercise [walking, 60%-70% of max heart rate (HR)] performed at +22°C and -15°C. Systolic brachial blood pressure (SBP), HR, electrocardiogram (ECG), and skin temperatures were recorded throughout the intervention. Rate pressure product (RPP) and ECG parameters were obtained. The combined effects of cold and submaximal exercise were additive for SBP and RPP and synergistic for HR when compared with rest in a neutral environment. RPP (mmHg·beats/min) was 17% higher during exercise in the cold (18,080 ± 3540) compared with neutral (15,490 ± 2,940) conditions ( P = 0.001). Only a few ST depressions were detected during exercise but without an effect of ambient temperature. The corrected QT interval increased while exercising in the cold compared with neutral temperature ( P = 0.023). Recovery of postexercise blood pressure was similar regardless of temperature. Whole body exposure to cold during submaximal exercise results in higher cardiac workload compared with a neutral environment. Despite the higher RPP, no signs of myocardial ischemia or abnormal ECG responses were observed. The results of this study are useful for planning year-round exercise-based rehabilitation programs for stable CAD patients.

The prevalence of heat-related cardiorespiratory symptoms: the vulnerable groups identified from the National FINRISK 2007 Study.

The prevalence of heat-related cardiorespiratory symptoms among vulnerable groups is not well known. We therefore estimated the prevalence of heat-related cardiorespiratory symptoms among the Finnish population and their associations with social and individual vulnerability factors. The data came from the National FINRISK 2007 Study, in which 4007 men and women aged 25-74 answered questions on heat-related cardiorespiratory symptoms in the Oulu Cold and Heat Questionnaire 2007. Logistic regression was used to calculate odds ratios (ORs), their 95 % confidence intervals (CIs), and model-predicted prevalence figures. The prevalence of heat-related cardiorespiratory symptoms was 12 %. It increased with age, from 3 % at the age of 25 years to 28 % at the age of 75 years. The symptoms were associated with pre-existing lung (OR 3.93; CI 3.01-5.13) and cardiovascular diseases (OR 2.27; 1.78-2.89); being a pensioner (OR 2.91; 1.65-5.28), unemployed (OR 2.82; 1.47-5.48), or working in agriculture (OR 2.27; 1.14-4.46) compared with working in industry; having only basic vs academic education (OR 1.98; 1.31-3.05); being female (OR 1.94; 1.51-2.50); being heavy vs light alcohol consumer (OR 1.89; 1.02-3.32); undertaking hard vs light physical work (OR 1.48;1.06-2.07); and being inactive vs active in leisure time (OR 1.97; 1.39-2.81). The adjusted prevalence of symptoms showed a wide range of variation, from 3 to 61 % depending on sex, age, professional field, education, and pre-existing lung and cardiovascular diseases. In conclusion, heat-related cardiorespiratory symptoms are commonly perceived among people with pre-existing lung or cardiovascular disease, agricultural workers, unemployed, pensioners, and people having only basic education. This information is needed for any planning and targeting measures to reduce the burden of summer heat.

The effects of skin and core tissue cooling on oxygenation of the vastus lateralis muscle during walking and running.

Skin and core tissue cooling modulates skeletal muscle oxygenation at rest. Whether tissue cooling also influences the skeletal muscle deoxygenation response during exercise is unclear. We evaluated the effects of skin and core tissue cooling on skeletal muscle blood volume and deoxygenation during sustained walking and running. Eleven male participants walked or ran six times on a treadmill for 60 min in ambient temperatures of 22°C (Neutral), 0°C for skin cooling (Cold 1), and at 0°C following a core and skin cooling protocol (Cold 2). Difference between oxy/deoxygenated haemoglobin ([diffHb]: deoxygenation index) and total haemoglobin content ([tHb]: total blood volume) in the vastus lateralis (VL) muscle was measured continuously. During walking, lower [tHb] was observed at 1 min in Cold 1 and Cold 2 vs. Neutral (P˂0.05). Lower [diffHb] was seen at 1 and 10 min in Cold 2 vs. Neutral by 13.5 ± 1.2 µM and 15.3 ± 1.4 µM and Cold 1 by 10.4 ± 3.1 µM and 11.1 ± 4.1 µM, respectively (P˂0.05). During running, [tHb] was lower in Cold 2 vs. Neutral at 10 min only (P = 0.004). [diffHb] was lower at 1 min in Cold 2 by 11.3 ± 3.1 µM compared to Neutral and by 13.5 ± 2.8 µM compared to Cold 1 (P˂0.001). Core tissue cooling, prior to exercise, induced greater deoxygenation of the VL muscle during the early stages of exercise, irrespective of changes in blood volume. Skin cooling alone, however, did not influence deoxygenation of the VL during exercise.

High indoor CO2 concentrations in an office environment increases the transcutaneous CO2 level and sleepiness during cognitive work.

The purpose of this study is to perform a multiparametric analysis on the environmental factors, the physiological stress reactions in the body, the measured alertness, and the subjective symptoms during simulated office work. Volunteer male subjects were monitored during three 4-hr work meetings in an office room, both in a ventilated and a non-ventilated environment. The environmental parameters measured included CO(2), temperature, and relative humidity. The physiological test battery consisted of measuring autonomic nervous system functions, salivary stress hormones, blood's CO(2)- content and oxygen saturation, skin temperatures, thermal sensations, vigilance, and sleepiness. The study shows that we can see physiological changes caused by high CO(2) concentration. The findings support the view that low or moderate level increases in concentration of CO(2) in indoor air might cause elevation in the blood's transcutaneously assessed CO(2). The observed findings are higher CO(2) concentrations in tissues, changes in heart rate variation, and an increase of peripheral blood circulation during exposure to elevated CO(2) concentration. The subjective parameters and symptoms support the physiological findings. This study shows that a high concentration of CO(2) in indoor air seem to be one parameter causing physiological effects, which can decrease the facility user's functional ability. The correct amount of ventilation with relation to the number of people using the facility, functional air distribution, and regular breaks can counteract the decrease in functional ability. The findings of the study suggest that merely increasing ventilation is not necessarily a rational solution from a technical-economical viewpoint. Instead or in addition, more comprehensive, anthropocentric planning of space is needed as well as instructions and new kinds of reference values for the design and realization of office environments.

Heat-related thermal sensation, comfort and symptoms in a northern population: the National FINRISK 2007 study.

BACKGROUND: The occurrence of subjective symptoms related to heat strain in the general population is unknown. The present study aimed to describe the temperatures considered to be comfortable or hot and the prevalence of heat-related complaints and symptoms in the Finnish population. METHODS: Four thousand and seven men and women aged 25-74 years, participants of the National FINRISK 2007 study, answered a questionnaire inquiring about the ambient temperatures considered to be hot and the upper limit of comfortable and about heat-related complaints and symptoms. The age trends in threshold temperatures and symptom prevalence were examined in 1-year groups by gender after smoothing with loess regression. The prevalence estimates were also adjusted for age. RESULTS: The temperature considered as hot averaged 26°C and the upper limit for thermal comfort was 22°C. Both temperatures declined with age (from 25 to 74 years) by 1-5°C. Approximately 80% of the subjects reported signs or symptoms of heat strain in warm weather, mostly thirst (68%), drying of mouth (43%), impaired endurance (43%) and sleep disturbances (32%). Cardiac and respiratory symptoms were reported by 6 and 7%, respectively, and their prevalence increased up to the age of 75 years. The exception was thirst, whose prevalence declined with age. Most symptoms and complaints were more prevalent in women than men. CONCLUSIONS: A large percentage of this northern European population suffers from heat-related complaints. Information on these is an aid in assessing the burden of summer heat on population health and is a prerequisite for any rational planning of pre-emptive measures.

Muscular, cardiorespiratory and thermal strain of mast and pole workers.

This field study evaluated the level of muscular, cardiorespiratory and thermal strain of mast and pole workers. We measured the muscular strain using electromyography (EMG), expressed as a percentage in relation to maximal EMG activity (%MEMG). Oxygen consumption (VO2) was indirectly estimated from HR measured during work and expressed as a percentage of maximum VO2 (%VO2max). Skin and deep body temperatures were measured to quantify thermal strain. The highest average muscular strain was found in the wrist flexor (24 ± 1.5%MEMG) and extensor (21 ± 1.0%MEMG) muscles, exceeding the recommendation of 14%MEMG. Average cardiorespiratory strain was 48 ± 3%VO2max. Nearly half (40%) of the participants exceeded the recommended 50%VO2max level. The core body temperature varied between 36.8°C and 37.6°C and mean skin temperature between 28.6°C and 33.4°C indicating possible occasional superficial cooling. Both muscular and cardiorespiratory strain may pose a risk of local and systemic overloading and thus reduced work efficiency. Thermal strain remained at a tolerable level.

Validation of the Fiala multi-node thermophysiological model for UTCI application.

The important requirement that COST Action 730 demanded of the physiological model to be used for the Universal Thermal Climate Index (UTCI) was its capability of accurate simulation of human thermophysiological responses across a wide range of relevant environmental conditions, such as conditions corresponding to the selection of all habitable climates and their seasonal changes, and transient conditions representing the temporal variation of outdoor conditions. In the first part of this study, available heat budget/two-node models and multi-node thermophysiological models were evaluated by direct comparison over a wide spectrum of climatic conditions. The UTCI-Fiala model predicted most reliably the average human thermal response, as shown by least deviations from physiologically plausible responses when compared to other models. In the second part of the study, this model was subjected to extensive validation using the results of human subject experiments for a range of relevant (steady-state and transient) environmental conditions. The UTCI-Fiala multi-node model proved its ability to predict adequately the human physiological response for a variety of moderate and extreme conditions represented in the COST 730 database. The mean skin and core temperatures were predicted with average root-mean-square deviations of 1.35 ± 1.00°C and 0.32 ± 0.20°C, respectively.

The UTCI-clothing model.

The Universal Thermal Climate Index (UTCI) was conceived as a thermal index covering the whole climate range from heat to cold. This would be impossible without considering clothing as the interface between the person (here, the physiological model of thermoregulation) and the environment. It was decided to develop a clothing model for this application in which the following three factors were considered: (1) typical dressing behaviour in different temperatures, as observed in the field, resulting in a model of the distribution of clothing over the different body segments in relation to the ambient temperature, (2) the changes in clothing insulation and vapour resistance caused by wind and body movement, and (3) the change in wind speed in relation to the height above ground. The outcome was a clothing model that defines in detail the effective clothing insulation and vapour resistance for each of the thermo-physiological model's body segments over a wide range of climatic conditions. This paper details this model's conception and documents its definitions.

From the subarctic to the tropics: effects of 4-month deployment on soldiers' heat stress, heat strain, and physical performance.

The aim of the study was to evaluate the heat stress of Finnish male soldiers (N = 20, age 22.0 ± 2.5 years, body mass 78.8 ± 11.5 kg, and height 180.2 ± 5.6 cm) during their 4-month deployment in a hot environment and to find out the effects on physical performance and body composition. The troops moved from 2.5° C (mean monthly temperature) in Finland to 31.9° C in Chad. During the deployment, temperatures varied between 13.5 and 57.0° C outdoors and in the vehicles and tents. During 1-day recording in the middle of the deployment, skin temperatures were 34-35° C during daytime and maximal core temperature remained mainly below 38.0° C. Body mass decreased (78.4 ± 11.5 kg vs. 75.6 ± 8.6, p = 0.007) during the deployment without changes in fat mass. The sit-up performance increased by 10.9% (46 ± 10 reps·min⁻¹ vs. 51 ± 7 reps·min⁻¹, p < 0.01), and the maximal force production of the leg extensor muscles increased (3,042 ± 614 N vs. 3,277 ± 706 N, p < 0.05) without change in the rate of force development. No changes were observed in the push-ups, repeated squats, maximal grip strength, and running distance during the 12-minute test. In conclusion, the soldiers were able to maintain or improve their physical performance during the deployment despite the heat stress. It is important to encourage soldiers to engage in physical training, especially during a thermally appropriate time of the day or in air-conditioned facilities. Monitoring of local heat stress is also recommended.

Evaluation of the thermal insulation of clothing of infants sleeping outdoors in Northern winter.

It is a common practice in Northern countries that children aged about 2 weeks to 2 years take their daytime sleep outdoors in prams in winter. The aim was to evaluate the thermal insulation of clothing of infants sleeping outdoors in winter. Clothing data of infants aged 3.5 months was collected, and sleep duration, skin and microclimate temperatures, humidity inside middle wear, air temperature and velocity of the outdoor environment were recorded during sleep taken outdoors (n = 34) and indoors (n = 33) in families' homes. The insulation of clothing ensembles was measured by using a baby-size thermal manikin, and the values were used for defining clothing insulation of the observed infants. Required clothing insulation for each condition was estimated according to ISO 11079. Clothing insulation did not correlate with ambient air temperature. The observed and required insulation of the study group was equal at about -5 °C, but overdressing existed in warmer and deficiency in thermal insulation in colder temperatures (r (s) 0.739, p < 0.001). However, even at -5 °C a slow cooling (ca. 0.012 °C/min) of mean skin temperature (T (sk)) was observed. When the difference between observed and required insulation increased, the cooling rate of T (sk) increased linearly (r (s) 0.605, p < 0.001) and the infants slept for a shorter period (r (s) 0.524, p = 0.001). The results of this study show the difficulty of adjusting systematically the optimal thermal insulation for outdoor sleeping infants during northern winter. Therefore, the necessity for guidelines is obvious. The study provides information for adequate cold protection of infants sleeping in cold conditions.

Recovery of hormonal, blood lipid, and hematological profiles from a North Pole expedition.

INTRODUCTION: This study examined the recovery patterns of hormonal, blood lipid, and hematological profiles following strenuous physical loading, continuous extreme cold exposure and energy deficit induced by a North Pole expedition. METHODS: Seven men completed an 850-km North Pole expedition in temperatures varying from -3 degrees C to -47 degrees C. Daily energy intake was approximately 23 MJ x d(-1) and was composed of approximately 60% fat. Blood samples were collected 2 wk before (Pre) the expedition and after 2 wk (Post 1), and 2 mo (Post 2). Additional samples were collected on the first (R1), third (R3), and fifth (R5) return days. RESULTS: Mean weight loss upon return was 10 kg. Energy expenditure was estimated to be 29.6 MJ x d(-1). Declines in cortisol (-237.29 nmol x L(-1)), total testosterone (-5.08 nmol x L(-1)), bioavailable testosterone (-0.37 nmol x L(-1)) and free thyroxin (-5.82 pmol x L(-1)) returned to normal values at R5 or Post 1 (P < 0.05). The increase in sex hormone-binding globulin (+17.5 nmol x L(-1)) rapidly returned to the pre-expedition concentration at R3 (P < 0.05). Significantly greater values were observed at Post 1 in the lipid (high-density lipoprotein +1.86 mmol x L(-1); low-density lipoprotein +4.23 mmol x L(-1)) and hematological (WBC +1.28 x 10(3)/L; platelets +51.86 x 10(3)/L) profiles (P < 0.05). RBC, hemoglobin, and hematocrit were all lower at Post 1 (P < 0.05). CONCLUSION: Although the expedition generated extreme physical stress, this was not directly reflected on hormonal recovery times as it was similar to other much less strenuous events. Despite important variations, all hormones returned to baseline values within 2 wk. Nonetheless, physical stress would appear to have more long-term effects on blood lipid and hematological profiles.

Infants sleeping outdoors in a northern winter climate: skin temperature and duration of sleep.

AIM: The aim of the study is to describe the relationships among thermal environment, skin temperatures and infants' daytime outdoor sleep duration in northern winter conditions. METHODS: This study is a cross-over observational study. Skin temperatures of three-month-old infants were recorded from seven skin sites continuously throughout outdoor (n = 34) and indoor sleep (n = 33) in the families' homes. The duration of the sleep was observed, and temperature and the air velocity of the environment were recorded. RESULTS: Skin temperatures increased towards the end of indoor sleeping, whereas they decreased during outdoor sleeping. The cooling rate of mean skin temperature (T(sk)) increased in lower outdoor temperatures (r(s) = .628, p < 0.001) in spite of increased clothing. On some occasions, cold extremities were observed, suggesting slight deviations from thermoneutrality. Sleep time was 92 min longer in outdoors than in indoors. However, outdoor sleep duration was shortened when the cooling rate of T(sk) increased (r(s) = 0.611, p < 0.001). CONCLUSION: The longest sleep was recorded outdoors when the cooling rate of T(sk) was minimal. Restriction of movements by clothing probably increases the length of sleep, and a cold environment makes swaddling possible without overheating. A decrease in ambient temperature increased the cooling rate, suggesting that the cold protection of the clothing compensated only partly for the increased heat loss.

Effect of local leg cooling on upper limb trajectories and muscle function and whole body dynamic balance.

This study was designed to find out if local leg cooling affects muscle function and trajectories of the upper limb during repetitive light work as well as capability to maintain dynamic balance. Nine healthy female subjects performed repetitive lifting task with right hand for 60 min while standing in front of a table with six target angles (30 degrees -220 degrees ) and with the legs inside a container with 15 degrees C cold water (Cold condition, C) or without water (Normal condition, N). Muscle temperature of the medial aspect of the gastrocnemius, rectal, and skin temperatures were measured continuously. The trajectories of the right upper limb were recorded with a 3D motion analysis system. Muscular strain (averaged EMG, a-EMG) and EMG gaps in eight muscles of the right upper limb were measured. End point excursion depicting the ability to maintain dynamic balance was measured before and after each experiment. Leg cooling decreased significantly (P < 0.05) the muscle and the mean skin temperature in C compared with N (6.7 and 2.2 degrees C, respectively). No marked changes in the trajectories or EMG activity were observed between the different environmental conditions. The end point excursion was significantly (P < 0.05) reduced in C compared with N and a positive correlation between excursion and muscle temperature was found at the end of the working period in C. In conclusion, local leg cooling did not affect upper limb muscle function or trajectories, but ability to maintain dynamic balance was reduced.

High Home Blood Pressure Variability Associates With Exaggerated Blood Pressure Response to Cold Stress.

BACKGROUND: Exaggerated sympathetic cardiovascular (CV) reactivity to stress associates with elevated risk for clinical and preclinical end points of CV disease. It would be useful to identify these individuals, preferably from feasible measurements commonly used in health care. Our study examined the association between home blood pressure (BP) variability and cardiac workload response to whole-body cold exposure. METHODS: Seventy-five men (55-65 years, 46 hypertensive) measured BP at home twice in the morning and evening for a week. We computed systolic home BP variability as SD of daily means and divided the subjects into groups demonstrating either high or low BP variability. They were exposed to whole-body cold exposure (-10 °C, wind 3 m/second, 15 minutes, winter clothes, standing). BP and heart rate were measured at 3-minute intervals during, and 15 minutes before and after the exposure. Rate-pressure product (RPP) was calculated to represent cardiac workload. RESULTS: Subjects with high systolic home BP variability demonstrated a greater RPP increase in cold conditions compared to those with low BP variability [mean change from baseline (95% CI): 1,850 (1,450 to 2,250) bpm × mm Hg vs. 930 (610, 1,250) bpm × mm Hg, P < 0.01]. This was related to the augmented systolic BP change [31(28, 35) mm Hg vs. 23(20, 26) mm Hg, P < 0.01]. Home BP variability correlated with cold-related RPP (rS = 0.34, P = 0.003) and systolic BP (rS = 0.38, P < 0.001) responses. CONCLUSIONS: Moderate whole-body cold exposure increased BP and cardiac workload more among those with higher systolic home BP variability, independently of home BP level. Elevated home BP variability may indicate augmented sympathetically mediated vascular reactivity for environmental stressors. PUBLIC TRIALS REGISTRY NUMBER: Trial Number NCT02007031.

Gait muscle activity during walking on an inclined icy surface.

The objective of this study was to explain the contribution of lower extremity muscle activity to gait kinetic and kinematic adaptations for maintaining gait dynamic balance when walking on an inclined icy surface and the biomechanical mechanisms used to counteract slip risk. A two-way factorial experimental design was applied. The two independent variables were the walkway surface (ice and treadmill) and the walkway inclination (0 masculine, 6 masculine, 8 masculine). The dependent variable was the amplitude of the surface EMG of four right lower extremity muscles (tibialis anterior TA, gastrocnemius lateralis GL, rectus femoris RF, and biceps femoris BF). Twelve healthy subjects (7 males and 5 females) participated in the walking trials. A two-way ANOVA analysis showed that on the icy surface in the heel contact phase, EMG amplitudes significantly decreased in TA and RF compared to those for the treadmill surface. In the mid-stance phase, the GL muscle activity significantly decreased on ice compared to treadmill and all four muscle activities increased significantly with the inclination. During the toe off phase, GL and RF activities increased with the inclination. The mechanisms identified may be applied to develop intervention, rehabilitation and training techniques, and to improve performance in human locomotion, such as for winter sports.

Seasonal levels of melatonin, thyroid hormones, mood, and cognition near the Arctic Circle.

INTRODUCTION: The associations between melatonin and thyroid hormones and changes in mood and cognitive performance caused by exposure to cold and darkness were examined in 12 circumpolar residents during winter and summer. METHODS: Each participant was exposed to three different experimental conditions in random order: 1) 22 degrees C and bright light; 2) 10 degrees C and bright light; and 3) 10 degrees C and dim light. The duration of each exposure was 24 h. RESULTS: Increased serum melatonin and thyrotropin were associated with decreased rectal temperature (r = -0.446 - -0.580) and increased mean skin temperature (r = 0.204-0.519). Higher serum melatonin was associated with increased vigor (r = 0.330) and decreased accuracy on simple cognitive tasks (r = -0.332 - -0.430). Increased serum free triiodothyronine (fT3) was associated with decreased negative mood scores (r = -0.365 - -0.483), decreased response time (RT) on the simple reaction time (SRT) task (r = -0.606), and decreased accuracy on the addition/subtraction task (r = -0.372). Higher serum free thyroxine was associated with decreased fatigue and anger (r = -0.409 - -0.522). Increased serum thyrotropin was associated with decreased accuracy and RT on the SRT task and decreased RT on the grammatical reasoning task (r = -0.315 - -0.415). CONCLUSIONS: Associations between serum melatonin and thyroid hormones with mood were consistent with the psychological changes associated with the polar triiodothyronine syndrome. Also, serum melatonin and thyrotropin were associated with impaired and fT3 with improved cognitive performance, supporting the decrements in cognitive performance associated with the polar triiodothyronine syndrome.

Autonomic nervous function during whole-body cold exposure before and after cold acclimation.

INTRODUCTION: Cold habituation could affect sympatho-vagal balance, which modulates cold stress responses. The study examined cardiovascular autonomic function at the sinus node level during controlled breathing and while undertaking isometric exercise during whole-body cold exposure before and after cold acclimation. METHODS: There were 10 male subjects who were exposed to control (25 degrees C) and cold (10 degrees C) environments for 2 h on 10 successive days in a laboratory. Time and frequency domain heart rate variability (HRV) in terms of root mean square of successive differences in RR intervals, total, high, and low frequency power were determined from controlled breathing at the beginning and end of cold acclimation. Heart rate and blood pressure during an isometric handgrip test (30% MVC for 3 min) were recorded at the beginning and end of cold acclimation. Catecholamines (NE and E), mean skin (Tsk), and rectal temperatures (Trect) were measured. RESULTS: Acute cold exposure increased total (36%), low (16%), and high frequency power (25%) and RMSSD (34%). Cold acclimation resulted in higher Tsk (0.6 degrees C) and lower NE (24%) response in cold. The cold-induced elevation in high frequency power became significant after cold acclimation, while other HRV parameters remained unchanged. A smaller increase in heart rate and blood pressure occurred at 10 degrees C during the handgrip test after cold acclimation. DISCUSSION: Cold exposure increased sympathetic activity, which was blunted after cold acclimation. Parasympathetic activity showed a minor increase in cold, which was enhanced after cold acclimation. In conclusion, cold habituation lowers sympathetic activation and causes a shift toward increased parasympathetic activity.

Health problems related to working in extreme cold conditions indoors.

OBJECTIVES: To identify health problems among workers performing cleaning, maintenance and machine operation tasks inside cold storage rooms with temperatures between -43 degrees C and -62 degrees C in a freeze drying coffee company. STUDY DESIGN: Descriptive study. METHODS: All 24 workers working inside the cold stores participated in the study. A questionnaire about cold-related health problems and the standardized Nordic questionnaire assessing muscle complaints were completed by all exposed workers. A physical examination was performed on each worker. RESULTS: The most relevant cold-related health problem was episodic finger symptoms (50%), followed by respiratory symptoms (21%), peripheral circulation symptoms (20%), and repeated pain in the musculoskeletal system (12%). Two subjects had a previous diagnosis of Raynaud's phenomenon (RP). The prevalence of musculoskeletal complains in the neck and low back was 21% in each. CONCLUSIONS: The prevalence found for various complaints among the freeze drying coffee workers implies that the cold conditions inside cold stores may present a real risk of cold-related health problems and, due to lowered concentration level, for injuries, too. Greater efforts should be made to minimize the cold exposure by designing automation processes to prevent continuous exposure to cold during freeze drying process. In addition, improving the cold-protective clothing and guaranteeing its appropriate use will reduce health risks.

Skin temperature responses to hand-arm vibration in cold and thermoneutral ambient temperatures.

Hand-arm vibration (HAV) from hand-held vibrating machines increases the risk of injury in the form of vasoconstriction in the fingers, commonly named as vibration induced white fingers (VWF). Cold temperature may increase that risk. This experimental study examined and compared the effects of the skin temperature of the hands during and after exposure to HAV in thermoneutral and cold conditions. Fourteen subjects were exposed to three conditions: 25°C with HAV, 5°C with HAV or 5°C without HAV. Their skin temperatures were continuously recorded for the thumbs, index fingers, palms, and back of hands. After 20 min of acclimatization, the subjects held, for five min, two handles where the right handle could vibrate at 5 m/s2 and the left was stationary. Finally, they released their grip and stood still for 10 more min. HAV had no additional cooling effect in cold during gripping of the handles. After the subjects released the handles there was only a HAV-induced cooling effect in the left palm with on average 0.5°C colder skin temperature. A single exposure to HAV will not cause an injury such as VWF, but as the present study show: short-term exposure to HAV causes some changes in skin temperature.