Performance and sensory aspects of work in cold environments: a review

Socio-Economic Impact of and Adaptation to Extreme Heat and Cold of Farmers in the Food Bowl of Nepal

Farmers worldwide have to deal with increasing climate variability and weather extremes. Most of the previous research has focused on impacts on agricultural production, but little is known about the related social and economic impacts on farmers. In this study, we investigated the social and economic impact of extreme weather events (EWE) on farmers in Nepal, and explored how they coped with and adapted to heat waves and cold spells between 2012 and 2017. To address these aims, we conducted a survey of 350 farms randomly selected from the Bardiya and Banke districts of the Terai lowlands of Nepal. They were specifically asked to rate the impacts of extreme temperatures, as well as their effect on labour productivity and collective farmer health, and the detailed preventative measures they had implemented. About 84% of the farmers self-reported moderate or severe heat stress during the last five years, and about 85%, moderate or severe cold stress. Likewise, the majority of respondents reported that both farmer health and labour productivity had been compromised by EWEs. Productivity loss had a strong association with the perceived levels of heat and cold stress, which, in turn, were more likely to be reported by farmers with previous EWE experience. Potentially due to the increased care required during EWEs, those farmers with livestock reported increased heat and cold stress, as, surprisingly, did those who had implemented adaptation measures. Farmers seemed to be less prepared for potential threats of cold spells than heat waves, and therefore less likely to adopt coping strategies, since these are a recent phenomenon. This study identified some limitations. The cross sectional and self-reported data, as a common source of information to estimate health impact, level of heat/cold stress and labour productivity loss. Community-based education/community engagement programs could be developed to facilitate proactive adaptation.

The Influence of Hand Immersion Duration on Manual Performance

OBJECTIVE

To investigate the effect of hand immersion duration on manipulative ability and tactile sensitivity.

BACKGROUND

Individuals in maritime settings often work with hands that have been immersed in water. Although research has shown that hand immersion duration differentially impacts skin adhesion and tactile sensitivity, the effect of hand immersion on manipulative ability has not been directly tested. Given how critical manipulative ability is for the safety and performance of those working at sea, the effect of hand immersion duration on manual performance was investigated.

METHOD

Tests of manipulative ability (Purdue Pegboard, Grooved Pegboard, reef knot untying) and tactile sensitivity (Touch-Test) were completed following no-exposure, short-exposure, and long-exposure hand immersions in thermoneutral water.

RESULTS

Compared to the no immersion condition, the Purdue Pegboard performance was reduced in both immersion conditions (short exposure, -11%; long exposure, -8%). A performance decrement was only observed in the short exposure condition (+15% in time to complete task) for the reef knot untying task. There were no statistical differences in the Grooved Pegboard or Touch-Test scores between exposure conditions.

CONCLUSION

Immersing the hands in water decreases manipulative ability except for when object properties reduce the slipperiness between the hand and object.

APPLICATION

Manual performance in a wet environment may be conserved by designing tools and objects with edges and textures that can offset the slipperiness of wet hands. To maintain safety, the time requirements for working with wet hands needs to be considered.

The influence of cooling forearm/hand and gender on estimation of handgrip strength

Handgrip strength is essential in manual operations and activities of daily life, but the influence of forearm/hand skin temperature on estimation of handgrip strength is not well documented. Therefore, the present study intended to investigate the effect of local cooling of the forearm/hand on estimation of handgrip strength at various target force levels (TFLs, in percentage of MVC) for both genders. A cold pressor test was used to lower and maintain the hand skin temperature at 14°C for comparison with the uncooled condition. A total of 10 male and 10 female participants were recruited. The results indicated that females had greater absolute estimation deviations. In addition, both genders had greater absolute deviations in the middle range of TFLs. Cooling caused an underestimation of grip strength. Furthermore, a power function is recommended for establishing the relationship between actual and estimated handgrip force. Statement of relevance: Manipulation with grip strength is essential in daily life and the workplace, so it is important to understand the influence of lowering the forearm/hand skin temperature on grip-strength estimation. Females and the middle range of TFL had greater deviations. Cooling the forearm/hand tended to cause underestimation, and a power function is recommended for establishing the relationship between actual and estimated handgrip force. Practitioner Summary: It is important to understand the effect of lowering the forearm/hand skin temperature on grip-strength estimation. A cold pressor was used to cool the hand. The cooling caused underestimation, and a power function is recommended for establishing the relationship between actual and estimated handgrip force.

STATEMENT OF RELEVANCE

Manipulation with grip strength is essential in daily life and the workplace, so it is important to understand the influence of lowering the forearm/hand skin temperature on grip-strength estimation. Females and the middle range of TFL had greater deviations. Cooling the forearm/hand tended to cause underestimation, and a power function is recommended for establishing the relationship between actual and estimated handgrip force.

PRACTITIONER SUMMARY

It is important to understand the effect of lowering the forearm/hand skin temperature on grip-strength estimation. A cold pressor was used to cool the hand. The cooling caused underestimation, and a power function is recommended for establishing the relationship between actual and estimated handgrip force

Combined effects of noise, vibration, and low temperature on the physiological parameters of labor employees

Noise, vibration, and low temperature render specific occupational hazards to labor employees. The purpose of this research was to investigate the combined effects of these three physical hazards on employees' physiological parameters. The Taguchi experimental method was used to simulate different exposure conditions caused by noise, vibration, and low temperature, and their effects on the physiological parameters of the test takers were measured. The data were then analyzed using statistical methods to evaluate the combined effects of these three factors on human health. Results showed that the factor that influenced the finger skin temperature, manual dexterity, and mean artery pressure (MAP) most was air temperature, and exposure time was the second most influential factor. Noise was found to be the major factor responsible for hearing loss; in this case, hand-arm vibration and temperature had no effect at all. During the study, the temperature was confined in the 5-25°C range (which was not sufficient to study the effects at extremely high- and low-temperature working conditions) because the combined effects of even two factors were very complicated. For example, the combined effects of hand-arm vibration and low temperature might lead to occupational hazards such as vibration-induced white finger syndrome in working labors. Further studies concerning the occupational damage caused by the combined effects of hazardous factors need to be conducted in the future.

Hand and finger dexterity as a function of skin temperature, EMG, and ambient condition

OBJECTIVE

This article examines the changes in skin temperature (finger, hand, forearm), manual performance (hand dexterity and strength), and forearm surface electromyograph (EMG) through 40-min, 11 degrees C water cooling followed by 15-min, 34 degrees C water rewarming; additionally, it explores the relationship between dexterity and the factors of skin temperature, EMG, and ambient condition.

BACKGROUND

Hand exposure in cold conditions is unavoidable and significantly affects manual performance.

METHOD

Two tasks requiring gross and fine dexterity were designed, namely, nut loosening and pin insertion, respectively. The nested-factorial design includes factors of gender, participant (nested within gender), immersion duration, muscle type (for EMG), and location (for skin temperature). The responses are changes in dexterity, skin temperature, normalized amplitude of EMG, and grip strength. Finally, factor analysis and stepwise regression are used to explore factors affecting hand and finger dexterity.

RESULTS

Dexterity, EMG, and skin temperature fell with prolonged cooling, but the EMG of the flexor digitorum superficialis remained almost unchanged during the nut loosening task. All responses but the forearm skin temperature recovered to the baseline level at the end of rewarming. The three factors extracted by factor analysis are termed skin temperature, ambient condition, and EMG. They explain approximately two thirds of the variation of the linear models for both dexterities, and the factor of skin temperature is the most influential.

CONCLUSION

Sustained cooling and warming significantly decreases and increases finger, hand, and forearm skin temperature. Dexterity, strength, and EMG are positively correlated to skin temperature. Therefore, keeping the finger, hand, and forearm warm is important to maintaining hand performance.

APPLICATION

The findings could be helpful to building safety guidelines for working in cold environments.

The effects of sensory impairments on product experience and personal well-being

To determine the roles that the sensory modalities play in user product interactions, one modality was blocked during the execution of eight simple tasks. Participants reported how they experienced the products and how they felt during the experiment. Blocking vision resulted in the largest loss of functional information, increased task difficulty and task duration, and fostered dependency. On the other hand, the other senses were used more and product experiences increased in perceived intenseness. When touch was blocked, the perceived loss of information was smaller and participants reported that familiar products felt less like their own. Blocking audition resulted in communication problems and a feeling of being cut off. Blocking olfaction mainly decreased the intenseness of the experience. These outcomes suggest that vision mainly plays a functional role in everyday user-product interactions, whereas the main role for olfaction lies in the affective domain. Sensory impairments change the way people experience products. Blocking a single modality during everyday tasks gives insight into the impact of impairments. These insights can be used to develop products for multiple user groups (inclusive design) or products used under extreme environmental conditions.

A meta-analysis of performance response under thermal stressors

OBJECTIVE

Quantify the effect of thermal stressors on human performance.

BACKGROUND

Most reviews of the effect of environmental stressors on human performance are qualitative. A quantitative review provides a stronger aid in advancing theory and practice.

METHOD

Meta-analytic methods were applied to the available literature on thermal stressors and performance. A total of 291 references were collected. Forty-nine publications met the selection criteria, providing 528 effect sizes for analysis.

RESULTS

Analyses confirmed a substantial negative effect on performance associated with thermal stressors. The overall effect size for heat was comparable to that for cold. Cognitive performance was least affected by thermal stressors, whereas both psychomotor and perceptual task performance were degraded to a greater degree. Other variables were identified that moderated thermal effects.

CONCLUSION

Results confirmed the importance of task type, exposure duration, and stressor intensity as key variables impacting how thermal conditions affect performance. Results were consistent with the theory that stress forces the individual to allocate attentional resources to appraise and cope with the threat, which reduces the capacity to process task-relevant information. This represents a maladaptive extension of the narrowing strategy, which acts to maintain stable levels of response when stress is first encountered.

APPLICATION

These quantitative estimates can be used to design thermal tolerance limits for different task types. Although results indicate the necessity for further research on a variety of potentially influential factors such as acclimatization, the current summary provides effect size estimates that should be useful in respect to protecting individuals exposed to adverse thermal conditions.

Glove thermal insulation: local heat transfer measures and relevance

When exposed to cold, the hands need to be protected against heat loss not only in order to reduce thermal discomfort, but also to keep their efficiency. Although gloves are usually the most common protection, their thermal insulation is generally unknown. The aim of this study was to measure the heat losses from a gloved hand with a special interest in local variations. Using a calorimetric hand placed in a cold box, several types of gloves were tested. The results indicated that depending on the glove and on the area covered the heat loss reduction may vary from almost 60% to 90%. When the least efficient pair of gloves was excluded, heat exchange coefficients varied from 1.8 to 4.8 W/m2 per degrees C for the palm and from 4.2 to 6.2 W/m2 per degrees C for the back of the hand. The three medium fingers seemed to be equally treated, with a heat exchange coefficient variation of 6.3-9.0 W/m2 per degrees C. The thumb and the little finger, which require better insulation, exhibited higher local heat transfer coefficients of 8.3-12.7 W/m2 per degrees C. Some practical aspects are evoked.

Feeling cold at work increases the risk of symptoms from muscles, skin, and airways in seafood industry workers

BACKGROUND

Norwegian workers in seafood industry plants are exposed to a cold and often wet environment.

METHODS

1,767 seafood industry workers participated in a questionnaire study. Seventeen plants were visited for thermal measurements.

RESULTS

15.9% of industrial workers and 1.7% of administrative workers reported that they often felt cold at work. Mean finger temperatures after 1 hr work varied between 16 and 22 degrees C. Foot temperature dropped from morning measurement until lunch time in 85% of the measurements. Industrial workers who reported that they often felt cold, had significantly increased prevalence of symptoms from muscles, skin, and airways while working, compared to workers who reported that they never felt cold at work.

CONCLUSIONS

Moderate cooling, caused by a cold indoor working environment, may increase muscle-, airway-, and skin symptoms. The prevalence of feeling cold may be a useful exposure estimate in moderate cold exposure situations.

Effects of wearing aircrew protective clothing on physiological and cognitive responses under various ambient conditions

Heat stress can be a significant problem for pilots wearing protective clothing during flights, because they provide extra insulation which prevents evaporative heat loss. Heat stress can influence human cognitive activity, which might be critical in the flying situation, requiring efficient and error-free performance. This study investigated the effect of wearing protective clothing under various ambient conditions on physiological and cognitive performance. On several occasions, eight subjects were exposed for 3 h to three different environmental conditions; 0 degrees C at 80% RH, 23 degrees C at 63% RH and 40 degrees C at 19% RH. The subjects were equipped with thermistors, dressed as they normally do for flights (including helmet, two layers of underwear and an uninsulated survival suit). During three separate exposures the subjects carried out two cognitive performance tests (Vigilance test and DG test). Performance was scored as correct, incorrect, missed reaction and reaction time. Skin temperature, deep body temperature, heart rate, oxygen consumption, temperature and humidity inside the clothing, sweat loss, subjective sensation of temperature and thermal comfort were measured. Rises in rectal temperature, skin temperature, heart rate and body water loss indicated a high level of heat stress in the 40 degrees C ambient temperature condition in comparison with 0 degrees C and 23 degrees C. Performance of the DG test was unaffected by ambient temperature. However, the number of incorrect reactions in the Vigilance test was significantly higher at 40 degrees C than at 23 degrees C (p = 0.006) or 0 degrees C (p = 0.03). The effect on Vigilance performance correlated with changes in deep-body temperature, and this is in accordance with earlier studies that have demonstrated that cognitive performance is virtually unaffected unless environmental conditions are sufficient to change deep body temperature.

A model for managing cold-related health and safety risks at workplaces

Cold conditions increase health and safety risks at work in several ways. The effects of cold have not been sufficiently taken into consideration in occupational safety and health practices. A systematic model and methods were developed for managing cold-related health and safety risks at workplaces. The development work was performed, in a context-bound manner, in pilot industries and workplaces. The model can be integrated into the company's occupational health and safety management system, such as OHSAS 18001. The cold risks are identified and assessed by using a checklist. The preventive measures are systematically planned in a written form specifically produced for cold workplaces. It includes the organisational and technical preventive measures, protective clothing and personal protective equipment, as well as training and information of the personnel. According to the model, all the workers, foremen, occupational safety personnel and occupational health care personnel are trained to recognise the cold risks and to conduct preventive actions. The developed model was evaluated in the context of cold outdoor (construction) and indoor work (fish processing), and by occupational health and safety professionals. According to the feedback, the model and methods were easy to use after a one-day introduction session. The continuum between the cold risk assessment and management worked well, although there was some overlap in the documentation. The cold risk management model and its methods form an essential part of ISO CD 15743 Strategy for risk assessment, management and work practice in cold environments.

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.

Computer use in cold environments

This study addresses computer work in cold environments with the two-fold aim to explore conditions for such work, and to add knowledge about the use of fingers at data entry in the cold. Five workplaces were visited and work contents and use of computers are briefly described. Effects of work in the cold were in line with those mentioned in the literature, and manual lifting of heavy goods the most impairing activity. Subjects contended with strenuous working postures--holding the computers in their hands or arms--and with cold fingers. Individual fingering for data input was noted. Forefinger or a pen were used, and a pen is recommendable for input, either as a touch pen or, simply to press the keys. A supportive rack could be recommended for portable workstations.

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.

Thermal responses from repeated exposures to severe cold with intermittent warmer temperatures

This study was conducted to evaluate physiological reaction and manual performance during exposure to warm (30 degrees C) and cool (10 degrees C) environments after exposure to very low temperatures (-25 degrees C). Furthermore, this experiment was conducted to study whether it is desirable to remove cold-protective jackets in warmer rooms after severe cold exposure. Eight male students remained in an extremely cold room for 20 min, after which they transferred into either the warm room or the cool room for 20 min. This pattern was repeated three times, and the total cold exposure time was 60 min. In the warm and cool rooms, the subjects either removed their cold-protective jackets (Condition A), or wore them continuously (Condition B). Rectal temperature, skin temperatures, manual performance, blood pressure, thermal, comfort and pain sensations were measured during the experiment. The effects of severe cold on almost all measurements in the cool (10 degrees C) environment were greater than those in the warm (30 degrees C) environment under both clothing conditions. The effects of severe cold on all measurements under Condition A except rectal temperature and toe skin temperature were significantly greater than those under Condition B in the cool environment but, not at all differences between Condition A and Condition B in the warm environments were significant. It was recognized that to remove cold-protective jackets in the cool room (10 degrees C) after severe cold exposure promoted the effects of severe cold. When rewarming in the warm resting room (30 degrees C), the physiological and psychological responses and manual performance were not influenced by the presence or absence of cold-protective clothing. These results suggest that it is necessary for workers to make sure to rewarm in the warm room outside of the cold storage and continue to wear cold-protective clothing in the cool room.

Therapeutic effects of heat, cold, and stretch on connective tissue

The anatomic architecture of connective tissue is dependent on the stresses associated with motion. Immobilization results in stress deprivation, causing structural changes in the tissue matrix. The structural changes that occur are due to the remodeling of tissue to its new resting length while being held immobile. The goal of remodeling stiffened, shortened tissues is to regain tissue length and promote unrestricted tissue gliding. The article reviews studies that examine the viscoelastic response of connective tissue to heat, cold, and stretch. An understanding of connective tissue response to these therapeutic interventions will enable clinicians to choose the appropriate modality and apply stretching techniques in a safe, efficient manner to enable patients to regain mobility.

Local cold exposure of the hands from cryosectioning work in histopathological and toxicological laboratories: signs and symptoms of peripheral neuropathy and Raynaud's phenomenon

OBJECTIVES

To study relations between cryosectioning work, skin temperature, early signs of neuropathy in the hands, and vasospastic and neurological symptoms. Microtome work is carried out at histological and toxicological laboratories all over the world. It implicates local cold exposure of -20 degrees C on the hands of exposed laboratory technicians.

METHODS

Thirty nine laboratory technicians who use microtomes at the preclinical and clinical laboratories at the University of Uppsala, Sweden were studied. An equal number of nonexposed laboratory technicians served as controls, matched for workplace, sex, age, and smoking habits. Information on symptoms, type of work, and personal factors were assessed by means of a self administered questionnaire. Two point discrimination ability was tested, and vibration perception threshholds were measured for both hands by a bio-thesiometer. Also, skin temperature was measured during cryosectioning work in those 15 technicians performing cryosectioning work during the study period.

RESULTS

Most laboratory technicians did not use any gloves during cryosectioning work, and direct contact with frozen materials sometimes occurred and resulted in a rapid cooling of the skin. In six of 15 exposed subjects (40%), the mean skin temperature during microtome work was below 20 degrees C. A later rise in skin temperature, due to a compensatory vasodilation, was found in two subjects. The group exposed to cold had signs of early neuropathy on the right hand, indicated both by vibrametry and two point discrimination test. Significant work related differences in clinical signs within the group exposed to cold was also found. No differences between exposed and nonexposed people were found for symptoms of Raynaud's phenomenon, numbness, or musculosceletal complaints.

CONCLUSION

Our study shows that cryosectioning laboratory work may cause adverse health effects--for example, peripheral neuropathy--and measures should be taken to protect the hands from the local cold exposure.

Thermal responses to light, moderate and heavy daily outdoor work in cold weather

Working in the cold is part of the normal routine in outdoor occupations in winter in the subarctic regions, but there are few data available on occupational exposure to cold during outdoor work. In the present study, thermal responses were measured in winter in Finland during 23 working days among young, healthy men working in heavy, moderate and light daily outdoor jobs. During the measurements ambient temperature ranged from +3 to -27 degrees C, air velocity from 0.2 to 4.3 m.s-1, and the subjects wore normal winter clothing. The skin temperatures measured often indicated disturbed performance, discomfort and a risk of adverse health effects, especially during the very cold days (ambient temperature less than -15 degrees C) in the light work. The most common problems were cooling of the extremities and the face and cool or cold sensations. The temperatures on the distal parts of the upper extremities correlated significantly with the heaviness of the work (r = 0.51, P = 0.014). The core temperature remained at the safety level in each case. Apart from clothing, an appropriate work load proved to be an effective way of keeping up the temperature of the extremities in cold work, and that should be taken into account when outdoor work is being planned.

Effects of repeated exposures to severely cold environments on thermal responses of humans

This study was conducted to investigate the effects of different exposure rates on thermal responses with the total cold exposure time the same under each of the conditions. After resting in a warm room (25 degrees C) for 10 minutes, six male students wearing standard cold protective clothing entered an adjoining cold room (-25 degrees C). Each 5-, 10- and 20-minute cold exposure was repeated 12, 6 and 3 times, respectively. Each cold exposure was followed by a similar duration of rest at 25 degrees C. Total cold exposure time was the same under the three conditions. Rectal temperature, skin temperatures, blood pressure, 17-hydroxycoyticoids (OHCS), counting task and subjective responses were measured. At the end of the cold exposure skin temperatures in the shorter exposures were higher than those in the other conditions, except on the foot. Discomfort due to cold was less in the shorter exposures and manifestation of discomfort was delayed. However, there were no differences among the three conditions in the fall of rectal temperature and urinary excretion of 17-OHCS, which are good indices of cold stress. Moreover, increase in blood pressure and decrease in counting task due to cold were not different among the three conditions. Even though the cold exposure time for each stay was short, when cold exposures were repeated frequently, cold stress of the whole body and decrease in manual task performance were the same as in the longer cold exposure.

Effects of cold on human information processing: application of a reaction time paradigm

Only a very few studies on the effects of cold on human information processing appear to exist. Therefore, the present experiment was designed to study the effects of the experimentally induced lowering of body core temperature on information processing, while applying a reaction time paradigm. Thirty healthy male volunteers performed a stimulus evaluation-response selection reaction time task after exposure to ambient temperatures of either 28 or 5 degrees C. A 0.5 degree C-decrease in body core temperature resulted in a significant increase in both reaction and movement time indicating a general deteriorating effect of lowering of body core temperature on information processing. Mean reaction times were 538 ms and 549 ms for the control and the cold group, respectively (p < .05). The respective mean movement times were 298 ms and 269 ms (p < .001). Speed of stimulus evaluation was not sensitive to decreases in body core temperature. However, response complexity and body core temperature showed a significant interaction in their effect on movement time (p < .05), indicating that lowering of body core temperature is more likely to affect response-related stages of central information processing rather than stimulus evaluation. Furthermore, movement time appeared to be more sensitive to cold-induced effects on information processing as compared to reaction time. Additional correlational analyses suggest that the observed effects can be considered as independent of changes in skin temperature and experienced levels of thermal discomfort. Taken together, the results indicate that lowering of body core temperature differentially affects various stages of information processing.

Pain, thermal sensation and cooling rates of hands while touching cold materials

Hand cooling and resulting comfort and pain were studied in 12 subjects, while touching six different materials (polyurethane foam, wood, nylon, rustproof steel, aluminium, and temperature-controlled metal) which were initially at ambient temperature. This was done for three ambient temperatures (-10 degrees, 0 degree and 10 degrees C), after pre-exposure exercise or rest, with bare hands or while wearing gloves. The observed cooling curves were analysed as Newtonian cooling curves. The observed time constants appeared to be significantly related to the materials' contact coefficients, the presence of hand protection, the preceding activity, and the interaction between contact coefficient and the presence of hand protection. These parameters also allowed a good description of the time constant (r2 = 0.8) of the related cooling curves. Thermal and pain sensation could be described in terms of the local skin temperature, ambient temperature and hand protection. Equal pain and thermal levels were associated with lower temperatures of the back of the hand than of the contact side. The slightly painful condition was associated with a skin temperature of 16 degrees C for the back and 19 degrees C for the palm of the hand. The pain level appeared to be inversely related to cooling speed. Skin freezing occurred at higher skin temperatures when touching cold objects than when exposed to cold air as a result of reduced supercooling. The regression equations determined allowed calculations to be made of safety limits for hand cooling while in contact with a wide range of materials.

Effects of temperature on electromyogram and muscle function

The effects of 30 min of cooling (15 degrees C water) and warming (40 degrees C water) on arm muscle function were measured. A reference condition (24 degrees C air) was included. Of nine young male subjects the maximal grip force (Fmax), the time to reach 66% of Fmax (rate of force buildup) and the maximal rhythmic grip frequency were determined, together with surface electromyographic activity (EMG) of a forearm muscle (flexor digitorum superficialis). The results showed that in contrast to warming, cooling resulted in a significant decrease of 20% in the Fmax and a significant 50% decrease in force build-up time and the maximal rhythmic grip frequency. The relationship between the root mean square value (rms) of the EMG and the static grip force did not change due to temperature changes. The median power frequency (MPF) in the power spectrum of the EMG signal decreased by 50% due to cooling but remained unchanged with heating. During a sustained contraction at 15% of Fmax (Fmax depending on the temperature) the increase in the rms value with contraction time was 90% larger in the warm condition and 80% smaller in the cold condition compared to the increase in the reference condition. The MPF value remained constant during the warm and reference conditions but in the cold it started at a 50% lower value and increased with contraction time.(ABSTRACT TRUNCATED AT 250 WORDS)