Cold-related pain in the face, upper limbs, and lower body among Thai chicken industry workers: a cross-sectional study.

OBJECTIVE: There is limited information on cold-related pain (CRP) in various parts of the body among workers employed in cold environments. We, therefore, determined the prevalence of CRP among Thai chicken industry workers and attempted to identify vulnerable subgroups. METHODS: Four hundred and twenty-two workers in four chicken meat factories in Thailand were asked about CRP in the face, upper limbs, and lower body. The results were expressed as adjusted prevalence and prevalence differences [PD; in percentage points (pp)] and their 95% confidence intervals (CI). RESULTS: Overall, 80% of the subjects suffered from CRP in at least one site on the body: 66% in the upper limbs, 65% in the lower body, and 44% in the face. In most sites, CRP increased from the lowest to the highest educational level, notably in the nose with a PD of 36 pp [95% CI 23, 49]. Forklift drivers experienced knee pain [PD 21 pp (0, 41)], and manufacturing [PD 27 pp (15, 38)] and storage workers [PD 24 pp (10, 37)] experienced thigh pain more often than office workers, while office workers reported CRP in the cheeks, ears, wrists, and fingers more often than other workers. Women had more CRP than men in several body sites. CONCLUSIONS: The majority of workers suffered from CRP. Intensified protective measures should be targeted not only for forklift drivers and storage and manufacturing workers, but also for the highly educated as well as the office staff who showed excessive prevalence of CRP in several body sites.

Cold-related symptoms and performance degradation among Thai poultry industry workers with reference to vulnerable groups: a cross-sectional study.

BACKGROUND: Few studies have examined cold-related symptoms among cold workplace workers in Thailand. This study aimed to determine the prevalence of cold-related cardiorespiratory, circulatory, and general symptoms and performance degradation among Thai chicken industry workers and identify vulnerable groups. METHODS: Overall, 422 workers aged from 18 to 57 years at four chicken meat factories in Thailand were interviewed for cold-related symptoms and complaints. The results were expressed in terms of model-based adjusted prevalence and prevalence differences (PDs) in percentage points (pp) with 95% confidence intervals (CIs). RESULTS: In total, 76.1% of the respondents reported cold-related respiratory symptoms, 24.6% reported cardiac symptoms, 68.6% reported circulatory symptoms, and 72.1% reported general symptoms. In addition, 82.7% of the respondents reported performance degradation. Cold-related respiratory symptoms increased by PD 29.0 pp. (95% CI 23.4-34.6) from the lowest to the highest educational group, with a similar pattern observed in performance degradation. Forklift drivers and storage and manufacturing workers complained of cold-related respiratory symptoms more than office staff (PD 22.1 pp., 95% CI 12.8-31.3; 12.0 pp., 95% CI 2.4-21.6; and 17.5 pp., 95% CI 11.5-23.6, respectively); they also reported more performance degradation (PD 24.1 pp., 95% CI 17.0-31.2; 19.8 pp., 95% CI 14.1-25.6; and 14.8 pp., 95% CI 8.0-22.6, respectively). Weekly alcohol consumers reported more performance problems owing to cold (PD 18.2 pp., 95% CI 13.9-22.6) than non-consumers of alcohol. Cardiac and circulation symptoms were more common in women than men (PD 10.0 pp., 95% CI 1.1-18.9; and 8.4 pp., 95% CI 0.5-16.4, respectively). The age trend in performance issues was curved, with the highest prevalence among those aged 35-44 years, while the oldest workers (45-57 years) perceived less cold-related symptoms, particularly thirst. CONCLUSIONS: Cold-related symptoms and performance degradation were found to be common in this industry, with vulnerable groups comprising of highly educated workers, forklift drivers, storage and manufacturing workers, weekly alcohol consumers, aging workers, and women. The results demonstrate a need for further research on the adequacy of protection provided against the cold, particularly given that global warming will increase the contrast between cold workplaces and outdoor heat.

Prevalence of cold-related symptoms among Thai chicken meat industry workers: association with workplace temperature and thermal insulation of clothing.

This study determined the association of cold-related symptoms with workplace temperature and thermal insulation of clothing among Thai chicken industry workers. Three hundred workers were interviewed regarding cold-related symptoms, which were regressed on worksite temperature and protective clothing. In total, 80% of workers reported respiratory symptoms; 23%, cardiac symptoms; 62%, circulation disturbances; 42%, thirst; 56%, drying of the mouth; and 82%, degradation of their performance. When adjusted for personal characteristics, respiratory symptoms were 1.1‒2.2 times more prevalent at -22‒10°C than at 10‒23°C. At -22‒10°C, cardiac symptoms increased by 45%, chest pain by 91%, peripheral circulation disturbances by 25%, and drying of the mouth by 57%. Wearing protective clothing with at least 1.1 clo units was associated with marked reductions in symptom prevalence. Therefore, temperatures lower than 10°C increased prevalence of cold-related symptoms, which are largely preventable by appropriate clothing use.

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.

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.

Thermal comfort sustained by cold protective clothing in Arctic open-pit mining-a thermal manikin and questionnaire study.

Workers in the Arctic open-pit mines are exposed to harsh weather conditions. Employers are required to provide protective clothing for workers. This can be the outer layer, but sometimes also inner or middle layers are provided. This study aimed to determine how Arctic open-pit miners protect themselves against cold and the sufficiency, and the selection criteria of the garments. Workers' cold experiences and the clothing in four Arctic open-pit mines in Finland, Sweden, Norway and Russia were evaluated by a questionnaire (n=1,323). Basic thermal insulation (Icl) of the reported clothing was estimated (ISO 9920). The Icl of clothing from the mines were also measured by thermal manikin (standing/walking) in 0.3 and 4.0 m/s wind. The questionnaire showed that the Icl of the selected clothing was on average 1.2 and 1.5 clo in mild (-5 to +5°C) and dry cold (-20 to -10°C) conditions, respectively. The Icl of the clothing measured by thermal manikin was 1.9-2.3 clo. The results show that the Arctic open-pit miners' selected their clothing based on occupational (time outdoors), environmental (temperature, wind, moisture) and individual factors (cold sensitivity, general health). However, the selected clothing was not sufficient to prevent cooling completely at ambient temperatures below -10°C.

Evaluating cold, wind, and moisture protection of different coverings for prehospital maritime transportation-a thermal manikin and human study.

INTRODUCTION: Prehospital maritime transportation in northern areas sets high demands on hypothermia prevention. To prevent body cooling and hypothermia of seriously-ill or injured casualties during transportation, casualty coverings must provide adequate thermal insulation and protection against cold, wind, moisture, and water splashes. OBJECTIVE: The aim of this study was to determine the thermal protective properties of different types of casualty coverings and to evaluate which would be adequate for use under difficult maritime conditions (cold, high wind speed, and water splashes). In addition, the study evaluated the need for thermal protection of a casualty and verified the optimum system for maritime casualty transportation. METHODS: The study consisted of two parts: (1) the definition and comparison of the thermal protective properties of different casualty coverings in a laboratory; and (2) the evaluation of the chosen optimum protective covering for maritime prehospital transportation. The thermal insulations of ten different casualty coverings were measured according to the European standard for sleeping bags (EN 13537) using a thermal manikin in a climate chamber (-5°C) with wind speeds of 0.3 m/s and 4.0 m/s, and during moisture simulations. The second phase consisted of measurements of skin and core temperatures, air temperature, and relative humidity inside the clothing of four male test subjects during authentic maritime prehospital transportation in a partially-covered motor boat. RESULTS: Wind (4 m/s) decreased the total thermal insulation of coverings by 11%-45%. The decrement of thermal insulation due to the added moisture inside the coverings was the lowest (approximately 22%-29%) when a waterproof reflective sheet inside blankets or bubble wrap was used, whereas vapor-tight rescue bags and bubble wrap provide the most protection against external water splashes. During authentic maritime transportation lasting 30 minutes, mean skin temperature decreased on average by 0.5°C when a windproof and water-resistant rescue bag was used over layered winter clothing. CONCLUSION: The selected optimum rescue bag consisted of insulating and water-resistant layers providing sufficient protection against cold, wind, and water splashes during prehospital transportation lasting 30 minutes in the uncovered portion of a motor boat. The minimum thermal insulation for safe maritime transportation (30 minutes) is 0.46 m²K/W at a temperature of -5°C and a wind speed of 10 m/s.

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.

Firefighters muscular recovery after a heavy work bout in the heat.

Occasionally firefighters need to perform very heavy bouts of work, such as smoke diving or clearing an accident site, which induce significant muscle fatigue. The time span for muscular recovery from such heavy work is not known. The purpose of this study was to evaluate firefighters' force-, neural-, metabolic-, and structural-related recovery after task-specific heavy work in the heat. Fifteen healthy firefighters (14 males and 1 female) performed a 20-min heavy work bout that simulated smoke diving and the clearance of an accident site at 35 °C. After the work, muscular recovery was evaluated by wrist flexion maximal voluntary contraction (MVC), average electromyography during MVC and during 10%MVC, rate of force production, motor response and stretch reflex responses, muscle oxygen consumption and oxygenation level, and wrist flexor muscle pennation angle. Recovery was followed for 4 h. Each of the 12 measured parameters changed significantly (p < 0.05) from those at baseline during the follow-up. Muscle oxygen consumption and the wrist flexor pennation angle remained elevated throughout the follow-up (oxygen consumption baseline, 12.9 ± 1.7 mL O2·min(-1)·(100 g)(-1); 4-h value, 17.5 ± 1.6 mL O2·min(-1)·(100 g)(-1); p < 0.05 and pennation angle baseline, 15.7 ± 0.8°; 4-h value, 17.8 ± 0.8°; p < 0.05). Muscle reoxygenation rate was elevated for up to 2 h (baseline, 2.3 ± 0.4 µmol·L(-1)·min(-1); 2-h value, 3.4 ± 0.4 µmol·L(-1)·min(-1); p < 0.05). The other 9 parameters recovered (were no longer significantly different from baseline) after 20 to 60 min. We concluded that the recovery order in main components of muscle function from fastest to slowest was force, neural, metabolic, and structural.

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.

Muscular activity and thermal responses in men and women during repetitive work in cold environments.

Thermal responses and muscular activity in repetitive work were studied in eight women and eight men at 19 degrees C (thermoneutral) and at 4 degrees C (cold). Furthermore, effect of a heating vest was studied at 4 degrees C. Women had lower (p < 0.05) mean skin temperature compared with men at each thermal condition. Muscular activity (microV) was generally higher in women compared with men, being significantly higher in m. deltoideus (p < 0.05). Women had lower (p < 0.01) maximal isometric strength compared with men, which may have influenced the observed higher muscular activity during work in women. However, compared with thermoneutral, working in cold increased (p < 0.05) muscular activity in the forearm and upper arm extensors only in men. The vest did not significantly counteract the increase in muscular activity. In conclusion, sex differences should be considered when evaluating cold protection and work load reduction in repetitive work in cold environments. Present results indicate that in identical work, sex affects thermal responses and muscular activity during repetitive work in conditions comparable with cooled departments in the food-processing industry. Sex differences should be considered when evaluating cold protection and preventive measures for work load reduction.

Heat stress and bulkiness of chemical protective clothing impair performance of medical personnel in basic lifesaving tasks.

The study examined the impact of chemical protective (CP) clothing on the performance of lifesaving tasks in thermoneutral and cold conditions. Eleven males performed pre-exercise followed by lifesaving tasks wearing either field combat uniform at 21 degrees C (U) or CP clothing at 21 degrees C (CPN) and -5 degrees C (CPC). The tasks were ventilating a doll (VA) and connecting an intravenous line (IV). Mean skin temperature was significantly higher for CPN compared to U and CPC during pre-exercise, VA and IV. Changes in blood pressure were significantly greater with CP clothing than without during VA and IV. The number of breaths per min (in VA) and time needed for IV increased by 19% (p < 0.05) and 18%, respectively, for CPN compared to U. Due to the cold, the additional increment was 5% and 17%, respectively, for CPC. Wearing of CP clothing in thermoneutral or in cold conditions may not prevent but, especially in the cold, significantly impede the performance of basic medical tasks. The findings of this study showed that performing medical tasks while wearing nuclear, biological and chemical protective clothing is impaired due to significant changes in physiological strain. This suggests that realistic training in local conditions as well as in cold conditions is needed to realise the restrictions due to protective clothing.

Cold and heat strain during cold-weather field training with nuclear, biological, and chemical protective clothing.

The objective of this study was to quantify the thermal strain of soldiers wearing nuclear, biological, and chemical protective clothing during short-term field training in cold conditions. Eleven male subjects performed marching exercises at moderate and heavy activity levels for 60 minutes. Rectal temperature (Tre), skin temperatures, and heart rate were monitored. Ambient temperature (Ta) varied from -33 to 0 degrees C. Tre was affected by changes in metabolism, rather than in Ta. Tre increased above 38 degrees during heavy exercise even at -33 degrees C. The mean skin temperature decreased to tolerance level (25 degrees C) at Ta below -25 degrees C with moderate exercise. Finger temperature decreased below 15 degrees C (performance degradation) at Ta of -15 degrees C or cooler. The present results from the field confirm the previous results based on laboratory studies and show that risk of both heat and cold strain is evident, with cooling of extremities being most critical, while wearing nuclear, biological, and chemical protective clothing during cold-weather training.

Changes in neuromuscular function due to intermittently increased workload during repetitive work in cold conditions.

OBJECTIVES: This study attempted to determine whether repetitive work in the cold affects the number of electromyographic (EMG) gaps and whether cold-induced deterioration in neuromuscular function can be restored by altering work intensity. METHODS: During 2 hours of simulated sausage packing, the occurrence of EMG gaps was studied in eight upper-extremity muscles at 19 degrees C and 4 degrees C. The additional effect of continuous, light repetitive work [wrist flexion-extension 10% of the maximal voluntary contraction (MVC), Cwork] and intermittently increased workload (10% or 30% MVC) (Iwork) on forearm muscle EMG gaps, the median frequency of the EMG spectrum, EMG activity, and muscle fatigue (as indicated by changes in the MVC of wrist flexion) at 4 degrees C was studied. RESULTS: During work simulation, the mean skin temperature decreased from 33.3 (SD 0.1) degrees C to 30.6 (SD 0.2) degrees C (P<0.05), and the number of EMG gaps diminished in seven muscles by 1.4-68.2% (P<0.05). During Iwork there were 44% and 37% more EMG gaps in the forearm flexors and extensors, respectively, and the median frequency shifted to higher frequencies (P<0.05) as compared with the situation in Cwork. The average EMG activity of the forearm flexors was 13% lower (P<0.05) during Iwork than during Cwork. Wrist flexion MVC decreased 18% and 15% in Cwork and Iwork, respectively. CONCLUSIONS: The cold-induced decrease in the number of EMG gaps and increased muscle strain and fatigue can be, at least partially, restored by intermittently increasing the workload (ie, breaking the monotonous work cycle).

Heat strain in cold.

In spite of increased environmental cold stress, heat strain is possible also in a cold environment. The body heat balance depends on three factors: environmental thermal conditions, metabolic heat production and thermal insulation of clothing and other protective garments. As physical exercise may increase metabolic heat production from rest values by ten times or even more, the required thermal insulation of clothing may vary accordingly. However, in most outdoor work, and often in indoor cold work, too, the thermal insulation of clothing is impractical, difficult or impossible to adjust according to the changes in physical activity. This is especially true with whole body covering garments like chemical protective clothing. As a result of this imbalance, heat strain may develop. In cold all the signs of heat strain (core temperature above 38 degrees C, warm or hot thermal sensations, increased cutaneous circulation and sweating) may not be present at the same time. Heat strain in cold may be whole body heat strain or related only to torso or core temperature. Together with heat strain in torso or body core, there can be at the same time even cold strain in peripheral parts and/or superficial layers of the body. In cold environment both the preservation of insulation and facilitation of heat loss are important. Development of clothing design is still needed to allow easy adjustments of thermal insulation.