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Prevention of heat strain by immersing hands and forearms in water
Abstract
The effectiveness of hand immersion in water at 10 degrees C, 20 degrees C and 30 degrees C as a technique for reducing heat strain in Royal Navy (RN) personnel has been investigated at the Institute of Naval Medicine (INM). Four subjects exercised at a moderate work rate, whilst wearing fire fighting clothing in an environmental chamber at 40 degrees C. The subjects reached heat strain safety limits within 45 minutes of commencing work at which point they rested in the heat for 30 minutes whilst they underwent one of four experimental conditions: without intervention (control); or with their hands immersed in water at 10 degrees C, 20 degrees C or 30 degrees C. The experiment was repeated on a further three days so that the subjects undertook each experimental condition in a balanced randomised order. During the control condition without hand immersion the subjects were unable to cool. Immersion of the hands in water (at 10 degrees C, 20 degrees C or 30 degrees C) significantly (P < 0.05) lowered body core (auditory canal) temperature within ten minutes. Assessing the effectiveness of this technique by the initial rates of core temperature reduction, revealed that immersion of the hands was more effective the colder the water. Following 20 minutes of hand immersion mean core temperature had dropped from 38.5C to: 36.9(standard deviation 0.19) degrees C, 37.3(0.18) degrees C, and 37.8(0.10) degrees C, in 10 degrees C, 20 degrees C and 30 degrees C water respectively. Cooling powers estimated from changes in mean body temperature were 334, 307 and 113 watts using 10 degrees C, 20 degrees C and 30 degrees C water respectively. These results indicate that hand immersion in water at a temperature of between 10 degrees C and 30 degrees C is an efficient means of cooling heat stressed personnel who have been exercising. This simple and effective technique may be applied to many industrial and military tasks to reduce heat strain, lower the risk of heat injury, and increase safe total work times in the heat. For the RN, hand immersion could be used in fire fighting, damage control and NBC operations where personnel alternately work and rest.
... PC studies often take multiple temperature measurements to assess the treatment's merits [1,14,20]. They include internal body heat measurements, as well as thermistors placed at several sites on the skin's surface to record temperatures [14,22]. Yet skin temperatures are, at best, an indirect and transitory index of the body's heat removal efforts as they do not quantify the absolute volume of heat transferred. ...
... Auditory canal temperature (ACT), an indirect estimate of body core and cerebral temperatures, was measured with a hand-held device (Braun; Winamac, IN) [24,25]. As an estimate of core temperatures, ACT was deemed superior to oesophageal measurements and have been used in both sedentary [25,26] and exercise-based studies [22,27]. Palm temperature and heat transfer data were also collected from subjects at this time. ...
... While skin temperature measurements were helped detect inter-treatment differences in PC studies with high-intensity exercise or exposure to warm environmental conditions [1,14,22], PC's efficacy has been likely underreported since heat transfer values were not provided. With a randomized within-subjects design, the current study was the first exercise-based investigation to measure heat transfer and other physiological variables. ...
BACKGROUND
Excess heat accrual is perhaps the body’s most dangerous exercise-induced stressor. While palm cooling uses conduction to reduce body temperatures, to date the volume of heat transferred by this treatment resulting from exercise is unknown.
OBJECTIVE
Asses continuous palm cooling’s impact on heat transfer and physiology.
METHODS
Thirty-one subjects did two workouts; one with, and one without, palm cooling. Workouts entailed consecutive stages of submaximal pedaling against prescribed workloads. Gloves were worn at workouts; for palm cooling 10.6 ∘ C gel packs were inserted into gloves at the workout’s start and conclusion. Heart rate, auditory canal and palm skin temperatures, and heat transfer across the palm were collected. Data were obtained pre-exercise, at the end of a warm-up, and at multiple times during the 25 minutes of pedaling and 30 minutes of recovery.
RESULTS
Auditory canal temperatures had a significant treatment effect (palm cooling [Formula: see text] non-palm cooling). Palm skin temperature had an interaction, with higher non-palm cooling values at multiple times. Conversely, heat transfer also produced an interaction, but palm cooling had significantly higher values at multiple times. Heat transfer was 32% higher for the palm cooling workout.
CONCLUSIONS
Continuous palm cooling produced significantly higher heat transfer from submaximal exercise.
... As for the specific anatomical characteristics of the thermal windows, those in the glabrous skin are characterised by a subcutaneous tissue where there are densely packed AVAs and associated venous plexuses. In the human hand, AVAs and associated venous plexuses are found under the nail beds, the tips of the digits, the palm, and the palmar surface of the fingers, but such structures are absent from the dorsal surface of the fingers and hand (see Figure 8d), (House et al., 1997). Figures 8a, 8b and 8c. ...
... Understanding the thermoregulatory role played by the glabrous skin in humans makes it possible to improve human thermoregulatory care models, especially for those persons in occupations where immersion tanks are not feasible. Practical application of this information has been taken up by the military (House et al.,1997), where recruits gain relief from activities in the heat by immersing their hands and forearms in ice cold water (see Figure 8e). ...
Thermal windows are specialized structures for heat exchange. In the dog its body surface which is available for cooling is unexpectedly restricted. This means that when dogs are suffering from exertional heat llness there is no point in hosing the whole dog. Specific cooling strategies which target the chest, inguinal region and paws are best concentrated upon. The rational fr cooling is outlined in this conference paper.
... The hands and feet are considered as two of the most effective body regions for alleviating heat strain using external cooling (House et al., 1997;Livingstone et al., 1995). In this study, PVC tubing was inserted in a water-perfused glove (3.0 m per glove, 6.0 m for a pair of gloves) and a sock (4.2 m per sock, 8.4 m for pair of gloves). ...
We investigated the effects of peripheral cooling using chemotherapy gloves and socks at three cooling temperatures on subjective perceptions. The hands and feet were cooled with 8, 11, and 14°C by water-perfused gloves or socks. Nine females participated in six experimental conditions: hands or feet cooling at 8, 11, and 14°C. The heat was extracted at 3.8, 5.4, and 7.7 kJ·min ¹ via the gloves and at 4.1, 6.0, and 9.0 kJ·min ⁻¹ via the socks. While the results showed that overall subjective perceptions did not differ among the three temperatures (~ 9.0 kJ·min ⁻¹ ), there were significant differences in local thermal comfort, pain sensation, and pain discomfort among the three cooling temperatures ( P < 0.05). When cooling the hands or feet at 8, 11 or 14°C, subjects felt ‘cold’ or ‘cool’, on average, at the end of 60-min cooling with no significant differences among the three temperatures, whereas subjects felt more uncomfortable at 8°C than 14°C for cooling either the hands or feet ( P < 0.05). Subjects felt more pain at 8°C than 14°C cooling for both hands and feet. These results indicate that the 8°C cooling for 60 min might cause uncomfortable pain sensation, especially for cold-vulnerable individuals. We recommend 1) a cooling bout of less than 60 min, 2) a cooling temperature higher than 8oC when cooling the hands or feet, and 3) a higher temperature for the feet when the hands are simultaneously cooled. However, the present results on subjective perceptions should be interpreted with peripheral vasoconstriction of fingers and toes while cooling.
... In circumstances where wholebody immersion is impossible or impractical, then cooling the upper limbs is a viable and effective option. Heat exchanges through the upper limbs were originally recommended by Livingstone et al. (1989), with others developing that concept for heat extraction in the workplace (Allsopp and Poole, 1991;House, 2003;House et al., 1997House et al., , 2003. ...
The Asia-Pacific contains over half of the world's population, 21 countries have a Gross Domestic Product <25% of the world's largest economy, many countries have tropical climates and all suffer the impact of global warming. That ‘perfect storm’ exacerbates the risk of occupational heat illness, yet first responders must perform physically demanding work wearing personal-protective clothing and equipment. Unfortunately, the Eurocentric emphasis of past research has sometimes reduced its applicability to other ethnic groups. To redress that imbalance, relevant contemporary research has been reviewed, to which has been added information applicable to people of Asian, Melanesian and Polynesian ancestry. An epidemiological triad is used to identify the causal agents and host factors of work intolerance within hot-humid climates, commencing with the size dependency of resting metabolism and heat production accompanying load carriage, followed by a progression from the impact of single-layered clothing through to encapsulating ensembles. A morphological hypothesis is presented to account for inter-individual differences in heat production and heat loss, which seems to explain apparent ethnic- and gender-related differences in thermoregulation, at least within thermally compensable states. The mechanisms underlying work intolerance, cardiovascular insufficiency and heat illness are reviewed, along with epidemiological data from the Asia-Pacific. Finally, evidence-based preventative and treatment strategies are presented and updated concerning moisture-management fabrics and barriers, dehydration, pre- and post-exercise cooling, and heat adaptation. An extensive reference list is provided, with >25 recommendations enabling physiologists, occupational health specialists, policy makers, purchasing officers and manufacturers to rapidly extract interpretative outcomes pertinent to the Asia-Pacific.
In many occupational settings, clothing must be worn to protect individuals from hazards in their work environment. However, personal protective clothing (PPC) restricts heat exchange with the environment due to high thermal resistance and low water vapor permeability. As a consequence, individuals who wear PPC often work in uncompensable heat stress conditions where body heat storage continues to rise and the risk of heat injury is greatly enhanced. Tolerance time while wearing PPC is influenced by three factors: (i) initial core temperature ( T c ), affected by heat acclimation, precooling, hydration, aerobic fitness, circadian rhythm, and menstrual cycle (ii) T c tolerated at exhaustion, influenced by state of encapsulation, hydration, and aerobic fitness; and (iii) the rate of increase in T c from beginning to end of the heat‐stress exposure, which is dependent on the clothing characteristics, thermal environment, work rate, and individual factors like body composition and economy of movement. Methods to reduce heat strain in PPC include increasing clothing permeability for air, adjusting pacing strategy, including work/rest schedules, physical training, and cooling interventions, although the additional weight and bulk of some personal cooling systems offset their intended advantage. Individuals with low body fatness who perform regular aerobic exercise have tolerance times in PPC that exceed those of their sedentary counterparts by as much as 100% due to lower resting T c , the higher T c tolerated at exhaustion and a slower increase in T c during exercise. However, questions remain about the importance of activity levels, exercise intensity, cold water ingestion, and plasma volume expansion for thermotolerance. Published 2013. Compr Physiol 3:1363‐1391, 2013.
INTRODUCTION: Space agencies will embark on manned journeys to Mars on smaller vehicles than those used previously. In-flight exercise on those flights must abate the adverse effects microgravity (μG) has on humans. Due to space constraints on these vehicles, a single exercise device must address multiple fitness needs. Exercise and μG individually cause body heat accrual. During in-flight exercise they conspire to exacerbate heat gain. Given the duration of Mars missions and volume of exercise they entail, excess heat accrual must be addressed.
METHODS: This review presents data on μG, thermoregulation, and exercise. Since their relationships are impacted by other variables, energy balance, body water, and cerebral and vascular physiology are discussed. Data are integrated to acknowledge the challenges long-term missions, and the in-flight exercise that accompanies them, impose on thermoregulation. Strategies to limit heat accrual are discussed.
RESULTS: Current in-flight exercise and hardware will not address heat accrual mitigation or operational performance needs for Mars missions.
DISCUSSION: This review suggests for future missions, crewmembers: 1) consume beverages with high sodium contents; 2) employ palm cooling for conductive heat transfer; and 3) perform plyometric exercise on gravity-independent hardware. Research should continue to evaluate these treatments to abate heat gain in μG.
Maguire K, Wydotis M, Bollinger L, Caruso J. Abating heat accrual during exercise in microgravity and implications for future long-term missions . Aerosp Med Hum Perform. 2025; 96(1):53–61.
INTRODUCTION: Space agencies will embark on manned journeys to Mars on smaller vehicles than those used previously. In-flight exercise on those flights must abate the adverse effects microgravity (μG) has on humans. Due to space constraints on these vehicles, a single exercise device must address multiple fitness needs. Exercise and μG individually cause body heat accrual. During in-flight exercise they conspire to exacerbate heat gain. Given the duration of Mars missions and volume of exercise they entail, excess heat accrual must be addressed.
METHODS: This review presents data on μG, thermoregulation, and exercise. Since their relationships are impacted by other variables, energy balance, body water, and cerebral and vascular physiology are discussed. Data are integrated to acknowledge the challenges long-term missions, and the in-flight exercise that accompanies them, impose on thermoregulation. Strategies to limit heat accrual are discussed.
RESULTS: Current in-flight exercise and hardware will not address heat accrual mitigation or operational performance needs for Mars missions.
DISCUSSION: This review suggests for future missions, crewmembers: 1) consume beverages with high sodium contents; 2) employ palm cooling for conductive heat transfer; and 3) perform plyometric exercise on gravity-independent hardware. Research should continue to evaluate these treatments to abate heat gain in μG.
Maguire K, Wydotis M, Bollinger L, Caruso J. Abating heat accrual during exercise in microgravity and implications for future long-term missions . Aerosp Med Hum Perform. 2025; 96(1):53–61.
O'Brien, IT, Kozerski, AE, Gray, WD, Chen, L, Vargas, LJ, McEnroe, CB, Vanhoover, AC, King, KM, Pantalos, GM, and Caruso, JF. Use of gloves to examine intermittent palm cooling's impact on rowing ergometry. J Strength Cond Res XX(X): 000-000, 2020-The aim of this study was to examine the use of gloves on intermittent palm cooling's impact on rowing ergometry workouts. Our methods had subjects (n = 34) complete 3 rowing ergometer workouts of up to 8 2-minute stages separated by 45- or 60-second rests. They were randomized to one of the following treatments per workout: no palm cooling (NoPC), intermittent palm cooling as they rowed (PCex), or intermittent palm cooling as they rowed and post-exercise (PCex&post). Palm cooling entailed intermittent cold (initial temperature: 8.1° C) application and totaled 10 (PCex) and 20 (PCex&post) minutes, respectively. Workouts began with 8 minutes of rest after which pre-exercise data were obtained, followed by a ten-minute warm-up and the workout, and 20 minutes of post-exercise recovery. Numerous physiological and performance variables were collected before, during, and after workouts, and each was analyzed with either a two- or three-way analysis of variance. Our results include, with a 0.05 alpha and a simple effects post hoc, the distance rowed analysis produced a significant workout effect with PCex, PCex&post > NoPC. There were also significant interworkout differences for heart rate (HR) (NoPC > PCex) and blood lactate concentration (NoPC > PCex, PCex&post). We conclude that lower HRs and blood lactate concentrations from intermittent cooling caused subjects to experience less fatigue during those workouts and enabled more work to be performed. Continued research should identify optimal cooling characteristics to expedite body heat removal. Practical applications suggest that intermittent palm cooling administered with gloves enhance performance by abating physiological markers of fatigue.
The purpose of this study was to evaluate upper-limb cooling following (treadmill) exercise performed in the heat (33℃, 70% relative humidity) at each of three speeds: light (6 km.h–1), intermediate (8 km.h–1) and moderate intensity (10 km.h–1). In all trials, exercise ceased when rectal temperature reached 39.0℃. Participants adopted a sitting position for a 20-min recovery, and liquid-cooling sleeves with cold water (6.3℃ were immediately positioned. The chosen work rates resulted in a two-fold difference in exercise duration across those trials, which terminated without significant between-trial differences within either auditory canal or rectal temperatures. Auditory canal temperature elevation rates became progressively faster as the work rate increased: 0.03℃.min–1 (light), 0.05℃.min–1 (intermediate) and 0.07℃.min–1 (moderate) (p<0.05). However, heat extraction during recovery did not differ among those treatments: –11.2 W (SE 0.5; light), –11.8 W (0.6; intermediate) and –12.3 W (0.5; moderate; p>0.05). That outcome was reflected in auditory canal cooling rates (0.03℃.min–1 [light], 0.04℃.min–1 [intermediate] and 0.05℃.min–1 [moderate]). Nevertheless, rectal temperatures continued to rise throughout recovery. It is concluded that heat extraction from moderately hyperthermic individuals, using upper-limb cooling sleeves, appears to be equally rapid, regardless of heating speed, providing the same level of hyperthermia was attained prior to initiating treatment.
Gray, WD, Jett, DM, Cocco, AR, Vanhoover, AC, Colborn, CE, Pantalos, GM, Stumbo, J, Quesada, PM, and Caruso, JF. Ergogenic and physiological outcomes derived from a novel skin cooling device. J Strength Cond Res XX(X): 000-000, 2020-Our study's purpose assessed a cooling headband's ergogenic and physiological impacts. Subjects (15 women and 13 men) completed six visits; the final 3 entailed rowing workouts with the following treatment conditions: no head cooling (NoHC), intermittent head cooling during exercise (HCex), and intermittent head cooling during exercise and post-exercise recovery (HCex&post). Data collection occurred at the following times (a) pre-exercise and post-warm-up, (b) between stages of up to eight 2-minute bouts, and (c) at 5, 10, 15, and 20 minutes post-exercise. In addition to distance rowed, thermal, cardiovascular, perceptual, and metabolic measurements were obtained. Results included a small yet significant intertreatment difference (HCex, HCex&post > NoHC) for distance rowed. Our cardiovascular and metabolic indices exhibited sex and time differences but likely did not contribute to the ergogenic effect. Yet, left hand temperatures (LHT) exhibited significant 2-way and 3-way interactions that were the likely source of the ergogenic effect. Auditory canal temperature (AUDT) results suggest the head is sensitive to heat increases, yet LHT data show headband use evoked significantly greater temperature increases at the hand's palmar surface, indicative of heat transfer. We conclude, and our practical applications suggest, the headband's ergogenic effect was manifested by cold-induced vasodilation at the hand's palmar surface, rather than heat losses through the head.
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