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The roles of hands and feet in temperature regulation in hot and cold environments

January 2009

Authors:

Mike Tipton

University of Portsmouth

Joanne N Caldwell Odgers

Monash University (Australia)

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In this paper, we briefly review the physiological and biophysical characteristics of the hands and feet, and their association with autonomic (physiological) and behavioural temperature regulation, and with thermal injury. A comprehensive review of this topic is not currently available within the literature. The temperatures of the skin and subcutaneous tissues, particularly those of the hands and feet, vary significantly as air temperatures move away from the thermal comfort zone. Mean skin temperature increases approximately 0.7oC for each 1oC elevation in air temperature, with smaller changes at the hands (0.46o.oC-1) and slightly larger changes at the feet (0.8o.oC-1: Bedford, 1936). These variations reflect local differences in metabolic rate, convective heat delivery (mass flow) and thermal exchanges with the thermal environment.

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University of Wollongong

Research Online

Faculty of Health and Behavioural Sciences - Papers Faculty of Health and Behavioural Sciences

2009

e roles of hands and feet in temperature

regulation in hot and cold environments

Nigel A.S. Taylor

University of Wollongong, nigel_taylor@uow.edu.au

Christiano Machado-Moreira

University of Wollongong, cam313@uow.edu.au

Anne van den Heuvel

University of Wollongong, amjvd453@uow.edu.au

Joanne Caldwell

University of Wollongong, jnc063@uow.edu.au

Elizabeth A. Taylor

University of Wollongong

See next page for additional authors

Research Online is the open access institutional repository for the

University of Wollongong. For further information contact Manager

Repository Services: morgan@uow.edu.au.

Publication Details

Taylor, N. A.S.., Machado-Moreira, C., van den Heuvel, A., Caldwell, J., Taylor, E. A.. & Tipton, M. J.. e roles of hands and feet in

temperature regulation in hot and cold environments. irteenth International Conference on Environmental Ergonomics; Boston,

USA: University of Wollongong; 2009. 405-409.

e roles of hands and feet in temperature regulation in hot and cold

environments

Abstract

In this paper, we briey review the physiological and biophysical characteristics of the hands and feet, and

their association with autonomic (physiological) and behavioural temperature regulation, and with thermal

injury. A comprehensive review of this topic is not currently available within the literature. e temperatures

of the skin and subcutaneous tissues, particularly those of the hands and feet, vary signicantly as air

temperatures move away from the thermal comfort zone. Mean skin temperature increases approximately

0.7oC for each 1oC elevation in air temperature, with smaller changes at the hands (0.46o.oC-1) and slightly

larger changes at the feet (0.8o.oC-1: Bedford, 1936). ese variations reect local dierences in metabolic

rate, convective heat delivery (mass ow) and thermal exchanges with the thermal environment.

Keywords

hot, hands, cold, environments, feet, temperature, regulation, roles

Publication Details

Taylor, N. A.S.., Machado-Moreira, C., van den Heuvel, A., Caldwell, J., Taylor, E. A.. & Tipton, M. J.. e roles

of hands and feet in temperature regulation in hot and cold environments. irteenth International

Conference on Environmental Ergonomics; Boston, USA: University of Wollongong; 2009. 405-409.

Authors

Nigel A.S. Taylor, Christiano Machado-Moreira, Anne van den Heuvel, Joanne Caldwell, Elizabeth A. Taylor,

and Michael J. Tipton

is conference paper is available at Research Online: hp://ro.uow.edu.au/hbspapers/190

Proceedings of the 13th International Conference on Environmental Ergonomics, Boston (USA), August 2-7, 2009

405

THE ROLES OF HANDS AND FEET IN TEMPERATURE REGULATION

IN HOT AND COLD ENVIRONMENTS.

Nigel A.S. Taylor1, Christiano A. Machado-Moreira1, Anne M.J. van den Heuvel1,

Joanne N. Caldwell1, Elizabeth A. Taylor1 and Michael J. Tipton2

1Thermal Physiology Laboratory, University of Wollongong, Wollongong, Australia

2Human and Applied Physiology Laboratory, University of Portsmouth, Portsmouth, England

Contact person: nigel_taylor@uow.edu.au

INTRODUCTION

In this paper, we briefly review the physiological and biophysical characteristics of the hands

and feet, and their association with autonomic (physiological) and behavioural temperature

regulation, and with thermal injury. A comprehensive review of this topic is not currently

available within the literature.

The temperatures of the skin and subcutaneous tissues, particularly those of the hands and feet,

vary significantly as air temperatures move away from the thermal comfort zone. Mean skin

temperature increases approximately 0.7oC for each 1oC elevation in air temperature, with

smaller changes at the hands (0.46o.oC-1) and slightly larger changes at the feet (0.8o.oC-1:

Bedford, 1936). These variations reflect local differences in metabolic rate, convective heat

delivery (mass flow) and thermal exchanges with the thermal environment.

NEURAL PATHWAYS

Thermoregulation is achieved by modulating physiological efferent functions (skin blood flow,

sweating, shivering) and implementing behavioural strategies, following the central integration

of thermal feedback from the deep body and superficial tissues. In all environments, cutaneous

thermoreceptors provide the first thermal feedback signals, giving rise to thermal sensations,

physiological adjustments and eventually to decisions relating to the pleasantness or comfort that

the environment and associated responses evoke.

The principal nerves carrying thermoreceptor feedback from the hand are the radial and median

nerves, with the latter having a more important sensory role. This feedback travels to the spinal

cord via the 6th, 7th and 8th cervical spinal nerves, and eventually to the hypothalamus. For the

foot, the corresponding nerves are the tibial, sural and superficial fibular nerves, which enter the

spinal cord via the 1st sacral and 5th lumbar spinal nerves: these nerves also relay efferent signals

that control blood flow, sweating and muscular function. The nerves that dictate thermoeffector

function of the hand leave the spinal cord at the thoracic segments (T2-T8), while those for the

foot leave at the thoracic and lumbar segments (T11-L2).

Most neurones of the sympathetic nervous system are noradrenergic. However, this does not

hold for the thermoefferent fibres, which possess at least three different neurotransmitters. For

instance, the fibres that innervate most eccrine sweat glands are cholinergic, with perhaps some

evidence of noradrenergic control at the glabrous (hairless) surfaces of the hands and feet. Skin

blood flow to these glabrous surfaces is determined solely by noradrenergically mediated

vasoconstrictor nerves (Kellogg, 2006). In contrast, blood flow to the non-glabrous (hairy) skin

regions is mediated by separate noradrenergic vasoconstrictor and active vasodilatory branches

Proceedings of the 13th International Conference on Environmental Ergonomics, Boston (USA), August 2-7, 2009

406

of the sympathetic nervous system; the neurotransmitter for the latter pathway awaits

identification (Kellogg, 2006).

VASCULAR FUNCTION AND DYSFUNCTION

Blood flow to the hands is provided through the radial and ulnar arteries, and via the deep palmar

arch, the superficial palmar branch, the metacarpal arteries and the digital arteries. In the foot,

blood enters from behind each of the malleoli (malleolar arteries) and across the upper surface of

the foot (dorsalis pedis artery). The positioning of these vessels with respect to the bones of the

foot has significant implications for shoe design. Cutaneous capillaries are located just below the

epidermis, with hand veins draining into either superficial or deep vessels, the largest of which

run along the dorsal hand and foot surfaces. Hands and feet also contain arteriovenous

anastomoses, and when these shunts are open, dramatic elevations in skin blood flow can occur.

Indeed, these vessels are responsible for the extremities behaving as very efficient heat

exchangers (radiators), with thermal homeostasis sometimes being achieved entirely through

subtle changes in skin blood flow through the anastomoses of the hands, face and feet (Hales,

1985).

Under thermoneutral conditions, hand blood flow (10 mL.100 mL-1.min-1; Roddie, 1983) is

typically 3-4 times greater than that of the foot (3 mL.100 mL-1.min-1; Colemont and Decoutere,

1981). When normalised to the skin surface area, hand blood flow is 4-5 times greater than the

rest of the body, and about twice that of the foot (Taylor et al., 2008a). During protracted cold

exposures, extremely low local blood flows are observed (hand: 0.15 mL.100 mL-1.min-1; foot:

0.2 mL.100 mL-1.min-1; Taylor et al., 2008a, b), and such flows can be below the metabolic

requirements of these tissues. In the heat, maximal hand blood flow approximates 30 mL.100

mL-1.min-1, while 18 mL.100 mL-1.min-1 appears maximal for the foot (Taylor et al., 2008a, b).

Finger blood flows have greater minimal (0.2 mL.100 mL-1.min-1) to maximal variations (120

mL.100 mL-1.min-1) with changes in whole-body thermal state (Nagasaka et al., 1987). In

addition, blood flow at the middle phalanx is only about 30% of that at the distal phalanx

(Wilkins et al., 1938).

The single most important determinant of hand and foot blood flow is the thermal status of the

body core (Ferris et al., 1947), with a 1oC change in mean skin temperature producing a 1.3 fold

change (10 mL.100 mL-1.min-1) in finger blood flow, and the corresponding change in core

temperature resulting in a 2.8-fold change (32 mL.100 mL-1.min-1; Wenger et al., 1975). Thus,

local temperatures can influence blood flow, but this affect is minimal when the body core is

either hot or cold, and it is greatest when deep body temperature is within the thermoneutral

range.

The blood supply to the hands and feet represents their primary source of heat, and the minimal

blood flows seen with deep and superficial tissue cooling, as a result of intense peripheral

vasoconstriction, represent a physiological amputation of these appendages. The consequence of

this is a loss of both sensation and function, and in particular manual dexterity. Insufficient tissue

perfusion and heat loss affect vascular smooth muscle contractility, which can, if core

temperature is normal or raised, result in vasodilatation. This cold-induced vasodilatation can

protect tissues from, and delay tissue damage. In the absence of tissue warming, extreme or

prolonged cooling of the extremities can result in non-freezing and freezing cold injury. The

Proceedings of the 13th International Conference on Environmental Ergonomics, Boston (USA), August 2-7, 2009

407

former condition has recently been associated with a cold-induced defect in vascular smooth

muscle contractility caused by a loss of NO-dependent endothelial function (Stephens et al.,

2009).

BIOPHYSICAL ATTRIBUTES

Relative to the entire body, the surface area to mass ratio for the hand is 4-5 larger, while that for

a foot is 2.5-3 larger (males-females). Therefore, these appendages provide an effective route for

heat exchange with the environment, as long as thermal energy can be delivered from the body

core via convective (mass flow) pathways.

The maximal hand and foot blood flows (30 and 18 mL.100 mL-1.min-1) can result in theoretical

peak heat transfers from the core to both hands of 12 W or 286 W.m-2 for a 1oC core-skin

gradient. The corresponding values for both feet are 16 W or 404 W.m-2. Thus, while the

absolute heat transfer to the hands and feet from the body core is not high, their surface-area

normalised transfer, when considered in combination with the huge capacity of the arteriovenous

anastomoses to elevate local skin blood flow, makes these appendages very important locations

for heat dissipation (Taylor et al., 2008a; 2008b).

This heat delivery, and its subsequent dissipation, is advantageous in the heat, as it facilitates

central cooling, but, as described above, it can be dangerous in the cold. Furthermore, these data

also represent maximal core-periphery transfers, and not that which occurs between the skin and

its surrounding environment. By using foot and hand temperatures observed during actual air

exposures to 15o, 27o and 45oC (Webb, 1992), the theoretical radiative and convective heat

transfers from each hand and foot to the surrounding air may be computed, and these represent

respective losses of 16.6 W and 25.5 W (15oC), and 7.7 W and 11.8 W (27oC), or gains of 18.1

W and 27.7 W (45oC). More impressive heat transfer occurs when the vasodilated appendages of

heated individuals are placed into cold water (Tipton et al., 1993). In this circumstance, heat loss

can range from 70-85 W (hands) and 90-95 W (feet: House and Tipton, 2002).

SUDOMOTOR FUNCTION

Sweat glands are widely distributed over the body surface, with a total of two-four million glands

capable of producing sweat at peak rates of 10-15 L.d-1. Each hand has approximately 160,000

eccrine sweat glands, with greater numbers on the palmar (115,000) than dorsal surface (46,000:

Machado-Moreira et al., 2008). Similarly, one foot has approximately 155,000 glands, with more

on the plantar (100,000) than the dorsal surface (55,000; Taylor et al., 2006).

Both the hands and feet display two general sweat patterns during heating: low secretion at the

glabrous surfaces, and moderate secretion from all other surfaces. During passive heating at rest

(40 min), where the average whole-body skin temperature was increased from 34.5oC to 35.9oC,

and core temperature was elevated to 37.2oC from 36.9oC, the palms and soles displayed the

lowest intra-segmental sweat rates (palm: 0.16 mg.cm-2.min-1; sole: 0.23 mg.cm-2.min-1).

Conversely, the dorsal surfaces of the distal phalanges of the fingers (0.62 mg.cm-2.min-1) and

the distal phalanx of the big toe (0.50 mg.cm-2.min-1) displayed the highest sweat rates. Under

these experimental conditions, sweating averaged 0.38 mg.cm-2.min-1 from the hands (Machado-

Moreira et al., 2008) and 0.45 mg.cm-2.min-1 from the feet (Taylor et al., 2006).

Proceedings of the 13th International Conference on Environmental Ergonomics, Boston (USA), August 2-7, 2009

408

When exercising in the heat, sweat gland recruitment occurs almost simultaneously across most

body surfaces, including the hands and feet, although the intra-segmental distribution is not

uniform. The dorsal surfaces of both appendages display a relatively consistent secretion rate,

accounting for approximately 65-70% of total sweat flow from each extremity. Peak hand sweat

rates during heavy exercise are: 4.0 mL.h-1 (palm); 16.8 mL.h-1 (volar fingers); 16.6 mL.h-1

(dorsal fingers); and 15.0 mL.h-1 (dorsal hand: Machado-Moreira et al., 2008). Corresponding

sweat production from the foot is: 14.5 mL.h-1 (dorsal), 5.4 mL.h-1 (medial) 5.0 mL.h-1 (lateral),

16.0 mL.h-1 (plantar), 2.9 mL.h-1 (dorsal toes), and 1.1 mL.h-1 (plantar toes; Taylor et al., 2006).

Therefore, the maximal theoretical evaporative cooling possible from a single hand is about 35.4

W (assuming 100% evaporation), and 27.6 W from one foot. Indeed, when normalised to surface

area, the potential for evaporative heat loss from the two hands is 110% greater than at the torso,

and 200% greater than at both feet, but only half that of the forehead (Taylor et al., 2008b).

THERMAL SENSATION AND DISCOMFORT

Thermal sensations arise within the somatosensory cortex. Sensory feedback from the face and

hands, and to a lesser extent the feet and toes, is very powerful as these areas provide feedback to

a larger volume of the somatosensory cortex (Penfield and Rasmussen, 1952). Discomfort drives

behaviour, based upon the pleasantness of a given thermal state, and while this sensation is

related to both the core and peripheral temperatures, it is believed that thermal comfort is

primarily determined by the thermal state of the core (Hensel, 1981). It is known that a

separation exists between local and whole-body discomfort, such that one can have

uncomfortable feet while the rest of body remains thermally comfortable. However, the face,

hands and feet are associated with significantly greater thermal discomfort with local tissue

temperature changes. Indeed, the hands and feet provide very powerful feedback relative to local

comfort, but play a minimal role relative to whole-body thermal discomfort (Cotter et al., 1996).

These high local sensitivities are important to clothing design, but are of less importance to

behavioural responses. The head, however, dominates whole-body thermal sensation and

discomfort (Cotter and Taylor, 2005), so the thermal status of the face has a more powerful role

in dictating thermoregulatory behaviour.

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ACKNOWLEDGEMENT

Some of the research reported within this review was supported by grants from W.L. Gore &

Associates GmbH (Germany) and from the Ministry of Defence (Republic of Slovenia).

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The association between the footwear microclimate and microbial community on the foot plantar skin was investigated by experiments with three participants. Novel methods were developed for measuring in-shoe temperature and humidity at five footwear regions, as well as the overall ventilation rate inside the footwear. Three types of footwear were tested including casual shoes, running shoes, and perforated shoes for pairwise comparison of footwear microclimate and corresponding microbial community on the skin. The major findings are as follows: (1) footwear types make a significant difference to in-shoe temperature at the instep region with the casual shoes sustaining the warmest of all types; (2) significant differences were observed in local internal absolute humidity between footwear types, with the casual shoes sustaining the highest level of humidity at most regions; (3) the perforated shoes provided the highest ventilation rate, followed by running and casual shoes, and the faster the gait, the larger the discrepancy in ventilation rate between footwear types; (4) the casual shoes seemed to provide the most favorable internal environment for bacterial growth at the distal plantar skin; and (5) the bacterial growth at the distal plantar skin showed a positive linear correlation with the in-shoe temperature and absolute humidity, and a negative linear correlation with the ventilation rate. The ventilation rate seemed to be a more reliable indicator of the bacterial growth. Above all, we can conclude that footwear microclimate varies in footwear types, which makes contributions to the bacterial growth on the foot plantar skin.

A 3D multi-segment thermoregulation model of the hand with realistic anatomy: Development, validation, and parametric analysis

Article

Full-text available

May 2021
BUILD ENVIRON

A three-dimensional (3D) multi-segment hand-specific thermoregulation model was developed as a fundamental tool for spatial and temporal skin temperature prediction. Cold-induced vasodilation in fingers was simulated by superimposing symmetrical triangular waveforms onto the basal blood flow. The model used realistic anatomical, physiological, and thermo-physical in formation of a standard human hand and forearm. The inhomogeneity of hand thermal and physiological properties was considered by dividing it into 17 segments: palm, dorsal, forearm, and five fingers, with each finger subdivided into fingertip, middle segment, and finger root except for the thumb, which has no middle segment. Each segment contained a bone core and an outer soft tissue layer. 3D scanning technology was employed to develop the geometrically realistic model of the hand and the bone. The thermo-physical and physiological properties of each segment and layer were obtained from a photogrammetric analysis of anatomic atlases and from literature. Heat transfer throughout the hand by metabolism, blood perfusion, and conduction between the tissue was considered. Heat loss by convection and radiation from the skin and the protective effects of gloves were also included in the model. The model showed good agreement with experimental data from the literature. The developed 3D hand model fills the knowledge gap and builds a bridge between existing knowledge of the hand’s physiology and its application, providing a science-based tool for decision making. The understanding from model studies may also help enhance the wearer’s working efficiency, safety, health, and wellbeing while working in indoor and outdoor cold environments.

Association between foot thermal responses and shear forces during turning gait in young adults

Article

Full-text available

Jan 2021

Background The human foot typically changes temperature between pre and post-locomotion activities. However, the mechanisms responsible for temperature changes within the foot are currently unclear. Prior studies indicate that shear forces may increase foot temperature during locomotion. Here, we examined the shear-temperature relationship using turning gait with varying radii to manipulate magnitudes of shear onto the foot. Methods Healthy adult participants ( N = 18) walked barefoot on their toes for 5 minutes at a speed of 1.0 m s ⁻¹ at three different radii (1.0, 1.5, and 2.0 m). Toe-walking was utilized so that a standard force plate could measure shear localized to the forefoot. A thermal imaging camera was used to quantify the temperature changes from pre to post toe-walking (ΔT), including the entire foot and forefoot regions on the external limb (limb farther from the center of the curved path) and internal limb. Results We found that shear impulse was positively associated with ΔT within the entire foot ( P < 0.001) and forefoot ( P < 0.001): specifically, for every unit increase in shear, the temperature of the entire foot and forefoot increased by 0.11 and 0.17 °C, respectively. While ΔT, on average, decreased following the toe-walking trials (i.e., became colder), a significant change in ΔT was observed between radii conditions and between external versus internal limbs. In particular, ΔT was greater (i.e., less negative) when walking at smaller radii ( P < 0.01) and was greater on the external limb ( P < 0.01) in both the entire foot and forefoot regions, which were likely explained by greater shear forces with smaller radii ( P < 0.0001) and on the external limb ( P < 0.0001). Altogether, our results support the relationship between shear and foot temperature responses. These findings may motivate studying turning gait in the future to quantify the relationship between shear and foot temperature in individuals who are susceptible to abnormal thermoregulation.

Damage to vascular endothelium and smooth muscle contribute to the development of non-freezing cold injury in the rat tail vascular bed in vitro

Conference Paper

Full-text available

Jan 2009

Damage to vascular endothelium and smooth muscle contribute to the development of non-freezing cold injury in the rat tail vascular bed in vitro

Article

Full-text available

Jan 2009

Skin arteriovenous anastomoses, their control and role in thermoregulation cardiovascular shunts

Article

Jan 1985

J.R.S. Hales

The distribution of cutaneous sudomotor and alliesthesial thermosensitivity in mildly heat-stressed humans: an open-loop approach

Article

May 2005

The distribution of cutaneous thermosensitivity has not been determined in humans for the control of autonomic or behavioural thermoregulation under open-loop conditions. We therefore examined local cutaneous warm and cool sensitivities for sweating and whole-body thermal discomfort (as a measure of alliesthesia). Thirteen males rested supine during warming (+4 degrees C), and mild (-4 degrees C) and moderate (-11 degrees C) cooling of ten skin sites (274 cm(2)), whilst the core and remaining skin temperatures were clamped above the sweat threshold using a water-perfusion suit and climate chamber. Local thermosensitivities were calculated from changes in sweat rates (pooled from sweat capsules on all limbs) and thermal discomfort, relative to the changes in local skin temperature. Thermosensitivities were examined across local sites and body segments (e.g. torso, limbs). The face displayed stronger cold (-11 degrees C) sensitivity than the forearm, thigh, leg and foot (P = 0.01), and was 2-5 times more thermosensitive than any other segment for both sudomotor and discomfort responses (P = 0.01). The face also showed greater warmth sensitivity than the limbs for sudomotor control and discomfort (P = 0.01). The limb extremities ranked as the least thermosensitive segment for both responses during warming, and for discomfort responses during moderate cooling (-11 degrees C). Approximately 70% of the local variance in sudomotor sensitivity was common to the alliesthesial sensitivity. We believe these open-loop methods have provided the first dear evidence for a greater facial thermosensitivity for sweating and whole-body thermal discomfort.

The rate of blood flow in normal fingers

Article

The Cerebral Cortex in Man

Article

Jan 1957
Arch Neurol Psychiatr

W. Penfield

This investigator briefly reviews the literature on the cerebral cortex. He discusses his observations on the stimulation of this area in conscious patients. Response is obtained most easily from the vicinity of the fissure of Rolando, but the responses were not obtained from exactly fixed areas. Penfield describes vocalization which he produced with the use of a thyratron stimulator, especially when area 12 was stimulated. Simple movements appeared to be involuntary in nature. Sensation, when produced electrically, was referred to the periphery but unexplained. In the dream state of an epileptic patient, a hallucination was presented by discharge within one portion of the cerebral cortex, but the patient retained insight into his real environment since other portions of the cortex retained their normal functions. Penfield supports the view of Hughlings Jackson that the sensorimotor cerebral cortex represents only a middle level of integration. There seems to be no reason why the neural mechanism of consciousness should migrate outward into the newer exfoliated hemisphere with the acquisition of man's new skills and new adjustments to his environment. This level of integration may lie below the cortex and above the midbrain. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Heat strain is reduced at different rates with hand, foot, forearm or lower leg cooling

Article

Dec 2005

Heat strain in aircrew is exacerbated when personal protective equipment is worn, due to the restriction of sweat evaporation. The most realistic solution to this problem in the military would be to adopt a cooling garment that removed heat from the body surface by direct conduction. Previous work has indicated that heat may be extracted more effectively from the limbs than the torso of the body: the approach traditionally used in conductive cooling garments. This experiment was conducted to test the hypothesis that heat extraction rates when a hand or foot was cooled were greater than that for cooling a forearm or lower leg. Twenty male subjects undertook a repeated-measures study in which heat strain was induced by exercising in a hot climate followed by natural cooling (control) or the application of cooling to the hand, foot, forearm or lower leg. Cooling interventions were undertaken by immersing the site in water at 10°C, but avoiding direct contact with the water by using a plastic bag. Cooling rates were determined from changes in mean body temperature calculated from insulated auditory canal and mean skin temperatures. Mean body temperature and heart rate fell at faster rates in all water-cooling conditions compared to the control (p<0.05). The hand was the most effective and the lower leg the least effective, with forearm and foot being similar and intermediate to these two (p<0.05). Assuming that the cooling rate for two hands is approximately double the rate of cooling for a single hand, and similarly for the other body sites, cooling both hands would extract heat at up to 200 W, similar to the rate of metabolic heat production of rotary-wing aircrew during flight. Cooling the other sites would cool at between 120 and 155 W. It is not known if the cooling achieved using multiple sites would be additive.

Control of peripheral blood flow: responses in the human hand when extremities are warmed.

Article

Aug 1947
Am J Physiol

Sweat Secretion from Palmar and Dorsal Surfaces of the Hands During Passive and Active Heating

Article

Dec 2008
AVIAT SPACE ENVIR MD

It is generally accepted that the palmar (volar) and dorsal surfaces of human hands display different sudomotor responses to mental or thermal stimuli. We tested the hypothesis that, during thermal stimulation, secretion from the dorsal surfaces would always exceed that from the volar aspect of the hand. Sweat secretion from 10 hand sites and the forehead was examined (ventilated capsules) in 10 subjects during passive heating (climate chamber: 36 degrees C, 60% relative humidity, water-perfusion suit: 40 degrees C) immediately followed by incremental cycling to volitional fatigue. This treatment significantly increased core temperature (39.3 degrees C), heart rate (178 bpm), and sweat rate at all sites. Mean sweat secretion during exercise was greater at the forehead (2.90 mg x cm(-2) x min(-1); +/- 0.19) than the hand (1.49 mg x cm(-2) min(-1); +/- 0.27). While no significant differences in sweating were observed among dorsal sites, a nonuniform secretion pattern was observed across the volar surface, with sweating at the palm being the lowest, and that from the volar aspect of the distal phalanges being equivalent to the dorsal hand. These differences became more evident as exercise progressed. Mean hand sweat rate during exercise was 41.7 ml x h(-1), with sweating from the palm accounting for only about 6% of sweat secretion. Sweat secretion from both the palmar and dorsal surfaces of the hand increases during exercise in the heat, although this occurs in a nonuniform fashion. It is possible that a greater sweat gland density on the fingers may account for variations across the volar surface. However, higher dorsal sweating with lower gland counts (high glandular flow) may be attributable to either larger sweat glands, or to a greater cholinergic sensitivity of these glands.

Thermoregulatory control of finger blood flow

Article

Jul 1975
J Appl Physiol

Three men exercised on a bicycle ergometer at 30, 50, asd 70 per cent of maximal aerobic power in ambient temperatures of 15, 25, and 35 degrees C with water vapor pressure less than 18 Torr. Exercies was used to vary internal temperature during as experiment, and different ambient temperatures were used to vary skin temperatures independently of internal temperature. Finger temperature was fixed at about 35.7 degrees C. Espohageal temperature (Tes) was measured with a thermocouple at the level of the left atrium, and mean skin temperature (Tsk) was calcualted from a weighted mean of thermocouple temperatures at eight skin sites. Finger blood flow (BF) was measured by electrocapacitance plethysmography. Although some subjects showed small and equivocal vasomotor effects of exercise, our data are well accounted for by an equation of the form BF equal to alTes + a2Tsk + b, independent of exercise intensity. For these subjects, the ratios a1/a2 (5.9, 8.6, 9.4) were similar to the ratios of the corresponding coefficients recently reported for thermaoregulatory sweating (8.6, 10.4) and for forearm blood flow (9.6).

The roles of hands and feet in temperature regulation in hot and cold environments

Abstract

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