Changes in Spirometric Parameters upon Local Heating of Forearm or Hand Skin

Local heating of the forearm or hand moderately decreases the respiratory volume parameters without changing bronchoconstriction. At the same time, a significant increase in the maximal expiratory flow (MEF₅₀ and MEF₇₅) indicates a limited enhancement of expiration upon local heating. In contrast, local cooling limits the maximum inspiration without affecting expiration.     

The human thermal portrait and its relations with aerobic working capacity and the blood lactate level

In a study on 53 healthy male volunteers with the use of an infrared thermograph, data that the thermal portrait, i.e., skin temperature distribution, under the conditions of muscular rest and minimal chemical thermoregulation activation is related to the maximal aerobic capacity (r = + 0.6) and the lactate level after critical muscle load (r = −0.7) were obtained. A series of pilot experiments on six volunteers showed that acute regional cooling (by placing feet into ice-cold water for 1 min) led to temperature rise in some local areas of the breast and back skin and increase in oxygen uptake, pulmonary ventilation and the respiratory quotient. Simultaneously, the lactate level in peripheral blood was reduced. On the basis of these results, it was assumed that brown adipose tissue (BAT) activity influenced the thermal portrait formation in the case of environmental temperature below thermoneutral. This hypothesis makes it possible to explain a negative correlation between the skin temperature and the body mass index and a twofold increase in the oxygen uptake during acute cold exposure. Nevertheless, further investigations are necessary to clarify the physiological mechanisms underlying the significant correlation between skin temperatures at rest under thermoneutral conditions and the maximal aerobic capacity, anaerobic threshold and lactate accumulation after critical muscle load.     

Differences in finger skin contact cooling response between an arterial occlusion and a vasodilated condition.

To assess the presence and magnitude of the effect of skin blood flow on finger skin cooling on contact with cold objects against the background of circulatory disorder risks in occupational exposures, this study investigates the effect of zero vs. close-to-maximal hand blood flow on short-term (< or =180 s) skin contact cooling response at a contact pressure that allows capillary perfusion of the distal pulp of the fingertip. Six male volunteers touched a block of aluminium with a finger contact force of 0.5 N at a temperature of -2 degrees C under a vasodilated and an occluded condition. Before both conditions, participants were required to exercise in a hot room for > or = 30 min for cutaneous vasodilation to occur (increase in rectal temperature of 1 degrees C). Under the vasodilated condition, forearm blood flow rate rose as high as 16.8 ml.100 ml(-1).min(-1). Under the occluded condition, the arm was exsanguinated, after which a blood pressure cuff was secured on the wrist inducing arterial occlusion. Contact temperature of the finger pad during the subsequent cold contact exposure was measured. No significant difference was found between the starting skin temperatures for the two blood flow conditions, but a distinct difference in shape of the contact cooling curve was apparent between the two blood flow conditions, with Newtonian cooling observed under the occluded condition, whereas a rewarming of the finger skin toward the end of the exposure occurred for the vasodilated condition. Blood flow was found to significantly increase contact temperature from 40 s onward (P < 0.01). It is concluded that, at a finger contact force compatible with capillary perfusion of the finger pad ( approximately 0.5 N), circulating blood provides a heat input source that significantly affects finger skin contact cooling during a vasodilated state.     

Respiratory system response to local cooling in subjects with single nucleotide polymorphism rs11562975 of the TRPM8 temperature-sensitive ion channel gene

Genome studies in ethnic Russians revealed subjects having a heterozygous genotype with allele C at the single-nucleotide polymorphism rs11562975 (G → C), which is in exon 6 of the TRPM8 temperature-sensitive ion channel gene. The subjects had increased sensitivity to cold and produced a hypometabolic response to local skin cooling and to temperature-independent activation of the TRPM8 ion channel by menthol, including a decrease in gas exchange, pulmonary ventilation, and oxygen extraction coefficient. Subjects with the homozygous genotype GG had a lower sensitivity to cold, and their response to local skin cooling was adequate in terms of thermoregulation, including a decrease in respiratory heat loss and an increase in lipid metabolism.     

Forearm oxygen uptake during maximal forearm dynamic exercise

This study was undertaken in an attempt to determine the maximal oxygen uptake in a small muscle group by measuring directly the oxygen expenditure of the forearm. Five healthy medical students volunteered. The subjects' maximal forearm work capacity was determined on a spring-loaded hand ergometer. Exercise was continued until exhaustion by pain or fatigue. Two weeks later intra-arterial and intravenous catheters were placed in the dominant arm. Blood samples for measurement of oxygen concentration were collected via the catheters. Forearm blood flow was measured by means of the indicator dilution technique. Oxygen uptake was determined according to the Fick principle. The forearm oxygen uptake attained at maximal work loads was a mean of 201 (SD +/- 56) mumol.min-1.100 ml-1. It was impossible at maximal exercise to discern a plateau of the oxygen uptake curve in relation to work output. It is suggested that a plateau in the oxygen uptake curve is not a useful criterion for maximal oxygen uptake in a small muscle group. Skeletal muscle may have an unused capacity for oxygen consumption even at maximal exercise intensity where muscle work cannot be continued due to muscle pain and fatigue.     

Combined effect of repetitive work and cold on muscle function and fatigue.

This study compared the effect of repetitive work in thermoneutral and cold conditions on forearm muscle electromyogram (EMG) and fatigue. We hypothesize that cold and repetitive work together cause higher EMG activity and fatigue than repetitive work only, thus creating a higher risk for overuse injuries. Eight men performed six 20-min work bouts at 25 degrees C (W-25) and at 5 degrees C while exposed to systemic (C-5) and local cooling (LC-5). The work was wrist flexion-extension exercise at 10% maximal voluntary contraction. The EMG activity of the forearm flexors and extensors was higher during C-5 (31 and 30%, respectively) and LC-5 (25 and 28%, respectively) than during W-25 (P < 0.05). On the basis of fatigue index (calculated from changes in maximal flexor force and flexor EMG activity), the fatigue in the forearm flexors at the end of W-25 was 15%. The corresponding values at the end of C-5 and LC-5 were 37% (P < 0.05 in relation to W-25) and 20%, respectively. Thus repetitive work in the cold causes higher EMG activity and fatigue than repetitive work in thermoneutral conditions.     

Thermal, cardiac and adrenergic responses to repeated local cooling

The aim of this study was to ascertain whether repeated local cooling induces the same or different adaptational responses as repeated whole body cooling. Repeated cooling of the legs (immersion into 12 degrees C water up to the knees for 30 min, 20 times during 4 weeks = local cold adaptation - LCA) attenuated the initial increase in heart rate and blood pressure currently observed in control subjects immersed in cold water up to the knees. After LCA the initial skin temperature decrease tended to be lower, indicating reduced vasoconstriction. Heart rate and systolic blood pressure appeared to be generally lower during rest and during the time course of cooling in LCA humans, when compared to controls. All these changes seem to indicate attenuation of the sympathetic tone. In contrast, the sustained skin temperature in different areas of the body (finger, palm, forearm, thigh, chest) appeared to be generally lower in LCA subjects than in controls (except for temperatures on the forehead). Plasma levels of catecholamines (measured 20 and 40 min after the onset of cooling) were also not influenced by local cold adaptation. Locally cold adapted subjects, when exposed to whole body cold water immersion test, showed no change in the threshold temperature for induction of cold thermogenesis. This indicates that the hypothermic type of cold adaptation, typically occurring after systemic cold adaptation, does not appear after local cold adaptation of the intensity used. It is concluded that in humans the cold adaptation due to repeated local cooling of legs induces different physiological changes than systemic cold adaptation.     

A physiologically discrete population of chromatophres in Octopus vulgaris (Mollusca)

Specimens of Octopus vulgaris (Cuvier) immersed in cold sea-water (4°C) exhibit a flashing display of brown chromatophores that we call "brown spots". The spots, which flashed approximately once every three seconds, are distributed over the dorsal skin of the head, mantle and arms and correspond mainly with the distribution of the white spots and white streaks previously described, and appear to act as a screen for the patches composing the white spots. Flashing brown spots could be evoked in animals with the supraoesophageal brain removed but not in animals with local denervation of the skin.
The precise site of action of the cold is unknown but it is proposed that the nerves supplying the brown spot units are normally tonically inhibited and that the cooling process removes this inhibition and allows the spots to flash. They are particularly useful for the in vivo study of the control of chromatophores because they can be reliably activated and isolated from responses of other chromatophores.     

The effect of cold adaptation on total gaseous metabolism and tissue respiration in gerbils]

Short-term adaptation to cold (-17-19 degrees) results in evident changes of energy metabolism of gerbiles. In cold-adapted Meriones unguiculatus, tissue oxygen consumption increases in all the tissues investigated. In M. tamariscinus, respiratory rate increased only in the cardiac muscle, whereas that in other organs and muscles remained unaffected. In contrast to these two cold-resistant species, M. erythrourus is less resistant to cooling. In the latter case, no changes were observed in total and tissues respiration after cold adaptation of animals.     

Effect of hand heating by a warm air box on O2 consumption of the contralateral arm.

Arterialization of venous blood is often used in studying forearm metabolism. Astrup et al. [Am. J. Physiol. 255 (Endocrinol. Metab. 18): E572-E578, 1988] showed that heating of the hand by a warming blanket caused a redistribution of blood flow in the contralateral arm and thus introduced errors in forearm skeletal muscle flux calculations. The present study was undertaken to investigate how hand heating by a warm air box (60 degrees C) would affect metabolism and blood flow in the contralateral arm before and during 3 h after a glucose load. Eleven healthy volunteers (5 males, 6 females) underwent an oral glucose tolerance test (70 g) on two different occasions, one test with and one without heating of the contralateral hand, in random order. Heating the hand for 30 min before glucose intake did not affect skin temperature, rectal temperature, deep venous oxygen saturation, forearm blood flow, or oxygen consumption of forearm skeletal muscle. Although, after the glucose load, heating significantly increased forearm blood flow (P less than 0.05), the integrated response after glucose was not significantly different between control and heating experiments [67 +/- 43 and 117 +/- 41 (SE) ml/100 ml tissue]. With both conditions, there was an increase in skin temperature (P less than 0.001, integrated response control: 369 +/- 79 and heating: 416 +/- 203 degrees C) and oxygen consumption of forearm muscle (control: 290 +/- 73, P less than 0.05 and heating: 390 +/- 130 mumol/100 ml, P less than 0.05) after glucose intake. These responses did not significantly differ between the conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aging and the skin blood flow response to the unloading of baroreceptors during heat and cold stress.

Control of skin blood flow (SkBF) is on the efferent arm of both thermoregulatory and nonthermoregulatory reflexes. To what extent aging may affect the SkBF response when these two reflex systems interact is unknown. To determine the response of aged skin to the unloading of baroreceptors in thermoneutral, cold stress, and heat stress conditions, sequential bouts of nonhypotensive lower body negative pressure (LBNP) were applied at -10, -20, and -30 mmHg in 14 young (18-25 yr) and 14 older (63-78 yr) men. SkBF was measured by laser-Doppler velocimetry (averaged over 2 forearm sites), and data are expressed as percentage of maximal cutaneous vascular conductance (%CVC(max)). Total forearm blood flow was measured by venous occlusion plethysmography, and forearm vascular conductance (FVC) was calculated as the ratio of forearm blood flow to mean arterial pressure. In young men, all three intensities of LBNP in thermoneutrality decreased FVC significantly (P < 0.05), but FVC at -10 mmHg did not change in the older men. There were no significant LBNP effects on %CVC(max). Application of LBNP during cold stress did not significantly change %CVC(max) or FVC in either age group. During heat stress, -10 to -30 mmHg of LBNP decreased FVC significantly (P < 0.05) in both age groups, but these decreases were attenuated in the older men (P < 0.05). %CVC(max) decreased at -30 mmHg in the younger men only. These results suggest that older men have an attenuated skin vasoconstrictor response to the unloading of baroreceptors in heat stress conditions. Furthermore, the forearm vasoconstriction elicited by LBNP in older men reflects that of underlying tissue (i.e., muscle) rather than that of skin, whereas -30 mmHg LBNP also decreases SkBF in young hyperthermic men.     

Intra- and extravascular volume changes in the human forearm after static hand grip exercise.

Studies have been conducted to evaluate intra- and extravascular volume changes and blood flow in the exercising human forearm by means of (1) combining plethysmographic and scintigraphic methods, (2) an indirect procedure using the relationship of blood flow and volume change from reactive hyperemia. A static hand grip exercise of 60% maximal voluntary contraction and 30 s duration increased the forearm volume by 3.03 +/- 0.65 ml/100 ml soft tissue, involving both the intra- and extravascular volume components. There is a quantitative and qualitative difference in the time course of change in these components, showing an extravascular part of about 50% for the 2-min post-exercise value and a substantially slower rate of recovery. Experiments involving muscle work at intervals (50% maximal voluntary contraction, 30 s duration, 2-min intervals) caused a further increase in extravascular volume. Furthermore, the study suggests that the flow-volume relationship from reactive hyperemia may be considered to be available for the determination of local blood volume changes in exercise hyperemia. The results are discussed in connection with the influence of anaerobic muscle metabolism and conclusions referring to this are drawn about the use of plethysmographic methods.     

Recovery of maximal isometric grip strength following cold immersion

The purpose of this study was to investigate the effects of various cold immersion durations on maximal grip strength and the subsequent recovery of grip strength. Sixteen healthy men between 20 and 42 years of age participated in this study. Maximal isometric grip strength was measured before, immediately after, and 5, 10, and 15 minutes after cold immersion. Subjects submerged their dominant elbow, forearm, and hand in a cold water whirlpool at 10 degrees C for 5, 10, 15, or 20 minutes. There was a significant decrease in isometric grip strength when the forearm was immersed in 10 degrees C water for durations between 5 and 20 minutes and no recovery of this strength loss for a period of 15 minutes following removal from the cold immersion (p = 0.0001). These findings suggest that clinicians should be aware of the alterations in isometric muscle strength that result from utilizing the temperature and time frames of cold application used in this study.     

Simulation of hand cooling due to touching cold materials

A simple analytical model has been developed to simulate the cooling of the hands due to touching various types of cold material. The model consisted of a slab of tissue, covered on both sides with skin. The only active mechanism was the skin blood flow. The blood flow was controlled by body core temperature, mean skin temperature, and local hand temperature. The blood flowed along the palm before returning via the back of the hand. The control function was adapted from an earlier study, dealing with feet, but enhanced with a cold induced vasodilatation term. The palm of the hand was touching materials that were specified by conductivity and heat capacity. The hand was initially at a steady-state in a neutral environment and then suddenly grabbed the material. The resulting cooling curves have been compared to data from an experiment including six materials (foam, wood, nylon, steel, aluminium and metal at a constant temperature), three temperatures (-10, 0, and 10 degrees C), two thermal states of the body (neutral and 0.4 degrees C raised), and with and without gloves. There was a fair general agreement between the model and the experiment but the model failed to predict three specific effects: the unequal effect of equal 10 degrees C steps in cold surface temperature on the temperature of the palm of the hand, the cooling effect of nylon, and the rapid drop in back of the hand temperature. Nevertheless the overall regression was 0.88 with a standard deviation between model and experiment of about 2.5 degrees C.     

Effects of age, sex, and physical fitness on responses to local cooling

The response to local cooling was estimated by the cold hand test (5 degrees C for 2 min) and the cold face test (0 degrees C with 66 km.h-1 wind for 2 min). Heart rate, blood pressure, and skin temperature were measured before, during, and after the tests. The increase in blood pressure (cold hand test) and the fall in Tsk (cold face test) were reduced in trained subjects. Similarly older subjects (53-60 yr of age) responded less to a cold hand test than younger subjects aged 20-40. However, the bradycardia caused by the cold face test was more pronounced in the older subjects. The responses to the cold hand and cold face tests were the same for male and female subjects. During the 2 min after the test, blood pressure and heart rate fell below initial values in the female group but not in the male. It is concluded that, besides adaptation to cold, individual factors such as age, sex, and physical fitness also have a relative importance in the responses to local cooling.     

Blood flow and muscle bio-energetics by 31P-nuclear magnetic resonance after local cold acclimation.

To clarify the origin of local cold adaptation and to define precisely its influence on muscle bio-energetics during local exercise, five subjects were subjected to repeated 5 degrees C cold water immersion of the right hand and forearm. The first aim of our investigation was therefore carried out by measuring local skin temperatures and peripheral blood flow during a cold hand test (5 degrees C, 5 min) followed by a 10-min recovery period. The 31P by nuclear magnetic resonance (31PNMR) muscle bio-energetic changes, indicating possible heat production changes, were measured during the recovery period. The second aim of our investigation was carried out by measuring 31PNMR muscle bioenergetics during handgrip exercise (10% of the maximal voluntary contraction for 5 min followed by a 10-min recovery period) performed both at a comfortable ambient temperature (22 degrees C; E) and after a cold hand test (EC), before and after local cold adaptation. Local cold adaptation, confirmed by warmer skin temperatures of the extremities (+30%, P less than 0.05), was related more to an increased peripheral blood flow, as shown by the smaller decrease in systolic peak [-245 (SEM 30) Hz vs -382 (SEM 95) Hz, P less than 0.05] than to a change in local heat production, because muscle bioenergetics did not vary. Acute local cold immersion decreased the inorganic phosphate:phosphocreatine (PC) ratio during EC compared to E [+0.006 (SEM 0.010) vs +0.078 (SEM 0.002) before acclimation and +0.029 (SEM 0.002) vs +0.090 (SEM 0.002) after acclimation respectively, P less than 0.05] without significant change in the PC:beta-adenosine triphosphate ratio and pH. Local adaptation did not modify these results statistically. The recovery of PC during E increased after acclimation [9.0 (SEM 0.2) min vs 3.0 (SEM 0.4) min, P less than 0.05]. These results suggested that local cold adaptation is related more to peripheral blood flow changes than to increased metabolic heat production in the muscle.     

Effect of rapid and slow cooling on thermoregulatory responses in hypertensive and normotensive rats after calcium administration

The effect of iontophoretic administration of calcium ions to skin in the area of cold stimulus application on the thermal thresholds and the magnitude of cold defense responses in normotensive Wistar and hypertensive ISIAH rats was studied. In thermoneutral conditions, administration of calciumions wos without effect on the measured thermoregulatory parameters. Under the effect of calcium, the thresholds of all the thermoregulatory responses to cooling (such as heat loss, oxygen consumption, shivering) are lowered and the values of heat loss and shivering thermogenesis are considerably increased. The effects of calcium on thermoregulatory responses depend on the rate of cooling. All changes are more expressive in hypertensive rats. The increased sensitivity of hypertensives to calcium suggests that change in their calcium metabolism may be a cause of the observed shifts in the thermoregulatory response to cold.     

Peripheral blood flow during rewarming from mild hypothermia in humans

During the initial stages of rewarming from hypothermia, there is a continued cooling of the core, or after-drop in temperature, that has been attributed to the return of cold blood due to peripheral vasodilatation, thus causing a further decrease of deep body temperature. To examine this possibility more carefully, subjects were immersed in cold water (17 degrees C), and then rewarmed from a mildly hypothermic state in a warm bath (40 degrees C). Measurements of hand blood flow were made by calorimetry and of forearm, calf, and foot blood flows by straingauge venous occlusion plethysmography at rest (Ta = 22 degrees C) and during rewarming. There was a small increase in skin blood flow during the falling phase of core temperature upon rewarming in the warm bath, but none in foot blood flow upon rewarming at room air, suggesting that skin blood flow seems to contribute to the after-drop, but only minimally. Limb blood flow changes during this phase suggest that a small muscle blood flow could also have contributed to the after-drop. It was concluded that the after-drop of core temperature during rewarming from mild hypothermia does not result from a large vasodilatation in the superficial parts of the periphery, as postulated. The possible contribution of mechanisms of heat conduction, heat convection, and cessation of shivering thermogenesis were discussed.     

Effect of cooling rate and intensity on the immune response and corticosterone blood level in rats

Changes in the rat antigen-induced immune activity were shown to depend on cooling depth: slight cooling activated the immune response whereas deep cooling inhibited it. Involvement of the skin cold receptors' dynamic activity in responses to rapid cooling attenuated the effect of cold exposure on the immune response as well as the corticosterone elevation in plasma.