Reduced Skin Temperature Research Articles

Post-exercise Hot Water Immersion Elicits Heat Acclimation Adaptations in Endurance Trained and Recreationally Active Individuals.

Hot water immersion (HWI) after exercise on 6 consecutive days in temperate conditions has been shown to provide heat acclimation adaptations in a recreationally active population. Endurance athletes experience frequent, sustained elevations in body temperature during training and competition; as a consequence, endurance athletes are considered to be partially heat acclimatized. It is therefore important to understand the extent to which endurance trained individuals may benefit from heat acclimation by post-exercise HWI. To this end, we compared the responses of eight endurance trained and eight recreationally active males (habitual weekly endurance exercise: 9 h vs. 3 h) to a 6-day intervention involving a daily treadmill run for 40 min (65% O2max) in temperate conditions followed immediately by HWI (≤40 min, 40°C). Before (PRE) and after the intervention (POST), hallmark heat acclimation adaptations were assessed during a 40-min treadmill run at 65% O2max in the heat (33°C, 40% RH). The 6 day, post-exercise HWI intervention induced heat acclimation adaptations in both endurance trained and recreationally active individuals. Training status did not significantly influence the magnitude of heat acclimation adaptations from PRE to POST (interactions P > 0.05) for: the reduction in end-exercise rectal core temperature (Tre, mean, endurance trained -0.36°C; recreationally active -0.47°C); the reduction in resting Tre (endurance trained -0.17°C; recreationally active -0.23°C); the reduction in Tre at sweating onset (endurance trained -0.22°C; recreationally active -0.23°C); and, the reduction in mean skin temperature (endurance trained -0.67°C; recreationally active -0.75°C: PRE to POST P < 0.01). Furthermore, training status did not significantly influence the observed reductions in mean O2, mean metabolic energy expenditure, end-exercise physiological strain index, perceived exertion or thermal sensation (PRE to POST P < 0.05). Only end-exercise heart rate was influenced by training status (P < 0.01, interaction); whereby, recreationally active but not endurance trained individuals experienced a significant reduction in end-exercise heart rate from PRE to POST (P < 0.01). In summary, these findings demonstrate that post-exercise HWI presents a practical strategy to reduce thermal strain during exercise-heat-stress in endurance trained and recreationally active individuals.

Small reductions in skin temperature after onset of a simulated hemorrhagic challenge improve tolerance in exercise heat-stressed individuals.

We investigated whether small reductions in skin temperature 60 s after the onset of a simulated hemorrhagic challenge would improve tolerance to lower body negative pressure (LBNP) after exercise heat stress. Eleven healthy subjects completed two trials (High and Reduced). Subjects cycled at ~55% maximal oxygen uptake wearing a warm water-perfused suit until core temperatures increased by ~1.2°C before lying supine and undergoing LBNP to presyncope. LBNP tolerance was quantified as cumulative stress index (CSI; product of each LBNP level multiplied by time; mmHg·min). Skin temperature was similarly elevated from baseline before LBNP and remained elevated 60 s after the onset of LBNP in both High (37.72 ± 0.52°C) and Reduced (37.95 ± 0.54°C) trials (both P < 0.0001). At 60%CSI skin temperature remained elevated in the High trial (37.51 ± 0.56°C) but was reduced to 34.97 ± 0.72°C by the water-perfused suit in the Reduced trial ( P < 0.0001 between trials). Cutaneous vascular conductance was not different between trials [High: 1.57 ± 0.43 vs. Reduced: 1.39 ± 0.38 arbitrary units (AU)/mmHg; P = 0.367] before LBNP but decreased to 0.67 ± 0.19 AU/mmHg at 60%CSI in the Reduced trial while remaining unchanged in the High trial ( P = 0.002 between trials). CSI was higher in the Reduced (695 ± 386 mmHg·min) relative to the High (441 ± 290 mmHg·min; P = 0.023) trial. Mean arterial pressure was not different between trials at presyncope (High: 62 ± 10 vs. Reduced: 62 ± 9 mmHg; P = 0.958). Small reductions in skin temperature after the onset of a simulated hemorrhagic challenge improve LBNP tolerance after exercise heat stress. This may have important implications regarding treatment of an exercise heat-stressed individual (e.g., soldier) who has experienced a hemorrhagic injury.

Mixed-methods pre-match cooling improves simulated soccer performance in the heat

ABSTRACTThis investigation examined the effects of three pre-match and half-time cooling manoeuvres on physical performance and associated physiological and perceptual responses in eight University soccer players during a non-motorised treadmill based individualised soccer-specific simulation [intermittent soccer performance test (iSPT)] at 30°C. Four randomised experimental trials were completed; following 30-min (pre-match) and 15-min (half-time) cooling manoeuvres via (1) ice slurry ingestion (SLURRY); (2) ice-packs placed on the quadriceps and hamstrings (PACKS); (3) mixed-methods (MM; PACKS and SLURRY concurrently); or no-cooling (CON). In iSPT first half, a moderate increase in total (Mean ± Standard Deviation: 108 ± 57 m, qualitative inference: most likely, Cohen’s d: 0.87, 90%CL: ±0.31), high-speed (56 ± 46 m, very likely, 0.68 ± 0.38) and variable run (15 ± 5 m, very likely, 0.81 ± 0.47) distance covered was reported in MM compared with CON. Additionally, pre-match reductions in thermal sensation (–1.0 ± 0.5, most likely, –0.91 ± 0.36), rectal (–0.6 ± 0.1°C, very likely, –0.86 ± 0.35) and skin temperature (–1.1 ± 0.3°C, very likely, –0.88 ± 0.42) continued throughout iSPT first half. Physical performance during iSPT first half was unaltered in SLURRY and PACKS compared to CON. Rectal temperature was moderately increased in SLURRY at 45-min (0.2 ± 0.1°C, very likely, 0.67 ± 0.36). Condition did not influence any measure in iSPT second half compared to CON. Only MM pre-match cooling augmented physical performance during iSPT first half, likely due to peripheral and central thermoregulatory factors favourably influencing first half iSPT performance. Further practical half-time cooling manoeuvres which enhance second half performance are still required.

Buspirone Nanovesicular Nasal System for Non-Hormonal Hot Flushes Treatment.

The aim of this work was to design and characterize a new nanovesicular nasal delivery system (NDS) containing buspirone, and investigate its efficiency in an animal model for the treatment of hot flushes. The presence of multilamellar vesicles with a mean size distribution of 370 nm was evidenced by transition electron microscopy (TEM), cryo-scanning electron microscopy (Cryo-SEM), and dynamic light scattering (DLS) tests. Pharmacodynamic evaluation of the nasal treatment efficacy with the new system was carried out in ovariectomized (OVX) rat—an animal model for hot flushes—and compared with other treatments. We found that the nasal administration of a buspirone NDS resulted in a significant reduction in tail skin temperature (TST). This effect was not observed in the control buspirone-treated groups. Buspirone levels in the plasma and brain of nasally-treated normal rats were quantified and compared with those of rats that had received oral administration by a LC-MS/MS assay. A significantly higher bioavailability was achieved with the new treatment relative to an oral administration of the same drug dose. No pathological changes in the nasal cavity were observed following sub-chronic nasal administration of buspirone NDS. In conclusion, the data of our investigation show that buspirone in the new nanovesicular nasal carrier could be considered for further studies for the development of a treatment for the hot flushes ailment.

THE EFFECT OF WHOLE BODY GAS CRYOTHERAPY ON THE HUMAN THERMAL STATE

The therapeutic effect of the whole body gas cryotherapy (WBGC) procedure is achieved when the average temperature of the human’s (patient’s) skin surface during the procedure is in a certain temperature range, and the rate of reduction of this temperature exceeds a certain threshold value. The paper presents the results of a theoretical analysis of the patient’s thermal state at the stage of the therapeutic effect of WBGC. The analysis was based on the results of the numerical simulation of temperature distribution in different parts of patients (mеn) of different body constitution (height, cm × mass, kg) 160 × 60, 175 × 75, 190 × 90. Particular attention was paid to the relationship between the amount of heat flow removed from the skin surface and the rate of cooling of the skin of a patient. The results of numerical modeling are presented graphically and are summarized as the ratio between the dimensionless average temperature of the skin at the treatment stage of the WBGC procedure and the time of the patient’s stay in the procedural chamber, referred to the time of the beginning of this stage. With regard to WBGC within the temperatures range of –160 to –110 °C the following regularities were found: 1) approximate constancy (descripancy less than 1 %) at the stage of therapeutic modality of the coefficient of heat transfer from the skin surface to the gas medium in the treatment chamber; 2) the exponential dependence of the value of cutaneous blood flow rate (blood perfusion) on the mean temperature of cooled cutaneous coverings; 3) linear dependence of the logarithm of the ratio of the rate of skin temperature reduction to the value of heat flux density removed by convection and radiation on the logarithm time.

Correlation Between Skin Temperature Over Myofascial Trigger Points in the Upper Trapezius Muscle and Range of Motion, Electromyographic Activity, and Pain in Chronic Neck Pain Patients

ObjectiveThe purpose of this study was to assess the correlation between skin temperature over a myofascial trigger point in the upper trapezius muscle and range of motion of the cervical spine, electromyographic activity, and pain in patients with chronic neck pain. MethodsThis is a single-blind cross-sectional study. Forty participants of both sexes, aged 18 to 45 years, with chronic neck pain and myofascial trigger points in the upper trapezius muscle were included in the study. The participants were assessed using the Numeric Rating Scale, the Neck Disability Index, infrared thermography, algometry, fleximetry, and electromyographic activity. ResultsA positive association was observed between skin temperature to the right with the range of motion of cervical flexion (r = 0.322, P = .043), the median frequency of isometrics to the right (r = 0.341, P = .032), and the median frequency of rest to the left (rs = 0.427, P = .006); as were a negative association between skin temperature to the right and the root mean square of rest to the right (rs = -0.447, P = .004), and a positive association of skin temperature to the left with the median frequency of isometrics to the right (r = 0.365, P = .020), and the median frequency of rest to the left (rs = 0.573, P < .001). ConclusionPatients with chronic neck pain who had reduction of skin temperature over myofascial trigger points in the upper trapezius muscle had reduced cervical range of motion for flexion, reduced median frequency at rest and during isometric contraction, and increased root mean square at rest.

Modest Reductions in Skin Temperature After the Onset of a Simulated Hemorrhagic Challenge Improve LBNP Tolerance Following Exercise Heat Stress

Soldiers are often deployed to warm environments where they are exposed to exercise and heat stress whilst wearing body armor, resulting in increased mean skin (Tskin) and core (Tcore) temperatures. Our aim was to investigate whether modestly lowering Tskin 60 seconds after the onset of a simulated hemorrhagic challenge (Lower Body Negative Pressure; LBNP) would improve LBNP tolerance following exercise heat stress. Ten healthy subjects (Age: 26 ± 5 yrs; Ht: 179.3 ± 7.2 cm; Wt: 81.4 ± 18.1 kg) completed two blinded and counterbalanced trials (Trial A and Trial B) where they cycled at 55.7 ± 4.5% of their predetermined VO2Max whilst wearing a warm water perfused suit. Participants then underwent LBNP to pre syncope. The increase in Tcore from the onset of exercise to pre‐LBNP was not different between trials (+1.1 ± 0.2 °C; P &gt; 0.05). In Trial A, Tskin remained elevated throughout LBNP while in Trial B, Tskin was modestly lowered 60 seconds after the onset of LBNP. LBNP tolerance was quantified as cumulative stress index (CSI; mmHg*min). Mean arterial pressure (MAP) was lowered following exercise (pre‐LBNP) relative to baseline in both trials (Trial A from: 90 ± 7 to: 81 ± 9 mmHg and Trial B from: 89 ± 11 to: 79 ± 5 mmHg; both P &lt; 0.05). Tskin was not different between Trial A and Trial B at baseline (32.5 ± 0.3 vs. 32.9 ± 0.7 °C), pre‐LBNP (38.0 ± 0.6 vs. 38.0 ± 0.6 °C), and 60 seconds after the onset of LBNP (37.7 ± 0.5 vs. 37.9 ± 0.6 °C) (all P &gt; 0.05). In Trial A, Tskin remained elevated throughout LBNP (40% CSI: 37.5 ± 0.5 °C and pre syncope: 37.4 ± 0.5 °C). In Trial B, Tskin was lower at 40% CSI and pre syncope (35.1 ± 1.2 and 34.8 ± 0.4 °C, respectively) relative to pre‐LBNP but remained higher relative to baseline (all P &lt; 0.05). In Trial B, Tskin was lower at 40% CSI and pre syncope relative to those respective time points in Trial A (both P &lt; 0.05). CSI was higher in Trial B (760 ± 400 mmHg*min) relative to Trial A (481 ± 272 mmHg*min; P = 0.033). MAP was not different between trials at pre syncope (Trial A: 63 ± 10 vs. Trial B: 64 ± 8 mmHg; P &gt; 0.05). These data indicate that modestly reducing skin temperature shortly after the onset of a simulated hemorrhagic challenge improves LBNP tolerance following an exercise heat stress. Importantly, LBNP tolerance was improved by a slight reduction in Tskin, such that mean skin temperatures were reduced relative to pre‐LBNP yet remained higher than at baseline. This suggests that following an exercise heat stress a modest reduction in skin temperature applied after the onset of a hemorrhagic challenge may improve an individual's tolerance to a hemorrhagic insult. This may have important implications regarding immediate treatment of an exercise and heat stressed individual (e.g. soldier or firefighter) who has experienced a hemorrhagic injury.Support or Funding InformationFunded by UCCS CRCW awardThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Face cooling reveals a relative inability to increase cardiac parasympathetic activation during passive heat stress.

What is the central question of this study? Does passive heat stress attenuate the increase in cardiac parasympathetic stimulation, vascular resistance and blood pressure evoked by face cooling? What is the main finding and its importance? Passive heat stress attenuates the capacity to increase cardiac parasympathetic activation and impairs the ability to increase vascular resistance during sympathoexcitation, which ultimately results in a relative inability to increase blood pressure. These findings cast doubt on the efficacy of face cooling at augmenting blood pressure during orthostasis while heat stressed. We tested the hypothesis that passive heat stress attenuates the increase in cardiac parasympathetic stimulation, vascular resistance and blood pressure evoked by face cooling. During normothermia and when intestinal temperature was elevated by 1.0±0.2°C, 10 healthy young adults underwent 3min of face cooling. Face cooling was accomplished by placing a 2.5litre bag of ice water (0±0°C) over the cheeks, eyes and forehead. Primary variables included forehead skin temperature, mean arterial pressure and systemic, forearm and cutaneous vascular resistances. Indices of heart rate variability in the time domain provided an index of cardiac parasympathetic activity. The magnitude of reduction in forehead skin temperature during face cooling was slightly greater during normothermia (-17.6±1.9 versus -16.3±3.0°C, P=0.03). Increases in heart rate variability evoked by face cooling were attenuated during heat stress. Changes in systemic, forearm and cutaneous vascular resistances during face cooling were virtually abolished during heat stress (P<0.01). However, when forearm and vascular data were reported as conductance, differences between normothermia and heat stress were not apparent (P≥0.62). Nevertheless, the increase in mean arterial pressure was attenuated during heat stress with face cooling (at 3min: 2±7mmHg) compared with normothermia (at 3min: 19±7mmHg, P<0.01). These data indicate that passive heat stress attenuates face cooling-evoked increases in cardiac parasympathetic activation, vascular resistance and blood pressure. However, they also indicate that changes in indices of vascular resistance do not always reflect equivalent changes in conductance.

A cool response-The influence of ambient temperature on capillary refill time.

To describe the effect of low ambient temperature on skin temperature and capillary refill (CR) time in forehead, sternum and finger pulp. An observational, nonrandomized experimental study on 15 healthy subjects (6 females) in a cold room (8°C). Outcome measures were skin temperature and quantified CR test after application of a standardized blanching pressure (9 N/cm2 ) using digital photographic polarization spectroscopy to generate CR times. The finger pulp showed marked temperature fall and prolonged CR times (>10 seconds). The CR registrations of the forehead and sternum were more comparable to curves observed in a control material at room temperature, and skin temperature falls were less marked. CR times were not prolonged in forehead measurements. At the sternum, some individuals showed CR times beyond guideline recommendations despite only a marginal reduction in skin temperature. Low ambient temperature is a strong independent factor for CR time at peripheral sites. Reservation about sternum as a site of measurement is warranted since cold provocation produced prolonged CR times in some individuals. We found that the forehead is the most thermostable of the 3 sites and thus the preferred site to avoid ambient temperature artifact in measuring CR time.

Cooling cows with sprinklers: Spray duration affects physiological responses to heat load

Sprayed water reduces heat load in cattle. Determining appropriate spraying strategies (i.e., time on and off) may improve cooling efficiency and reduce water use. Our objective was to evaluate the effects of a single spray on the surrounding air temperature (AT), time it takes the coat to dry, and physiological responses to heat load in dairy cows. In a crossover design, spray duration (0, 0.5, 1.5, 3, and 13 min; flow rate: 4.9 L/min) was tested in 15 Holstein cows (milk yield: 37.7 ± 2.6 kg/d) restrained in shaded head gates at the feed bunk for up to 1.75 h. Each treatment was replicated on 3 d (15 d total/cow) when AT, humidity, and temperature-humidity index averaged 31 ± 3°C, 27 ± 10%, and 76 ± 2, respectively (mean ± SD). Water temperature at the nozzle outlet and dripping from the cow was measured every 1 s and averaged (mean ± SD) 29.7 ± 1.4 and 30.3 ± 0.8°C, respectively. Respiration rate, skin temperature of the shoulder and upper leg, and the surrounding AT were measured before and after the spray application and every 3 min for 30 min. At the same intervals, using water-sensitive paper we measured the time the coat took to dry. In contrast to the control, immediately after the spray was turned off, all water treatments reduced skin temperature on the shoulder (range of mean ± SE: -1.1 to -4.4 ± 0.2°C). Within the same period, treatments ≥1.5 min reduced respiration rate (range: -7 to -24 ± 2 breaths/min) and the surrounding AT (range: -0.3 to -1.7 ± 0.0°C). Only spraying cows for ≥3 min reduced leg surface temperature during spray duration (range of reduction: -0.1 to -0.6 ± 0.0°C). Spray duration had little effect on the time it took the coat to dry. Cows sprayed for 13 min took 2 min longer to dry compared with the other treatments (15.9 vs. 13.8, 14.9, and 14.2 ± 0.6 min, respectively, for 0.5, 1.5, and 3 min). No additional cooling was observed in this phase except on windier days, when leg temperature and respiration rate reductions tended to be more marked (slope estimates: -0.06 and -3.6, respectively). Cooling benefits, as well as changes in AT surrounding the leg, were more pronounced when water was sprayed for longer. In this study, cooling was observed primarily when water was turned on, not during the time it took the coat to dry.

Effects of Herbal Mixture Extract on Menopausal Hot Flashes and Pharmacokinetics in Ovariectomized Rat Models

This study was conducted to evaluate the effects of Cynanchum wilfordii Hemsley, Phlomis umbrosa Turcz., and Angelica gigas Nakai extract (CPAE) on the reduction of tail skin temperature (TST) in ovariectomized (OVX) rats. To evaluate TST reduction in ovariectomized rats, 125, 250, and 1000 mg/kg CPAE was administered to rats for 1 week. The measurement of TST after the induction of artificial stress revealed a significant temperature reduction effect in the CPAE administration group (ppp<0.01). In addition, in a drug interaction test between tamoxifen, an anti-estrogen drug, and CPAE, no significant difference was found between the pharmacokinetic (PK) profiles after the administration of tamoxifen only and the combination of tamoxifen and CPAE. We also found that CPAE did not affect CYP2d4 and CYP3a2, which affect tamoxifen metabolism, in a subsequent experiment on liver tissues extracted during the drug interaction test. In this study, we found that CPAE inhibited temperature increase on the tail skin of OVX rats, and therefore is effective in the improvement of hot flashes. CPAE may be potentially used for the improvement of hot flashes induced by the administration of tamoxifen.

Internal and external cooling methods and their effect on body temperature, thermal perception and dexterity.

ObjectiveThe present study aimed to compare a range of cooling methods possibly utilised by occupational workers, focusing on their effect on body temperature, perception and manual dexterity.MethodsTen male participants completed eight trials involving 30 min of seated rest followed by 30 min of cooling or control of no cooling (CON) (34°C, 58% relative humidity). The cooling methods utilised were: ice cooling vest (CV0), phase change cooling vest melting at 14°C (CV14), evaporative cooling vest (CVEV), arm immersion in 10°C water (AI), portable water-perfused suit (WPS), heliox inhalation (HE) and ice slushy ingestion (SL). Immediately before and after cooling, participants were assessed for fine (Purdue pegboard task) and gross (grip and pinch strength) manual dexterity. Rectal and skin temperature, as well as thermal sensation and comfort, were monitored throughout.ResultsCompared with CON, SL was the only method to reduce rectal temperature (P = 0.012). All externally applied cooling methods reduced skin temperature (P<0.05), though CV0 resulted in the lowest skin temperature versus other cooling methods. Participants felt cooler with CV0, CV14, WPS, AI and SL (P<0.05). AI significantly impaired Purdue pegboard performance (P = 0.001), but did not affect grip or pinch strength (P>0.05).ConclusionThe present study observed that ice ingestion or ice applied to the skin produced the greatest effect on rectal and skin temperature, respectively. AI should not be utilised if workers require subsequent fine manual dexterity. These results will help inform future studies investigating appropriate pre-cooling methods for the occupational worker.

Mitigating the impact of cold air exposure on soldier wellbeing and performance

Throughout human history there are many stark examples of the toll of cold weather on soldier performance, health, and ultimately survival. Upon exposure to a cold environment a cutaneous vasoconstriction, primarily mediated by reductions in local skin temperature, directs warm blood away from the body shell towards the body core. The resultant decline in peripheral blood flow in extreme cases has been shown to be analogous to the occlusion of blood flow with a blood pressure cuff inflated above arterial blood pressure – leading to a “physiological amputation” of the extremities. In advance of this scenario, vast decrements in manual dexterity, which in a military context can have a profound effect on soldier performance, are observed with peripheral cooling, most likely due to a decline in muscle and joint temperatures as opposed to reductions in nerve conduction velocity. In sub-zero environments the risk of skin freezing is elevated especially if the soldier is required to touch cold objects with high thermal conductivity. The magnitude skin freezing risk is subsequently associated with sex, hand size and the extent that blood flow to the skin is maintained, which itself is determined by both physiological (degree of vasoconstriction) and physical (contact pressure) factors. Factors that mitigate the effects of cold stress include shivering thermogenesis, which has the capacity to increase metabolic rate up to five-fold. However, such responses can heavily impact the capacity to perform fine motor tasks and over a prolonged period can lead to large energy deficits. The capacity to defend body temperature in the cold through shivering is also compromised by the low oxygen partial pressure at high altitude. The rate of body cooling in the cold is strongly influenced by physical factors such as surface area-to-mass ratio and the thickness of subcutaneous fat, and the evidence supporting the notion of a physiological adaptive capacity to repeated cold exposure seems to be scarce. It follows that the most impactful way in which humans can maintain optimal health and performance in the cold is through behavioural adaptations, most notably wearing appropriate clothing, which can be configured to maximize operational performance.

Sympathetic function during whole body cooling is altered in hypertensive adults.

During moderate cold exposure, cardiovascular-related morbidity and mortality increase disproportionately in hypertensive adults (HTN); however, the mechanisms underlying this association are not well defined. We hypothesized that whole body cold stress would evoke exaggerated increases in blood pressure (BP) and muscle sympathetic nerve activity (MSNA) in HTN compared with normotensive adults (NTN) and that sympathetic baroreflex function would be altered during cooling in HTN. MSNA (peroneal microneurography) and beat-to-beat BP (Finometer) were measured continuously in 10 NTN (6 men/4 women; age 53 ± 3 yr; resting BP 125 ± 3/79 ± 1 mmHg) and 13 HTN (7 men/6 women; age 58 ± 2 yr; resting BP 146 ± 5/88 ± 2 mmHg) during whole body cooling-induced reductions in mean skin temperature (Tsk; water-perfused suit) from 34.0 to 30.5°C. During cooling, the increase in mean arterial pressure was greater in HTN (NTN: Δ6 ± 2 vs. HTN: Δ11 ± 1 mmHg; P = 0.02) and accompanied by exaggerated increases in MSNA (NTN: Δ8 ± 3 vs. HTN: Δ20 ± 3 bursts/100 heart beats; P < 0.01). The slope of the relation between MSNA and diastolic BP did not change during cooling in NTN (Tsk 34.0°C: -4.4 ± 0.8 vs. Tsk 30.5°C: -5.0 ± 0.3 bursts·100 heart beats-1·mmHg-1; P = 0.47) but increased in HTN (Tsk 34.0°C: -3.6 ± 0.4 vs. Tsk 30.5°C: -5.4 ± 0.4 bursts·100 heart beats)-1·mmHg-1; P = 0.02). These findings demonstrate that the cooling-induced increases in BP and MSNA are exaggerated in HTN. Furthermore, during cooling, sympathetic baroreflex sensitivity increases in HTN, but not NTN, presumably to allow for baroreflex-mediated buffering of excessive cooling-induced increases in BP. Collectively, these findings suggest that sympathetic function is altered during whole body cooling in hypertension. NEW & NOTEWORTHY These novel findings demonstrate that whole body cooling-induced reductions in mean skin temperature elicited greater increases in blood pressure and muscle sympathetic nerve activity in hypertensive adults. In addition, during moderate cold exposure, sympathetic baroreflex sensitivity increased in hypertensive, but not normotensive, adults.

Achilles Tendon Penetration for Continuous 810 nm and Superpulsed 904 nm Lasers Before and After Ice Application: An In Situ Study on Healthy Young Adults.

There is a lack of knowledge about the influence tissue temperature may have on laser light penetration and tendon structure. The purpose of this study was to investigate whether penetration of laser energy in human Achilles tendons differed before and after ice pack application. The Achilles tendons (n = 54) from 27 healthy young adults were irradiated with two class 3B lasers (810 nm 200 mW continuous mode laser and a 904 nm 60 mW superpulsed mode laser). The optical energy penetrating the Achilles area was measured before and after 20 min of ice application. Measurements were obtained after 30, 60, and 120 sec irradiation with the 904 nm laser and after 30 and 60 sec irradiation with the 810 nm laser. Achilles tendon thickness was measured with ultrasonography. Optical energy penetration increased significantly (p < 0.01) after ice application for both lasers and at all time points from 0.34% to 0.39% of energy before ice application to 0.43-0.52% of energy after ice application for the 904 nm laser and from 0.24% to 0.25% of energy before ice application to 0.30-0.31% of energy after ice application for the 810 nm laser. The energy loss per centimeter of irradiated tissue was significantly higher (p < 0.05) at all time points after ice application. Ultrasonography imaging of skin-to-skin and transversal tendon thickness was significantly reduced after ice application at p = 0.05 and p = 0.03, respectively. Achilles tendon thickness in the longitudinal plane remained unchanged (p = 0.49). The penetration of laser light increased significantly through healthy Achilles tendons subjected to 20 min of cooling. These findings occurred in the presence of a significant reduction in skin temperature and Achilles tendon thickness.

Sympathetic Function During Whole‐Body Cooling is Altered in Hypertensive Adults

Acute cold exposure activates the sympathetic nervous system and elicits a robust systemic pressor response. In hypertensive adults (HTN), cardiovascular‐related morbidity and mortality peak during cold winter months; however, the mechanisms underlying this association are not well defined. We hypothesized that whole‐body cold stress would evoke exaggerated increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) in HTN compared to normotensive adults (NTN). MSNA (peroneal microneurography), beat‐to‐beat BP (Finometer), and heart rate (HR; ECG) were measured continuously in 10 NTN (6 M/4 W; age 53±3 yrs; resting BP 125±3/79±1 mmHg) and 10 HTN (5 M/5 W; age 57±2 yrs; resting BP 149±6/88±3 mmHg) during whole‐body cooling‐induced reductions in mean skin temperature (Tsk; water‐perfused suit) from 34.0 to 30.5°C. MSNA at 34.0°C was not different between groups (NTN: 51±4 v. HTN: 54±5 bursts· (100 heartbeats)−1; P=0.71). During cooling, the increase in MSNA was exaggerated in HTN (NTN: Δ = 8±3, HTN: Δ = 19±3 bursts· (100 heartbeats)−1; P=0.02). The cooling‐induced increases in both systolic BP (NTN: 9±3, HTN: 19±3 mmHg; P=0.03) and mean arterial pressure (NTN: 6±2, HTN: 10±2 mmHg; P=0.08) were greater in HTN. The HR response to cooling was not different between groups (P=0.16). The slope of the relation between MSNA burst incidence and diastolic BP did not change during cold stress in NTN (Tsk = 34.0°C: ‐4.0±0.7 v. Tsk = 30.5°C: ‐5.0±0.3 bursts· (100 heartbeats)−1·mmHg−1; P=0.17) but increased in HTN (Tsk = 34.0°C: ‐2.9±0.5, Tsk = 30.5°C: ‐5.0±0.4 bursts· (100 heartbeats)−1·mmHg−1; P=0.04). These data demonstrate that the whole‐body cooling‐induced increases in MSNA and BP are augmented in HTN. Further, sympathetic baroreflex sensitivity increases during cooling in HTN, but not NTN, presumably to allow for baroreflex‐mediated buffering of excessive cooling‐induced increases in BP. Collectively, these findings suggest that sympathetic function during cold stress is altered in human hypertension, likely contributing to increased cold‐associated cardiovascular risk.Support or Funding InformationHL093238 (LMA) and HL120471 (JLG)

Cooling Effects of Wearer-Controlled Vaporization for Extravehicular Activity.

The extravehicular activity suit currently used by the United States in space includes a liquid cooling and ventilation garment (LCVG) that controls thermal conditions. Previously, we demonstrated that self-perspiration for evaporative cooling (SPEC) garment effectively lowers skin temperature without raising humidity in the garment. However, the cooling effect is delayed until a sufficient dose of water permeates and evaporates. In the present study, we hypothesized that wearer-controlled vaporization improves the cooling effect. Six healthy subjects rode a cycle ergometer under loads of 30, 60, 90, and 120 W for durations of 3 min each. Skin temperature and humidity on the back were measured continuously. Subjects wore and tested three garments: 1) a spandex garment without any cooling device (Normal); 2) a simulated LCVG (s-LCVG) or spandex garment knitted with a vinyl tube for flowing and permeating water; and 3) a garment that allowed wearer-controlled vaporization (SPEC-W). The use of s-LCVG reduced skin temperature by 1.57 ± 0.14°C during 12 min of cooling. Wearer-controlled vaporization of the SPEC-W effectively and significantly lowered skin temperature from the start to the end of cycle exercise. This decrease was significantly larger than that achieved using s-LCVG. Humidity in the SPEC-W was significantly lower than that in s-LCVG. This preliminary study suggests that SPEC-W is effective in lowering skin temperature without raising humidity in the garment. The authors think it would be useful in improving the design of a cooling system for extravehicular activity.Tanaka K, Nagao D, Okada K, Nakamura K. Cooling effects of wearer-controlled vaporization for extravehicular activity. Aerosp Med Hum Perform. 2017; 88(4):418-422.

Optimal cooling intervention for construction workers in a hot and humid environment

This study aims to determine the optimal cooling intervention of a newly designed hybrid cooling vest. 10 males participated in three random experiments, i.e., cooling vest worn during exercise and recovery (ALL-COOL), cooling vest worn during passive recovery (REC-COOL) and control (CON) in a climatic chamber controlled at 37 °C temperature, 60% relative humidity, 0.3 m/s air velocity, and 450 W/m2 solar radiation to simulate the summer working environment of construction sites. The work–rest protocol was adopted to compare the effectiveness of ALL-COOL and REC-COOL. Physiological (core temperature, skin temperature, and heart rate) and perceptual (ratings of perceived exertion, thermal sensation, and wetness sensation) parameters were measured during the entire heat exposure. The cooling vest worn during exercise improved thermal comfort but did not alleviate heat strain or prolong work duration, as shown by the significant reduction in skin temperature and thermal sensation in ALL-COOL compared with CON (p < 0.05; d = 0.53–0.95, moderate to large effect). The cooling vest used during recovery largely hastened thermoregulatory and cardiovascular strain recovery, as indicated by the significant reduction of body core temperature and heart rate (p < 0.01; d = 0.82–1.04, large effect). Findings implied that post-exercise cooling by the cooling vest can be an appropriate and practical countermeasure in reducing body heat strain in construction sites where repeated bouts of construction work are required.

Limb Hypothermia for Preventing Paclitaxel-Induced Peripheral Neuropathy in Breast Cancer Patients: A Pilot Study.

Peripheral neuropathy (PN) due to paclitaxel is a common dose-limiting toxicity with no effective prevention or treatment. We hypothesize that continuous-flow limb hypothermia can reduce paclitaxel-induced PN. An internally controlled pilot trial was conducted to investigate the neuroprotective effect of continuous-flow limb hypothermia in breast cancer patients receiving weekly paclitaxel. Patients underwent limb hypothermia of one limb for a duration of 3 h with every paclitaxel infusion, with the contralateral limb used as control. PN was primarily assessed using nerve conduction studies (NCSs) before the start of chemotherapy, and after 1, 3, and 6 months. Skin temperature and tolerability to hypothermia were monitored using validated scores. Twenty patients underwent a total of 218 cycles of continuous-flow limb hypothermia at a coolant temperature of 22°C. Continuous-flow limb hypothermia achieved mean skin temperature reduction of 1.5 ± 0.7°C and was well tolerated, with no premature termination of cooling due to intolerance. Grade 3 PN occurred in 2 patients (10%), grade 2 in 2 (10%), and grade 1 in 12 (60%). Significant correlation was observed between amount of skin cooling and motor nerve amplitude preservation at 6 months (p < 0.0005). Sensory velocity and amplitude in the cooled limbs were less preserved than in the control limbs, but the difference did not attain statistical significance. One patient with a history of diabetes mellitus had significant preservation of compound muscle action potential in the cooled limb on NCS analysis. This study suggests that continuous limb hypothermia accompanying paclitaxel infusion may reduce paclitaxel-induced PN and have therapeutic potential in select patients and warrants further investigation. The method is safe and well tolerated.

Hand-arm vibration effects on performance, tactile acuity, and temperature of hand

Effects of vibration appear as mechanical and psychological disorders, including stress reactions, cognitive and movement disorders, problem in concentration and paying attention to the assigned duties. The common signs and symptoms of hand-arm vibration (HAV) in the fingers and hands may appear as pins and needles feeling, tingling, numbness, and also the loss of finger sensation and dexterity. Laboratory Virtual Instrument Engineering Workbench programming software designed for occupational vibrations measurement was used to calculate HAV acceleration. Hole steadiness test is designed to measure involuntary movement of people. V-Pieron test is designed for one of the other aspects of the psycho motor phenomena of steadiness by moving the stylus across a V-form ruler. The two points test was an experiment of touch acuity, which used a caliper by placing the two styli very close on the pad of finger knuckles. The temperature of finger skin is also measured simultaneous to the above tests. Wilcoxon test indicated that a significant decrement in hand steadiness occurred after gripping a vibrating handle for 2 min (P ≤ 0.003). Wilcoxon test also represented a significant change in errors after gripping a grinder vibratory handle (P ≤ 0.003). The differences at all of the knuckles were significant with a confidence interval percentage of 99%. There was a significant reduction in finger skin temperature before and after exposure to vibration (mean = 0.45°C, based on paired sample test). The obtained results considerably demonstrated the relation between hand performance and vibrations due to gripping a grinder. It can be concluded that an injury or accident may happen after exposure to vibrations for the fine duties, in fast actions.