The cellular coding of temperature in the mammalian cortex.

Temperature is a fundamental sensory modality separate from touch, with dedicated receptor channels and primary afferent neurons for cool and warm1-3. Unlike for other modalities, however, the cortical encoding of temperature remains unknown, with very few cortical neurons reported that respond to non-painful temperature, and the presence of a 'thermal cortex' is debated4-8. Here, using widefield and two-photon calcium imaging in the mouse forepaw system, we identify cortical neurons that respond to cooling and/or warming with distinct spatial and temporal response properties. We observed a representation of cool, but not warm, in the primary somatosensory cortex, but cool and warm in the posterior insular cortex (pIC). The representation of thermal information in pIC is robust and somatotopically arranged, and reversible manipulations show a profound impact on thermal perception. Despite being positioned along the same one-dimensional sensory axis, the encoding of cool and that of warm are distinct, both in highly and broadly tuned neurons. Together, our results show that pIC contains the primary cortical representation of skin temperature and may help explain how the thermal system generates sensations of cool and warm.

Quantitative interpretation of infrared images of lower limbs in individuals with and without type 2 diabetes mellitus.

BACKGROUND: The quantitative interpretation of the radiometric information extracted from infrared (IR) images in individuals with and without type 2 diabetes mellitus (DM2) is an open problem yet to be solved. This is of particular value given that DM2 is a worldwide health problem and onset for evolution toward diabetic foot disease (DFD). Since DM2 causes changes at the vascular and neurological levels, the metabolic heat distribution on the outer skin is modified as a consequence of such alterations. Of particular interest in this contribution are those alterations displayed over the skin's heat patterns at the lower limbs. At the core of such alterations is the deterioration of the vascular and neurological networks responsible for procuring systemic thermoregulation. It is within this context that IR imaging is introduced as a likely aiding tool to assist with the clinical diagnosis of DM2 at stages early enough to prevent the evolution of the DFD. METHODS: IR images of lower limbs are acquired from a cohort of individuals clinically diagnosed with and without DM2. Additional inclusion criteria for patients are to be free from any visible wound or tissue-related trauma (e.g., injuries, edema, and so forth), and also free from non-metabolic comorbidities. All images and data are equally processed and analyzed using indices that evaluate the spatial and temporal evolution of temperature distribution in lower limbs. We studied the temporal response of individuals' legs after inducing an external stimulus. For this purpose, we combine the information of the asymmetry and thermal response index (ATR) and the thermal response index (TRI), computed using images at different times, improving the results previously obtained individually with ATR and TRI. RESULTS: A novel representation of the information extracted from IR images of the lower limbs in individuals with and without DM2 is presented. This representation was built using the ATR and TRI indices for the anterior and posterior views (PVs), individually and combining the information from both views. In all cases, the information of each index and each view presents linearity properties that allow said information to be interpreted quantitatively in a well-defined and limited space. This representation, built in a polar coordinate space, allows obtaining sensitivity values of 86%, 97%, and 97%, and specificity values of 83%, 72%, and 78% for the anterior view (AV), the PV, and the combined views, respectively. Additionally, it was observed that the angular variable that defines this new representation space allows to significantly (p < 0.01) differentiate the groups, while correlating with clinical variables of interest, such as glucose and glycated hemoglobin. CONCLUSION: The linearity properties that exist between the ATR and TRI indices allow a quantitative interpretation of the information extracted from IR images of the lower extremities of individuals with and without DM2, and allow the construction of a representation space that eliminates possible ambiguities in the interpretation, while simplifying it, making it accessible for clinical use.

The application of heating film to hands reduces the decline in manual dexterity performance associated with cold exposure.

PURPOSE: Exposure to cold temperatures decreases finger temperature (Tfing) and dexterity. Decreased manual function and dexterity can be serious safety risks, especially in tasks that require fine motor movements that must be performed outdoors. The aim of this study was to determine whether hand heating with a minimal power requirement (14.8 W) results in a smaller reduction in Tfing and manual dexterity performance during mild cold exposure compared to a non-heated control condition. METHODS: In a randomized crossover design, twenty-two healthy participants were exposed to a moderately cold environment (5  ºC) for 90 min. One condition had no intervention (CON), while the other had the palmar and dorsal hands heated (HEAT) by using electric heating films. Tfing and cutaneous vascular conductance (CVC) were continuously monitored using laser Doppler flowmetry. Manual dexterity performance and cognitive function were assessed by the Grooved Pegboard Test (GPT) and Stroop Color-Word (SCW) test, respectively, during the baseline period and every 30 min during the cold exposure. RESULTS: After the cold exposure, Tfing was higher in HEAT relative to CON (CON 9.8 vs. HEAT 13.7 ºC, p < 0.0001). GPT placing time, as an index of dexterity performance, was also shorter in HEAT by 14.5% (CON 69.10 ± 13.08 vs. HEAT 59.06 ± 7.99 s, p < 0.0001). There was no difference in CVC between the two conditions during the cold exposure (p > 0.05 for all). Cognitive function was similar between two conditions (p > 0.05 for all). CONCLUSION: The proposed hand heating method offers a practical means of heating fingers to maintain dexterity throughout prolonged cold exposure.

Sex differences in thermophysiological responses of elderly to low-intensity exercise during uncompensable heat strain.

PURPOSE: The rising frequency of extreme heat events poses an escalating threat of heat-related illnesses and fatalities, placing an additional strain on global healthcare systems. Whether the risk of heat-related issues is sex specific, particularly among the elderly, remains uncertain. METHODS: 16 men and 15 women of similar age (69 ± 5 years) were exposed to an air temperature of 39.1 ± 0.3 °C and a relative humidity (RH) of 25.1 ± 1.9%, during 20 min of seated rest and at least 40 min of low-intensity (10 W) cycling exercise. RH was gradually increased by 2% every 5 min starting at minute 30. We measured sweat rate, heart rate, thermal sensation, and the rise in gastrointestinal temperature (Tgi) and skin temperature (Tsk). RESULTS: Tgi consistently increased from minute 30 to 60, with no significant difference between females and males (0.012 ± 0.004 °C/min vs. 0.011 ± 0.005 °C/min; p = 0.64). Similarly, Tsk increase did not differ between females and males (0.044 ± 0.007 °C/min vs. 0.038 ± 0.011 °C/min; p = 0.07). Females exhibited lower sweat rates than males (0.29 ± 0.06 vs. 0.45 ± 0.14 mg/m2/min; p < 0.001) in particular at relative humidities exceeding 30%. No sex differences in heart rate and thermal sensation were observed. CONCLUSION: Elderly females exhibit significantly lower sweat rates than their male counterparts during low-intensity exercise at ambient temperatures of 39 °C when humidity exceeds 30%. However, both elderly males and females demonstrate a comparable rise in core temperature, skin temperature, and mean body temperature, indicating similar health-related risks associated with heat exposure.

Short-term cocoa bioflavanol supplementation does not improve cold-induced vasodilation in young healthy adults.

PURPOSE: Cold-induced vasodilation (CIVD) is an oscillatory rise in blood flow to glabrous skin that occurs in cold-exposed extremities. Dietary flavanols increase bioavailable nitric oxide, a proposed mediator of CIVD through active vasodilation and/or withdrawal of sympathetic vascular smooth muscle tone. However, no studies have examined the effects of flavanol intake on extremity skin perfusion during cold exposure. We tested the hypothesis that acute and 8-day flavanol supplementation would augment CIVD during single-digit cold water immersion (CWI). METHODS: Eleven healthy adults (24 ± 6 years; 10 M/1F) ingested cocoa flavanols (900 mg/day) or caffeine- and theobromine-matched placebo for 8 days in a double-blind, randomized, crossover design. On Days 1 and 8, CIVD was assessed 2 h post-treatment. Subjects immersed their 3rd finger in warm water (42 °C) for 15 min before CWI (4 °C) for 30 min, during which nail bed and finger pad skin temperature were measured. RESULTS: Flavanol ingestion had no effect on CIVD frequency (Day 1, Flavanol: 3 ± 2 vs. Placebo: 3 ± 2; Day 8, Flavanol: 3 ± 2 vs. Placebo: 3 ± 1) or amplitude (Day 1, Flavanol: 4.3 ± 1.7 vs. Placebo: 4.9 ± 2.6 °C; Day 8, Flavanol: 3.9 ± 1.9 vs. Placebo: 3.9 ± 2.0 °C) in the finger pad following acute or 8-day supplementation (P > 0.05). Furthermore, average, nadir, and apex finger pad temperatures during CWI were not different between treatments on Days 1 or 8 of supplementation (P > 0.05). Similarly, no differences in CIVD parameters were observed in the nail bed following supplementation (P > 0.05). CONCLUSION: These data suggest that cocoa flavanol ingestion does not alter finger CIVD. Clinical Trial Registration Clinicaltrials.gov Identifier: NCT04359082. April 24, 2020.

Sensory Processing of Cutaneous Temperature in the Peripheral and Central Nervous System.

Thermal perception is critical for sensing environmental temperature, keeping body temperature consistent, and avoiding thermal danger. Central to thermal perception is the detection of cutaneous (skin) temperature information by the peripheral nerves and its transmission to the spinal cord, thalamus, and downstream cortical areas including the insular cortex, primary somatosensory cortex, and secondary somatosensory cortex. Although much is still unknown about this process, advances in technology have enabled significant progress to be made in recent years.This chapter summarizes our current understanding of how the peripheral nerves, spinal cord, and brain process cutaneous temperature information to give rise to conscious thermal perception.

Evaluating Vascular Depth-Dependent Changes in Multi-Wavelength PPG Signals Due to Contact Force.

Photoplethysmography (PPG) is a non-invasive method used for cardiovascular monitoring, with multi-wavelength PPG (MW-PPG) enhancing its efficacy by using multiple wavelengths for improved assessment. This study explores how contact force (CF) variations impact MW-PPG signals. Data from 11 healthy subjects are analyzed to investigate the still understudied specific effects of CF on PPG signals. The obtained dataset includes simultaneous recording of five PPG wavelengths (470, 525, 590, 631, and 940 nm), CF, skin temperature, and the tonometric measurement derived from CF. The evolution of raw signals and the PPG DC and AC components are analyzed in relation to the increasing and decreasing faces of the CF. Findings reveal individual variability in signal responses related to skin and vasculature properties and demonstrate hysteresis and wavelength-dependent responses to CF changes. Notably, all wavelengths except 631 nm showed that the DC component of PPG signals correlates with CF trends, suggesting the potential use of this component as an indirect CF indicator. However, further validation is needed for practical application. The study underscores the importance of biomechanical properties at the measurement site and inter-individual variability and proposes the arterial pressure wave as a key factor in PPG signal formation.

Preliminary Application of Infrared Thermography to Monitoring of Skin Temperature Asymmetries in Professional Padel Players.

The aim of the present study was to evaluate skin temperature (Tsk) asymmetries, using infrared thermography, in professional padel players before (PRE), after (POST) and 10 min after training (POST10), and their relationship with perceptual variables and training characteristics. Thermal images were taken of 10 players before, after and 10 min after a standardized technical training. After training, Tsk of the dominant side was higher than before training in the anterior forearm (30.8 ± 0.4 °C vs. 29.1 ± 1.2 °C, p < 0.01; ES = 1.9), anterior shoulder (31.6 ± 0.6 °C vs. 30.9 ± 0.6 °C, p < 0.05; ES = 1.0) posterior arm (29.5 ± 1.0 °C vs. 28.3 ± 1.2 °C, p < 0.05; ES = 1.0), and posterior forearm (30.8 ± 0.9 °C vs. 29.3 ± 1.6 °C, p < 0.05; ES = 1.1). Likewise, these differences were significant POST10 in the anterior arm, anterior forearm, anterior shoulder, posterior arm and posterior forearm. Comparing the different moments of measurement (PRE, POST and POST10), the temperature was higher POST10 in all the regions analyzed except for the shoulder, abdominals, and lower back. Also, correlations were found between fatigue variation and temperature variation between limbs (Tsk dominance), and no correlation was found except between age and posterior thigh (|r| = 0.69; p < 0.05), and between the racket mass and anterior knee (|r| = 0.81; p < 0.01). In conclusion, infrared thermography allows monitoring of skin asymmetries between limbs in professional padel players, but these asymmetries were not related to overall fatigue variation, overall pain variation, years of experience and training hours.

Unobtrusive Skin Temperature Estimation on a Smart Bed.

The transition from wakefulness to sleep occurs when the core body temperature decreases. The latter is facilitated by an increase in the cutaneous blood flow, which dissipates internal heat into the micro-environment surrounding the sleeper's body. The rise in cutaneous blood flow near sleep onset causes the distal (hands and feet) and proximal (abdomen) temperatures to increase by about 1 °C and 0.5 °C, respectively. Characterizing the dynamics of skin temperature changes throughout sleep phases and understanding its relationship with sleep quality requires a means to unobtrusively and longitudinally estimate the skin temperature. Leveraging the data from a temperature sensor strip (TSS) with five individual temperature sensors embedded near the surface of a smart bed's mattress, we have developed an algorithm to estimate the distal skin temperature with a minute-long temporal resolution. The data from 18 participants who recorded TSS and ground-truth temperature data from sleep during 14 nights at home and 2 nights in a lab were used to develop an algorithm that uses a two-stage regression model (gradient boosted tree followed by a random forest) to estimate the distal skin temperature. A five-fold cross-validation procedure was applied to train and validate the model such that the data from a participant could only be either in the training or validation set but not in both. The algorithm verification was performed with the in-lab data. The algorithm presented in this research can estimate the distal skin temperature at a minute-level resolution, with accuracy characterized by the mean limits of agreement [-0.79 to +0.79 °C] and mean coefficient of determination R2=0.87. This method may enable the unobtrusive, longitudinal and ecologically valid collection of distal skin temperature values during sleep. Therelatively small sample size motivates the need for further validation efforts.

New, Optimized Skin Calorimeter Version for Measuring Thermal Responses of Localized Skin Areas during Physical Activity.

We present an optimized version of the skin calorimeter for measuring localized skin thermal responses during physical activity. Enhancements include a new holding system, more sensitive thermopiles, and an upgraded spiked heat sink for improved efficiency. In addition, we used a new, improved calorimetric model that takes into account all the variables that influence the measurement process. Resolution in power measurement is 1 mW. Performance tests under air currents and movement disturbances showed that the device maintains high accuracy; the deviation produced by these significant disturbances is less than 5%. Human subject tests, both at rest and during exercise, confirmed its ability to accurately measure localized skin heat flux, heat capacity, and thermal resistance (less than 5% uncertainty). These findings highlight the calorimeter's potential for applications in sports medicine and physiological studies.

The Effect of Dimple Insole Design on the Plantar Temperature and Pressure in People with Diabetes and in Healthy Individuals.

An increase in plantar pressure and skin temperature is commonly associated with an increased risk of diabetic foot ulcers. However, the effect of insoles in reducing plantar temperature has not been commonly studied. The aim was to assess the effect of walking in insoles with different features on plantar temperature. Twenty-six (F/M:18/8) participants-13 with diabetes and 13 healthy, aged 55.67 ± 9.58 years-participated in this study. Skin temperature at seven plantar regions was measured using a thermal camera and reported as the difference between the temperature after walking with an insole for 20 m versus the baseline temperature. The mixed analyses of variance indicated substantial main effects for the Insole Condition, for both the right [Wilks' Lambda = 0.790, F(14, 492) = 4.393, p < 0.01, partial eta squared = 0.111] and left feet [Wilks' Lambda = 0.890, F(14, 492) = 2.103, p < 0.011, partial eta squared = 0.056]. The 2.5 mm-tall dimple insole was shown to be significantly more effective at reducing the temperature in the hallux and third met head regions compared to the 4 mm-tall dimple insole. The insoles showed to be significantly more effective in the diabetes group versus the healthy group, with large effect size for the right [Wilks' Lambda = 0.662, F(14, 492) = 8.037, p < 0.000, Partial eta-squared = 0.186] and left feet [Wilks' Lambda = 0.739, F(14, 492) = 5.727, p < 0.000, Partial eta-squared = 0.140]. This can have important practical implications for designing insoles with a view to decrease foot complications in people with diabetes.

IoT-Based Assessment of a Driver's Stress Level.

Driver Monitoring Systems (DMSs) play a key role in preventing hazardous events (e.g., road accidents) by providing prompt assistance when anomalies are detected while driving. Different factors, such as traffic and road conditions, might alter the psycho-physiological status of a driver by increasing stress and workload levels. This motivates the development of advanced monitoring architectures taking into account psycho-physiological aspects. In this work, we propose a novel in-vehicle Internet of Things (IoT)-oriented monitoring system to assess the stress status of the driver. In detail, the system leverages heterogeneous components and techniques to collect driver (and, possibly, vehicle) data, aiming at estimating the driver's arousal level, i.e., their psycho-physiological response to driving tasks. In particular, a wearable sensorized bodice and a thermal camera are employed to extract physiological parameters of interest (namely, the heart rate and skin temperature of the subject), which are processed and analyzed with innovative algorithms. Finally, experimental results are obtained both in simulated and real driving scenarios, demonstrating the adaptability and efficacy of the proposed system.

Energy expenditure and physiological markers during a city mountain hike in the heat: A case study.

Background: Energy expenditure may be difficult to assess when hiking difficult trails. Case presentation: We measured physical activity exercise energy expenditure (PAEE) directly from oxygen uptake using a mobile device (cardiopulmonary exercise testing, CPET), and by using a formula based on heart rate (HR), or metabolic equivalent values from the Compendium of Physical Activity, and other physiological outcomes. Outcomes and implications: Total PAEE (1342 kcal) using CPET showed a two-fold difference between ascending and descending (887 vs. 455 kcal) during a 124-min hike. For HR, PAEE was 1893kcal (+551 kcal overreporting), while compendium-based scenarios ranged from 1179 to 1446 kcal, which was in closer range (-163 to +104 kcal/min) compared to the CPET data. Fluid consumption was 1300 mL/hour, with 1.1% bodyweight loss, peak skin temperature of 35.2°C and core body temperature of 39.2°C. Recommendations: Tables reasonably predict energy expenditure while not precisely reflecting the actual situation.

Momentary physiological indices related to eating disorders: A systematic and methodological review.

Eating disorders (ED) are serious psychiatric illnesses, with no everyday support to intervene on the high rates of relapse. Understanding physiological indices that can be measured by wearable sensor technologies may provide new momentary interventions for individuals with ED. This systematic review, searching large databases, synthesises studies investigating peripheral physiological (PP) indices commonly included in wearable wristbands (heart rate [HR], heart rate variability [HRV], electrodermal activity [EDA], peripheral skin temperature [PST], and acceleration) in ED. Inclusion criteria included: (a) full peer-reviewed empirical articles in English; (b) human participants with active ED; and (c) containing one of five wearable physiological measures. Kmet risk of bias was assessed. Ninety-four studies were included (Anorexia nervosa [AN; N = 4418], bulimia nervosa [BN; N = 916], binge eating disorder [BED; N = 1604], other specified feeding and eating disorders [OSFED; N = 424], and transdiagnostic [N = 47]). Participants with AN displayed lower HR and EDA and higher HRV compared to healthy individuals. Those with BN showed higher HRV, and lower EDA and PST compared to healthy individuals. Other ED and Transdiagnostic samples showed mixed results. PP differences are indicated through various assessments in ED, which may suggest diagnostic associations, although more studies are needed to validate observed patterns. Results suggest important therapeutic potential for PP in ED, and larger studies including diverse participants and diagnostic groups are needed to fully uncover their role in ED.

Heel skin microclimate control: Secondary analysis of a self-controlled randomized clinical trial.

OBJECTIVE: this study was undertaken to evaluate the efficacy of multilayer polyurethane foam with silicone (MPF) compared to transparent polyurethane film (TPF) dressings in the control of heel skin microclimate (temperature and moisture) of hospitalized patients undergoing elective surgeries. METHOD: the study took of a secondary analysis of a randomized self-controlled trial, involving patients undergoing elective surgical procedure of cardiac and gastrointestinal specialties in a university hospital in southern Brazil, from March 2019 to February 2020. Patients served as their own control, with their heels randomly allocated to either TPF (control) or MPF (intervention). Skin temperature was measured using a digital infrared thermometer; and moisture determined through capacitance, at the beginning and end of surgery. The study was registered in the Brazilian Registry of Clinical Trials: RBR-5GKNG5. RESULTS: significant difference in the microclimate variables were observed when the groups (intervention and control) and the timepoint of measurement (beginning and end of surgery) were compared. When assessing temperature, an increase (+3.3 °C) was observed with TPF and a decrease (-7.4 °C) was recorded with MPF. Regarding skin moisture, an increase in moisture (+14.6 AU) was recorded with TPF and a slight decrease (-0.3 AU) with MPF. CONCLUSIONS: The findings of this study suggest that MPF is more effective than TPF in controlling skin microclimate (temperature and moisture) in heels skin of hospitalized patients undergoing elective surgeries. However, this control should be better investigated in other studies.

Infrared Thermometry and Thermography in Detecting Skin Temperature Variations to Predict Venous Leg Ulcer Reulceration: A Case Report.

BACKGROUND: We aimed to determine whether monitoring skin temperature (Tsk) over recently healed venous leg ulcers (VLUs) can provide an objective approach to predicting reulceration. The cases presented in this article were part of a larger, multisite, 6-month randomized clinical trial of a cooling intervention to prevent ulcer recurrence among patients with chronic venous disease (CVD) and with recently healed VLUs. CASES: We report a series of four patients with CVD, three experienced VLU reulceration, and one case remained free of recurrence. Assessments of recurrence likelihood is based on daily patient Tsk self-reports using a handheld infrared (IR) thermometer and clinic visits using a combination digital and long-wave IR camera. All three cases with reulceration demonstrate a persistent 2°C above baseline average Tsk increase and a "dip-and-spike" pattern from -3°C to +5°C for several days prior to reulceration. In contrast, the patient who remained free of VLU recurrence showed a stable pattern of Tsk with minimal daily fluctuations. Thermal images showed Tsk of the affected extremity is warmer compared with the contralateral limb and increased between visits when ulcers recurred. CONCLUSION: Using IR devices to monitor Tsk among patients with CVD at risk of reulceration is an objective and reliable approach to detect changes over time. Consistent Tsk elevation over the affected area as compared to the contralateral limb and a "dip-and-spike" pattern may predict reulceration. Infrared devices showed effectiveness in detecting changes indicative of Tsk changes in recently healed leg skin over scar tissue after VLU healing.

Effects of a mattress cover with special airflow technology on the structure and function of the sacral and heel skin during loading: A two-arm exploratory crossover trial.

Prolonged mechanical loading of the skin and underlying soft tissue cause pressure ulceration. The use of special support surfaces are key interventions in pressure ulcer prevention. They modify the degree and duration of soft tissue deformation and have an impact on the skin microclimate. The objective of this randomized cross-over trial was to compare skin responses and comfort after lying for 2.5 h supine on a support surface with and without a coverlet that was intended to assist with heat and moisture removal at the patient/surface interface. In addition, physiological saline solution was administered to simulate an incontinence episode on the mattress next to the participants' skin surface. In total, 12 volunteers (mean age 69 years) with diabetes mellitus participated. After loading, skin surface temperature, stratum corneum hydration and skin surface pH increased, whereas erythema and structural stiffness decreased at the sacral area. At the heel skin area, temperature, erythema, and stratum corneum hydration increased. These results indicate occlusion and soft tissue deformation which was aggravated by the saline solution. The differences in skin response showed only minor differences between the support surface with or without the coverlet.

The correlation between sub-epidermal moisture assessment and other early indicators of pressure ulcer development: A prospective cohort observational study. Part 2. The correlation between sub-epidermal moisture assessment, temperature, epidermal hydration and pain.

There is growing interest in the roles of temperature, epidermal hydration (EH) and pain in pressure ulcer (PU) development. Investigating correlations between these measures and sub-epidermal moisture (SEM) will address this knowledge deficit. A prospective observational study enrolled 60 surgical patients from February to November 2021. SEM, temperature, EH and pain were assessed using a SEM scanner, thermography imaging, skin hydration device and numeric pain intensity scale, respectively. Measurements were taken at the sacrum, both heels and a control site, before and after surgery for 3 days. Data were analysed using Pearson or Spearman's correlation. Of the participants, 50% were male with a mean age of 58 years (±13.46). Low positive/negative correlations between SEM and temperature were found at the sacrum. However, after removing outliers, these results were not statistically significant. Other sites and follow-up days showed negligible correlations. No evidence of a correlation, to low correlations between SEM and EH were observed, but unreliable due to little variation in EH at the heels. Pain showed negligible correlations with SEM. This study did not find consistent evidence of a correlation between SEM, temperature, EH and pain, highlighting the unreliability of temperature and EH for early PU detection. Post-operative pain may also confound accurate pain assessments.

Age comparison of changes in local warm and cold sensitivity due to whole body cooling.

PURPOSE: This study investigated the influence of whole body cooling on local thermal sensitivity to warm (40°C) and cold (20°C) stimuli in 10 young (age: 24 ± 2 yrs) and 10 older males (age: 69 ± 4 yrs). METHODS: Local warm and cold sensitivity was assessed at eight body regions using a 25 cm2 pressure controlled thermal probe after 40 min of whole body exposure to a thermoneutral (NEUT: 25°C/40% RH) and a cold (COLD: 12°C/50% RH) environment. Gastrointestinal temperature (Tgi), mean and local skin temperature, heart rate, whole body thermal sensation and comfort, and skin blood flow were also measured. RESULTS: Whole body cooling blunted local cold sensitivity but warm sensitivity was maintained in both age groups. Furthermore, a significant age-related decline (from young to older group) in sensitivity to a warm stimulus was observed in both NEUT and COLD conditions. Older males also had a greater ΔTgi compared to the young but had similar thermal sensation and comfort responses. CONCLUSION: The observed interaction effect of local cold stimulation and whole body cooling may be related to both stimuli triggering similar TRP channels, whereas the lack of interaction between local warm stimuli and whole body cooling may be related to these two stimuli triggering different TRP channels. The findings reiterate the potential thermoregulatory risks (e.g. cold injury and hypothermia) associated with ageing, even with such short exposure times.

Relationship between infrared thermography and muscle damage markers in physically active men after plyometric exercise.

Plyometric training has been used in several sports and fitness programs to improve jumping ability and explosive strength, both in individual and team sports. Eccentric muscle actions, such as those performed during plyometric jumps, induce muscle damage and consequently a rise in skin temperature (Tsk). Thus, the purpose of this study is to assess the response of infrared thermography measurement as an indirect marker of muscle damage after a protocol of plyometric jumps in physically active subjects. Therefore, for the aim of this study ten male subjects with no previous experience in plyometric training participated in the research (age 22.5 ± 3.3 years, weight 71.7 ± 11.0 kg, height 171.1 ± 5.3 cm, and fat mass 15.5 ± 4.7%). To assess the muscle damage, countermovement jump (CMJ), creatine kinase (CK), delayed-onset muscle soreness (DOMS) and infrared thermography (IRT) were measured at 24, 48, and 72 h after plyometric exercise. The acute exercise protocol of plyometric jumps induced muscle damage, as shown by the CK and DOMS (24 and 48 h, p < 0.05) but no statistical difference was shown between the moments analyzed in Tsk (warm zone). Nevertheless, when comparing baseline to 48h, a moderate effect was found in the Tsk (warm zone) for anterior right thigh (ES = 1.1) and posterior left thigh (ES = 0.9) and large effect was found for anterior left thigh (ES = 1.4) and posterior right thigh (ES = 1.3). A moderate effect in the Tsk (warm zone) was found for posterior right and left thigh (ES = 0.9 and ES = 1.1, respectively) when comparing baseline to 72h of IRT. These results suggest that a plyometric jumping session alters CK and DOMS, as well as the thigh's skin temperature in an evident way, bringing up a possible relation with markers of muscle damage.