Mean Skin Temperature Research Articles

Optimal duration of whole-body cryostimulation exposure to achieve target skin temperature: influence of body mass index—a randomized cross-over controlled trial

BackgroundThe efficacy of whole-body cryostimulation (WBC) may be influenced by individual characteristics. The aim of this study is to determine the optimal exposure time required to reach the analgesic threshold of 13.6 °C, which has been proposed to be a target temperature to be reached at skin level. Our objective is also to follow the skin temperature changes during and after WBC considering the participants body mass index (BMI).MethodsThirty healthy men were assigned into 2 groups based on their BMI [normal weight (n = 15; BMI = 21.53 ± 1.63 kg·m−2) and overweight (n = 15; BMI = 27.98 ± 1.16 kg·m−2)]. In a random order, each participant experienced a 4-min WBC exposure, as well as a control session with no cold exposure. Skin temperature was measured using a thermal imaging camera during and after cold exposure.ResultsNormal weight participants reached the threshold in 4 min, whereas overweight participants reached it in 3 min 30 s. Following WBC, a rapid mean skin temperature (MsT°) increase was observed for both groups, immediately after exposure. However, after 30 min, MsT° remained significantly lower than at baseline.ConclusionOur findings suggest that appropriate WBC dosage may differ according to BMI. Understanding the impact of such variable on cold exposure outcomes can help to optimize WBC treatments and maximize potential benefits.

Improving Outdoor Thermal Comfort for Agricultural Workers: A Study of Heat Stress Relief Measures Using Sun Protection Lotions

The entire study was carried out on a group of 100 female farm workers at the CTAE university campus in Udaipur during the wheat crop harvesting season, with the aim of examining the effectiveness of various heat stress relief measures (sun protection lotion with different sun protection factors, SPF) in improving outdoor thermal comfort. The experiments were designed to assess the average skin temperature of Indian female farm workers under five fixed Wet Bulb Globe Temperature (WBGT) conditions (28, 29, 30, 31, 32°C), all falling within the heat stress category as per American Conference of Governmental Industrial Hygienists (ACGIH) standards. The mean skin temperature was determined using the Hardy du-bois 7-point model formula, which involved measuring the mean temperature of specific body parts of the 100 female farm workers. A variation of ± 0.5°C was considered due to the challenge of achieving precise thermal conditions in open field settings. The experiment aimed to evaluate the thermal and physiological responses of the participants. The findings revealed that the use of sun protection lotion alone resulted in increased cooling effect, thereby expanding the thermal comfort range. Additionally, the application of sun protection lotion alone reduced the mean skin temperature by 0.39, 0.38, 0.36, 0.30, 0.27°C by the end of the work period.

Reproducibility of Thermography for Measuring Skin Temperature of Upper Limbs in Breast Cancer Survivors

Background/Objectives: Breast cancer-related lymphedema (BCRL) is a chronic condition that has early diagnosis as a critical component for proper treatment. Thermography, a non-invasive imaging method, is considered a promising complementary tool for the diagnosis and monitoring of BCRL, especially in subclinical stages. The present study aimed to evaluate the intra- and inter-examiner reproducibility of thermography for measuring the skin temperature of the upper limbs (UL) of women with and without BCRL. Methods: This study, conducted with women who underwent a unilateral mastectomy, assessed BCRL using indirect volumetry. Maximum, minimum, and mean skin temperatures were measured in five regions of interest (ROI) of each UL (C1, C2, C3, C4, and Cup) in four different postures. Reproducibility measures were assessed using an intraclass correlation coefficient, 95% confidence interval, and coefficient of variation. Results: The sample comprised 30 women; 14 were diagnosed with BCRL. A total of 120 thermograms were recorded in different postures, and 3600 ROI were analyzed in the UL with and without BRCL. The intraclass correlation coefficient of the analyses indicated intra- and inter-examiner reproducibility from good to excellent (0.82 to 1.00) for all skin temperatures evaluated (maximum, minimum, and mean). The coefficient of variation for all measures was below 10%, indicating low variability. Conclusions: Our findings demonstrate that thermography shows good-to-excellent reproducibility across multiple postures and regions of interest, reinforcing its potential as a non-invasive and reliable method for assessing lymphedema in breast cancer survivors. This study establishes a foundation for incorporating thermography into clinical practice for early BCRL detection, particularly in subclinical stages, thus improving patient management and outcomes.

Evaluating a novel portable semiconductor liquid cooling garment for reducing heat stress of healthcare workers in a hot-humid environment

Limited research focused on exploring personal cooling garments (PCGs) that offer excellent portability, along with a substantial, long-lasting, and consistent cooling effect for healthcare workers exposed to extreme heat while combating the COVID-19 pandemic. To address this gap, a novel, energy-efficient, and portable semiconductor liquid cooling garment (SLCG) was introduced, which incorporates a semiconductor-powered cold source and a cooling vest crafted from a semi-transparent thermoplastic polyurethane (TPU) film that offers extensive body coverage. Its practical cooling efficacy was assessed through a human trial involving ten male participants engaging in two protocols under a hot-humid environment (i.e., 30 ± 0.5 °C, RH = 80 ± 5 %). These protocols included both low-intensity (Prot.1) and moderate-intensity (Prot.2) exercises, mimicking the physical demands faced by healthcare workers. SLCG significantly reduced the mean, torso and local skin temperatures during both Prot.1 and Prot.2 (p < 0.05), also with a notable reduction in heart rate and sweat loss during Prot.1 (p < 0.05). Rating of perceived exertion as well as thermal sensations, wetness sensations and comfort sensations in the whole-body and local-body (i.e., head & neck, trunk, arms and legs) were all remarkably improved using SLCG during Prot.1 (p < 0.05). These perceptual sensations in SLCG were only improved in the whole body during the resting stage, and in the trunk region during Prot.2 (p < 0.05). Furthermore, participants felt no significant added weight or movement restrictions with SLCG in either protocol.

Photobiomodulation using red and infrared spectrum light emitting-diode (LED) for the healing of diabetic foot ulcers: a controlled randomized clinical trial.

Assessing the responses to the application of photobiomodulation using red and infrared spectrum light-emitting diodes (LED) on diabetic foot ulcers. Diabetic volunteers, of both genders, aged between 30 and 65 years, with grade I or II ulcers, were randomized into the groups: red LED, infrared LED, LED associated, and control. Home-based interventions took place on a daily basis for 12 weeks. Assessments of sample characterization were performed on day 1 and 90, and the variables wound healing index, mean skin temperature, sensitivity and pain in the wound area were measured at the pre-intervention time on days 1, 30, 60 and 90, with subsequent follow-up 30 days after the end of treatment. For statistical analysis, the software SPSS, version 17.0, intention-to-treat analysis, data normality was tested, and the linear mixed effects model, with a significance level of 5%. Magnitudes of clinical effect by Cohen's d. At the pre vs post intervention time of 90 days, we found a large clinical effect of G-LED V (d=1.7) and G -LED IV (d=1.6) in relation to G-C, where these intervention groups showed a tendency for faster wound healing compared to G-C. We also observed small clinical effect of G-LED IV, which showed greater reduction in the area in relation to G-LED V (d=0.4) and G-LED A (d=0.3). Conclusion: The use of individually applied red and infrared LED phototherapy clinically tended to be more effective for the reduction of diabetic foot ulcer areas, and infrared LED was the most effective. Trial registration: NCT03250533 (clinicaltrials.gov).

A modified multi-node human thermoregulation model with improved sweating response to simulate human physiological behaviours in warm and hot environments

The present research developed a modified multi-node thermoregulation model derived from the renowned Tanabe and JOS series models (JOS-2 and JOS-3). The JOS-3 model's predictions showed an abrupt spike in mean skin temperature, contradicting the findings from experiments. The JOS-3 model's sweating mechanism exhibits an inconsistency, and the sweating mechanism is not triggered promptly and accurately, leading to a sudden rise in skin temperature. This disparity significantly impacts the ability of the model to precisely replicate thermoregulatory responses under various climatic conditions and levels of physical activity. The proposed modified thermoregulation model extends the JOS-3 model by modifying the set-point temperature and sweating signals. The performance of the developed modified thermoregulation model is thoroughly analyzed under various conditions involving different environmental conditions, activity levels, and clothing types. The proposed model eliminates abrupt rise in the mean skin temperature and improves its prediction accuracy, notably reducing mean skin temperature RMSE in hot-humid conditions (0.66 °C vs. 0.85 °C) compared to the JOS-3 model. In hot-dry settings, improvements are significant, reducing the mean skin temperature and core temperature RMSE (0.48 °C vs. 0.06 °C and 0.05 °C vs. 0.02 °C, respectively). Overall, the modified thermoregulation model offers a reliable and accurate solution to analyze human physiological conditions for a wide range of practical problems.

Evaluation of pedestrian thermal comfort from a whole-trip perspective: An outdoor empirical study

Pedestrian thermal comfort is a critical factor influencing urban livability and sustainability. However, existing models often overlook its cumulative impact from dynamic thermal experiences throughout the whole-trip. This study builds on previous findings, conducting outdoor mobile observations in Guangzhou's urban blocks on clear summer days. Methods for assessing thermal comfort during pedestrian travel were tested and refined, taking into account participants' skin temperatures and accumulated heat storage. The research found that the dynamic changes and non-uniform distribution of radiant temperature are the main characteristics of pedestrians' thermal experiences during summer clear weather and are critical factors affecting their thermal comfort. Non-uniform exposure to direct solar radiation can cause variations in pedestrians' instantaneous thermal sensations, and dynamic thermal experiences can lead to the formation of memorized thermal sensations, causing a deviation between instantaneous and whole-trip thermal sensations. There is a significant correlation between pedestrians' mean skin temperature and heat storage and their thermal experiences over the past 10–25 min. Regression analysis provided different weights that could represent the memory component in whole-trip thermal sensations. The findings provide a theoretical basis for understanding pedestrian thermal comfort in dynamic outdoor environments and will help improve the thermal quality of outdoor travel spaces.

Comparison Of Weighting Formulas For Mean Skin Temperature Calculation During Work In Cold Environments

Comparison Of Weighting Formulas For Mean Skin Temperature Calculation During Work In Cold Environments

A Comparison of Passive Rewarming Systems Following Cold Water Immersion.

We studied field rewarming using a typical winter sleeping bag versus two heated hypothermia wrap systems in a semi-realistic lab simulation. 10 participants (8 M, 2 F) were cooled to 36.1°C core temperature through 10.5-11.5°C water immersion, then performed 60 min of passive rewarming in 0°C air. The rewarming methods tested were: 1) a -9°C rated mummy-style Sleeping Bag; 2) Doctor Down Rescue Wrap; and 3) Thermal Yielding Vascular Airway Capsule (TYVAC) system; the latter two methods included vapor barriers and two heating pads. Rectal and skin temperatures, along with metabolic heat production calculated via indirect calorimetry, were measured throughout rewarming. One male participant was removed from analysis due to lack of sufficient cooling. Rectal temperature decreased in the remaining participants by ∼1.1-1.2°C to 36.1°C during the initial immersion phase. Over the 60 min of rewarming, rectal temperature changes were Δ0.0 ± 0.6°C in a sleeping bag, Δ+0.2 ± 0.3°C in Doctor Down, and Δ+0.2 ± 0.3°C in TYVAC, with no significant differences across methods. Mean skin temperatures, metabolic heat production, and perceptual measures were also similar across methods with no method×time interactions. After 60 min of passive rewarming in cold conditions, all three rewarming methods were able to stall continued core cooling to levels at or slightly above post-immersion temperatures. With no differences in any physiological measures, it appears that all three rewarming methods are equally viable options for wilderness responders, and the choice should come down to environmetal conditions, availability, convenience, and ergonomics rather than rewarming efficacy.

A comprehensive study on the impacts of thermal comfort on occupants’ thermophysiology and cognitive performances in a radiant cooling environment using physiological measurements

Radiant cooling (RC) systems are increasingly implemented in public buildings to enhance human thermal comfort and reduce building energy consumption. The quality of the indoor thermal environment significantly impacts occupants’ learning and work performance. This investigation explores indoor occupants’ dynamic physiological regulation, thermal comfort, and cognitive performance under radiant whole-wall cooling (RWWC) systems. Twenty-eight participants underwent a summer exposure test task at varying ambient temperatures, yielding four collected data types: indoor physical parameters, physiological parameters (including skin temperature (ST), heart rate (HR)/heart rate variability (HRV), and electroencephalography (EEG)), performance index (PI), and thermal perception. Results indicate that the RWWC system notably improves thermal perception and comfort, with 93 % of participants reporting comfort at a target temperature of 24℃. Air temperature (AT) exerted the most significant effect on changes in ST on the right upper arm (p < 0.01) and left hand back (p < 0.01) at 30℃ compared to the 22℃. The difference in whole-body mean skin temperature (MST) is 2.68℃. The HR decline was more pronounced in higher temperatures, and the HRV representativeness index approached ‘1′ at 24℃. PI was affected by temperature and task type, displaying a non-linear correlation with AT (R2 = 0.6056) and an inverted “U” shaped curve with TSV (R2 = 0.9523). Thermal perception correlates with MST, HRV, and EEG. The study carries implications for the reasonable design of comfortable and healthy RC environments.

The effect of seasonal heat acclimatization on cool-seeking behaviour during passive heat stress in young adults.

Seasonal heat acclimatization is known to enhance autonomic thermoeffector responses, whereas the behavioural response following seasonal heat acclimatization remains unknown. We investigated whether seasonal heat acclimatization would alter autonomic and behavioural thermoregulatory responses. Sixteen healthy participants (eight males and eight females) underwent two trials involving 50 min of lower-leg passive heating (lower-leg submersion in 42°C water) with (Fan trial) and without (No fan trial) the voluntary use of a fan in a moderate thermal environment (27°C, 50% relative humidity) across winter and summer months. In Fan trials, participants were allowed to use a fan to maintain thermal comfort, but this was not allowed in the No fan trials. Cool-seeking behaviour was initiated at a lower change in rectal temperature [mean (SD): 0.21 (0.18)°C vs. 0.11 (0.13)°C, P=0.0327] and change in mean skin temperature [2.34 (0.56)°C vs. 1.81 (0.32)°C, P<0.0001], and cooling time was longer [16.46 (5.62) vs. 20.40 (4.87) min, P=0.0224] in summer compared with winter. However, thermal perception was not modified by season during lower-leg passive heating (all P>0.0864). Furthermore, rectal temperature was higher in summer (P=0.0433), whereas mean body temperature and skin temperature were not different (all P>0.0631) between the two seasons in Fan trials. In conclusion, seasonal heat acclimatization enhanced the cool-seeking behaviour from winter to summer.

Effects of hypobaric hypoxia on human physiological and psychological responses in hot-humid environments

The hot-humid and hypobaric hypoxic environment hampers human physiological and psychological responses. In this study, 10 healthy participants were recruited to walk on a treadmill at 4 km/h in a hypobaric chamber under nine experimental conditions involving three air temperatures (Ta = 33, 37, and 40 °C), and three barometric pressures (PB = 96.5, 65.7, and 63.2 kPa). At 33 and 37 °C, the mean skin temperature, oral temperature, and sweat rate were not significantly affected by hypobaric hypoxia. The diastolic blood pressure, systolic blood pressure, and oxygen saturation decreased significantly, while the heart rate increased significantly under hypobaric hypoxic conditions. At 40 °C, the heart rate and diastolic blood pressure were not significantly affected by hypobaric hypoxia, while the oral temperature was significantly higher at 63.2 kPa than at 65.7 and 95.6 kPa. The remaining physiological parameters exhibited similar patterns as those at 33 and 37 °C. In conclusion, higher Ta had the most substantial effects on the cardiovascular system. Additionally, individuals should not work in environments where the Ta exceeds the body core temperature, especially at higher altitudes, as the risk of heat-related injuries could increase. At various Ta, the thermal sensation and acceptability were not significantly affected by hypobaric hypoxia, while a decrease in PB to 63.2 kPa resulted in a significant increase in tolerance, along with a notable reduction in exposure time. Therefore, this study provides valuable information concerning the physiological and psychological responses of humans exposed to working conditions similar to those tested.

Effects of firefighters’ protective gloves on physiological responses, psychological responses, and manual performance in a cold environment

This study aimed to investigate the effects of firefighters' protective gloves on physiological responses, psychological responses, and manual performance in a cold environment through human trials. Twelve participants wearing firefighter protective equipment were exposed to a 16 °C environment, while their hands were exposed to a small chamber of 0 °C with (FPG) and without (CON) firefighting protective gloves. During the trials, physiological responses (core temperature (Tc), the mean skin temperature (Tsk), and heart rate (HR)), psychological responses (thermal sensation vote (TSV) and pain sensation vote (PSV)), and manual performance (handgrip strength, manual dexterity, maximum finger flexion, and tactile sensitivity)) were obtained. The results indicated a significant difference (p < 0.05) between FPG and CON regarding Tsk. Furthermore, pain sensation occurred when the mean skin temperature of the hand was between 15 °C and 20 °C. Gloves significantly (p < 0.05) reduced handgrip strength, manual dexterity, and tactile sensitivity in the cold exposure. This study provides fundamental knowledge for cold strain assessment and high-performance protective glove development with the potential to improve firefighters’ safety and health.

Assessment of alternative metrics in the application of infrared thermography to detect muscle damage in sports.

Objective.The association between muscle damage and skin temperature is controversial. We hypothesize that including metrics that are more sensitive to individual responses by considering variability and regions representative of higher temperature could influence skin temperature outcomes. Here, the objective of the study was to determine whether using alternative metrics (TMAX, entropy, and pixelgraphy) leads to different results than mean, maximum, minimum, and standard deviation (SD) skin temperature when addressing muscle damage using infrared thermography.Approach.Thermal images from four previous investigations measuring skin temperature before and after muscle damage in the anterior thigh and the posterior lower leg were used. The TMAX, entropy, and pixelgraphy (percentage of pixels above 33 °C) metrics were applied.Main results.On 48 h after running a marathon or half-marathon, no differences were found in skin temperature when applying any metric. Mean, minimum, maximum, TMAX, and pixelgraphy were lower 48 h after than at basal condition following quadriceps muscle damage (p< 0.05). Maximum skin temperature and pixelgraphy were lower 48 h after than the basal condition following muscle damage to the triceps sural (p< 0.05). Overall, TMAX strongly correlated with mean (r= 0.85) and maximum temperatures (r= 0.99) and moderately with minimum (r= 0.66) and pixelgraphy parameter (r= 0.64). Entropy strongly correlates with SD (r= 0.94) and inversely moderately with minimum temperature (r= -0.53). The pixelgraphy moderately correlated with mean (r= 0.68), maximum (r= 0.62), minimum (r= 0.58), and TMAX (r= 0.64).Significance.Using alternative metrics does not change skin temperature outcomes following muscle damage of lower extremity muscle groups.

Experimental and numerical investigation on the effect of ease allowance of clothing on thermal comfort

The heat transfer within the microclimate of clothing directly affects the thermal sensation of the human body, holding significant implications for both heat dissipation and cold protection. To investigate the variations in the heat transfer performance of the microclimate under the clothing influenced by distinct air gap thicknesses and diverse body postures, twelve female subjects participated in experiments wearing T-shirts with various ease allowances, conducting tasks in both sitting and standing positions within a climate chamber set at 20 °C and 50 % RH. Physiological parameters and subjective evaluations of comfort were recorded. Additionally, we constructed a three-dimensional model of the air gap featuring realistic morphology for numerical simulations of microclimatic heat transfer in a standing posture. The experimental results indicate that air gap thickness significantly impacts core temperature, mean skin temperature, local skin temperature, and thermal sensation. While postural differences did not show statistical significance, temperatures and thermal sensations were generally higher in the sitting position. Based on the results of numerical simulation, under this environmental condition, approximately 27 % of heat transfer was through radiation, with both the percentage of radiative heat transfer and the overall heat flux increasing with greater ease allowance. Furthermore, airflow under the clothing became more disorganized at thicker air layers, primarily concentrating in folds, hems, and sides of the body. This study provides a theoretical support for the workwear design and similar clothing and helps to reduce energy consumption in office environments.

Sex differences in body temperature and thermal perception under stable and transient thermal environments: A comparative study

Sex difference stands as a crucial factor necessitating consideration in personalized thermal environment control, with the mechanisms of its emergence potentially differing across different thermal environments. However, a comparative analysis of sex differences regarding body temperature (skin and core body temperature) and thermal perception across different environments is lacking. A stable environmental experiment (comprising three conditions: 16 °C, 20 °C, and 24 °C) and a transient environmental experiment (involving a whole-body step-change from 19 °C to 35 °C and back to 19 °C) were conducted, with participation from 20 young males and 20 young females. Skin temperature and core body temperature were continuously recorded during the experiments, and three types of thermal perceptions were regularly collected. The results showed that: (1) The impact of thermal environment on females' skin temperature surpassed that on males, in stable environment, with every 1 °C rise in ambient temperature, the mean skin temperature increased by 0.28 °C for males and 0.35 °C for females respectively; in transient environment, females' mean skin temperature raise and fell at a faster rate. (2) Males exhibited stronger thermal regulation abilities than females, particularly evident during sudden increase in ambient temperature (from 19 °C to 35 °C), where the reduction magnitude of males' core body temperature was notably larger. (3) Whether in stable or transient environments, significant sex differences often occurred in skin temperature and thermal sensation at distal parts, particularly at the hand. (4) Males typically fed back higher levels of thermal comfort and thermal acceptability than females, suggesting that in addition to physiological sex differences, psychological sex distinctions also play a role. In summary, personalized design for stable thermal environment can focus on sex differences in skin temperature, while transient thermal environment requires consideration of both skin temperature and core body temperature. A comprehensive consideration of physiological and psychological sex differences aids in creating personalized thermal environments with greater precision.

Different humidity environments do not affect the subsequent exercise ability of college football players after aerobic high-intensity interval training

Previous studies have explored the effect of differing heat and relative humidity (RH) environments on the performance of multiple anaerobic high-intensity interval training (HIIT). Still, its impact on physiological responses and performance following aerobic HIIT has not been well studied. This study examined the effects of differing RH environments on physiological responses and performance in college football players following HIIT. Twelve college football completed HIIT under four different environmental conditions: (1) 25 °C/20% RH (Control group); (2) 35 °C/20% RH (H20 group); (3) 35 °C/40% RH (H40 group); (4) 35 °C/80% RH (H80 group). The heart rate (HR), mean arterial pressure (MAP), lactate, tympanic temperature (TT), skin temperature (TS), thermal sensation (TS), and rating of perceived exertion (RPE) were recorded continuously throughout the exercise. The heart rate variability (HRV): including root mean squared differences of the standard deviation (RMSSD)、standard deviation differences of the standard deviation (SDNN)、high frequency (HF), low frequency (LF), squat jump height (SJH), cycling time to exhaustion (TTE), and sweat rate (SR) were monitored pre-exercise and post-exercise. The HR, MAP, lactate, TT, Ts, TS, and RPE in the 4 groups showed a trend of rapid increase, then decreased gradually. There was no significant difference in HR, MAP, TT, or RPE between the 4 groups at the same time point (p > 0.05), in addition to this, when compared to the C group, the lactate, Ts, TS in the other 3 groups significant differences were observed at the corresponding time points (p < 0.05). The RMSSD, SDNN, HF, and LF levels in the 4 groups before exercise were not significantly different. The RMSSD and HF in the H40 and H80 groups were significantly decreased and other HRV indicators showed no significant difference after exercise. In sports performance measurement, the SJH and TTE were significantly decreased, but there was no significant difference in the 4 groups. The SR was no significant difference in the 4 groups after exercise. In conclusion, heat and humidity environments elicited generally greater physiological effects compared with the normal environment but did not affect sports performance in college football players.

A Contrast Experiment on the Ventilation Direction towards Human Head in Personalized Environmental Control System (PECS)

A heating, ventilation, and air-conditioning system is designed for the entire space but falls short in meeting diverse individual needs. Therefore, the personalized environmental control system is proposed to address individual thermal requirements and it has been widely accepted and produced to have significant practical value for humans. In order to enhance the comfort level based on the PECS, the impact of the airflow direction towards the head in terms of physiological and psychological sensations was investigated. Different airflow directions were considered as follows: front blowing (FB-PV), side blowing (SB-PV), back blowing (BB-PV), top blowing (TB-PV), and a control group No-PV. A total of 56 participants were invited to assess the thermal environment, and their skin temperature was measured. The results revealed that the airflow towards the head improved thermal comfort and reduced the mean skin temperature by 0.4–0.6 °C, with FB-PV showing particularly promising results. TB-PV demonstrated the highest level of comfort with a score of +1.05 (slightly higher than “Just comfortable (+1)”) and scored significantly higher in overall willingness at +1.21 (higher than “Willing (+1)”). Conversely, FB-PV resulted in a discomfort level due to restricted breathing under the continuous airflow condition.

The effects of cold water immersion and partial body cryotherapy on subsequent exercise performance and thermoregulatory responses in hot conditions

This study investigated the effects of cold water immersion (CWI) and partial body cryotherapy (PBC) applied within a 15-min post-exercise recovery period on thermoregulatory responses, subjective perceptions, and exercise performance under hot conditions (39 °C). Twelve male soccer players participated in team-sports-specific assessments, including Agility T-test (T-test), 20-m sprint test (20M-ST), and Yo-Yo Intermittent Endurance Test Level 1 (YY-T), during two exercise bouts (1st bout and 2nd bout) with a 15-min post-exercise recovery period. Within the recovery period, a 3-min of PBC at −110 °C or CWI at 15 °C or a seated rest (CON) was performed. Mean skin temperature (Tskin) decreased by 4.3 ± 1.08°C (p < 0.001) immediately after PBC, while CWI induced a reduction of 2.5 ± 0.21°C (p < 0.01). Furthermore, PBC and CWI consistently reduced Tskin for 15 and 33 min, respectively (p < 0.05). During the 2nd bout, core temperature (Tcore) was significantly lower in PBC compared to CON (p < 0.05). Heart rate (HR) was significantly lower in CWI compared to CON and PBC during the intervention period. Thermal sensation (TS) was significantly greater in PBC compared to CON and CWI (p < 0.05). Compared to the 1st bout, PBC alleviated the declines in T-test (p < 0.05) and 20M-ST (p < 0.05), while CWI alleviated the decreases in T-test (p < 0.05) and YY-T (p < 0.05), concurrently significantly enhancing 20M-ST (p < 0.05). 20M-ST and YY-T was greater from PBC (p < 0.05) and CWI (p < 0.05) compared with CON in 2nd bout. Additionally, the T-test in CWI was significantly greater than CON (p < 0.05). These results indicate that both PBC and CWI, performed between two exercise bouts, have the potential to improve thermoregulatory strain, reduce thermal perceptual load, and thereby attenuate the subsequent decline in exercise performance.

Effects of fan cooling with an air-perfused rucksack on physiological and perceptual strains in young men while running in uncompensable hot environment.

Cooling devices reduce thermal strain during pre-, between-, and postexercise. However, their efficacy during moderate/intensity runs in hot conditions with airflow equivalent to the running speed remains unclear. This study assessed physiological and perceptual responses to neck and upper back fan-cooling through an air-perfused rucksack under such conditions. Ten young men ran at 60% V̇O<inf>2peak</inf> for 30 min in 35 °C, 50% relative humidity with (FAN) and without (CON) air-perfused rucksacks with a hood in a randomized order. Headwind equal to running speed was provided in both conditions. The fan-cooling trial consisted of upper back and neck fan cooling with airflow at 4-5 m/s via two fans attached on either side of the rucksack. Rectal and skin temperatures, whole-body thermal sensation, thermal comfort, and changes in body mass were measured. Upper back skin temperature and thermal sensation were significantly lower throughout the exercise in the FAN than in the CON, whereas thermal comfort was significantly higher at 15-40 min in the FAN (all P≤0.05). Heart rate elevation during 30 min of running was attenuated in the FAN compared to that in the CON (P≤0.05). No significant differences in rectal and mean skin temperatures, or total body mass loss were observed between the two trials. These results indicate that additional fan-cooling on the upper back and neck during running in uncompensable hot conditions with a headwind had limited physiological benefits. However, whole-body-based thermal sensation and comfort are partially improved with the use of an air-perfused rucksack.