Thermal Imaging of Cutaneous Temperature Modifications in Runners During Graded Exercise

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.

Estimation of Heat Production Rate using Thermal Data During Exercise in Indoor Environments: A Study of Heat Storage Rate in Male Athletes

The increasing preference for indoor exercise spaces highlights the relationship between indoor thermal environments and physiological responses, particularly concerning thermal comfort during physical activity. Determining the metabolic heat production rate during exercise is essential for optimizing the thermal comfort, well-being, and performance of individuals engaged in physical activities. This value can be determined during the activity using several methods, including direct calorimetry measurement, indirect calorimetry that uses analysis of respiratory gases, or approximations using collected data such as speed, body mass, and heart rate. The study aimed to calculate the metabolic heat production rate by infrared thermal evaluation (ITE) based on the body's thermal balance approach and compare it with the values determined by indirect calorimetry (IC). Fourteen participants volunteered for the study, using a cycling ergometer in a controlled climatic chamber. After the familiarization sessions, maximal O2 intake levels (VO2max) were determined through maximal graded exercise tests. Subsequently, constant work rate exercise tests were performed at 60% of VO2max for 20 min. The metabolic heat production rates were calculated by IC and ITE for each athlete individually. Respiratory gases were used to determine IC, while body skin and core temperatures, along with physical environmental data, were applied to calculate ITE using the human body thermal balance approximation of ASHRAE. According to the results, heat storage rates were misleading among the body's heat transfer modes, particularly during the first 8 min of the exercise. ITE showed a moderate level of correlation with IC (r: 0.03-0.86) with a higher level of dispersion relative to the mean (CV%: 12-84%). Therefore, a new equation (ITEnew) for the heat storage rates was proposed using the experimental data from this study. The results showed that ITEnew provided more precise estimations for the entire exercise period (p > 0.05). Correlations between ITEnew and IC values were consistently strong throughout the exercise period (r: 0.62-0.85). It can be suggested that ITEnew values can predict IC during the constant work rate steady-state exercise.

Exercise-induced changes in lower limbs skin temperature against plasma ATP among individuals with various type and level of physical activity

The objective of the study was to examine the lower limbs skin temperature (TSK) changes in response to exhaustive whole-body exercise in trained individuals in reference to changes in plasma adenosine triphosphate (ATP). Eighteen trained participants from distinct sport type ‒ endurance (25.2 ± 4.9 yr) and speed-power (25.8 ± 3.1 yr), and 9 controls (24,9 ± 4,3 yr) ‒ were examined. Lower limbs TSK and plasma ATP measures were applied in parallel in response to incremental treadmill test and during 30-min recovery period. Plasma ATP kinetics were inversely associated to changes in TSK. The first significant decrease in TSK (76-89% of V˙ O2MAX) occurred shortly before a significant plasma ATP increase (86-97% of V˙ O2MAX). During recovery, TSK increased, reaching pre-exercise values (before exercise vs. after 30-min recovery: 31.6 ± 0.4 °C vs. 32.0 ± 0.8 °C, p = 0.855 in endurance; 32.4 ± 0.5 °C vs. 32.9 ± 0.5 °C, p = 0.061 in speed-power; 31.9 ± 0.7 °C vs. 32.4 ± 0.8 °C, p = 0.222 in controls). Plasma ATP concentration did not returned to pre-exercise values in well trained participants (before exercise vs. after 30-min recovery: 699 ± 57 nmol l-1 vs. 854 ± 31 nmol l-1, p < 0.001, η2 = 0.961 and 812 ± 35 nmol l-1 vs. 975 ± 55 nmol l-1, p < 0.001, η2 = 0.974 in endurance and speed-power, respectively), unlike in controls (651 ± 40 nmol l-1 vs. 687 ± 61 nmol·l-1, p = 0.58, η2 = 0.918). The magnitude of TSK and plasma ATP response differed between the groups (p < 0.001, η2 = 0.410 for TSK; p < 0.001, η2 = 0.833 for plasma ATP). We conclude that lower limbs TSK change indirectly corresponds to the reverse course of plasma ATP during incremental exercise and the magnitude of the response depends on the level of physical activity and the associated to it long-term metabolic adaptation.

Skin temperature of women: A prospective longitudinal study

INTRODUCTION

The different phases of a woman's life, such as the reproductive phase and menopause, are points of great hormonal oscillation, especially estrogen and progesterone, which can interfere with skin temperature.

OBJECTIVE

To describe and compare skin temperatures of women during their physiological menstrual cycle, the use of exogenous hormones and menopause over a period of 28 days.

METHOD

This is a prospective observational study using a quantitative approach. A total of 45 volunteers participated and were equally allocated into three groups: Exogenous Hormone Group (EHG), Physiological Menstrual Cycle Group (PMCG) and Menopause Group (MG). All were submitted once a week to body composition measurements over a period of 28 days using an InBody 120 bioimpedance scale, and skin temperature using a FLIR model T-360 thermographic camera.

RESULTS

No significant differences were found between the mean skin temperature of women with a physiological cycle using exogenous hormones and menopause in relation to the evaluation time or between groups. However, younger women had higher temperatures in specific skin regions, such as in the breast, lower abdomen and thigh (P < 0.05) compared to menopausal women. In addition, negative correlations were observed between body fat and skin temperature of the breasts, trunk, abdomen, upper limbs and right lower limb (P < 0.05).

CONCLUSION

It was observed that the general skin temperature of women is not altered due to exogenous hormones, menstrual cycle phase or menopause, and that skin temperature tends to be lower in regions with an accumulation of adipose tissue.

Relationship between aerobic fitness and lower limb skin temperature during cycling exercise testing among well-trained athletes and nonathletes: a cross-sectional study

Background

During prolonged physical exercise, the skin plays an important role in thermoregulation by dissipating heat to maintain core temperature. Moreover, thermal variation may be influenced by the physical fitness level of an individual. The aim of the present study was to determine the relationship between aerobic fitness and lower limb skin temperature during graded cycling exercise testing in well-trained athletes and nonathletes.

Methods

Twelve trained athletes (mean ± SD maximal oxygen consumption [VO2max], 52.44 ± 4.5 ml/kg/min) and 12 nonathletes (VO2max, 36.95 ± 4.9 ml/kg/min) participated in this study. The regional skin temperature over the lower limbs was monitored continuously during incremental exercise testing using a thermal camera, and cardio-respiratory parameters were assessed and recorded using a metabolic analyzer (K5, COSMED, Rome, Italy).

Results

The mean skin temperature of athletes at a high intensity of exercise was 27.23 ± 0.3 °C while that of nonathletes was 29.03 ± 0.44 °C, a difference that was statistically significant (p < 0.05). A negative correlation was observed between skin temperature and cardiovascular parameters (VO2max and heart rate) in athletes, while no such correlation was found among nonathletes.

Conclusion

The present study demonstrated a negative correlation between oxygen consumption and lower limb skin temperature in athletes, while the correlation was poor in nonathletes. This suggests that physical fitness level may influence the pattern of alterations in lower limb skin temperature, which supports the hypothesis that athletes exhibit better heat dissipation mechanisms than nonathletes.

Thermal resting pattern and acute skin temperature response to exercise in older adults: Role of cardiorespiratory fitness

BACKGROUND

Infrared thermography is a growing area of interest in sports science due to the potential of skin temperature (Tsk) measurements to provide valuable information from rest to exercise. However, limited research exists on Tsk in older adults and the impact of factors such as sex and cardiorespiratory fitness (CRF) on Tsk. This study aims to investigate Tsk at rest and after acute exercise in older adults and assess whether sex or CRF influences Tsk.

METHODS

Ninety-two participants (41 women, 68.48 ± 3.01 years) were examined with a thermographic camera in a conditioned room (23.02 ± 3.01 °C) at rest and after a graded protocol. The Tsk of 25 regions of interest (ROIs) were extracted and analysed.

RESULTS

Men had higher overall Tsk at rest in 76% of ROIs, showing significant differences (p < 0.010) in six specific ROIs, independent of CRF. Both sexes had similar Tsk responses after graded exercise, with increases in distal parts (1.06 ± 0.50 °C), decreases in proximal parts (-0.62 ± 0.42 °C), and stable central Tsk (0.23 ± 0.59 °C). Increases in lower limb Tsk were significantly associated with CRF in men and women (β = 0.438, p = 0.001, and β = 0.535, p < 0.001, respectively), explaining 17% and 27% of the variance, respectively.

CONCLUSIONS

This study demonstrates a sex-specific effect on resting Tsk in older adults, suggesting that sex-specific Tsk patterns should be considered when analysing Tsk in this population. Additionally, the association between increases in lower limb Tsk and CRF suggests that Tsk could be a promising predictor of CRF in older adults.

Determination of the Effects of a Series of Ten Whole-Body Cryostimulation Sessions on Physiological Responses to Exercise and Skin Temperature Behavior following Exercise in Elite Athletes

The present study investigated the effects of a series of 10 whole-body cryostimulation (WBC) sessions (3 min; -110 °C) on physiological and thermal responses to a submaximal exercise test in 17 elite athletes. Participants performed an exercise test twice at similar levels of intensity before and after a series of ten WBC sessions. Before and during the test, each participant's oxygen uptake (VO2), heart rate (HR), internal temperature (Ti), and skin temperature in selected areas of the skin were measured, and the mean arterial pressure (MAP), physiological strain index (PSI), and mean skin temperature (Tsk) were calculated. The results show that during exercise, increases in Ti and the PSI were significantly lower after the WBC sessions, and although there were no significant changes in HR or the MAP, the Tsk was significantly higher. Following exercise, an increase in skin temperature asymmetry over the lower-body muscles was detected. A series of WBC sessions induced a tendency toward a decrease in temperature asymmetry over the thigh muscles. In conclusion, a series of ten WBC sessions does not induce significant modifications in physiological variables but does influence the PSI and Ti during exercise. Moreover, a series of ten WBC sessions influences the distribution of skin temperature and the magnitude of temperature asymmetries in the early phase of recovery.

Association between physical demands, skin temperature and wellbeing status in elite football players

The demanding nature of elite football requires players to be closely monitored to ensure optimal performance and minimize injury risk. This study aimed to evaluate the relationship between physical demands, skin temperature, and well-being status in 30 elite football players over a 12-week competitive period. Thermography assessments, weekly Well-being questionnaires, and daily training and match load recordings were used to gather data. Results indicated that along the microcycles there was a decrease in high-intensity accelerations and decelerations distance completed, while maintaining other high-intensity actions. Furthermore, it was found that high-intensity movements contribute to the generation of thermal asymmetries in the thighs; the adductor thermal asymmetry showed a positive relationship with stress and muscle soreness, the knee thermal asymmetry had a positive relationship with fatigue and a negative relationship with rest and quality of rest, and finally the hamstrings muscles exhibited significant differences between the thermal asymmetry groups, with the high asymmetry completing less high intensity actions than the low asymmetry group. In conclusion, this study highlights the interconnections between physical demands, skin temperature, and well-being in elite football players and provides valuable insights for coaches and trainers in their efforts to optimize performance and health.

Acute physiological responses to a pyramidal exercise protocol and the associations with skin temperature variation in different body areas

This study aimed to examine the skin temperature (Tsk) variations in five regions of interest (ROI) to assess whether possible disparities between the ROI's Tsk could be associated with specific acute physiological responses during cycling. Seventeen participants performed a pyramidal load protocol on a cycling ergometer. We synchronously measured Tsk in five ROI with three infrared cameras. We assessed internal load, sweat rate, and core temperature. Reported perceived exertion and calves' Tsk showed the highest correlation (r = -0.588; p < 0.01). Mixed regression models revealed that the heart rate and reported perceived exertion were inversely related to calves' Tsk. The exercise duration was directly associated with the nose tip and calf Tsk but inversely related to the forehead and forearm Tsk. The sweat rate was directly related to forehead and forearm Tsk. The association of Tsk with thermoregulatory or exercise load parameters depends on the ROI. The parallel observation of the face and calf Tsk could indicate simultaneously the observation of acute thermoregulatory needs and individual internal load. The separate Tsk analyses of individual ROI appear more suitable to examine specific physiological response than a mean Tsk of several ROI during cycling.

Acute Effects of Varied Back Squat Activation Protocols on Muscle-Tendon Stiffness and Jumping Performance

ABSTRACT

Krzysztofik, M, Wilk, M, Pisz, A, Kolinger, D, Tsoukos, A, Zając, A, Stastny, P, and Bogdanis, GC. Acute effects of varied back squat activation protocols on muscle-tendon stiffness and jumping performance. J Strength Cond Res 37(7): 1419-1427, 2023-Intensity, movement velocity, and volume are the principal factors to successfully use postactivation performance enhancement. Therefore, 15 resistance-trained volleyball players completed 3 different back squat configurations as a conditioning activity (CA) in randomized order: (a) 3 sets of 3 repetitions at 85% 1RM (HL); (b) a single set of back squats at 60% 1RM until 10% mean velocity loss (VB); (c) and 2 sets of back squats at 60% 1RM until 10% mean velocity loss (2VB) on subsequent countermovement jump performance, Achilles tendon, and vastus lateralis stiffness with concomitant front thigh skin surface temperature assessment. The measurements were performed 5 minutes before the CA and at 2, 4, 6, 8, and 10 minutes. The jump height was significantly increased in the second minute and at peak, post-CA compared with baseline for all conditions ( p = 0.049; ES = 0.23 and p < 0.001; ES = 0.37). Skin surface temperature was significantly increased for all post-CA time points compared with baseline in the 2VB condition ( p from <0.001-0.023; ES = 0.39-1.04) and in the fourth minute and at peak post-CA in HL condition ( p = 0.023; ES = 0.69 and p = 0.04; ES = 0.46), whereas for the VB condition, a significant decrease in peak post-CA was found ( p = 0.004; ES = -0.54). Achilles tendon stiffness was significantly decreased for second, fourth, eighth, 10th, and peak post-CA in comparison to baseline for all conditions ( p from p = 0.004-0.038; ES = -0.47 to -0.69). Vastus lateralis stiffness was significantly decreased for peak post-CA compared with baseline for all conditions ( p = 0.017; ES = -0.42). We recommend using a single set of barbell squats with a 10% velocity loss as a mechanism of fatigue control to acutely improve jump height performance and avoid unnecessary increases in training volume.

Joint Response to Exercise Is Affected by Knee Osteoarthritis: An Infrared Thermography Analysis

Infrared thermography can be used to evaluate the inflammation characterizing the joint environment of OA knees, but there is limited evidence on the response to physical exercise. Identifying the response to exercise of OA knees and the influencing variables could provide important information to better profile patients with different knee OA patterns. Sixty consecutive patients (38 men/22 women, 61.4 ± 9.2 years) with symptomatic knee OA were enrolled. Patients were evaluated with a standardized protocol using a thermographic camera (FLIR-T1020) positioned at 1 m with image acquisition of an anterior view at baseline, immediately after, and at 5 min after a 2-min knee flexion-extension exercise with a 2 kg anklet. Patients' demographic and clinical characteristics were documented and correlated with the thermographic changes. This study demonstrated that the temperature response to exercise in symptomatic knee OA was affected by some demographic and clinical characteristics of the assessed patients. Patients with a poor clinical knee status presented with a lower response to exercise, and women showed a greater temperature decrease than men. Not all evaluated ROIs showed the same trend, which underlines the need to specifically study the different joint subareas to identify the inflammatory component and joint response while investigating knee OA patterns.

The effects of transcranial laser photobiomodulation and neuromuscular electrical stimulation in the treatment of post-stroke dysfunctions

Post-stroke sequelae includes loss functions, such as cognitive and sensory-motor which lead to emotional and social problems, reducing quality of life and well-being. The main aim of our study was to investigate the effects of transcranial laser photobiomodulation together with neuromuscular electrical stimulation (NMES) in post-stroke patients. We performed a clinical trial and an ex vivo study. For the clinical trial, hemiplegic patients were separated into two groups: Treated Group (TG): Hemiplegics treated with transcranial laser (on) associated with NMES (on) and; Placebo Group (PG): Hemiplegics treated with placebo transcranial laser (off) associated with NMES (on). The cluster prototype includes 12 diode laser beams (4 × 660 nm, 4 × 808 nm and 4 × 980 nm) with average power of 720 mW per cluster applied during one minute, leading to 43.2 J energy per cluster. Fifteen regions for all head were irradiated by cluster, leading to 648 J energy per session. The parameters of NMES of the paretic limbs to generate extension wrist and ankle dorsiflexion were symmetrical biphasic rectangular waveforms, 50 Hz frequency, 250 μs pulse duration, and adjustable intensity to maintain the maximum range of motion (amplitude between 0 and 150 mA). Our clinical trial showed improvement of cognitive function, pain relief, greater manual dexterity, enhancement of physical and social-emotional health which lead to better quality of life and well-being. There was also increased temperature in the treated regions with laser and NMES. For the ex vivo study, the distribution of infrared and red radiation after penetration through the cranium and hemihead of cadavers were showed. Therefore, transcranial laser photobiomodulation associated with NMES can be an important therapeutic resource for rehabilitation after stroke.

Effect of Whole-, Upper-, and Lower-Body High-Intensity Rowing Exercise on Skin Temperature Measured by Thermography

Purpose: Despite the growing works analyzing exercise-induced thermoregulatory adjustments through thermography, the skin temperature (Tsk) response of the same muscle groups underwent to different exercise demands has not been investigated. This study analyzed the behavior of Tsk of the same muscle groups when exercised with different demands in rowing. Methods: Eighteen men underwent three performance tests on a rowing ergometer: whole-body 2,000 m test (RT_WB), upper-body (RT_UB), and lower-body (RT_LB) tests. In each condition, thermograms were recorded before (pre), immediately after test (post), and at 10 (REC₁₀), 20 (REC₂₀), and 30 (REC₃₀) minutes post-exercise recovery. Tsk was measured at the pectoral (control body region), upper back, quadriceps, brachial biceps, and forearm. Results: Pectoral-Tsk reduced comparably in response to all testing conditions (p < .05). Upper back-Tsk decreased post (p < .001) and returned to baseline in the RT_UB (REC₁₀, p = 1.0) and RT_WB (REC₃₀, p = .128), while remained reduced in the RT_LB (p < .001). Quadriceps-Tsk reduced post (p < .05) and returned to baseline in the RT_WB and RT_LB at REC₁₀ (p = 1.0), remaining reduced in the RT_UB during recovery (p < .05). Regarding the upper limbs, Tsk increased more markedly in the RT_UB versus RT_WB during the recovery period (p < .05); in the RT_LB, biceps-Tsk remained below baseline over time (p < .05), whereas the forearm-Tsk was restored at REC₁₀ (p = 1.0). Conclusion: Manipulating the muscle groups involved in rowing alters the Tsk response within equal ROI. Exercise-induced Tsk changes can reflect local hemodynamic and thermoregulatory adjustments.

An exploratory, intra- and interindividual comparison of the deep neural network automatically measured calf surface radiation temperature during cardiopulmonary running and cycling exercise testing: A preliminary study

Non-invasive and contactless infrared thermography (IRT) measurements have been claimed to indicate acute neural, cardiovascular, and thermoregulatory adaptations during exercise. Due to challenging comparability, reproducibility, and objectivity, investigations considering different exercise types and intensities, and automatic ROI analysis are currently needed. Thus, we aimed to examine surface radiation temperature (T_sr) variations during different exercise types and intensities in the same individuals, ROI, and environmental conditions. Ten healthy, active males performed a cardiopulmonary exercise test on a treadmill in the first week and on a cycling ergometer the following week. Respiration, heart rate, lactate, rated perceived exertion, the mean, minimum, and maximum T_sr of the right calf (CT_sr (°C)), and the surface radiation temperature pattern (CP_sr) were explored. We executed two-way rmANOVA and Spearman's rho correlation analyses. Across all IRT parameters, mean CT_sr showed the highest association to cardiopulmonary parameters (E.g., oxygen consumption: r_s = -0.612 (running); -0.663 (cycling); p < .001). A global significant difference of CT_sr was identified between all relevant exercise test increments for both exercise-types (p < .001; η²_p = .842) and between both exercise-types (p = .045; η²_p = .205). Differences in CT_sr between running and cycling significantly appeared after a 3-min recovery period, whereas lactate, heart rate, and oxygen consumption were not different. High correlations between the CT_sr values extracted manually and the CT_sr values processed automatically by a deep neural network were identified. The applied objective time series analysis enables crucial insights into intra- and interindividual differences between both tests. CT_sr variations indicate different physiological demands between incremental running and cycling exercise testing. Further studies applying automatic ROI analyses are needed to enable the extensive analysis of inter- and intraindividual factors influencing the CT_sr variation during exercise to allow determine the criterion and predictive validity of IRT parameters in exercise physiology.

Investigation of the thermal comfort of the sportswear by standing thermal manikin and thermal imaging techniques

Garments should not overload the body during activity and should be chosen in accordance with the ambient conditions. Especially in active sports, sportswear should make a person feel comfortable and increase performance by easily removing excess heat and moisture from the body without interrupting physical activity. In this study, five T-shirts with the same size and weight characteristics, but in different yarn types were produced and analysed. The thermal and water vapour resistance properties of these garments were measured using a thermal manikin system. In addition, thermal camera images were taken at 10-minute intervals during the 50-minute wear trial programme, and skin temperatures were measured from the upper front body and the upper back body with two sensors. The results showed that POS and PM-coded garments made of polyester with low clothing insulation (clo) values were statistically different from CS and CPS coded cotton-containing garments in terms of front and back surface thermal camera images. It was observed that cotton-containing garments were more uncomfortable than polyester and Tencel owing to their higher thermal resistance, garment surface temperature, and skin temperature values. The Tencel garment was measured similarly to the CS and CPS coded garments at the beginning of the activity and measured similarly to the POS and PM coded garments at the end of the activity on both surfaces.

Intra- and inter-session reliability and repeatability of an infrared thermography device designed for materials to measure skin temperature of the triceps surae muscle tissue of athletes

Background

Infrared thermography devices have been commonly applied to measure superficial temperature in structural composites and walls. These tools were cheaper than other thermographic devices used to measure superficial human muscle tissue temperature. In addition, infrared thermography has been previously used to assess skin temperature related to muscle tissue conditions in the triceps surae of athletes. Nevertheless, the reliability and repeatability of an infrared thermography device designed for materials, such as the Manual Infrared Camera PCE-TC 30, have yet to be determined to measure skin temperature of the triceps surae muscle tissue of athletes.

Objective

The purpose was to determine the procedure's intra- and inter-session reliability and repeatability to determine skin temperature within the Manual Infrared Camera PCE-TC 30 thermography device in the triceps surae muscle tissue of athletes, which was initially designed to measure the superficial temperature of materials.

Methods

A total of 34 triceps surae muscles were bilaterally assessed from 17 healthy athletes using the Manual Infrared Camera PCE-TC 30 thermography device to determine intra- (at the same day separated by 1 h) and inter-session (at alternate days separated by 48 h) reliability and repeatability of the skin temperature of the soleus, medial and lateral gastrocnemius muscles. The triceps surae complex weas measured by a region of interest of 1 cm² through five infrared thermography images for each muscle. Statistical analyses comprised intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimum detectable change (MCD), systematic error of measurement, correlation (r), and Bland-Altman plots completed with linear regression models (R ²).

Results

Intra- and inter-session measurements of the proposed infrared thermography procedure showed excellent reliability (ICC_(1,2) = 0.968-0.977), measurement errors (SEM = 0.186-0.232 °C; MDC = 0.515-0.643 °C), correlations (r = 0.885-0.953), and did not present significant systematic error of measurements (P > 0.05). Adequate agreement between each pair of measurement moments was presented by the Bland-Altman plots according to the limits of agreement and non-significant linear regression models (R ² = 0.000-0.019; P > 0.05).

Conclusions

The proposed procedure to determine skin temperature within the Manual Infrared Camera PCE-TC 30 thermography device presented excellent intra- and inter-session reliability and repeatability in athletes' triceps surae muscle tissue. Future studies should consider the SEM and MDC of this procedure to measure the skin temperature of soleus, medial, and lateral gastrocnemius muscles to promote triceps surae muscle prevention and recovery in athletes.

Face Thermal Map of the Mexican Population in the Basal State

There has been a wide use of thermal images of the human body in recent years, specifically images with thermal information of regions of interest (ROI) in the face; this information can be used for epidemiological, clinical, and/or psychological purposes. Due to this, it is important to have plenty of information on temperature in these ROIs in the basal state that allows their use as a reference in terms of their thermal analysis. In this work, a face thermal map of the Mexican population in the basal state (n = 196) is created, adding the comparison between different population groups, such as gender, age, and clinical status, obtaining results of great interest for future research. The t-test for independent samples was applied to the ROIs with normal distribution and Mann−Whitney u-test to the ones that did not present normal distribution. Statistically significant differences were found in some of the ROI comparisons like the corrugator, the supraorbitals, and the chin between the control and clinical groups, as well as in the differentiation by age (p < 0.05).

Acute effects of combined isometric and plyometric conditioning activities on sports performance and tendon stiffness in female volleyball players

This study aimed to compare the effects of bilateral and unilateral conditioning activities (CA; combined isometric and plyometric) on countermovement jump performance, modified t-agility test, Achilles tendon stiffness and skin surface temperature. Thirteen female semi-professional volleyball players performed two CAs in random order: 1) bilateral isometric half back squats followed by bilateral drop jumps (BI-CA); and 2) unilateral isometric half back squats followed by unilateral drop jumps (UNI-CA). To assess the effects of CAs, countermovement jump, modified t-agility test, Achilles tendon stiffness and skin surface temperature measurements were performed 5 min before and 6 min after the CA. Both CAs significantly increased thigh skin surface temperature from pre- to post-CA (BI-CA, p < 0.001; effect size [ES] = 1.41 and UNI-CA, p = 0.001; ES = 1.39) but none of them influenced modified t-agility test time (interaction: p = 0.338, main effect of time: p = 0.121 and condition: p = 0.819). The countermovement jump height and modified reactive strength index significantly increased from pre-to post-CA during the BI-CA condition (p = 0.003, ES = 0.45, and p = 0.008, ES = 0.48) but not for UNI-CA (p = 0.061, ES = 0.18 and p = 0.065, ES = 0.26). No significant impact has been found for countermovement depth (interaction: p = 0.054, main effect of time: 0.097, and condition: p = 0.41) as well as for contraction time (interaction: p = 0.536, main effect of time: p = 0.224, and condition: p = 0.807). Moreover, stronger and weaker limb CMJ relative peak force significantly decreased from pre-to post-CA (p = 0.014, ES = −0.31, and p = 0.027, ES = −0.26; respectively) during UNI-CA condition but not for BI-CA (p = 0.096, ES = 0.23, and p = 1.41, ES = 0.18). The stronger and weaker limb Achilles tendon stiffness significantly increased from pre-to post-CA during the UNI-CA condition (p = 0.013, ES = 0.60 and p < 0.001, ES = 0.79; respectively) but not for BI-CA (p = 0.66; ES = 0.15 and p = 0.265; ES = 0.42). Furthermore, the post-CA stronger limb Achilles tendon stiffness during the UNI-CA was significantly higher than that noted during the BI-CA (p = 0.006, ES = 0.7). The present study showed that combined isometric and plyometric bilateral CA effectively improved the countermovement jump but did not enhance the t-agility test performance. These findings indicate that exercise combinations could effectively produce a post-activation performance enhancement effect but should replicate the following explosive task as much as possible.

Behavior of skin temperature during incremental cycling and running indoor exercises

The study of the human body's energy behavior has received more attention over the past years. The development of thermal infrared cameras brought new possibilities for evaluating physical exercise performance. This work aims to study the skin temperature distribution during treadmill running and cycle ergometer tests with a graded load exercise until exhaustion. Eight amateur athletes performed both tests. In addition, the ventilatory and metabolic data were measured by indirect calorimetry. The thermoregulatory system is highly requested to maintain the internal body temperature. Consequently, the average skin temperature decreased during running and cycling tests, although with a higher variation in running. It was observed that the lower limbs had a similar performance for both exercises; on the other hand, the upper limbs had a higher temperature decrease for running. This may be explained by increased body energy transfer to the environment due to higher degrees of freedom during the test. The main contribution is comparing the thermal behavior of the person's skin performing two different activities, constructing a basis for future energy and exergy analysis of the human body under physical activities complementary to the literature.

The use of thermal imaging for monitoring the training progress of professional male sweep rowers

This study assesses the thermal profile of the skin in highly trained rowers and investigates the relationship between resting skin temperature (Ts) and the muscle peak torque (PT) measured in statics at the beginning (autumn) and the end (spring) of the preparatory period. Ten professional male sweep rowers, members of the Polish national rowing team, were investigated. A thermal imaging camera was used to analyze the Ts. The PT of the muscles involved in the rowing cycle were measured isometrically. No significant temperature asymmetries were found, except in front of arms after exercise in the spring (p = 0.0228). In contrast, the PT test in the autumn confirmed the significant asymmetry of the knee joint extensors (p = 0.0192). In spring compared to autumn, Ts in many areas of the body were slightly higher, as was PT of underlying muscles. Significant correlations between resting Ts and PT of the underlying muscles were found. Thermal imaging makes it possible to observe changes in skin temperature and symmetry before and after exercise. At this stage, it does not appear to be a method that, without supporting of other methods such as those assessing muscle function, will allow monitoring of training progress.

Thermovision as a Tool for Athletes to Verify the Symmetry of Work of Individual Muscle Segments

In the presented research, we characterised the temperature profiles and the degree of preparation for exercise of individual muscle groups of athletes We hypothesise that by means of thermal imaging studies, the effectiveness of the warm-up can be monitored to determine whether the effort of individual muscles is equal and symmetrical, which can help to avoid a potential injury. In the study, thermographic imaging was performed on a group of athletes exercising on a rowing ergometer involving almost 80% of the muscle parts of the human body for intense and symmetrical exercise. Thermovision studies have confirmed, based on the increased temperature of the muscle areas, that the rowing ergometer involves many muscle groups in training. Moreover, based on the shape of the temperature function obtained from individual body regions of interest, it was shown that conventional exercise on a rowing ergometer causes almost symmetrical work of the right and left sides of the body. Obtained temperature changes in most of the studied muscle areas showed minimum temperature reached the beginning of training—mostly phases 1 and 2. During the subsequent phases, the temperature increase was monitored, stopping at resting temperature. Significantly, temperature variations did not exceed 0.5 °C in all post-training phases. Statistical analyses did not show any significant differences in the symmetry of right and left muscle areas corresponding to the muscle location temperature. Thermal imaging may be an innovative wholly non-invasive and safe method, because checking induces adaptation processes, which may become indicators of an athlete’s efficiency. The imaging can be continuously repeated, and automatic comparison of average temperature or temperature difference may provide some clues that protect athletes from overtraining or serious injuries.

Towards Exercise Radiomics: Deep Neural Network-Based Automatic Analysis of Thermal Images Captured During Exercise

Infrared thermography is increasingly applied in sports science due to promising observations regarding changes in skin's surface radiation temperature ( T_sr) before, during, and after exercise. The common manual thermogram analysis limits an objective and reproducible measurement of T_sr. Previous analysis approaches depend highly on expert knowledge and have not been applied during movement. We aimed to develop a deep neural network (DNN) capable of automatically and objectively segmenting body parts, recognizing blood vessel-associated T_sr distributions, and continuously measuring T_sr during exercise. We conducted 38 cardiopulmonary exercise tests on a treadmill. We developed two DNNs: body part network and vessel network, to perform semantic segmentation of 1 107 855 captured thermal images. Both DNNs were trained with 263 training and 75 validation images. Additionally, we compare the results of a common manual thermogram analysis with these of the DNNs. Performance analysis identified a mean IoU of 0.8 for body part network and 0.6 for vessel network. There is a high agreement between manual and automatic analysis (r = 0.999; p 0.001; T-test: p = 0.116), with a mean difference of 0.01 ^C (0.08). Non-parametric Bland Altman's analysis showed that the 95% agreement ranges between -0.086 ^C and 0.228 ^C. The developed DNNs enable automatic, objective, and continuous measurement of T_sr and recognition of blood vessel-associated T_sr distributions in resting and moving legs. Hence, the DNNs surpass previous algorithms by eliminating manual region of interest selection and form the currently needed foundation to extensively investigate T_sr distributions related to non-invasive diagnostics of (patho-)physiological traits in means of exercise radiomics.

Evaluation of Changes in Polymer Material Properties Due to Aging in Different Environments

With the increase in awareness of the importance of engagement in physical activities, high requirements have been placed on polymers intended for use in sports. A number of authors investigated the influence of aging factors on the performance of the polymer. Still, there is a lack of aging protocols that would be product-centered, especially when high performance is imperative. This paper presents a new approach to polymer aging and examines the change of the identified set of properties due to aging under different conditions, and the duration of each (topography, thickness, moisture management, elongation, and bursting force). The results of the testing revealed the increase in thickness due to exposure, especially to the sun-exposed materials. The ability of materials to elongate until the moment of rupture decreases due to exposure to the sun (strong relationship to the time of exposure; R2 reaches 0.99) and the bursting force (up to 6.8%). Furthermore, results indicate the significantly impaired capacity of the polymer material to absorb moisture. The results of measurements indicated (derived) by spectroscopic studies, based on the ATR-FTIR (attenuated total reflectance) method, showed that there was no detectable influence of aging in the sun or shade on the chemical structure of polyester samples.

Central and Peripheral Thermal Signatures of Brain-Derived Fatigue during Unilateral Resistance Exercise: A Preliminary Study

Simple Summary

Fatigue is considered a brain-derived emotion that could impact performance during the execution of physical exercises. Infrared thermography is a valuable technique able to measure the psychophysiological state associated with emotions in a contactless manner. The aim of the study is to test the capability of infrared thermography to evaluate the central and peripheral physiological effect of fatigue through facial skin and muscle temperature modulations collected during the execution of a unilateral resistance exercise of the lower limb. Both time- and frequency-domain analyses were performed on the temperature time course of the face and limbs. Particularly, significant correlations between features extracted from the thermal signals and the perceived exertion were found. These findings confirmed the ability of thermal imaging to detect both peripheral and central effects of fatigue in response to physical exercises. These results could foster the employment of infrared thermography to monitor the psychophysiological state of the athletes during training. The possibility to calibrate the training load in accordance with the psychophysiological conditions could improve the performance of the athletes during the training process and competitions.

Abstract

Infrared thermography (IRT) allows to evaluate the psychophysiological state associated with emotions from facial temperature modulations. As fatigue is a brain-derived emotion, it is possible to hypothesize that facial temperature could provide information regarding the fatigue related to exercise. The aim of this study was to investigate the capability of IRT to assess the central and peripheral physiological effect of fatigue by measuring facial skin and muscle temperature modulations in response to a unilateral knee extension exercise until exhaustion. Rate of perceived exertion (RPE) was recorded at the end of the exercise. Both time- (∆T_ROI: pre–post exercise temperature variation) and frequency-domain (∆PSD: pre–post exercise power spectral density variation of specific frequency bands) analyses were performed to extract features from regions of interest (ROIs) positioned on the exercised and nonexercised leg, nose tip, and corrugator. The ANOVA-RM revealed a significant difference between ∆T_ROI (F_(1.41,9.81) = 15.14; p = 0.0018), and between ∆PSD of myogenic (F_(1.34,9.39) = 15.20; p = 0.0021) and neurogenic bands (F_(1.75,12.26) = 9.96; p = 0.0034) of different ROIs. Moreover, significant correlations between thermal features and RPE were found. These findings suggest that IRT could assess both peripheral and central responses to physical exercise. Its applicability in monitoring the psychophysiological responses to exercise should be further explored

Environmental Temperature in Thermal Comfort Under Different Virtual Tourism Activity Intensities: Based on Microclimate Simulation Experiment

Although COVID-19 lockdowns and travel regulations have restricted the spatial area for human activities, tourists can still use virtual devices and applications for travel purposes. This study aimed to explore the thermal comfort and satisfaction of tourists under various tourist activity intensities, using experimental and semi-structured interview methods, combined with microclimate simulation experiments and electrocardiogram data to monitor physiological indicators. The results showed that: (1) The thermal comfort of virtual tourists had a significant correlation with the environmental temperature. (2) The thermal comfort of virtual tourists differed under various activity intensities. The virtual tourism activity intensity moderated the relation between environmental temperature and tourists’ thermal comfort. (3) In the state of exercise (slow walking, fast walking), the environmental temperature affected tourists’ physiological indicators. (4) Virtual tourism that integrates realistic visual, audio, and tactile sensations can improve tourists’ perception and satisfaction. The results provide a new perspective for the study of the virtual tourism experience and thermal comfort. In addition, it provides theoretical and practical support for the development of virtual tourism scenes in the environmental temperature context.

Temperature and creatine kinase changes during a 10d taper period in sprinters

Objective.The aim of this prospective cohort study, performed during a 10 d training camp, was to analyze the effect of a series of successive speed-power training sessions on the concurrent circadian changes in resting leg skin temperature and blood creatine kinase (CK) levels and to determine the correlation between them.Approach. Seventeen elite sprinters, aged 22-31 years, were examined. Every morning and evening, capillary blood samples were drawn to assay CK levels. Lower limb skin temperature was measured simultaneously, and thermal images were taken using an infrared camera.Main results. From the first day of the training camp, the base temperature levels began to drop to obtain a significant reduction from the 6th day (male) and from the 8th day (female) to the end of the camp. Simultaneously, CK levels increased in the male group from 8th to the end of the camp, but it did not change significantly in females. Regarding the circadian rhythm, the CK levels always rose during the day and declined during the night. The temperature decreased during the day and increased during the night until the 6th day. After that, the temperature changed oppositely till the end of camp, i.e. it increased during the day and decreased during the night. This could suggest that the training microcycle should last about a week because after this time there may be a disturbance in the temperature circadian rhythm and a significant CK accumulationSignificance. Multi-day speed-power training induced a progressive reduction in resting skin temperature and an elevation in CK levels. It also altered the circadian rhythm of the body skin temperature, which may indicate that after about 6 d of regular exercise, physiological deregulation may occur.

Short-Term Skin Temperature Responses to Endurance Exercise: A Systematic Review of Methods and Future Challenges in the Use of Infrared Thermography

BACKGROUND

Body temperature is often assessed in the core and the skin. Infrared thermography has been used to measure skin temperature (Tsk) in sport research and clinical practice. This study aimed to explore the information reported to date on the use of infrared thermography to detect short-term Tsk responses to endurance exercise and to identify the methodological considerations and knowledge gaps, and propose future directions.

METHOD

A web search (PubMed, Science Direct, Google Scholar, and Web of Science) was conducted following systematic review guidelines, and 45 out of 2921 studies met the inclusion criteria (endurance sports, since 2000, English, full text available).

RESULTS

A total of 45 publications were extracted, in which most of the sample were runners (n = 457, 57.9%). Several differences between IRT imaging protocols and ROI selection could lead to potential heterogeneity of interpretations. These particularities in the methodology of the studies extracted are widely discussed in this systematic review.

CONCLUSIONS

More analyses should be made considering different sports, exercise stimuli and intensities, especially using follow-up designs. Study-derived data could clarify the underlying thermo physiological processes and assess whether Tsk could be used a reliable proxy to describe live thermal regulation in endurance athletes and reduce their risk of exertional heat illness/stroke. Also more in-depth analyses may elucidate the Tsk interactions with other tissues during exercise-related responses, such as inflammation, damage, or pain.

Implementation of Thermal Camera for Non-Contact Physiological Measurement: A Systematic Review

Non-contact physiological measurements based on image sensors have developed rapidly in recent years. Among them, thermal cameras have the advantage of measuring temperature in the environment without light and have potential to develop physiological measurement applications. Various studies have used thermal camera to measure the physiological signals such as respiratory rate, heart rate, and body temperature. In this paper, we provided a general overview of the existing studies by examining the physiological signals of measurement, the used platforms, the thermal camera models and specifications, the use of camera fusion, the image and signal processing step (including the algorithms and tools used), and the performance evaluation. The advantages and challenges of thermal camera-based physiological measurement were also discussed. Several suggestions and prospects such as healthcare applications, machine learning, multi-parameter, and image fusion, have been proposed to improve the physiological measurement of thermal camera in the future.

The use of infrared thermography for the dynamic measurement of skin temperature of moving athletes during competition; methodological issues

Objective. To investigate the use of infrared thermography (IRT) for skin temperature measurement of moving athletes during competition and its sensitivity to factors that are traditionally standardised.Approach. Thermograms were collected for 18 female athletes during the 20 km racewalk at the 2019 World Athletics Championships, with a medium-wave, cooled indium antimonide medium wave infrared band (MWIR) and a long-wave, uncooled microbolometer longwave infrared band (LWIR) infrared camera.Main results. The MWIR provided greater clarity images of motion due to a shorter exposure and response time and produced a higher percentage of acceptable images. Analysing acceptable images only, the LWIR and WMIR produced good levels of agreement, with a bias of -0.1 ± 0.6 °C in mean skin temperature for the LWIR. As the surface area of an ROI was reduced, the measured temperature became less representative of the whole ROI. Compared to measuring the whole area ROI, a single central pixel produced a bias of 0.3 ± 0.3 °C (MWIR) and 0.1 ± 0.4 °C (LWIR) whilst using the maximum and minimum temperature pixels resulted in deviations of 1.3 ± 0.4 °C and -1.1 ± 0.3 °C (MWIR) and 1.2 ± 0.3 °C and -1.3 ± 0.4 °C (LWIR). The sensitivity to air and reflected temperatures was lower for the LWIR camera, due to the higher emissivity of skin in its wavelength.Significance. IRT provides an appropriate tool for the measurement of skin temperature during real-world competition and critically during athlete motion. The cheaper LWIR camera provides a feasible alternative to the MWIR in low rate of motion scenarios, with comparable precision and sensitivity to analysis. However, the LWIR is limited when higher speeds prevent the accurate measurement and ability to capture motion.

Regions of interest selection and thermal imaging data analysis in sports and exercise science: a narrative review

OBJECTIVE

Infrared thermography (IRT) is a non-invasive, contactless and low-cost technology that allows recording of the radiating energy that is released from a body, providing an estimate of its superficial temperature. Thanks to the improvement of infrared thermal detectors, this technique is widely used in the biomedical field to monitor the skin temperature for different purposes (e.g. assessing circulatory diseases, psychophysiological state, affective computing). Particularly, in sports and exercise science, thermography is extensively used to assess sports performance, to investigate superficial vascular changes induced by physical exercise, and to monitor injuries. However, the methods of analysis employed to treat IRT data are not standardized, and hence introduce variability in the results.

APPROACH

This review focuses on the methods of analysis currently used for thermal imaging in sports and exercise science.

MAIN RESULTS

Firstly, the procedures employed for the selection of regions of interest (ROIs) from anatomical body districts are reviewed, paying attention also to the potentialities of morphing algorithms to increase the reproducibility of thermal results. Secondly, the statistical approaches utilized to characterize the temperature frequency and spatial distributions within ROIs are investigated, showing their strengths and weaknesses. Moreover, the importance of employing tracking methods to analyze the temporal thermal oscillations within ROIs is discussed. Thirdly, the capability of employing procedures of investigation based on machine learning frameworks on thermal imaging in sports science is examined.

SIGNIFICANCE

Finally, some proposals to improve the standardization and the reproducibility of IRT data analysis are provided, in order to facilitate the development of a common database of thermal images and to improve the effectiveness of IRT in sports science.

A simplified approach to describe the mean skin temperature variations during prolonged running exercise

Skin blood flow and skin temperature play a fundamental role in the thermoregulatory processes and are expected to largely change in response to a prolonged running exercise. The skin temperature changes have been documented in the literature, mainly through infrared thermographic measurements performed before, after, and, in a limited number of studies, during the exercise. After an initial reduction probably ascribed to skin vasoconstriction, the further skin temperature modifications with time, measured in reference papers during a steady and prolonged run, do not show a common behaviour, probably due to different exercise intensities and environmental conditions reported in these studies. This research aimed to develop a simplified method for describing the skin temperature changes during running exercise through the theoretical solutions of the dynamic energy balance of the human body in the early and late time periods, i.e., close to the onset and the end of exercise. These two asymptotic solutions for the skin temperature, having a largely dissimilar trend, collide at a time instant likely associated with the switch from skin vasoconstriction to vasodilation. Examples of application of the proposed method, based on the intersection of asymptotes, were provided. It was also demonstrated its capability to interpret the experimental skin temperature variations with time for constant-load running exercises reported in the literature under different levels of exercise intensity and environmental conditions.

Lactate Concentration Is Related to Skin Temperature Variation After a Specific Incremental Judo Test

ABSTRACT

Gomes Moreira, D, José Brito, C, de Almeida Ferreira, JJ, Bouzas Marins, JC, López Díaz de Durana, A, Couceiro Canalejo, J, Butragueño Revenga, J, and Sillero-Quintana, M. Lactate concentration is related to skin temperature variation after a specific incremental judo test. J Strength Cond Res 35(8): 2213-2221, 2021-This study aimed to analyze the skin temperature (tsk) response in judokas after a specific incremental test and to determine whether anthropometric and physiological measures can be explained by the variation in mean tsk. A total of 23 male judo athletes (age: 20.1 ± 4.7 years; height: 173.1 ± 8.1 cm; and body mass: 71.7 ± 8.1 kg) performed a specific incremental judo test. Skin temperature evaluations were collected in 26 regions of interest (ROIs), and the mean tsk was calculated using an equation including 10 of them. The time points before the test (pre-test), immediately after (0 minutes), and after 5, 10, and 15 minutes of the test were established to measure the tsk, mean tsk, auricular temperature (tau), and blood lactate (LAC). The athletes completed a mean of 7.0 ± 1.0 stages of the test, 95% confidence interval (CI; 6.2-7.1). The V̇o2peak achieved was 48.7 ± 5.3 ml·kg-1·min-1, 95% CI (46.4-51.0). Compared with pre-test values, only the forehead significantly decreased 5 minutes after the test (p < 0.05). The posterior right arm and posterior left arm remained increased 10 minutes after the test (p < 0.05). After 15 minutes, 19 of the 26 ROIs analyzed were significantly decreased (p < 0.05). Among all tested models of linear regression, only 2 were significant, the difference of tsk 5 minutes compared with pre-test (F1, 21 = 16.49, p = 0.001) and the difference of tsk 10 minutes compared with pre-test, to predict LAC concentration at the end of the test (F1, 21 = 9.30, p = 0.006). We concluded that 5 minutes after the test, the judokas present a higher tau and a higher tsk in 7 ROIs, and the tsk decreases 15 minutes after the test in 19 of the considered ROIs. The variation of mean tsk 5 and 10 minutes after the test compared with pre-test values is associated with blood LAC at the end of the test.

Evaluation of tractor driving vibration fatigue based on multiple physiological parameters

The vibration generated by tractor field operations will seriously affect the comfort and health of the driver. The low frequency vibration generated by the engine and ground excitation is similar to the natural frequency of human organs. Long term operation in this environment will resonate with the organs and affect drivers' health. To investigate this possibility, in this paper we carried out a collection experiment of human physiological indicators relevant to vibration fatigue. Four physiological signals of surface electromyography, skin electricity, skin temperature, and photoplethysmography signal were collected while the subjects experienced vibration. Several features of physiological signals as well as the law of signal features changing with fatigue are studied. The test results show that with the increase of human fatigue, the overall physiological parameters show the following trends: The median frequency of the human body surface electromyography and the slope of skin surface temperature decreases, the value of skin conductivity and the mean value of the photoplethysmography signal increases. Furthermore, this paper proposes a vibration comfort evaluation method based on multiple physiological parameters of the human body. An artificial neural network model is trained with test samples, and the prediction accuracy rate reaches 88.9%. Finally, the vibration conditions are changed by the shock-absorbing suspension of a tractor, verifying the effectiveness of the physiological signal changing with the vibration of the human body. The established prediction model can also be used to objectively reflect the discomfort of the human body under different working conditions and provide a basis for structural design optimization.

Non-obstructive monitoring of muscle fatigue for low intensity dynamic exercise with infrared thermography technique

Surface electromyography (sEMG) has been widely used in evaluating muscle fatigue among athletes where electrodes are attached on the skin during the activity. Recently, infrared thermography technique (IRT) has gain popularity and shown to be another preferred method in monitoring and predicting muscle fatigue non-obstructively. This paper investigates the correlation between surface temperature and muscle activation parameters obtained using both IRT and sEMG methods simultaneously. Twenty healthy subjects were required to perform a repetitive calf raise exercise with various loads attached around their ankle for 3 min to induce fatigue on the targeted gastrocnemius muscles. Average temperature and temperature difference information were extracted from thermal images, while root mean square (RMS) and median frequency (MF) were extracted from sEMG signals. Spearman statistical analysis performed shows that there is a significant correlation between average temperature with RMS and between temperature difference with MF values at p<0.05. While ANOVA test conducted shows that there is significant impact of loads on RMS and MF where F=12.61 and 3.59, respectively, at p< 0.05. This study suggested that skin surface temperature can be utilized in monitoring and predicting muscle fatigue in low intensity dynamic exercise and can be extended to other dynamic exercises.

Thermal Imaging of Exercise-Associated Skin Temperature Changes in Swimmers Subjected to 2-min Intensive Exercise on a VASA Swim Bench Ergometer

An important element of swimming training is the improvement of muscle strength and the technique of swimming movements on dry land. The heat generated by the muscles involved in the effort contributes to a change in the temperature of the skin surface, which can be assessed by the IRT method. The aim of the study was to assess the symmetry and dynamics of changes in surface temperatures of selected areas of the body in swimmers after exercise on a swimming ergometer with the use of IRT. A total of 12 swimmers (aged 19 ± 1.3 years) completed a two-minute stress test (front crawl swimming movements) using a VASA Swim Ergometer, with a load of 5. Using an IRT camera (FLIR E60), postexercise changes in back and upper limbs surface temperature in relation to the resting values were observed. After exercise, the temperature value of all assessed areas decreased, apparently in the area of the back and the back of the arms, returning to the baseline values after 12 min of observation. There was no asymmetry in mean temperature values between the right and left upper limbs. IRT is a noninvasive and sensitive tool for the individual analysis of changes in body surface temperature in swimmers after training on dry land.

Investigation of thermal changes in the thyroid gland region of individuals with hypothyroidism and fibromyalgia by analyzing the temperature of brown adipose tissue

This exploratory retrospective study aims to investigate the thermal changes in the thyroid gland region of patients with hypothyroidism and fibromyalgia by analyzing the temperature of the brown adipose tissue (BAT). A total of 166 individuals from 1000 thermographic electronic medical records were classified into four groups: Group HP + FM-50 individuals with hypothyroidism and fibromyalgia; Group FM-56 individuals with fibromyalgia only; Group HP-30 individuals with hypothyroidism only, and Group Control-30 healthy individuals. The thermal images from the electronic medical records were acquired by a FLIR T650SC infrared camera (used for thermometry) and the temperature data for each group were statistically analyzed. Group HP + FM showed r = 0, meaning that the average temperatures of the thyroid and BAT are independent of each other. Groups FM, HP and Control showed r = 1, meaning that the average temperatures of the thyroid and BAT were directly related. Our findings showed that the average temperatures of the thyroid and BAT regions are similar. Also, there was no correlation between thyroid gland temperature and the presence of hypothyroidism or fibromyalgia using thermometry.

Comparison of the Immediate Effect of Petrissage Massage and Manual Lymph Drainage Following Exercise on Biomechanical and Viscoelastic Properties of the Rectus Femoris Muscle in Women

CONTEXT

Fast and adequate recovery after exercise and activity is important for increasing performance and preventing injuries. Inadequate recovery usually causes changes in the biomechanical and viscoelastic properties of the muscle.

OBJECTIVE

To compare the immediate effect of petrissage massage (PM) and manual lymph drainage (MLD) following submaximal exercise on the biomechanical and viscoelastic properties of the rectus femoris muscle in healthy women.

DESIGN

Cross-sectional, repeated-measures.

SETTING

Marmara University.

PARTICIPANTS

18 healthy female students.

INTERVENTION(S)

Following the submaximal quadriceps strengthening exercise performed in 3 sets of 8 repetitions with intensity of 75% of 1 maximum repetition, participants' right leg received a 5-minute PM (PM group) and the contralateral leg received a 5-minute MLD application (MLD group).

MAIN OUTCOME MEASURES

Skin temperature was measured using P45 thermographic thermal camera (Flir System; ThermaCAM, Danderyd, Sweden), and muscle tone, biomechanical, and viscoelastic features were measured with a myometer (Myoton AS, Tallinn, Estonia) at baseline, immediately postexercise, post-PM/MLD application, and 10 minutes postexercise.

RESULTS

In the PM group, the tonus (P = .002) and stiffness (P < .001) values measured after the massage and at the end of the 10-minute resting period were found to be statistically different than those measured right after the exercise (P < .05). Relaxation time and creep values at all measurement times were significantly different (P < .05). In the MLD group, it was observed the tonus (P < .001), stiffness (P = .025), and relaxation time (P < .01) values decreased significantly after the MLD compared with the values measured after the exercise; however, the creep value was found to be significantly different in all measurements (P < .05).

CONCLUSION

PM and MLD reduce passive tissue stiffness and improve the extent of muscle extensibility over time against the muscle tensile strength. PM and MLD are therapeutic methods that can be used to support tissue recovery after exercise and prevent injuries.

ACUTE EFFECT OF SPEED TEST ON THE SKIN TEMPERATURE OF ELITE SOCCER PLAYERS

ABSTRACT Introduction Infrared thermography has been used in several areas, mainly in sports training, and specifically in soccer. Objectives The objectives of the study were to verify the acute effect of a displacement speed test on the skin temperature of elite female soccer players, to observe pre- and post-test thermal asymmetries, and to compare responses in the anterior and posterior regions of lower limbs. Methods Cross-sectional study that evaluated 17 soccer players of the 2018 Brazilian Championship. They were submitted to thermography before and 10 minutes after performing the displacement speed test. Thermographic images were collected using a FLIR® model 8 thermal imager and changes in skin temperature in the anterior and posterior regions of the lower limbs were analyzed, according to the areas of interest. Descriptive statistics were performed and mean and standard deviation of the temperatures of the areas of interest were analyzed. The normality of the data was verified, and then the Student’s t test for normal paired and independent samples and the Mann-Whitney test for non-normal samples were conducted, with p <0.05 being adopted for significance level. Results It was possible to observe that after the test there was an increase in skin temperature in all the regions analyzed, both on the dominant and non-dominant sides (p <0.05). Regarding the analysis of the anterior region, it was possible to observe a higher temperature (p <0.05) in the region of the tibial muscles than in the region of the quadriceps muscles. Conclusion It is concluded that thermography helps to understand the thermal responses of lower limbs after applying the displacement speed test. The study shows that thermographic evaluation can guide the organization of the training session when motor tests have previously been applied, and in the detection of abnormal overloads, helping to prevent injuries. Level of evidence IV; Therapeutic studies - Investigation of treatment results.

Non-Contact Assessment of Peripheral Artery Haemodynamics Using Infrared Video Thermography

Skin temperature has long been used as a natural indicator of vascular diseases in the extremities. Considerable correlation between oscillations in skin surface temperature and oscillations of skin blood flow has previously been demonstrated. We hypothesised that the impairment of blood flow in stenotic (subcutaneous) peripheral arteries would influence cutaneous temperature such that, by measuring gradients in the temperature distribution over skin surfaces, one may be able to diagnose or quantify the progression of vascular conditions in whose pathogenesis a reduction in subcutaneous blood perfusion plays a critical role (e.g. peripheral artery disease). As proof of principle, this study investigates the local changes in the skin temperature of healthy humans (15 male, [Formula: see text] years old, BMI [Formula: see text] kg/m ²) undergoing two physical challenges designed to vary their haemodynamic status. Skin temperature was measured in four central regions (forehead, neck, chest, and left shoulder) and four peripheral regions (left upper arm, forearm, wrist, and hand) using an infrared thermal camera. We compare inter-region patterns. Median temperature over the peripheral regions decreased from baseline after both challenges (maximum decrease: [Formula: see text] °C at 60 s after exercise; [Formula: see text] and [Formula: see text] °C at 180 s of cold-water immersion; [Formula: see text]). Median temperature over the central regions showed no significant changes. Our results show that the non-contact measurement of perfusion-related changes in peripheral temperature from infrared video data is feasible. Further research will be directed towards the thermographic study of patients with symptomatic peripheral vascular disease.

Influence of artificial turf temperature on physical performance and muscle contractile properties in football players after a repeated-sprint ability test

This study aimed to analyse the effect of playing surface temperature on muscular and thermal response to a repeated-sprint ability (RSA) test in football players. Thirty-two male football players (23 ± 5 years; 1.77 ± 0.06 m; 71.2 ± 6.7 kg) from two squads of a third-division football club participated in the study. An RSA test was carried out at a high surface temperature (45.34 ± 2.53 °C) and low surface temperature (27.21 ± 2.17 °C). Before and after this test, the muscular response of the players was assessed through tensiomyography and thermograms. The results revealed that performance in the RSA test particularly increased at a higher surface temperature, especially in the first 5 m of the 30 m sprint test. While a reduction in maximal radial displacement (Dm) in the biceps femoris post-RSA was observed at lower surface temperatures, a higher temperature on the thigh, hamstring and calf was found in the higher surface temperature group. In conclusion, higher surface temperatures had an influence on players’ thermal and tensiomyographic profile and improved performance in their repeated-sprint ability. These results suggest a need for coaches and players to be aware of these parameters to ensure adequate functionality and safety of the playing surface.

Occupational Risk Evaluation Through Infrared Thermography: Development and Proposal of a Rapid Screening Tool for Risk Assessment Arising from Repetitive Actions of the Upper Limbs

Risk analysis is one of the main tools for preventing the occurrence of Work-Related Musculoskeletal Disorders. New methods of risk analysis should seek to be more agile and simplified, encouraging them to be widely applied in work environments. This paper aimed to develop a rapid tool for assessing the risk of developing Work-Related Musculoskeletal Disorders (WMSDs) arising from repetitive actions of the upper limbs, while using a thermographic camera to measure skin temperature variation. A workstation was developed in an environmentally controlled laboratory, representing the five levels of risk presented by the Occupational Repetitive Actions Index (OCRA) Index, which were performed by 32 participants for 20 min. each level. There was a significant change in forearm skin temperature at all risk levels (p < 0.001), with a positive linear correlation (r = 0.658 and p < 0.001), which led the authors to perform linear regression analysis for the forearm region. The Predicted OCRA Index calculation equation was successfully developed (R = 0.767 and R² = 0.588), while using as independent variables: air temperature and temperature variation of the forearm skin. The Predicted OCRA Index can be applied as a screening tool for large numbers of workers in the same company or sector, due to its speed of application and the determination of risk level, but it does not replace the original OCRA Index.

Exercise on a vibratory platform increases blood perfusion on the stifle joint and rectal temperature in healthy dogs

ABSTRACT The effects of two vibration platform (VP) exercise protocols on stifle and rectal temperatures were evaluated. Eleven animals participated in two exercise protocols, different in duration in each exercise. Exercise protocol 1 (EP1) took 30 seconds and EP2, 60 seconds, with different vibratory levels in both cases (L1 = acceleration ≅ 1g, L4 = acceleration ≅ 2.5g, and L7 = acceleration ≅ 5g). The animals were evaluated before and 1 minute after the exercise, using infrared thermography to obtain stifle temperatures. The rectal temperature (RT) was also checked at each moment. The dogs had higher stifle temperatures in EP1 at all vibratory levels compared to the time before the exercise; EP2 resulted in higher temperature only at maximum vibration intensity (L7). Increase in TR was observed only in EP2. The results suggested that the short duration protocol (EP1) increased the muscular and peripheral vascular activities of the joint, regardless of the vibration intensity. The long duration protocol (EP2) with maximum vibration intensity increased the RT, demonstrating activity beyond the stifle muscle group. It is concluded that exercises on the VP can be used as complementary therapy for low-impact muscle activity in dogs and may be adequate for efficient energy consumption.

Infrared thermography of the crânio-cervico-mandibular complex in wind and string instrumentalists

PURPOSE

Musculoskeletal disorders can be common in wind and string instrumentalists. The musical gesture technique associated to musical performance can promote an asymmetrical isometric contraction with the hyperactivity of specific muscular groups and the overload of articular surfaces which can cause discomfort or pain. The aim of this investigation was to assess specific anatomical regions of interest within the cranio-cervico-mandibular complex in order to determine and evaluate the presence of muscular hyperactivity associated to musical performance.

METHODS

An infrared imaging camera, FLIR®, was used to record the regions of interest in wind (n = 48) and string instrumentalists (n = 29). Bilateral temperature differences were considered as thermal asymmetries with a conventional threshold of 0.3 ºC to distinguish pathological from healthy states. The regions of interest (ROI) were the anterior triangle of the neck, the sternocleidomastoid and trapezius muscles regarding the postural and stabilizing muscles of the head and neck. On the orofacial region, the anatomical sites were the anterior temporal muscle, the masseter muscle and the temporomandibular joint. A Pearson chi-square test was performed to compare the assessed areas.

RESULTS

Between 30-37% of all participants showed ROI in an asymmetric pattern. The most affected sites were the temporal muscle and the TMJ for both groups. The anterior triangle of the neck showed statistical differences (p = 0.044) between string and wind instrumentalists, while the temporal (p = 0.034) and trapezius muscle (p = 0.028) when comparing large and small mouthpieces of brass instruments. Although female participants showed a higher prevalence of asymmetrical patterns regarding the ROI, no statistical differences were found between genders.

CONCLUSIONS

Infrared thermography exhibited significant differences between wind and string instruments within the CCMC. Regarding the issue of occupational health in performing arts, it is an advantage being able to quantify asymmetrical patterns sites of the CCMC to understand the underlying physiological responses to repetitive movements, overloading and muscular hyperactivity that occur during musical performance.

THE USE OF THERMOGRAPHY AND ITS CONTROL VARIABLES: A SYSTEMATIC REVIEW

ABSTRACT Introduction: Muscle injuries are the most frequent cause of physical disability in sports, representing a large percentage of all sports injuries. In high-performance sports in particular, there is great interest in optimizing the process of diagnosis and rehabilitation of muscle injuries in order to reduce the amount of time taken off by athletes due to their injuries. Infrared thermography, or cutaneous thermometry, is a technique used for complementary investigation of pain. It provides thermal imaging with an infrared camera, to measure the surface temperature of the body. Objective: To conduct a systematic review of the use of thermography as a functional evaluation for the identification and prevention of muscle injuries, and of the control variables used in its applicability. Methods: A systematic review was conducted in the MEDLINE, ResearchGate and Scielo databases, using the search terms: “thermography”, “muscle injury”, “rehabilitation” and “diagnosis”, searching on articles published from 2000 to 2017, in Portuguese, English and Spanish. The eligibility criteria for the studies was the use of thermography as an outcome, and the reporting of standards for evaluating skin temperature variation in athletes. Results: Following the systematic review, 94 studies were retrieved. Of these, only 12 met the criteria for inclusion in the study. Conclusion: Thermography is a suitable tool for the evaluation and prevention of muscle injuries in athletes, and care should be taken with the control variables during its use. The most efficient variables for capturing the thermographic image appear to be an environment with a temperature of between 18 and 25°C, for 15 minutes for acclimatization, and with the individual placed in a pre-determined position, depending on the body segment being evaluated, without contact with another object. Level of evidence I; Systematic review.