Methodological Aspects of Infrared Thermography in Human Assessment

Impact of relative lower-limb length on heat loss and body temperature during running

OBJECTIVES

Long lower limbs relative to body size are thought to be an adaptation to prevent excessive increases in body temperature during running in hot climate. The advantage of long lower limbs relative to body size is usually explained by an increase in body surface area relative to mass; however, the influence of limb length on relative body surface area was shown to be minor. We aimed to experimentally test the effect of relative lower-limb length (LLL) on body temperature changes during running. Furthermore, we tested the effect of relative LLL on relative body surface area.

MATERIALS AND METHODS

Adult men (n = 37) ran for 40 min on a treadmill, while their core temperature (ingestible thermometer), skin temperature (infrared thermography), and oxygen consumption (indirect calorimetry) were measured. Relative LLL was calculated as residuals from linear regression of LLL on stature. Linear regression was used to test the effect of relative LLL on standardized heat loss (heat loss/heat production), mean body temperature (weighted mean of skin and core temperatures), and body surface area.

RESULTS

Relative LLL had a positive effect on standardized heat loss and a negative effect on mean body temperature change during running. Relative LLL had a positive effect on the proportion of body surface area allocated to the lower limbs but not on the relative body surface area.

DISCUSSION

The reduced increase in mean body temperature associated with long lower limbs suggests an advantage of relatively long lower limbs for greater endurance and speed during persistence hunting or contemporary running events.

Automatic Segmentation of Facial Regions of Interest and Stress Detection Using Machine Learning

Stress is a factor that affects many people today and is responsible for many of the causes of poor quality of life. For this reason, it is necessary to be able to determine whether a person is stressed or not. Therefore, it is necessary to develop tools that are non-invasive, innocuous, and easy to use. This paper describes a methodology for classifying stress in humans by automatically detecting facial regions of interest in thermal images using machine learning during a short Trier Social Stress Test. Five regions of interest, namely the nose, right cheek, left cheek, forehead, and chin, are automatically detected. The temperature of each of these regions is then extracted and used as input to a classifier, specifically a Support Vector Machine, which outputs three states: baseline, stressed, and relaxed. The proposal was developed and tested on thermal images of 25 participants who were subjected to a stress-inducing protocol followed by relaxation techniques. After testing the developed methodology, an accuracy of 95.4% and an error rate of 4.5% were obtained. The methodology proposed in this study allows the automatic classification of a person's stress state based on a thermal image of the face. This represents an innovative tool applicable to specialists. Furthermore, due to its robustness, it is also suitable for online applications.

Theory and applications of InfraRed and thermal image analysis in ergonomics research

Designing products and services to fit human needs, wants and lifestyle require meaningful data. With Industry 4.0 and the internet of things, we have many ways to capture data using sensors and other means. InfraRed (IR) cameras are quite ubiquitous, especially for screening illness and wellness. They can provide a wealth of data on different objects and even people. However, their use has been limited due to processing complexities. With reducing cost and increasing accuracy of IR cameras, access to thermal data is becoming quite widespread, especially in medicine and people-related applications. These cameras have software to help process the data, with a focus on qualitative analyses and rather primitive quantitative analyses. In ergonomics, data from multiple users are essential to make reasonable predictions for a given population. In this study, using 4 simple experiments, several quantitative analysis techniques such as simple statistics, multivariate statistics, geometric modeling, and Fourier series modeling are applied to IR images and videos to extract essential user and population data. Results show that IR data can be useful to provide user and population data that are important for design. More research in modeling IR data and application software is needed for the increased application of IR information in ergonomics applications.

Pre-exercise skin temperature evolution is not related with 100 m front crawl performance

During the transition between warm-up and competition there is a change in core, muscle and (eventually) skin temperature that may affect swimming performance. We have aimed to assess skin temperature evolution during transition phases of different durations before a typical front crawl effort and to investigate its relationship with performance. Following a standardized warm-up, nine adolescent male swimmers performed three maximal randomized 100 m maximum front crawl trials after 10, 20 and 45 min transition phases. Skin temperature, performance (time, stroke frequency, length and index, and propelling efficiency), heart rate, lactate and perceived effort were assessed. Data showed a skin temperature log increase over time (R² > 0.96, p < 0.01) without differences from the 15 min with the following instants. Performance and psychophysiological variables were similar between transition phases. However, skin temperature at the end of the transition periods, i.e., just before the 100 m trials, was lower in the 10 min than the 20 and 45 min transitions (32.0 ± 0.6 vs 33.0 ± 0.4 and 33.5 ± 0.5 °C, respectively). The main finding was that no relevant relationships were observed between pre-test skin temperature and performance times (|r| < 0.6, p > 0.05) for the studied transition phases. We have concluded that transitions longer than 10 min will not present thermal changes and that, within the physiologic limits studied, pre-exercise skin temperature does not influence swimming performance.

Effect of a Marathon on Skin Temperature Response After a Cold-Stress Test and Its Relationship With Perceptive, Performance, and Oxidative-Stress Biomarkers

CONTEXT

Although skin-temperature assessment has received much attention in recent years as a possible internal-load measurement, scientific evidence is scarce.

PURPOSE

To analyze baseline skin temperature and its rewarming through means of a cold-stress test before and after performing a marathon and to study the association between skin temperature and internal/external-load measurements.

METHODS

A total of 16 runners were measured 48 and 24 h before and 24 and 48 h after completing a marathon. The measurements on each day of testing included urine biomarkers of oxidative stress, pain and fatigue perception, skin temperature (at baseline and after a cold-stress test), and jump performance.

RESULTS

Reduced jump performance (P < .01 and effect size [ES] = 0.5) and higher fatigue and pain perception were observed 24 h after the marathon (P < .01 and ES > 0.8). Although no differences in baseline skin temperature were observed between the 4 measuring days, posterior legs presented lower constant (P < .01 and ES = 1.4) and higher slope (P = .04 and ES = 1.1) parameters in the algorithmic equations fitted for skin-temperature recovery after the cold-stress test 24 h after the marathon than on the day before the marathon. Regressions showed that skin-temperature parameters could be predicted by the ratio of ortho-tyrosine isomer to phenylalanine (oxidative stress biomarker) and body fat composition, among others.

CONCLUSIONS

Although baseline skin temperature was not altered 24 or 48 h after a marathon, the application of cold stress after the marathon would appear to be a good method for providing information on vasoconstriction and a runner's state of stress.

Effect of Exercise on Athletes Performing in Fencing Uniforms: Methodology and Preliminary Results of the Use of Infrared Thermography to Detect the Thermal Behaviour of Fencers

In recent times, infrared thermography has been often applied to sport science, in order to evaluate athletes’ performance in relation to their thermal behaviour. As there is a lack of studies for the sport of fencing, this paper aims to provide preliminary results showing the thermal behaviour of fencers of different competitive level and to provide a methodology for its assessment. In particular, thermal images were acquired before, during and after the training, as well as the metabolic rate and the rate of perceived exertion, for eight fencers with different competitive levels (international/national/veteran). Results showed that in moderate environments there was any correlation between the environmental parameters and temperature trend on athletes’ bodies, while competitive level and thermal behaviour were connected. The presence of thermal asymmetries was also detected. In general, from these preliminary results, professional athletes presented the same temperature trend. Therefore, further studies should be carried out in order to investigate these findings on a larger sample of elite athletes, as their thermal response may be important for improving their performance.

Immediate Effect of Whole-Body Vibration on Skin Temperature and Lower-Limb Blood Flow in Older Adults with Type 2 Diabetes: Pilot Study

The purpose of this study was to evaluate the response of a single whole-body vibration (WBV) training session to peripheral skin temperature and peripheral blood flow of older adults with type 2 diabetes. A double-blind, controlled clinical trial was conducted following the Consolidated Standards of Reporting Trials (CONSORT) guidelines. A single session of WBV (24 Hz; amplitude 4 mm; vibration time 45 s, with a series of eight repetitions with recovery between repetitions of 30 s; total time of 10 min) or sham vibration on the Kikos P204 Vibrating Platform was employed. To assess skin temperature, the FLIR E40bxs thermographic camera and the ultrasonic vascular Doppler for flow velocity were used. Evaluation occurred before and after a WBV or sham intervention. The sample consisted of three men and 17 women. In the WBV group, there was a decrease in the temperature from 29.7 °C (±1.83) to 26.6 °C (±2.27), with p = 0.01. Temperature following sham decreased from 28.6 °C (±1.84) to 26.3 °C (±2.49), with p = 0.01. Regarding blood flow, there was a decrease in the analyzed arteries, especially the left posterior tibial artery, where there was a statistically significant flow reduction from 27.1 m/s (±25.36) to 20.5 m/s (±19.66), post WBV (p = 0.01). In the sham group, an increased flow velocity was observed for all the arteries analyzed, except for the left dorsal artery. Immediately following a full-body vibration session, peripheral skin temperature and lower-limb blood flow tend to decrease in diabetic patients. However, from the design of study developed, we cannot infer the maintenance of this effect in the medium and long term.