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

Abstract

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.

Is Continuous Monitoring of Skin Surface Temperature a Reliable Proxy to Assess the Thermoregulatory Response in Endurance Horses During Field Exercise?

“…In summary, IRT techniques differ widely in human and equine medicine, including positioning of the camera and environmental control measures ( 22 , 24 , 75 ). A consensus guideline has been developed only recently, addressing the multiple data collection methods of the human T sk using IRT ( 84 ), while Soroko and Howell ( 22 ) described a protocol using IRT in equine medicine.…”

“…One exception is the study by Soroko et al ( 37 ), who reported dynamic IRT monitoring every 15 s during treadmill exercise. To be precise, a review of the use of IRT in human endurance athletes reported that 25 of the 45 studies were conducted over the last 5 years (2017–2021), but, up until now, only five real-life field endurance studies have been performed ( 24 ). The latter review concluded that further analysis is required to assess whether T sk could be used as a reliable proxy to describe real-time thermoregulation ( 24 ).…”

“…Another elegant approach to monitoring the thermoregulatory response in exercising horses in the field could be continuous monitoring of surface skin temperature (T sk ) as a reliable proxy for monitoring thermoregulatory wellbeing. Advantages of using tools, such as infrared thermography (IRT), to assess T sk include the non-invasive nature and easy collection of temperature data ( 22 – 24 ). Notably, most exercise studies use such monitoring methods to assess T sk only pre- or post-exercise, not during exercise.…”

“…To illustrate, a recent systematic review of T sk studies performed in human endurance athletes has reported that only a few studies involved the continuous monitoring of T sk ; only two out of the 45 exercise studies monitored T sk every 30 s, one study every 180 s, and four studies every 5 min ( 24 ). Also, these human studies highlight the existence of essential inter-individual differences with respect to the T sk response time profile ( 24 ). Important inter-individual T sk differences have been reported in all mammals ( 23 , 25 ).…”

“…To identify a reliable proxy for thermoregulatory response in the field, a solid correlation must exist between that specific proxy and T c evolvement, despite the existence of a time lag ( 24 , 47 ). However, currently, very few equine studies have involved the simultaneous continuous monitoring of T c (either using carotid artery temperature, or a GI pill, or the T re ), together with an additional temperature monitoring device during field exercise ( 19 , 20 , 51 ).…”