Infrared Thermography Correlates with Lactate Concentration in Blood during Race Training in Horses

SIMPLE SUMMARY: Thoroughbreds commence race training at a very young age, carrying a high risk for the occurrence of musculoskeletal lesions. Despite clinical examination and trainers’ opinions, the most acceptable way for the accurate and objective evaluation of adaptation to increased exertion is via blood testing. However, this requires blood sampling at three different time points, which may be expensive and stressful for the horse. Additionally, legal regulations often forbid any invasive procedures during equestrian sporting events. As muscle activity increases, there is a progressive increase in body surface temperature. These changes in body surface temperature can be measured by infrared thermography (IRT), which was recently widely incorporated into equine veterinary medicine. However, there is a lack of studies about monitoring race horse training. Thus, the aim of this study was to find a relationship between lactate blood concentration and body surface temperatures, as measured by IRT. This study is the first to present that IRT may supplement blood measurements. In the future, IRT may become an alternative procedure to evaluate horse fitness during race training. ABSTRACT: In horse racing the most acceptable way to objectively evaluate adaptation to increased exertion is to measure lactate blood concentration. However, this may be stressful for the horse, therefore, a simple, noninvasive procedure to monitor race progress is desirable. Forty Thoroughbreds attended race training, with blood samples collected at rest, immediately after, and 30 min after exercise. The lactate concentration was determined 60 s after blood collection using an Accusport(®). Thermal imaging of the neck and trunk areas was performed following international veterinary standards from a distance of approximately 2 m from the horse using the same protocol as the blood sampling. The Spearman rank correlation coefficients (ρ) between the changes in the blood lactate concentration and surface temperature measures were found for the regions of interest. The highest positive correlation coefficients were found in the musculus trapezius pars thoracica region for the maximal temperature (T Max; ρ = 0.83; p < 0.0001), the minimal temperature (T Min; ρ = 0.83; p < 0.0001), and the average temperature (T Aver; ρ = 0.85; p < 0.0001) 30 min after the exercise. The results showed that infrared thermography may supplement blood measurements to evaluate adaptation to increased workload during race training, however, more research and references values are needed.