Changes in the Infrared Thermographic Response of the Triceps Suralis Muscle During Ankle Flexion-Extension Until Exhaustion in Healthy Adults

Abstract

Background: Infrared thermography and acute muscle fatigue are often correlated in sports medicine for assessing muscle health during and after exercise, but there are no known studies describing the response throughout exercise; therefore, this study aims to observe the variation in skin temperature (Tsk) during the execution of a maximal muscle fatigue protocol using concentric exercises in the triceps suralis.

Methods: An open cross-sectional descriptive observational study of the posterior region of the leg (triceps suralis) was performed using 98 healthy subjects. Volunteers were subjected to a maximal fatigue protocol, with thermographic images analyzed at 25%, 50%, 75%, and 100% cumulative maximal fatigue.

Results: Results showed a significant difference in time (p = 0.039; η2p = 0.026) and side (p =≤ 0.001; η2p = 0.120). Tukey's post hoc analysis detected a significant difference in Tsk B between the R and L side (R, 30.3 ± 1.39 °C; L, 30.2 ± 1.39 °C), in Tsk at 25% (R, 30.2 ± 1. 27 °C; L; 30.1 ± 1.27 °C), in Tsk at 50% (R, 30.2 ± 1.29 °C; L, 30.1 ± 1.29 °C), and in Tsk at 75% (R, 30.3 ± 1.33 °C; L, 30.2 ± 1.33 °C).

Conclusions: The results observed in this study show that infrared thermography is a valid tool for the measurement, analysis, and quantification of the tissue metabolic response of the muscular system, pre, during, and after exercise. Therefore, we believe that, for future studies, it would be interesting to find relationships between Tsk variations and other performance and metabolic variables. The focus on a single muscle and not directly measuring muscle activity are two limitations of this study.