What is the skin temperature response when running 10 kilometers?
This is the research question that Priego-Quesada et al. solved in their recently published study. They try to analyze the response of the temperature of the skin after running 10 kilometers (km) in a control group that did not perform any previous activity.
The research group of the University of Valencia (Research Group in Sports Biomechanics (GIBD)), led by Priego-Quesada, is a prolific group around research in thermography applied to sports sciences. With more than 20 articles published on this subject, they use thermal imaging cameras and ThermoHuman software to carry out some of their research, for example this 10 km study.
In this case, the behavior of skin temperature after running 10 km was analyzed. They divided 28 recreational runners with experience into two groups (an experimental group and a control group). The time at the end of the 10 km was 49 ± 8 minutes for the experimental group.
The methodology to analyze the effect of the 10 km.
The researchers performed the baseline measurement of lower limb temperature using a FLIR E60 thermal imaging camera with a resolution of 320×240, after a period of acclimatization. In addition, they measured the set of Reactive Oxygen Species (ROS) and Heart Rate Variability (HRV) before the test. Finally, they performed a 3-minute thermal stress test to assess how much the temperature reduced and how much it was recovered.
The participants of the control group waited at rest until the experimental group finished the 10 km.
The same measurements were made in both groups. One measurement at the end of the test, another at 2 hours after finishing the test, one more at 5 hours after finishing the test, another at 9 hours after, and a last one at 24 hours after (Table 1).
The results after running 10 km.
Regarding the skin temperature data, the control group obtained a significant increase concerning their baseline values, at 5 and 9 hours in the main muscle regions. The measurements were made between 7 and 9 in the morning, so these changes could be derived from the circadian rhythm itself.
In the experimental group, there were significant changes from moderate to large effect size in all measurements after 5 hours and up to 24 hours after. In addition, these changes are larger when compared to the experimental group, so there is a significant difference between aerobic exercise in body temperature (Table 2).
Table 2. Results of body temperature variation over measurements. differences with the Pre moment (control group: #p < 0.05, ##p < 0.01 and ###p < 0.001; experimental group: *p < 0.05, **p < 0.01 and ***p < 0.001), and differences between groups (ͳ p < 0.05, ͳ ͳ p < 0.01 and ͳ ͳ ͳ p <0.001). Letters are used to show the Cohen effect size (S – small effect size, M – moderate effect size, L – large effect size).
On the other hand, evaluations with HRV show a significant difference up to 2 hours after the test but do not affect 24 hours after the test.
Regarding the relationships between the variables, body temperature shows a moderate positive relationship (0.49; p=0.01) with the perception of fatigue in general and in the legs at 24 hours and a negative relationship with HRV values (-0.45; p=0.02) at 24 hours, especially with the RMSSD variable (root mean square of successive difference).
The authors mention circadian rhythm as an important influencing factor to be considered in changes in body temperature (Costa et al., 2016; Marins et al., 2015). Previous studies have observed that there is a variation of approximately 1ºC positive between morning and afternoon time in the legs (Marins et al., 2015).
The aerobic run of 10 km increases the temperature of the skin of the exercised regions, reaching the peak between 5 and 9 hours after the effort, remaining significantly increased up to 24 hours later in the exercised musculature.
These values can serve as a reference for further studies on body temperature control.
ThermoHuman additional note on the effect of the 10 km.
For the ThermoHuman staff, this study reinforces the importance of analyzing 24 hours after exercise to control the internal training load through infrared thermography.
In addition, it provides results in line with previous research by Fernandez-Cuevas et al. (2012) on the hyperthermic response in regions exercised after moderate to low-intensity aerobic exercise.
Priego-Quesada, J. I., Catalá-Vilaplana, I., Bermejo-Ruiz, J. L., Gandia-Soriano, A., Pellicer-Chenoll, M. T., Encarnación-Martínez, A., … & Salvador-Palmer, R. (2022). Effect of 10 km run on lower limb skin temperature and thermal response after a cold-stress test over the following 24 h. Journal of Thermal Biology, 105, 103225.
Costa, C. M. A., Sillero-Quintana, M., Cano, S. P., Moreira, D. G., Brito, C. J., Fernandes, A. A., … & Marins, J. C. B. (2016). Daily oscillations of skin temperature in military personnel using thermography. BMJ Military Health, 162(5), 335-342.
Marins, J. C. B., Formenti, D., Costa, C. M. A., de Andrade Fernandes, A., & Sillero-Quintana, M. (2015). Circadian and gender differences in skin temperature in militaries by thermography. Infrared Physics & Technology, 71, 322-328.
Fernández-Cuevas, I. (2012). Efecto del entrenamiento de resistencia, velocidad y fuerza en la temperatura de la piel a través de la termografía infrarroja (Doctoral dissertation, Dissertation, Universidad Politécnica de Madrid).