Exercise-induced changes in lower limbs skin temperature against plasma ATP among individuals with various type and level of physical activity

The objective of the study was to examine the lower limbs skin temperature (T_SK) changes in response to exhaustive whole-body exercise in trained individuals in reference to changes in plasma adenosine triphosphate (ATP). Eighteen trained participants from distinct sport type ‒ endurance (25.2 ± 4.9 yr) and speed-power (25.8 ± 3.1 yr), and 9 controls (24,9 ± 4,3 yr) ‒ were examined. Lower limbs T_SK and plasma ATP measures were applied in parallel in response to incremental treadmill test and during 30-min recovery period. Plasma ATP kinetics were inversely associated to changes in T_SK. The first significant decrease in T_SK (76–89% of $\dot{V}$ O_2MAX) occurred shortly before a significant plasma ATP increase (86–97% of $\dot{V}$ O_2MAX). During recovery, T_SK increased, reaching pre-exercise values (before exercise vs. after 30-min recovery: 31.6 ± 0.4 °C vs. 32.0 ± 0.8 °C, p = 0.855 in endurance; 32.4 ± 0.5 °C vs. 32.9 ± 0.5 °C, p = 0.061 in speed-power; 31.9 ± 0.7 °C vs. 32.4 ± 0.8 °C, p = 0.222 in controls). Plasma ATP concentration did not returned to pre-exercise values in well trained participants (before exercise vs. after 30-min recovery: 699 ± 57 nmol l⁻¹ vs. 854 ± 31 nmol l⁻¹, p < 0.001, η² = 0.961 and 812 ± 35 nmol l⁻¹ vs. 975 ± 55 nmol l⁻¹, p < 0.001, η² = 0.974 in endurance and speed-power, respectively), unlike in controls (651 ± 40 nmol l⁻¹ vs. 687 ± 61 nmol·l^-1, p = 0.58, η² = 0.918). The magnitude of T_SK and plasma ATP response differed between the groups (p < 0.001, η² = 0.410 for T_SK; p < 0.001, η² = 0.833 for plasma ATP). We conclude that lower limbs T_SK change indirectly corresponds to the reverse course of plasma ATP during incremental exercise and the magnitude of the response depends on the level of physical activity and the associated to it long-term metabolic adaptation.