Correlation between strength and skin temperature asymmetries in the lower limbs of Brazilian elite soccer players before and after a competitive season

This study aimed to investigate the correlation between strength and skin temperature (T-sk) asymmetries in the lower limbs of elite soccer players before and after a competitive season. The sample (n = 20) was composed of elite male soccer players. Strength asymmetry and T-sk asymmetry was measured through the countermovement jump (CMJ) test and infrared thermography, respectively. Asymmetries were quantified using the symmetry angle (SA) equation. A strong correlation was found between the SA of rate of force development (RFD) and the SA of T-sk before (baseline) (r = 0.7; r(2) = 0.43; p = 0.03) and after (r = 0.6; r(2) = 0.42; p = 0.04) the competitive season. Moreover, after the competitive season there were significant decreases in Peak force (p < 0.018), Impulse (p < 0.04), RFD (p = 0.0001) and CMJ height (p = 0.05), and significant increases in T-sk (p < 0.03), C-reactive protein (p = 0.03), Creatine kinase = 0.0001) and Cortisol (p = 0.04), even after a 3-day rest interval (no training). These results suggest that the CMJ test can be combined with infrared thermography for monitoring strength asymmetry and contribute to the prevention of muscle injuries.