Changes in the Sprint, Vertical Jump and Quadriceps Strength after a Capacitive Resistive Electric Transfer Therapy Intervention—A Randomized Clinical Trial

Generating large mechanical power during actions such as sprinting or jumping is a crucial factor in many sports. These types of actions require a good warm-up activation. Capacitive-Resistive Electric Transfer (CRET) is a non-invasive therapy based on the application of radio frequency electric currents within the range of 300 kHz–1.2 MHz to accelerate tissue metabolic activity. This study aimed to evaluate the effectiveness of adding CRET to an active warm-up protocol in young adult athletes. For the double-blind randomized clinical trial, 60 healthy athletes were recruited and divided into an Experimental group (EG) and a Sham group (SG). EG received a CRET protocol in addition to an active warm-up. SG carried out the same warm-up but with a placebo CRET. The main outcome measures were isometric extension force, countermovement-jump (CMJ), 30 m-sprint test, and surface electromyography (sEMG). There is no statistically significant interaction (group–time) for any of the variables studied. Significant main effects for time were found in isometric extension force (p = 0.008); 30 m sprint (p = 0.017); rectus femoris sEMG during CMJ (p = 0.002); vastus lateralis sEMG during CMJ (p = 0.012); vastus medialis during CMJ (p = 0.010) and rectus femoris sEMG during the 30 m sprint test (p = 0.012). Non-significant differences between means are observed in the isometric extension force (48.91 EG; 10.87 SG) and 30 m sprint (−0.13 EG; −0.04 SG) variables. To conclude, a non-significant tendency was observed in sprint and quadriceps strength following CRET therapy, compared to the individuals’ pre-treatment state. Future research should use more treatment sessions to observe this tendency.