Capacitive Resistive Electric Transfer Therapy on Muscle Recovery

This study aims to evaluate the effectiveness of Capacitive Resistive Electric Transfer (CRET) therapy combined with post-competition massage in the recovery and muscle function of professional athletes. It is designed as a randomized, double-blind, crossover clinical trial. The primary objective is to analyze the efficacy of this combined protocol in muscle recovery after performing the Wingate anaerobic power and capacity test. Secondary objectives include assessing changes in muscle fatigue, muscle function of the rectus femoris and vastus lateralis, physiological changes in blood lactate concentration and oxygen saturation, and intramuscular structural changes through ultrasound before and after the intervention.

The study will recruit professional athletes from disciplines that require anaerobic muscle metabolism, such as cycling, athletics, triathlon, CrossFit, and duathlon. Participants must be federated athletes who train at least four times per week and actively compete at regional, national, or international levels. Exclusion criteria include recent sports injuries preventing test performance, prior exposure to CRET therapy, allergies to conductive gel, language barriers, participation in other research studies, or ongoing pharmacological treatment that could interfere with measurements.

Participants will attend four study sessions, divided into two sets of two consecutive days. On the first day, they will perform the Wingate test followed by the assigned post-competition massage with either CRET therapy or a placebo intervention. On the second day, they will repeat the Wingate test. After a three-week washout period, participants will switch to the opposite group. The intervention group will receive a 60-minute CRET therapy session with both resistive and capacitive modes applied at different power intensities, combined with a standardized recovery massage. The placebo group will receive the same massage while undergoing a simulated CRET therapy, with the machine turned on but without power application to prevent participant awareness of the placebo condition.

The study will analyze various dependent variables, including Wingate test performance, blood lactate levels, subjective fatigue perception using the modified Borg scale, muscle stiffness and tone through myotonometry, muscle oxygen saturation via near-infrared spectroscopy (NIRS), cross-sectional muscle area and grayscale values from ultrasound imaging, body composition using a Tanita analyzer, maximum isometric quadriceps strength via handheld dynamometry, and muscle activity measured by surface electromyography (sEMG). Each of these variables will be assessed at specific time points before, during, and after the intervention.

The estimated sample size is approximately 50 subjects, with 25 participants per group, determined through a preliminary pilot study. Statistical analyses will be conducted using IBM SPSS Statistics 26.0. Descriptive statistics will be calculated for quantitative and qualitative variables. A linear mixed model will be applied to compare changes between and within groups over five measurement periods using a one-way mixed ANOVA. If the sphericity assumption is violated, the Greenhouse-Geisser correction will be applied. Statistically significant effects will undergo post-hoc analysis with Bonferroni correction for multiple comparisons. All originally enrolled participants will be included in the final analysis following an intention-to-treat approach, and effect sizes will be calculated using eta squared. The significance level will be set at p \< 0.05.


Eligibility Criteria:
Inclusion Criteria:

* Athletes who practice a type of sport that requires the use of anaerobic muscle metabolism (cycling, athletics, triathlon, crossfit, spinning and duathlon)
* Athletes must be federated and train a minimum of 4 days/week
* Active participation in regional, national or international competitions.

Exclusion Criteria:

* Volunteers who have suffered a sports injury that makes it impossible for them to perform the test
* Having received the CRET therapy technique.
* Subjects who report allergies to the conductive cream.
* Subjects undergoing pharmacological medical treatment that may interfere with the measurements.