The Effect of Capacitive and Resistive Electrical Transfer Therapy (CRET) on the Return to Play Time in Elite Soccer Players With Hamstring Strain Injuries

Hamstring injuries are the most prevalent pathology in professional football, primarily due to the demands of high-speed running. Beyond threatening athlete health, these injuries account for 12-17% of all time-loss injuries, directly impacting a team's seasonal performance. Research has shown that teams with fewer pre-season hamstring injuries achieve greater success, while the annual financial burden on clubs reaches hundreds of millions of pounds. Recent analyses of 21 years of data from the Union of European Football Associations (UEFA) Elite Club Injury Study reveal that, despite advancements in preventive strategies and training science, hamstring injury rates have not decreased but rather increased by 30% in recent years (5). Given this substantial financial cost, it is evident that current prevention and rehabilitation programs are insufficient, highlighting the need to integrate new therapeutic modalities that optimize tissue healing into clinical practice.

Capacitive and Resistive Electric Transfer (CRET) is a non-invasive electro-physical modality that generates deep endogenous hyperthermia using radiofrequency currents, typically at a stable frequency of 448 kilohertz (kHz). Recent systematic reviews highlight that this method accelerates tissue regeneration not only through its thermal effect but also via biostimulation, which enhances ion mobility by balancing cell membrane potential. By increasing the permeability of ion channels in the cell membrane, it optimizes sodium-potassium (Na/K) pump activity, thereby helping injured and depolarized cells restore their membrane potential. CRET operates through two distinct modes (capacitive and resistive) that focus energy on specific layers based on tissue resistance, allowing it to selectively increase arterial blood perfusion even in deep muscle groups. While these studies recommend CRET for muscle regeneration, there are no randomized controlled trials investigating its efficacy specifically in hamstring injury rehabilitation. Therefore, this study aims to evaluate the effects of CRET-frequently used in clinics and sports clubs-on professional football players with hamstring injuries. The investigators hypothesized that CRET would have positive effects on tissue healing during the subacute phase.