# Enhancing functional recovery after ACL injury. A protocol for a randomized control trial of transcranial direct current stimulation over the motor cortex

## TL;DR

This study explores using brain stimulation to improve recovery after ACL injuries, aiming to enhance muscle function and reduce reinjury risk.

## Contribution

The novel contribution is integrating transcranial direct current stimulation with standard rehabilitation for ACL recovery.

## Key findings

- Combining tDCS with rehabilitation may improve neuromuscular control and muscle activation.
- The study will assess cortical excitability and plasticity using EEG and TMS.
- Outcomes will be evaluated at four time points post-surgery to determine long-term effects.

## Abstract

Anterior cruciate ligament (ACL) tears are common in athletic and nonathletic populations, often resulting from activities involving rapid directional changes that place stress on the knee. Although advances in surgery and rehabilitation have improved recovery, many patients still struggle to regain pre-injury performance and face increased risk of re-injury. We hypothesize that combining standard rehabilitation with transcranial direct current stimulation (tDCS) may accelerate recovery, improve neuromuscular control, and strengthen key muscles like the hamstrings and hip abductors, reducing reinjury risk.

This randomized controlled trial protocol, approved by the Ethics Committee of the Catholic University of Valencia, follows a double-blind, comparative, longitudinal design per SPIRIT guidelines. Elite athletes will be randomized 1:1 into two age- and sex-matched groups: non-invasive brain stimulation (NIBS) + rehabilitation (ProtocolRHB) or sham NIBS + ProtocolRHB. The NIBS intervention uses tDCS to deliver low-intensity direct current to modulate cortical excitability. Data collection spans April 2025 to December 2027 with outcomes assessed at four postsurgical time points. The primary outcome is electromyographic (EMG) activity to evaluate muscle activation, crucial for restoring knee stability and function. Secondary outcomes include knee function (Lysholm Scale) and ACL-specific quality of life. EEG and TMS will assess cortical excitability and plasticity during voluntary muscle contraction.

This study integrates neurophysiology with rehabilitation, offering a novel approach to enhance functional recovery and lower reinjury risk post-ACL reconstruction, potentially informing future evidence-based sports medicine and neurorehabilitation strategies.