The Effects of Transcranial Direct Current Stimulation on Quadriceps Muscle Function in Individuals with a History of Anterior Cruciate Ligament Reconstruction

Context: Altered quadriceps activation is common following anterior cruciate ligament reconstruction (ACLR), and can persist for years after surgery. These neural deficits are partially due to chronic central nervous system alterations. Transcranial direct current stimulation (tDCS) is a non-invasive modality that is believed to immediately increase motor neuron activity by stimulating the primary motor cortex, making it a promising modality to use during ACLR rehabilitation. Objective: The aim of this study was to determine if a single treatment of tDCS would result in increased quadriceps activity and decrease levels of self-reported pain and function during exercise. Design: Randomized crossover design. Setting: Controlled laboratory setting. Patients: 10-participants with a history of ACLR (5 male/5 female, 22.9±4.23yrs, 176.57±12.01cm, 80.87±16.86kg, 68.1±39.37 months since ACLR). Interventions: Active tDCS and Sham tDCS. Measures: Percent-maximum electromyographic (EMG) data of vastus medialis and lateralis, voluntary isometric strength, percent voluntary activation, self-reported pain and symptom scores. Results: There was a significant time main effect for quadriceps percent-maximum EMG (vastus medialis, F9,1 = 11.931, P = 0.007; vastus lateralis F9,1 = 9.132, P = 0.014), isometric strength (F9,1 = 5.343, P= 0.046), and subjective scores for pain (F9,1 = 15.499, P= 0.044) and symptoms (F9,1 = 15.499, P = 0.044). Quadriceps percent-maximum EMG, isometric strength, and voluntary activation and showed an immediate decline from pre to post time points. However, subjective scores improved slightly after each condition. Conclusions: One session of active tDCS did not have an immediate effect on quadriceps activity and subjective scores of pain and symptoms