Does the inclusion of transcranial direct current stimulation of the brains motor cortex improve outcomes when combined with rehabilitation following Anterior Cruciate Ligament (ACL) reconstruction.

Exercise rehabilitation Participants will follow the Melbourne ACL rehabilitation guide that details the rehabilitation requirements for each phase. The rehabilitation protocol to be followed will be provided by one of five different physiotherapists working at SportsMed Subiaco, but each participant will be followed through via the same physiotherapist, and participants will attend for supervised rehabilitation and program upgrades at the following timepoints (some flexibility based on participants schedule): 2 weeks post-op, 4 weeks post-op, 6 weeks post-op, 8 weeks post-op, 12 weeks post-op and then monthly until they achieve the final exit criteria to return to play with assessments performed by an independent investigator not completing participant rehabilitation. Rehabilitation duration will vary from between 15 minutes to 60 minutes depending on the stage of the program and the physical demands of this individual. Participants will record exercise adherence using the Physitrack software. Exercises will initially start with body weight exercises (e.g., bridging or sit to stand), progress into more complex movements (e.g., deadlifts) and machine resistance training (e.g., leg press) before incorporating running, agility and sport specific exercises. Participants will be provided complimentary access to the gym at SportsMed Subiaco to complete their rehabilitation. Alternatively, if they have an existing gym membership we will provide the supervised consultation to set/ upgrade the program at SportsMed Subiaco and allow them to use their own gym membership if more convenient. Modifications to exercise rehabilitation can be incorporated into the initial rehabilitation program as required, especially within Phase One of the Melbourne ACL rehabilitation guide 2.0. Transcranial direct current stimulation (tDCS) All participants will have a screening session with a medical doctor (CW) to assess relevant medical history, medication use and suitability for tDCS. Participants will then be instructed in how to use the tDCS device. Transcranial direct current stimulation is a safe, non-invasive form of brain stimulation which passes a weak direct electrical current (typically <2 mA, c.f., 800-900mA for ECT) between an anodal and cathodal electrode placed on the scalp and has an excellent safety profile. Generally, cortical excitability is increased with the application of anodal tDCS (anode applied to the target cortical region). There is evidence that tDCS application to the primary motor cortex may promote an increase in muscular maximal voluntary contraction and possibly muscular endurance, improve balance performance, gait retraining, multi-task performance and motor learning of sport specific skills and tasks. The potential benefits of tDCS application align with ACL rehabilitation goals, namely preventing the loss of/regaining muscular strength, regaining and improving neuromuscular control and the re-introduction of sport specific movements and tasks. Single session and repeated tDCS are widely used in research involving both healthy participants and those with pain disorders, stroke, neurocognitive disorders and neuropsychiatric disorders. Both single session and repeated tDCS have been shown to be safe when applied with stimulation parameters in line with published guidelines for the safe use of tDCS. Adverse effects associated with tDCS are either rare or mild (commonly reported sensations include mild tingling or itching of the scalp). Given the location of the quadriceps/knee representation in the primary motor cortex, participants will have an anodal electrode applied to the vertex of the scalp, overlying the bilateral lower limb primary motor cortex (M1) representation. This area can be located using the International 10/20 system (an internationally recognised method to describe scalp electrode locations). The cathode will be applied to the contralateral shoulder (i.e. opposite shoulder to the injured lower limb). Participants will receive tDCS at 2 milliamps (mA) for 20 minutes, during which time rehabilitation exercises will commence (tDCS is considered to be online, referring to rehabilitation occurring while stimulation is being applied, however rehabilitation exercises will continue after the completion of 20 minutes of tDCS). The tDCS device will be fitted by the onsite physiotherapist. For maximal benefit tDCS application during rehabilitation will be encouraged up to three times per week during the intervention period at a similar time of day.