Feasibility of using non-invasive brain stimulation to improve outcomes in patients with Achilles Tendinopathy

Participants will undergo an 8-week exercise intervention consisting of 24 strength-training sessions (3 times per week) using transcranial direct current stimulation (tDCS). The exercise intervention used is informed by previous research and will be identical between the groups, to allow us to assess the feasibility, acceptability and effectiveness of the tDCS intervention independently to the exercise intervention. To complete the exercise intervention, participants will be provided a 16-week gym membership (8-weeks during the intervention and 8-week follow up period) at the provider physiotherapy clinic, but they may alternatively perform the intervention at a location of their choosing. As per the intervention outlined by Van Der Vilst & colleagues (2020) (ClinicalTrials.gov NCT02996409), the program will consist of three consecutive phases: (1) isometric-focus, (2) concentric-focus, and (3) eccentric-focus. The isometric-focus phase consists of a single leg straight knee heel raise hold and a single leg bent knee (seated) heel raise hold, participants will hold for 45 seconds for a total of 3-4 repetitions. The concentric-focus phase consists of single or double leg heel raises completed with a straight knee and a bent knee (seated) with weight specific to the participant, they will complete 3 sets of 15 repetitions. The eccentric-focus phase consists of raising up on both toes, then slowly lowering for the count of 4 on the affected side. This will be completed with the knee straight and bent, for 3 sets of 15 repetitions. Participants will perform the exercises one-on-one with the physiotherapist at the start, and at each progression point in 30-minute supervised exercise sessions during week 2, 4 and 6. Participants can progress to the next phase or increase the weight when Achilles pain is less than or equal to 3/10 on the visual analogue scale (VAS) within the 24 hours following exercise. If a participant has a flare up in symptoms (Achilles pain greater than or equal to 5/10 VAS within the 24 hours following exercise), the exercises will be regressed in intensity, or they will return to the exercises in the previous phase. Exercise videos and descriptions will be delivered to participants via physitrack (https://www.physitrack.com/en-au). Physitrack will also monitor participant adherence to the exercise program. The tDCS device (Brain Premier tDCS E1 Plus) will deliver a weak current (2 milliamps [mA]) from a 35 x 35 mm anodal electrode on the scalp at the vertex (overlaying primary motor cortex of the more symptomatic limb) to a cathodal electrode placed over the deltoid tubercle of the upper arm (on the contralateral arm to the symptomatic limb). The primary researcher (MEC) will train the participants how to self-perform tDCS on unsupervised days and will be available to help if required during these un-supervised sessions. Participants will set up and turn on the device before commencing their rehabilitation exercises. They will keep the device on for the 20-minute dose, after which they may remove the device and continue their exercises if necessary. Physitrack will monitor adherence.