## 2 Materials and Methods  
In this case-control study, a total of 48 patients diagnosed with HV were recruited. Patients were selected at Bari University Hospital between January 2023 and December 2023. The included patients had HV classified as moderate/severe according to the Manchester scale [19]. The inclusion criteria were as follows: patients with HV classified as moderate or severe according to the Manchester scale of deformity; patients willing to participate in a comprehensive rehabilitation program, older than 18 years of age, and able to provide and sign informed consent. The exclusion criteria were as follows: patients suffering from any other orthopedic, rheumatological, or neurological disease involving the lower limbs; patients who had previously undergone foot surgery; and patients who had undergone any rehabilitation or local injection treatment in the previous 6 months. The initial patient evaluations and diagnoses were performed by specialized medical doctors in a foot orthopedic and rehabilitation outpatient service. Radiographic images of the deformity were obtained and analyzed, ensuring that the radiographs had been performed within 6 months prior to medical evaluation. The participants were randomly divided into two groups, namely the case group and the control group, using STATA MP15 software. These groups were homogeneous for age, gender (male vs. female), the pathological foot side, and the radiological and clinical grade of deformity. The case group underwent a one-month rehabilitation protocol specifically designed to address their foot deformity, whereas the control group received no intervention during the study period. The rehabilitation protocol included four key exercises aimed at enhancing the activation of the abductor hallucis (AH) muscle. The exercises were as follows:  
* Toe Spread Out (TSO): The patients sit with their feet flat on the ground and spread their toes apart as widely as possible, maintaining this position for a set duration of time. * Short Foot (SF): During this exercise, the patient sits with their feet on the floor and is asked to'shorten' the foot by pulling the toes toward the heel without lifting either the toes or heel off the ground. This action engages the muscles of the arch, improving proprioception and stability. * Forefoot Adduction (FA): To perform this exercise, the patient stands with their feet shoulder-width apart and consciously attempts to bring the toes together while keeping the heels aligned. FA helps to improve the coordination and control of foot movements, thereby promoting more neutral alignment of the metatarsophalangeal joints over time. * Flexion of the Metatarsophalanges (FM): To perform this exercise, the patient is positioned in a seated posture and is instructed to flex the toes at the metatarsophalangeal joints, bringing them closer to the plantar surface of the foot. This movement is typically held for several seconds and can be repeated in sets. The intervention comprised three sessions conducted each week, with each session lasting 40 min and led by a physical therapist with 10 years of experience in the field. Each session was structured as follows: 5 min of warm-up exercises for the lower limb muscles, followed by 5 sets of 10 repetitions for each exercise, with a 3-min rest period between sets. This resulted in a total of 5 repetitions per exercise per session. Each exercise was chosen for its potential to strengthen the intrinsic foot muscles, improve alignment, and alleviate the symptoms associated with HV. Both groups were assessed at baseline (T0), and again at the end of the rehabilitation period (T1), which lasted for one month and was performed only by the case group. The evaluation was conducted by measuring AH activity during execution of the aforementioned exercises. AH was monitored using mDurance (mDurance Solutions SL-Granada, Spain), a surface electromyography (sEMG) system that provides real-time feedback.