Acute Effects of Capacitive-Resistive Radiofrequency Therapy in People With Parkinson's Disease

This is an experimental, randomized-sequence, within-subject crossover study designed to evaluate the safety, tolerability, and acute effects of capacitive-resistive radiofrequency therapy (TECAR) applied to the lower limbs of people with Parkinson's disease.

Each participant will receive four TECAR treatment protocols in separate sessions: (1) capacitive mode for 15 minutes per leg; (2) resistive mode for 15 minutes per leg; (3) a mixed capacitive-resistive protocol consisting of 10 minutes of capacitive treatment followed by 5 minutes of resistive treatment per leg; and (4) a mixed resistive-capacitive protocol consisting of 10 minutes of resistive treatment followed by 5 minutes of capacitive treatment per leg. Treatment intensity will be individually adjusted to produce a clear but comfortable thermal effect.

The order of the four interventions will be randomized individually for each participant to minimize potential period, learning, and carryover effects. A washout period of at least 7 days will separate treatment sessions. Participants will continue their usual antiparkinsonian medication and usual medical care throughout the study. Assessments will be performed during the pharmacological "ON" state, approximately 60-90 minutes after the participant's usual dopaminergic medication.

The primary outcome will be lower-limb muscle stiffness measured objectively using MyotonPRO myotonometry. Measurements will be obtained from standardized anatomical sites, including the medial gastrocnemius, tibialis anterior, rectus femoris, and biceps femoris muscles.

Secondary outcomes will include functional mobility assessed with the Timed Up and Go test, walking speed assessed with the 10-Metre Walk Test, range of motion of the ankle, knee, and hip measured by goniometry, and lower-limb musculoskeletal pain assessed using a Numeric Rating Scale.

Outcomes will be assessed immediately before each intervention, immediately after each intervention, and 48 hours after each treatment session. Adverse events and treatment-related discomfort will also be recorded during each intervention and at the 48-hour assessment to evaluate the safety and tolerability of the different TECAR protocols.

The study plans to recruit 20 participants with idiopathic Parkinson's disease, Hoehn and Yahr stages II-III, who have functional walking ability and clinically relevant lower-limb rigidity.

Inclusion criteria

• Age between 55 and 90 years. Clinical diagnosis of idiopathic Parkinson's disease confirmed by a Neurology specialist.

Hoehn and Yahr stage II or III. Functional walking ability. Clinically relevant lower-limb rigidity in at least one leg, defined as a score ≥2 on item 3.3d (right lower limb) or 3.3e (left lower limb) of Part III of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS).

Stable antiparkinsonian pharmacological treatment during the previous 4 weeks, with no planned changes during the intervention period.

Ability to understand and follow simple instructions, defined as a score >24 on the validated Spanish version of the Mini-Mental State Examination (MMSE-MEC).

Provision of written informed consent.

Exclusion criteria

• Advanced Parkinson's disease, defined as Hoehn and Yahr stage >III, with severe postural instability.

Other neurological or musculoskeletal conditions that could interfere with the assessment of lower-limb rigidity or gait.

Skin lesions, open wounds, or infection in the area where radiofrequency therapy will be applied.

Presence of a pacemaker, defibrillator, other implanted electronic device, or another contraindication to TECAR therapy, such as altered thermal sensitivity.

Lower-limb surgery within the previous 6 months.