The goal of this clinical trial is to investigate the effects of dual-task training on upper extremity function and muscle thickness in individuals with Parkinson's disease. The main questions it aims to answer are:

Does dual-task training improve upper extremity function in individuals with Parkinson's disease? Does dual-task training lead to changes in upper extremity muscle thickness measured by ultrasonography?

Researchers will compare a dual-task training group with a control group receiving routine care to determine whether 8 weeks of dual-task training results in greater improvements in upper extremity outco

Participants will:

complete baseline and post-intervention assessments of upper extremity function, muscle thickness, grip strength, and pinch strength be assigned to either a control group or a dual-task training group receive dual-task training 3 days per week for 8 weeks if assigned to the intervention group

Inclusion Criteria:

• Diagnosis of idiopathic Parkinson's disease confirmed by a neurologist
• Modified Hoehn and Yahr stage 2 to 3
• No medication or dosage change within the last 6 months
• Cognitive capacity sufficient to understand and follow instructions, defined as Montreal Cognitive Assessment score ≥21
• Voluntary participation with written informed consent

Exclusion Criteria:

• Atypical or secondary parkinsonism
• Advanced orthopedic condition affecting the upper extremity
• Surgery, trauma, or immobilization involving the upper extremity within the last 6 months
• Wound or dermatological condition preventing upper extremity ultrasonographic evaluation
• Severe visual or hearing loss
• Severe depression, psychosis, or communication difficulty
• Any additional health problem preventing regular participation in the study