The goal of this clinical trial study is to learn about the effect of aquatic exercise in parkinson's patients. The main questions it aims to answer are:

• What is the effect of exercise in water on balance in parkinson's patients?
• What is the effect of exercise in water on muscle strength in parkinson's patients?
• What is the effect of exercise in water on flexibility in parkinson's patients? Parkinson's patients in this study will do some functional tests. One group of them will do exercises in water 3 times weekly for 8 weeks.

Parkinson's disease (PD) is a progressive, neurodegenerative movement disorder characterised by the motor symptoms bradykinesia, tremor, rigidity, and postural instability. These are commonly associated with non-motor disturbances, neurobehavioural symptoms and reduced quality of life.

Exercise is currently recommended as an additional strategy to manage PD-induced disability and is a key component of rehabilitation programs for people with PD.

Aquatic exercise is another form of non-conventional exercise that has been growing in popularity in the context of neurorehabilitation.16 The aquatic setting offers specific mechanical advantages due to the hydrostatic and hydrodynamic principles of buoyancy, viscosity and drag.

Due to its ability to enhance functional mobility whilst also being enjoyable,aquatic exercise has become a very popular form of physical training in the management of neurodegenerative disorders.

Recent studies suggest that high-intensity interval training (HIIT) is promising for promoting neuroplasticity in human PD, with short training time and reduced burden. Biomarkers for neuroplasticity such as brain-derived neurotrophic factor (BDNF) and neurodegeneration (including neurofilament light chain ((NfL) and α-synuclein) may play a role, but their response to HIIT is not well-investigated.

The aims of this study are to investigate the effects of HIIT exercises in water on balance, muscle strength, flexibility and gait speed in PD patients.

Inclusion Criteria:

• clinical diagnosis of idiopathic PD, from mild to moderate stages (severity from 1 to 4), according to the original version of the Hoehn & Yahr scale (HY)17, assessed by the neurologist
• Having medical certificate for performing physical activities and attending heated pools

Exclusion Criteria:

• Having another neurological pathology
• Having limiting orthopedic or heart associated conditions
• changing physical activities or L-dopa-based drug intake parameters

Individual participant data that underlie the results reported in the published article, after deidentification are to be shared.

The data will be available after the paper is published. No end date.

Data will be accessible with no criteria. Anyone who wishes will have access to data.

A research project collaborator who is not informed about grouping of participants will obtain outcome measurements of the functional tests. Outcome adjudicators and data analysts will be kept blinded to the allocation. Moreover, all investigators, staff, and participants will be kept masked to outcome measurements and trial results.