Inclusion Criteria:  Have been diagnosed according with PD to the clinical criteria of the United Kingdom Parkinson's Disease Society Brain Bank diagnostic criteria being in phase 1-3 according to the Hoehn-Yahr (H-Y) scale, being under anti-parkinson's treatment, and being in the "on"period.  Exclusion Criteria:  • dyskinesia, (which may be obstacles to the tests),  chronic respiratory disease, dementia, co-operation difficulty, cognitive impairment (mini-mental test score <24), and other neurologic, cardiovascular or musculoskeletal problems that impede walking.