**9. Conclusion**

Evidence has indicated that no single mechanism can account for parkinsonian rigidity, which is influenced by a multitude of physiological phenomena and biomechanical features. Treatment of rigidity primarily involves an administration of dopaminergic medication. However, serious side effects usually occur after a few years' drug treatment. Therefore, rehabilitative programs are highly desirable for patients with Parkinson's disease. A better understanding of the comprehensive characteristics of parkinsonian rigidity is crucial for designing effective evidence-based exercise program and physical therapy intervention. An objective assessment of rigidity is essential for evaluating the efficacy of therapeutic interventions, especially in large clinical studies in which trials are conducted across multiple centers.
