The main mechanisms of airway protection include a properly functioning swallowing process and a cough. Studies focusing on patients with Parkinson's disease (PD) have previously demonstrated impairments in both swallowing (dysphagia) and coughing (dystussia). Aspiration pneumonia is the leading cause of death in individuals with PD. Swallowing function is directly related to body posture. Postural abnormalities (PA) are a common symptom of PD and significantly contribute to patient disability, affect respiratory function, and reduce quality of life. Previous research has shown that more than 20% of PD patients suffer from some form of PA. Most PD patients with a forward trunk flexion angle greater than 30 degrees report specific difficulties, such as dysphagia. A link has previously been demonstrated between postural abnormalities associated with flexed posture and restrictive ventilatory impairment. It can be assumed that this restrictive ventilatory impairment, which reduces the amount of air the patient can inhale into the lungs and subsequently exhale, negatively affects the strength of voluntary cough. However, this hypothesis has not yet been verified in the mentioned patient group. The primary aim of the study will be to examine the effect of forward trunk flexion (FTF) in Parkinson's disease on the airway defense system.