Inclusion criteria:  Informed consent Clinical diagnosis of Parkinson's disease by a movement disorder specialized neurologist with Hoehn and Yahr staging 1.5 to 3. 15 individuals with self-reported personal experience of positive altitude effect. 5 individuals without self-reported personal experience of positive altitude effect.  Exclusion criteria:  Individuals with diseases leading to restrictive and obstructive pulmonary diseases, pulmonary diffusion deficits, apnea and cardiac output deficits, such as pulmonary fibrosis, COPD, sleep apnea or excessive alcoholic intake, and congestive heart failure respectively. Arterial blood gas abnormalities at screening day (as per normal limits) Individuals with shortness of breath or other airway or breathing-related inconvenience related to lack of dopaminergic medication will be excluded. Inability to comply to intervention in off-medication condition (for example due to extreme discomfort, distress or severe head tremor due to being OFF, i.e. without dopaminergic medication). Individuals with unstable dopaminergic medication dose (changes in the last month) Individuals likely to start dopaminergic treatment in the next month, also judged by their treating neurologist Individuals with active deep brain stimulation Individuals unable to provide informed consent.