Limitations
PD
DISEASE
The present study is not without limitations. Since recruited participants belonged to stages 1–3 of the Hoehn and Yahr modified scale and stages 4–5 were excluded, the results of this study cannot be generalized to patients with advanced PD because often more impaired lung functions are observed in later stages of this disease. Therefore, future studies should be performed on patients in the advanced stages of the disease, and those results should be compared with patients in the early stages. Also, long-term follow-up was not performed, it may be possible that observed improvements were short-lived, and after cessation of IS or TIMT training, the respiratory functions may return to baseline level. In addition to the above limitations, the history of anti-Parkinson medications was not considered when recruiting participants. It may be possible that the current use of the medications may have contributed to improvements in patient symptoms. The present study did not perform MIP according to the ATS/ERS guidelines. Due to a lack of resources, in the present study, only MIP, FVC, FEV1, and PEFR were measured; however, the measurement of more variables like maximal voluntary ventilation (MVV), total lung capacity (TLC), residual volume (RV), closing volumes, and FEF