Study protocol

Pre-intervention assessment: Most data were collected after breakfast and lunch (3–5 pm).Maximum inspiratory pressure (MIP): The MIP was measured using a portable MicroRPM machine. The participants were asked to sit comfortably on a chair, hold the instrument with both hands, and close their lips around the mouthpiece. A nose clip was also applied to prevent the air leak from the nose. Participants were asked to exhale as much as possible, then inhale maximally for more than one second. Before the final measurement, participants were asked to familiarize themselves with the procedurePulmonary function tests (PFT): FVC, FEV1, and PEFR were measured. The PFTs were performed using a computerized Pulmonary Function Test Machine (RMS Helios 401). Participants were asked to sit comfortably, and a nose clip was applied. The mouthpiece was placed in the mouth, and participants were asked to close their lips around it. They were asked to inhale as much as they could and then exhale maximally till no further air could be exhaled. Before taking the final measurements, participants were asked to familiarize themselves with the procedure6-min walk distance (6-MWD): Participants were asked not to exert themselves vigorously 2 h before the test. This test was carried out indoors, along a 30 m long flat straight corridor. This distance was marked using two cones. Before starting the test, participants were asked to rest in a chair for 10 min. Then a timer was used and set at 6 min. Instructions were given to the participants. The total distance walked by the participants in 6 min was noted for baseline measurementIntervention: The participants were divided into the Incentive Spirometer (IS) and Threshold Inspiratory Muscle Trainer (TIMT) groups. In group IS and TIMT, inspiratory muscle training was performed using the volume-based IS and TIMT, respectively. In both groups, the intervention was performed for six weeksIncentive spirometer (IS) group: IMT was performed using the PORTEX Coach 2 incentive spirometer in this group. The participants were allowed to sit comfortably. They were asked to hold the spirometer with their hands, exhale normally, and then put the mouthpiece into the mouth with the lips closing it tightly. They were asked to inhale as slowly and deeply as possible and raise the ball in the chamber. At full inspiration, the mouthpiece was removed, followed by 3–5 s of breath-hold and then normal exhalation. This training was performed for 15 min twice a day (a total of 30 min) for six days a weekThreshold inspiratory muscle trainer (TIMT) group: IMT was performed using the Threshold IMT device in this group. Participants were asked to put the mouthpiece into the mouth and put on the nose clips. Initially, training intensity was set at 30% of MIP with progression by 5% of MIP every week. The participants had to inhale from the mouthpiece, hold their breath for 2–3 s, and then exhale. This training was also performed for 15 min twice daily (a total of 30 min) six days a week. This training session also lasted for a total of 6 weeks.Post-intervention assessment: MIP, PFT (FVC, FEV