The content of breathing exercises was planned as thoracic expansion exercises. These exercises were applied to the lower, middle, and upper lobes in 3 sets of 3x10 (90 times breathing in one area) and lasted for an average of 20 minutes. These exercises were first taught by the physiotherapist and performed under her supervision. Participants were asked to inhale as deeply as possible into the relevant area, hold their breath for 3 seconds, and then slowly exhale the entire breath.

Vagus stimulation was applied bilaterally through the ear. taVNS was performed with the Vagustim device. The stimulation pulse width was 300 microseconds, the frequency was 10 Hz, and it was biphasic with a 20-minute duration. Electrodes were placed on the concha and tragus parts of the ear, and the current was increased through these electrodes until the participant felt pain. When the participant felt pain, the intensity was reduced to a comfortable sensation.

Vagus nerve stimulation group: Vagus stimulation was applied bilaterally through the ear. taVNS was performed with the Vagustim device. The stimulation pulse width was 300 microseconds, the frequency was 10 Hz, and it was biphasic with a 20-minute duration. Electrodes were placed on the concha and tragus parts of the ear, and the current was increased through these electrodes until the participant felt pain.

Autonomic measurements of each individual participating in the study before and after the intervention were performed with heart rate variability parameters. For this purpose, the Elite HRV device was used. The device has a finger sensor and an application compatible with the phone. Elite HRV application is a software that can synchronize with a personal monitor by collecting peak-to-peak intervals for instant analysis of pulse rate variability (PRV). In addition to all these assessments, blood pressure measurements of the participants were also evaluated using an Omron M2 electronic sphygmomanometer on the right arm.

Participants in both groups underwent pulmonary function test evaluation on the first and last day. Since the study was conducted in healthy individuals, it was deemed appropriate to look at the pulmonary function test before and after exertion to see possible changes. Medwelt SP10 spirometer was used for pulmonary function tests in our study. Each individual was measured in a sitting position using a separate mouthpiece.

Participants in both groups underwent pulmonary function test evaluation on the first and last day. Since the study was conducted in healthy individuals, it was deemed appropriate to look at the pulmonary function test before and after exertion to see possible changes. Medwelt SP10 spirometer was used for pulmonary function tests in our study. Each individual was measured in a sitting position using a separate mouthpiece.