Investigation of the Acute Effects of Inspiratory Muscle Training at Different Intensities on Vital Signs and Peripheral and Respiratory Muscle Strength in Male Smokers

Cigarette smoking can impair respiratory muscle function by reducing inspiratory strength and endurance; Inspiratory Muscle Training (IMT) is a rehabilitative strategy that uses resistive breathing to strengthen the diaphragm and accessory inspiratory muscles. It may temporarily influence autonomic responses and muscle performance. This randomised, parallel-group study will investigate the immediate effects of two IMT intensities in male smokers. Thirty-four male participants who currently smoke will be randomly assigned to one of two groups: IMT at 30% of maximal inspiratory pressure (MIP) or IMT at 60% of MIP. Prior to IMT, all participants will complete a standardised diaphragmatic breathing warm-up (3 sets of 10 repetitions; approximately 5 minutes). IMT will be administered with a threshold device (e. g., Powerbreathe®), with each group performing 3 sets of 30 breaths at the assigned intensity over approximately 15 minutes under supervision. Participants will be monitored for transient discomfort or fatigue. Outcomes will be assessed immediately before and after the session. These will include respiratory muscle strength (MIP, maximal expiratory pressure, MEP), peripheral muscle performance (handgrip strength in both dominant and non-dominant hands), and vital signs (heart rate, oxygen saturation, respiratory rate, systolic and diastolic blood pressure), along with perceived exertion using the Borg scale. The primary outcome will be a change in MIP (cmH₂O and % predicted); secondary outcomes will include changes in MEP, handgrip strength, vital signs, and perceived exertion. Data will be analysed using appropriate paired and independent tests (parametric or non-parametric based on distributional checks) in IBM SPSS v 27. By comparing low- and higher-intensity IMT within a single supervised session, the study aims to identify a practical early-intervention intensity that can acutely enhance inspiratory muscle function in male smokers and potentially inform broader pulmonary rehabilitation strategies.