Inspiratory muscle training in cardiac rehabilitation: evidence, prescription, and clinical applications

Inspiratory muscle training (IMT) is a targeted respiratory exercise intervention that may complement conventional cardiac rehabilitation by improving the strength and endurance of the diaphragm and other inspiratory muscles. Respiratory muscle weakness is frequently observed in patients with chronic heart failure and may also develop after cardiac surgery because of anaesthesia, mechanical ventilation, and postoperative pain, reduced mobility, and altered thoracic mechanics. These impairments can increase the work of breathing, intensify exertional dyspnea, and restrict participation in aerobic exercise and daily activities. IMT generally uses a threshold-loading or resistive-breathing device to provide a controlled inspiratory workload, commonly prescribed as a percentage of maximal inspiratory pressure (MIP). Recent systematic reviews and meta-analyses suggest that IMT can improve MIP and may produce additional benefits in six-minute walk distance, peak oxygen uptake, ventilatory efficiency, dyspnea, and health-related quality of life, particularly in selected patients with heart failure and individuals undergoing coronary artery bypass graft surgery. Preoperative respiratory muscle training may also reduce postoperative pulmonary complications and hospital stay, although the certainty of evidence varies among outcomes and interventions. This review discusses the physiological rationale, clinical evidence, patient assessment, training prescription, practical technique, and clinical applications of IMT in cardiac rehabilitation. It also examines its integration with aerobic and resistance exercise, safety precautions, adherence strategies, outcome monitoring, and the role of physiotherapists in individualized programme delivery. Current evidence supports IMT as a complementary intervention for appropriately selected and clinically stable patients rather than a replacement for comprehensive cardiac rehabilitation or guideline-directed medical treatment. Further high-quality trials are required to establish optimal training intensity, identify patients most likely to benefit, and determine whether improvements in respiratory muscle performance translate into sustained reductions in cardiovascular events, hospitalization, and long-term disability.