Cardiopulmonary exercise testing (CPET) is the reference method for the objective assessment of exercise capacity because it provides an integrated appraisal of cardiovascular, respiratory and metabolic responses to exertion. However, CPET alone quantifies the magnitude of functional impairment without fully resolving the central and peripheral mechanisms that determine exercise intolerance. The integration of CPET with exercise stress echocardiography and near-infrared spectroscopy (NIRS) has therefore emerged as a clinically relevant multimodal strategy. Stress echocardiography provides real-time information on ventricular reserve, filling pressures, pulmonary pressure response, valvular function, pulmonary congestion and dynamic outflow obstruction, whereas NIRS provides continuous insight into skeletal muscle oxygen delivery, extraction and utilization. This narrative review summarizes the physiological rationale, practical workflow, methodological limitations and clinical applications of combined CPET, stress echocardiography and NIRS across heart failure, pulmonary hypertension, peripheral artery disease, cardiomyopathies and sports cardiology. By linking systemic gas exchange, central hemodynamics and peripheral oxygen handling, this approach may move exercise evaluation from a descriptive measure of performance toward a mechanism-based framework for phenotyping, risk stratification and individualized therapeutic decision-making. Further studies are needed to harmonize protocols, validate reproducible multimodal indices and demonstrate incremental prognostic value over conventional testing.