This study demonstrates that explaining athletic performance solely through cardiovascular or musculoskeletal factors is insufficient in modern sports science, and that the respiratory system plays a decisive role in sustaining high-intensity and prolonged performance. The strength and endurance of the respiratory muscles, ventilatory control mechanisms, and ventilatory thresholds (VT1–VT2) directly influence oxygen distribution, metabolic balance, fatigue development, and intermuscular blood flow. Assessment methods such as spirometry, MIP/MEP measurements, respiratory muscle endurance tests, and cardiopulmonary exercise testing (CPET) enable a multidimensional evaluation of athletes’ physiological capacity, with CPET and ventilatory thresholds providing more functional indicators of sustainable performance than VO₂max alone. In addition, respiratory-focused interventions such as inspiratory muscle training (IMT) and inspiratory muscle warm-up (IMW) are highlighted for their ability to reduce ventilatory cost, delay respiratory muscle fatigue, lower perceived exertion, and ultimately enhance athletic performance.