This study material deals with the topic of functional diagnostics, focusing on spiroergometry and the diving reflex. In the first section, it describes in detail the indications for spiroergometric testing, the various types of ergometers (bicycle ergometer, treadmill, rowing machine), the methodology for titrating the exercise load, and the development and principles of exhaled air analysis. It goes on to explain the calculation, reference ranges and diagnostic significance of key cardiorespiratory parameters, such as heart rate ($TF_{max}$, $W_{170}$), maximum power output ($W_{max}$), minute ventilation ($VE_{max}$), tidal volume, oxygen consumption ($VO_{2max}$), oxygen consumption, ventilation equivalent and respiratory exchange ratio (RER). Particular attention is paid to objective criteria for maximum exertion and to methods for determining the anaerobic threshold using both invasive (lactate curve) and non-invasive methods (V-slope method, Conconi test). The second part of the material focuses on the autonomic diving reflex, its neural pathway, examination methods and associated haemodynamic changes and cardiac arrhythmias from the perspective of sports medicine assessment.