The early stage of exercises is crucial in sports training; however, its physiological mechanism is still unclear. The hemodynamic response was reported to be associated with respiratory exchange. Here, we aimed to explore the relationship between oxy-hemoglobin concentration change (HbO₂) and respiratory exchange ratio (RER) during the early phase of exercises. Sixteen athletes of middle-distance race were selected from Wuhan Institute of Physical Education to conduct intermittent exercises on MERCURY4.0 at 80% VO_2peak intensity. Multiple physiological parameters were acquired by use of a near-infrared spectroscopy muscle oxygen monitor, a Cardiopulmonary Function MAX-II and a P-Lar, including HbO₂, RER and others. A significant correlation was found between RER and HbO₂ in quadriceps muscle in the thigh during the early phase of exercises. Thus, NIRS is capable of supervising sports training in terms of HbO₂, which actually acted as an interpreter of RER change.