The relative change between inflection points of respiratory quotient (RQ) and HbO2 in skeletal muscle during the process of increased intensity sports is investigated. The occurrence priority and interval regularity of the two based on time is compared, and the physiological mechanism of synchronisms is analyzed. 12 rowing athlete candidates are chosen to test to do increased intensity sports on dynamometer (CONCEPT Ⅱ). The output power of initial load is 50 W, and then increased by 50 W every 3 min until exhaustive. The relative changes of HbO2 in Quadriceps by near-infrared spectroscopy (NIRS) during sports are monitored. Simultaneously the oxygen uptake of candidates in sports is determined and recorded, including the intake of oxygen (VO2) and exhaled volume of carbon dioxide (VCO2) by the Cardiopulmonary Function Instrument MAX-Ⅱ. The inflection point of RQ is relatively changing to ΔHbO2. That means there is a time delay in RQ. The delay in VO2 and VCO2 relative to HbO2, which is affirmed in the single-factor variance analysis test, is do exist. During increased intensity sports, the respiratory quotient changes regularly accompanied with the inflection point, and content of muscle oxygen (ΔHbO2) in quadriceps changes regularly with unconventional inflection point which might denote that of respiratory quotient. Inflection point of respiratory quotient has a regular delay time relative to that of ΔHbO2. The phenomenon provides powerful evidence for us to speculate inflection point of respiratory quotient by measuring ΔHbO2 in Muscle-Oxygen Monitoring System. It may provide new methods to measure oxygen uptake.