This study examined the changes in muscle deoxygenation (HHb) following repeated 30s Wingate power tests to determine the muscle power-deoxygenation relationship. It was hypothesized that tissue HHb would correlate with changes in anaerobic power, reflecting the energy contribution following repeated Wingate trials. Muscle HHb was used to reflect O2 utilization, and total blood volume (tHb) was calculated from the oxy-Hb and HHb signal (HbO2 + HHb). Eleven competitive male cyclists (mean ± SD age, height, mass =21.8±7.6 yr; 177.5±5.7 cm; 73.7±10.4 kg) volunteered to perform three 30s anaerobic Wingate power tests (Wn1, Wn2, Wn3) with 60s rest between trials on a Monark cycle ergometer. The resistance was set at 90 g/kg. Tissue oxygenation was monitored continuously from the right vastus lateralis muscle using dual wavelength near infrared spectroscopy (NIRS). Mean (n=11) maximal power (Watts) was significantly reduced with each consecutive Wingate, from Wn1 (598±135W), to Wn2 (475±74W), to Wn3 (446±97W), with the fatigue index = 40-44%. Muscle HHb closely tracked these power changes but did not reach peak muscle HHb until 20s after the start of each Wn test. As well, muscle HHb was reduced and remained below baseline during the recovery period between Wingate tests. Average 30s power was significantly (ANOVA; p<0.05) reduced from Wn1 (474±79W) to Wn2 (377±62W) to Wn3 (338±61W), as was HHb for Wn1 (0.273±0.26OD), Wn2 (0.176±0.26OD), and Wn3 (0.108±0.25OD). A significant correlation was found between anaerobic power vs. HHb for Wn1 (r= -0.79) and Wn2 (r= -0.78), but not for Wn3 (r= -0.29). Significant correlations were also found for tHb change vs. anaerobic power (r=0.72-0.87). These results suggest that 1) NIRS can track changes in muscle HHb and tHb during anaerobic power testing and that decreases in muscle power correlated with muscle HHb and tHb; and 2) the muscle began to deoxygenate at the onset of maximal exercise during the Wingate tests suggesting that aerobic metabolism contributed significantly to energy production.