Rectus Femoris Oxygenation During A Vo2 Max Test With The Bruce Protocol

Bruce protocol is one the most used VO2 max testing protocols, clinically and for exercise performance. This graded exercise protocol entails considerable changes in treadmill inclination to induce fatigue, and the rectus femoris is one of the primary muscles used during such increases. PURPOSE: Investigate the rectus femoris oxygenation during the Bruce protocol VO2max test. METHODS: 24 young adults (2 Females; Age:23.79 ± 5,16 years, BMI: 24.77 ± 3.38 kg/m2, VO2max: 48.4 ± 9.4 ml/kg/min)) performed a VO2max test using the Bruce protocol. A muscle oxygenation sensor (Artinis, Portamon) was positioned on the Rectus femoris, placed at 50% of the line from the anterior spinal iliac superior to the superior part of the patella. Muscle oxygenation was obtained by the Tissue Saturation index (TSI%) of oxygen. Data was analyzed during 1-minute windows of Rest (TSI%_Rest), 50% of the protocol (TSI%_Exercise), the last minute of the protocol (TSI%_End), and 1 minute immediately after the end of the protocol (TSI%_Recovery). One-way repeated measures with a post-test of Tukey were used to compare the difference between time points. RESULTS: At the end of the test, individuals reported an RPE = 18.2 ± 1.7 and had an RER = 1.22 ± 0.09 and HR = 193.5 ± 7.6 BPM. Muscle oxygenation significantly (p < 0.001) decreased from Rest to Exercise (TSI%_Rest: 66.5 ± 5.69 vs. TSI%_Exercise: 62.4 ± 5.26), End of exercise (TSI%_Rest: 66.5 ± 5.69 vs. TSI%_End: 49.6.4 ± 9.64), and increased during recovery (TSI%_End: 49.6.4 ± 9.64 vs TSI%_Recovery: 63.1 ± 8.98). CONCLUSIONS: These results indicate that lack of oxygenation on the rectus femoris at the end of the protocol may be related to muscle-induced fatigue and exercise termination. Research was sponsored by the U.S. Army DEVCOM Soldier Center and was accomplished under Cooperative Agreement Number W911QY-19-2-0003