Cardiac output (Q) and stroke volume (V S) represent primary determinants of cardiovascular performance and should therefore be determined for performance diagnostics purposes. Since it is unknown, whether measurements of Q and V S can be performed by means of Innocor™ during standard graded exercise tests (GXTs), and whether current GXT stages are sufficiently long for the measurements to take place, we determined Q and V S at an early and late point in time on submaximal 2min GXT stages. 16 male cyclists (age 25.4±2.9years, body mass 71.2±5.0kg) performed three GXTs and we determined Q and V S after 46 and 103s at 69, 77, and 85% peak power. We found that the rebreathings could easily be incorporated into the GXTs and that Q and V S remained unchanged between the two points in time on the same GXT stage (69% peak power, Q: 18.1±2.1 vs. 18.2±2.3lmin−1, V S: 126±18 vs. 123±21ml; 77% peak power, Q: 20.7±2.6 vs. 21.0±2.3lmin−1, V S: 132±18 vs. 131±18ml; 85% peak power, Q: 21.6±2.4 vs. 21.8±2.7lmin−1, V S: 131±17 vs. 131±22ml). We conclude that Innocor™ may be a useful device for assessing Q and V S during GXTs, and that the adaptation of Q and V S to exercise-to-exercise transitions at moderate to high submaximal power outputs is fast enough for 1 and 2min GXT stage duration
