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Purpose: The present study investigated whether larger splenic emptying augments faster excess post-exercise O2 consumption (EPOC) following aerobic exercise cessation. Methods: Fifteen healthy participants (age 24 ± 4, 47% women) completed 3 laboratory visits at least 48-h apart. After obtaining medical clearance and familiarizing themselves with the test, they performed a ramp-incremental test in the supine position until task failure. At their final visit, they completed three step-transition tests from 20 W to a moderate-intensity power output (PO), equivalent to V ˙ O2 at 90% gas exchange threshold, where data on metabolic, cardiovascular, and splenic responses were recorded simultaneously. After step-transition test cessation, EPOCfast was recorded, and the first 10 min of the recovery period was used for further analysis. Blood samples were collected before and immediately after the end of exercise. Results: In response to moderate-intensity supine cycling ( V ˙ O2 = ~ 2.1 L·min−1), a decrease in spleen volume of ~ 35% (p = 0.001) was observed, resulting in a transient increase in red cell count of ~ 3–4% (p = 0.001) in mixed venous blood. In parallel, mean blood pressure, heart rate, and stroke volume increased by 30–100%, respectively. During recovery, mean τ V ˙ O2 was 45 ± 18 s, the amplitude was 2.4 ± 0.5 L·min−1, and EPOCfast was 1.69 L·O2. Significant correlations were observed between the percent change in spleen volume and (i) EPOCfast (r = − 0.657, p = 0.008) and (ii) τ V ˙ O2 (r = − 0.619, p = 0.008), but not between the change in spleen volume and (iii) V ˙ O2 peak (r = 0.435, p = 0.105). Conclusion: Apparently, during supine cycling, individuals with larger spleen emptying tend to have slower V ˙ O2 recovery kinetics and a greater EPOCfast. [ABSTRACT FROM AUTHOR]

Purpose: The role of splenic emptying in O2 transport during aerobic exercise still remains a matter of debate. Our study compared the differences in spleen volume changes between aerobically trained and untrained individuals during step-transition supine cycling exercise at moderate-intensity. We also examined the relationship between spleen volume changes, erythrocyte release, and O2 uptake parameters. Methods: Fourteen healthy men completed all study procedures, including a detailed medical examination, supine maximal O2 uptake ( V ˙ O 2 max.) test, and three step-transitions from 20 W to a moderate-intensity power output, equivalent to V ˙ O 2 uptake at 90% gas exchange threshold. During these step-transitions pulmonary V ˙ O 2 p , near-infrared spectroscopy of the vastus lateralis, and cardiovascular responses were continuously measured. In parallel, minute-by-minute ultrasonic measurements of the spleen were performed. Blood samples were taken before and immediately after step-transition cycling. Results: On average, V ˙ O 2 max. was 10 mL kg min−1 (p = 0.001) higher in trained compared to their aerobically untrained peers. In response to supine step-transition cycling, the splenic volume was significantly reduced, and the largest reduction (~ 106 to 115 mL, ~ 38%, p = 0.001) was similar in both aerobically trained and untrained individuals. Erythrocyte concentration and platelet count transiently increased after exercise cessation, with no differences observed between groups. However, the vastus lateralis deoxygenation amplitude was 30% (p = 0.001) greater in trained compared to untrained individuals. No associations existed between: (i) spleen volumes at rest (ii) spleen volume changes (%), (iii) resting hematocrit and oxygen uptake parameters. Conclusion: Greater splenic emptying and subsequent erythrocyte release do not lead to a slower τ V ˙ O 2 p , regardless of individual V ˙ O 2 max. readings. [ABSTRACT FROM AUTHOR]