Larger splenic emptying correlate with slower EPOC kinetics in healthy men and women during supine cycling

Abstract

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 $\dot{V}$O₂ at 90% gas exchange threshold, where data on metabolic, cardiovascular, and splenic responses were recorded simultaneously. After step-transition test cessation, EPOC_fast 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 ($\dot{V}$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$\dot{V}$O₂ was 45 ± 18 s, the amplitude was 2.4 ± 0.5 L·min⁻¹, and EPOC_fast was 1.69 L^·O₂. Significant correlations were observed between the percent change in spleen volume and (i) EPOC_fast (r = − 0.657, p = 0.008) and (ii) τ$\dot{V}$O₂ (r = − 0.619, p = 0.008), but not between the change in spleen volume and (iii) $\dot{V}$O₂ peak (r = 0.435, p = 0.105).

Conclusion

Apparently, during supine cycling, individuals with larger spleen emptying tend to have slower $\dot{V}$ O₂ recovery kinetics and a greater EPOC_fast.