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Abstract The human spleen acts as a reservoir for red blood cells, which is mobilized into the systemic circulation during various conditions such as hypoxia and physical exertion. Cross-country (XC) skiers, renowned for their exceptional aerobic capacity, are regularly exposed to high-intensity exercise and local oxygen deficits. We investigated a putative dose-dependent relationship between splenic contraction and concomitant hemoglobin concentration (Hb) elevation across four exercise intensities in well-trained XC skiers. Fourteen male XC skiers voluntarily participated in a 2-day protocol, encompassing a serial apnea test and a V̇ V ˙ O 2max test (day 1), followed by three submaximal exercise intensities on a roller skiing treadmill corresponding to 55, 70, and 85% of V̇ V ˙ O 2max (day 2). Spleen volume was measured via ultrasonic imaging, and venous blood samples were used to determine Hb levels. Baseline spleen volume was similar (266 (35) mL) for all conditions (NS). Notably, all conditions induced significant splenic contractions and transient Hb elevations. The V̇ V ˙ O 2max test exhibited the most pronounced splenic contraction (35. 8%, p < 0. 001) and a Hb increase of 8. 1%, while the 85% exercise intensity led to 27. 1% contraction and the greatest Hb increase (8. 3%, < 0. 001) compared to baseline. The apnea test induced relatively smaller responses (splenic contraction: 20. 4%, Hb = 3. 3%, p < 0. 001), akin to the response observed at the 70% exercise intensity (splenic contraction = 23%, Hb = 6. 4%, p < 0, 001) and 55% (splenic contraction = 20. 0%, Hb = 4. 8%, p < 0. 001). This study shows a discernible dose-dependent relationship between splenic contraction and Hb increase with levels of exercise, effectively distinguishing between submaximal and maximal exercise intensity.
Lindblom et al. (Fri,) studied this question.