Marina FEELEY, Go ITO, Shogo TSUBOTA, Toru SAWAI, Hideomi NAKATA, Shingo OTSUKI, Tadayoshi MIYAMOTO
Vol. 13 (2024) p. 35-42

Background: Alterations in central blood volume (CBV) play a pivotal role in the functionality of the respiratory and circulatory systems. This study elucidates the adaptive changes in respiration, cerebral circulation, and cardiovascular function in response to orthostatic stress in male volleyball players compared to healthy non-athletes. The athletes’ unique physiological adaptability may help them cope with the frequent CBV changes related to their sports activities.

Methods: Fourteen male university students participated in this study; seven were volleyball players and seven were non-athletes. Participants underwent a maximal ramp exercise test and a lower body negative pressure (LBNP) test conducted to examine the cardiorespiratory response under LBNP and no-LBNP conditions. Respiratory, metabolic, hemodynamic, and cardiac measurements were collected and analyzed.

Results: Volleyball players (Ath group) were significantly taller and exhibited higher maximal oxygen uptake (VO2max) and maximum work rate compared to non-athletes (Non-Ath group). Under the LBNP condition, end-tidal CO2 partial pressure (PETCO2) decreased by 4.1% in the Non-Ath group, but was maintained stable in the Ath group. The CBV reduction rate due to LBNP was notably less in the Ath group (−12.5%) compared to the Non-Ath group (−24.5%). In all participants, a significant correlation was observed between the CBV and PETCO2 reduction rates. However, cerebral blood flow and cardiovascular responses to LBNP load did not differ between the two groups.

Conclusion: Male volleyball players demonstrate distinctive adaptability in response to orthostatic stress, specifically in maintaining stable PETCO2 and attenuating CBV reduction rate under LBNP load. These findings suggest that the sport-specific training in volleyball may induce some protective mechanisms against abrupt changes in CBV, although cerebral blood flow and cardiovascular responses appear unaffected. Further research is warranted to understand the underlying mechanisms of these adaptations.