Late cardiovascular drift observable during ultra endurance exercise.

• Introduction: The present study investigates the adaptation of the central circulation to ultraenduranceexercise, including the relative contributions of changes in stroke volume (SV) andarterio-venous oxygen difference (a-v O2 diff) to the increased oxygen pulse (VO2/HR).Methods: We evaluated subjects undergoing 12h of mixed exercise at controlled intensity(n=8) and a 53h Adventure race (n=20). Heart rate (HR), oxygen uptake (VO2), and cardiacoutput determined using non-invasive gas rebreathing (CORB) were measured during cyclingat fixed work rate after 0, 4, 8, 12 hours, and 0, 20, and 53 hours of continuous exercise in the12 and 53 h protocol, respectively.Results and Conclusion: The central circulation changed in several steps in response to ultraenduranceexercise. Compared to initial levels, VO2 was increased at every time-point measured.The increase was attributed to peripheral adaptations, confirmed by a close correlation betweenchange in VO2 and change in a-v O2 diff. The first step of the circulatory response was typical ofnormal (early) cardiovascular drift, with increased HR and concomitantly decreased SV andVO2/HR, occurring over the first 4-6 h. The second step, which continued until approximately 12h, included reversed HR-drift, with normalization of SV and VO2/HR. When exercise continueduntil 50 h late cardiovascular drift was noted, characterized by increased VO2/HR, (indicatingmore efficient energy distribution), decreased peripheral resistance, increased stroke volume, anddecreased work of the heart. Since cardiac output was maintained at all time points we interpretthe changes as physiologically appropriate adaptations to ultra-endurance exercise.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

Keyword

Cardiac output

oxygen uptake

heart rate

stroke volume

oxygen pulse

adventure race

Physiology

Fysiologi

Medicin/Teknik

Medicine/Technology

Publication and Content Type

ref (subject category)

art (subject category)