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Articles in PresS, published online ahead of print November 15, 2002
J Appl Physiol, 10.1152/jap.00457.2002
Submitted on May 23, 2002
Accepted on November 11, 2002
1 The Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark
2 Academic Medical Center, Department of Medicine, University of Amsterdam, Amsterdam, The Netherlands
3 The Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark; Rigshospitalet, Department of Anesthesia, University of Copenhagen, Copenhagen, Denmark
* To whom correspondence should be addressed. E-mail: fpott{at}yahoo.com.
Lifting of a heavy weight may lead to "black out" and occasionally also to cerebral hemorrhage, indicating pronounced consequences for the blood flow through the brain. We hypothesized that especially strenuous respiratory straining (a Valsalva-like maneuver) associated with intense static exercise would lead to a precipitous rise in mean arterial (MAP) and central venous pressures (CVP) and in turn, influence the middle cerebral artery blood velocity (MCA Vmean) as a noninvasive indicator of changes in cerebral blood flow. In 10 healthy subjects MCA Vmean was evaluated in response to maximal static two-legged exercise performed either with a concomitantly performed Valsalva maneuver or with continued ventilation, and also during a Valsalva maneuver without associated exercise (n=6). During static two-legged exercise the largest rise for MAP and MCA Vmean was established at the onset of exercise performed with a Valsalva-like maneuver (by 42 ± 5 mmHg and 31 ± 3% vs. continued ventilation: by 22 ± 6 mmHg and 25 ± 6%, respectively; p<0.05). Profound reductions in MCA Vmean were observed both following exercise with continued ventilation (-29 ± 4% together with a reduction in the arterial CO2 tension by -5 ± 1 mmHg) and during the maintained Valsalva maneuver (-21 ± 3% together with an elevation in CVP to 40 ± 7 mmHg). Responses to performance of the Valsalva maneuver with and without exercise were similar, reflecting the deterministic importance of the Valsalva maneuver for the central and cerebral hemodynamic response to intense static exercise. Continued ventilation during intense static exercise may limit the initial rise in arterial pressure and may in turn reduce the risk of hemorrhage. On the other hand, "black out" during and following intense static exercise may reflect a reduction in cerebral blood flow due to expiratory straining and/or hyperventilation.
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