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1 The Copenhagen Muscle Research Center and 2 Department of Anesthesia, Rigshospitalet, University of Copenhagen, DK-2100 Copenhagen, Denmark; and 3 Department of Medicine, Academic Medical Center, University of Amsterdam, 1100 DE Amsterdam, The Netherlands
Lifting of a heavy weight
may lead to "blackout" 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 and central venous pressures 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 mean arterial pressure and MCA Vmean
was established at the onset of exercise performed with a Valsalva-like
maneuver (by 42 ± 5 mmHg and 31 ± 3% vs. 22 ± 6 mmHg
and 25 ± 6% with continued ventilation; P < 0.05). Profound reductions in MCA Vmean were
observed both after exercise with continued ventilation (
29 ± 4% together with a reduction in the arterial CO2 tension
by
5 ± 1 Torr) and during the maintained Valsalva
maneuver (
21 ± 3% together with an elevation in central venous
pressure 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, blackout during and after intense static exercise may
reflect a reduction in cerebral blood flow due to expiratory straining
and/or hyperventilation.
cerebral perfusion pressure; mean blood velocity; near infrared spectroscopy; subarachnoid aneurysmal hemorrhage; weight lifting
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