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Title: Influence of age on syncope following prolonged exercise: differential responses but similar orthostatic intolerance
Authors: Murrell, C
Cotter, JD
George, K
Shave, R
Wilson, L
Thomas, K
Williams, MJA
Lowe, T
Ainslie, PN
Issue Date: 2009
Publisher: The Physiological Society
Citation: The Journal of Physiology 587(pt 24): 5959–5969, Dec 2009
Abstract: Orthostatic tolerance is reduced with increasing age and following prolonged exercise. The aim of this study was to determine the effect of age on cardiovascular and cerebrovascular responses to orthostatic stress following prolonged exercise. Measurements were obtained before, and within 45 min after, 4 h of continuous running at 70–80% of maximal heart rate in nine young (Y; 27 ± 4 years; 59 ± 10 ml kg−1 min−1) and twelve older (O; 65 ± 5 years; 46 ± 8 ml kg−1 min−1) athletes. Middle cerebral artery blood flow velocity (MCAv; transcranial Doppler ultrasound), blood pressure (BP; Finometer) and stroke volume (SV) were measured continuously whilst supine and during 60 deg head-up tilt for 15 min or to pre-syncope. Orthostatic tolerance was reduced post-exercise (tilt completed (min:s, mean ±s.d.): Pre, 14:39 ± 0:55; Post, 5:59 ± 4:53; P < 0.05), but did not differ with age (P > 0.05). Despite a 25% higher supine MCAv in the young, MCAv at syncope was the same in both groups (Y: 34 ± 10 cm s−1; O: 32 ± 13; P > 0.05). Although the hypotensive response to syncope did not differ with age, the components of BP did; SV was lowered more in the young (Y: –57 ± 16%; O: –34 ± 13%; P < 0.05); and total peripheral resistance was lowered in the older athletes but was unchanged in the young (Y: +8 ± 10%; O: –21 ± 12%; (at 10 s pre-syncope) P < 0.05). Despite a lower MCAv in the older athletes, time to syncope was similar between groups; however, the integrative mechanisms responsible for syncope did differ with age. The similar MCAv at pre-syncope indicates there is an age-independent critical cerebral blood flow threshold at which syncope occurs.
Description: This article is available from the specified link - Copyright @ 2009 The Physiological Society
ISSN: 0022-3751
Appears in Collections:Sport
Community Health and Public Health
Dept of Life Sciences Research Papers

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