title: The prevalence and significance of post-exercise (postural) hypotension in ultramarathon runners.
abstract: A consistent finding in exercise-associated collapse is a marked postural fall in the systolic blood pressure associated with a tachycardia. The prevalence and significance of these post-exercise (postural) changes in blood pressure among noncollapsed ultradistance athletes has not been well documented. The aim of this study was to compare pre- and post-race changes in systolic and diastolic blood pressures with changes in body weight and plasma volume and with symptoms of post-exercise hypotension, including the effects of posture, among a group of 31 runners competing in an 80-km footrace. During the race, runners developed a mean (+/- SD) weight loss of 3.5 (+/- 1.2) kg and plasma volume change of 12.8% (+/- 9.1). Asymptomatic postural hypotension defined as a fall in systolic blood pressure of greater than 20 mm Hg from the supine to the erect position without syncopal symptoms was present in two runners (7%) before the race and in 21 runners (68%) afterward. The degree of postural variation in systolic blood pressure was unrelated to changes in body weight or a fall in plasma volume. We conclude that (i) all runners were dehydrated by the race activity with a range of 1% to 7% and an average of 4.6%; (ii) asymptomatic post-exercise (postural) hypotension developed in the majority (68%) of ultramarathon runners in this study; (iii) the post-exercise hypotension is likely of multifactorial origin and is not entirely related to whole body dehydration or a reduction in plasma volume; and (iv) despite marked levels of dehydration among our sample of runners, their cardiovascular status in the supine position was not greatly compromised.
authors.affiliation: Department of Physiology, University of Cape Town, Observatory, South Africa.
authors.forename: L M
authors.initials: LM
authors.lastname: Holtzhausen
authors.forename: T D
authors.initials: TD
authors.lastname: Noakes
mesh_terms: D000328:Adult; D001774:Blood Chemical Analysis; D001794:Blood Pressure; D001835:Body Weight; D003681:Dehydration / Q000209:etiology; D006321:Heart / Q000502:physiology; D006339:Heart Rate; D006801:Humans; D007024:Hypotension, Orthostatic / Q000209:etiology*; D010953:Plasma Volume; D011187:Posture; D015995:Prevalence; D012420:Running / Q000502:physiology*; D016683:Supine Position; D013575:Syncope; D013610:Tachycardia / Q000209:etiology; D015431:Weight Loss