Weight-Lifters' Blackout

Compton, David M.; Hill, Paul; Sinclair, John

doi:10.1016/s0140-6736(73)90974-4

Cited by 48 publications

(50 citation statements)

References 9 publications

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“…This apparent selective control mechanism may lead to unusually low cerebral perfusion during the diastolic phase of velocity. Although these alterations had no apparent effect on our subjects, these findings may prove important in understanding the decreases in cerebral perfusion that occur during recovery from dynamic exercise and especially from resistance exercise where grayouts or blackouts develop (4,9).…”

Section: Discussionmentioning

confidence: 71%

“…Together with the present data, these findings indicate that as PP increases and the pulse interval decreases with an increase in workload, dynamic CA becomes less able to regulate transient decreases in cerebral blood flow. These findings may prove important in understanding the decreases in cerebral perfusion that occur during the recovery from dynamic exercise and especially from resistance exercise where grayouts or blackouts develop (4,9).…”

Section: Discussionmentioning

confidence: 91%

See 1 more Smart Citation

Middle cerebral artery flow velocity and pulse pressure during dynamic exercise in humans

Ogoh

Fadel

Zhang³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

107

120

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Middle cerebral artery flow velocity and pulse pressure during dynamic exercise in humans. Am J Physiol Heart Circ Physiol 288: H1526 -H1531, 2005. First published December 9, 2004; doi:10.1152/ajpheart. 00979.2004.-Exercise challenges cerebral autoregulation (CA) by a large increase in pulse pressure (PP) that may make systolic pressure exceed what is normally considered the upper range of CA. This study examined the relationship between systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) and systolic (V s), diastolic (Vd). and mean (Vm) middle cerebral artery (MCA) blood flow velocity during mild, moderate, and heavy cycling exercise. Dynamic CA and steady-state changes in MCA V in relation to changes in arterial pressure were evaluated using transfer function analysis. PP increased by 37% and 57% during moderate and heavy exercise, respectively (P Ͻ 0.05), and the pulsatility of MCA V increased markedly. Thus exercise increased MCA V m and Vs (P Ͻ 0.05) but tended to decrease MCA V d (P ϭ 0.06). However, the normalized low-frequency transfer function gain between MAP and MCA V m and between SBP and MCA Vs remained unchanged from rest to exercise, whereas that between DBP and MCA V d increased from rest to heavy exercise (P Ͻ 0.05). These findings suggest that during exercise, CA is challenged by a rapid decrease rather than by a rapid increase in blood pressure. However, dynamic CA remains able to modulate blood flow around the exercise-induced increase in MCA V m, even during high-intensity exercise. cerebral circulation; diastolic velocity; systolic velocity CEREBRAL AUTOREGULATION (CA) maintains steady-state cerebral blood flow relatively stable over a range of perfusion pressures from 60 to 150 mmHg (21), but it takes ϳ3 s for CA to be established (1), explaining why the velocity (V) in basal cerebral arteries fluctuates in parallel with blood pressure throughout the cardiac cycle. Thus exercise presents a challenge to CA by the rapid and large increases in pulse pressure (PP). This is exemplified during rowing where the rapid fluctuations in blood pressure associated with each stroke result in similar fluctuations in middle cerebral artery (MCA) mean blood flow velocity (V m ) (17). Equally, during rhythmic resistance exercise fluctuations in arterial pressure with each muscle contraction are too rapid to be countered by CA (9). Despite such large changes in the MCA V waveforms with exercise, the averaged MCA V m remains unchanged (9), slightly decreased (7), or increased when exercise does not cause large fluctuations in blood pressure (3,16,17). However, the MCA V m may not fully reflect the dynamic control of CA (15,24,26,27), and this may be relevant especially when PP increases systolic pressure beyond the CA range.Dynamic CA is frequency dependent (10,15,24,26,27), and frequency-domain analyses of CA allows for evaluation of the influence of exercise-induced changes in arterial blood pressure on MCA V. Brys et al. (3) used frequency-domain analysis to ev...

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Section: Discussionmentioning

confidence: 71%

Section: Discussionmentioning

confidence: 91%

Middle cerebral artery flow velocity and pulse pressure during dynamic exercise in humans

Ogoh

Fadel

Zhang³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

107

120

View full text Add to dashboard Cite

show abstract

“…The stiffness of the lumbar spine is increased by high intra-abdominal pressures (129) and respiratory muscle effort (252), and both athletes and workers sometimes perform Valsalva maneuvers while lifting heavy objects. However, lifting very heavy weights, if done with a Valsalva maneuver, results in high intrathoracic pressure and striking arterial hypertension, followed at times by hypotension and syncope after release of the weight and opening the glottis (52,256). The increase in blood pressure is much reduced if the lifting is accompanied by a slow exhalation rather than glottic closure (199), and this approach is widely recommended.…”

Section: Influence Of Breathing On Postural Controlmentioning

confidence: 99%

Coordination of Breathing with Nonrespiratory Activities

Bartlett¹,

Leiter²

2012

Comprehensive Physiology

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Many articles in this section of Comprehensive Physiology are concerned with the development and function of a central pattern generator (CPG) for the control of breathing in vertebrate animals. The action of the respiratory CPG is extensively modified by cortical and other descending influences as well as by feedback from peripheral sensory systems. The central nervous system also incorporates other CPGs, which orchestrate a wide variety of discrete and repetitive, voluntary and involuntary movements. The coordination of breathing with these other activities requires interaction and coordination between the respiratory CPG and those governing the nonrespiratory activities. Most of these interactions are complex and poorly understood. They seem to involve both conventional synaptic crosstalk between groups of neurons and fluid identity of neurons as belonging to one CPG or another: neurons that normally participate in breathing may be temporarily borrowed or hijacked by a competing or interrupting activity. This review explores the control of breathing as it is influenced by many activities that are generally considered to be nonrespiratory. The mechanistic detail varies greatly among topics, reflecting the wide variety of pertinent experiments.

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“…Certain weight lifting maneuvers have been known to trigger syncope [14].While executing a "clean-and-jerk" lift (which includes rising from a squatted position) some individuals perform Valsalva-like straining that increases intra-thoracic pressure. This is sometimes confounded by deliberate hyperventilation prior to the effort, and the combination can reduce cerebral blood flow, leading to syncope.…”

Section: Special Circumstancesmentioning

confidence: 99%

Exercise related syncope, when it?s not the heart

et al. 2004

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Syncope or pre-syncope in association with physical exercise may be the first indication of a dangerous underlying cardiovascular condition. Thus, the diagnostic workup of patients presenting with exercise-related syncope must include assessment of the risk for acute cardiac death. When potentially lethal conditions have been ruled out, several hypotensive syndromes that are associated with exercise should be considered. This review aims to give a concise overview of several forms of exercise- related functional hypotensive syndromes causing syncope, including the physiology of post-exercise hypotension. The focus is on underlying mechanisms, clinical considerations, and outlining treatment strategies for these syndromes.

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Weight-Lifters' Blackout

Cited by 48 publications

References 9 publications

Middle cerebral artery flow velocity and pulse pressure during dynamic exercise in humans

Middle cerebral artery flow velocity and pulse pressure during dynamic exercise in humans

Coordination of Breathing with Nonrespiratory Activities

Exercise related syncope, when it?s not the heart

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