Cardiovascular responses to an orthostatic challenge and electrical-stimulation-induced leg muscle contractions in individuals with paraplegia

Raymond, Jacqui; Davis, Glen M.; Bryant, Grace; Clarke, Jill

doi:10.1007/s004210050583

Cited by 27 publications

(28 citation statements)

References 23 publications

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“…Electrically stimulated leg muscle contractions increased peripheral resistance, heart rate and cardiac output, and blunted the fall in stroke volume that normally occurs during orthostasis. [49][50][51] However, perhaps most importantly, these induced contractions prevented or reduced the orthostatic hypotension normally seen in these SCI patients. Thus, it seems possible that the orthostatic hypotension associated with SCI is due, in part, to the failure to activate skeletal muscle pumps in paralysed dependant limbs during postural challenge.…”

Section: Lack Of Skeletal Muscle Pumping Activitymentioning

confidence: 95%

“…One reason for this may be the fact that although resting supine sympathetic activity (and thus blood pressure) tends to be low after SCI, some studies do report an appropriate increase in peripheral resistance when upright in SCI individuals, despite presumed disruption of the sympathetic control. [49][50][51] It is likely that some other mechanism is responsible for the increased peripheral resistance following orthostasis in SCI individuals. This could be related to production of catecholamines by the adrenal medulla, 50 although recent evidence suggests that this is unlikely (see below), a large and rapid release of vasopressin upon postural change to levels sufficient to exert a pressor effect, 52 spinal reflexes and veno-arteriolar reflexes 6 or peripheral a-adrenoceptor hyper-responsiveness.…”

Section: Mechanisms Underlying Orthostatic Hypotension In Scimentioning

confidence: 99%

“…Sympathetic nervous system dysfunction 6,28 Altered baroreceptor sensitivity 62,64 Lack of skeletal muscle pumps [49][50][51] Cardiovascular deconditioning 69 Altered salt and water balance 74 The level and severity of spinal cord injury, and the extent to which other systems are affected will play a significant role in the development of orthostatic hypotension of cervical SCI individuals in whom catecholamine levels failed to increase following head-upright tilting. 53,54 These data suggest that there is severe impairment of descending tonic cardiovascular control to the spinal autonomic circuits in individuals with cervical SCI, such that there is insufficient sympathetic outflow to release noradrenaline, and consequently impaired vascoconstriction.…”

Section: Predisposing Factorsmentioning

confidence: 99%

“…50 The lack of skeletal muscle contractions during postural challenge has been demonstrated to have a powerful effect upon orthostatic changes in blood pressure in a number of studies. [49][50][51] These investigators performed electrically stimulated leg muscle contractions in paraplegic and tetraplegic volunteers, simulating the skeletal muscle pumping effect normally present in able-bodied persons during standing. Electrically stimulated leg muscle contractions increased peripheral resistance, heart rate and cardiac output, and blunted the fall in stroke volume that normally occurs during orthostasis.…”

Section: Lack Of Skeletal Muscle Pumping Activitymentioning

confidence: 99%

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Orthostatic hypotension following spinal cord injury: understanding clinical pathophysiology

2005

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Motor and sensory deficits are well-known consequences of spinal cord injury (SCI). During the last decade, a significant number of experimental and clinical studies have focused on the investigation of autonomic dysfunction and cardiovascular control following SCI. Numerous clinical reports have suggested that unstable blood pressure control in individuals with SCI could be responsible for their increased cardiovascular mortality. The aim of this review is to outline the incidence and pathophysiological mechanisms underlying the orthostatic hypotension that commonly occurs following SCI. We describe the clinical abnormalities of blood pressure control following SCI, with particular emphasis upon orthostatic hypotension. Possible mechanisms underlying orthostatic hypotension in SCI, such as changes in sympathetic activity, altered baroreflex function, the lack of skeletal muscle pumping activity, cardiovascular deconditioning and altered salt and water balance will be discussed. Possible alterations in cerebral autoregulation following SCI, and the impact of these changes upon cerebral perfusion are also examined. Finally, the management of orthostatic hypotension will be considered.

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Section: Lack Of Skeletal Muscle Pumping Activitymentioning

confidence: 95%

Section: Mechanisms Underlying Orthostatic Hypotension In Scimentioning

confidence: 99%

Section: Predisposing Factorsmentioning

confidence: 99%

Section: Lack Of Skeletal Muscle Pumping Activitymentioning

confidence: 99%

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Orthostatic hypotension following spinal cord injury: understanding clinical pathophysiology

2005

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“…5 In the upright position, venous blood accumulates in the lower extremities, such as legs and thoraco-abdominal vascular beds. SCI patients with their reduced skeletal muscle pump due to muscle paralysis/paresis are more predisposed to 'circulatory hypokinesis' during upright postures.…”

Section: Introductionmentioning

confidence: 99%

Electrical stimulation-evoked contractions blunt orthostatic hypotension in sub-acute spinal cord-injured individuals: two clinical case studies

et al. 2014

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Study design: Prospective study of two cases. Objectives: To describe the effects of electrical stimulation (ES) therapy in the 4-week management of two sub-acute spinal cordinjured (SCI) individuals (C7 American Spinal Injury Association Impairment Scale (AIS) B and T9 AIS (B)). Setting: University Malaya Medical Centre, Kuala Lumpur, Malaysia. Methods: A diagnostic tilt-table test was conducted to confirm the presence of orthostatic hypotension (OH) based on the current clinical definitions. Following initial assessment, subjects underwent 4 weeks of ES therapy 4 times weekly for 1 h per day. Post-tests tilt table challenge, both with and without ES on their rectus abdominis, quadriceps, hamstrings and gastrocnemius muscles, was conducted at the end of the study (week 5). Subjects' blood pressures (BP) and heart rates (HR) were recorded every minute during pretest and post-tests. Orthostatic symptoms, as well as the maximum tolerance time that the subjects could withstand head up tilt at 60°, were recorded.

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The effect of previous weight training and concurrent weight training on endurance for functional electrical stimulation cycle ergometry

Petrofsky

Laymon

2004

European Journal of Applied Physiology

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Forty-five paraplegic subjects participated in three series of experiments to examine the interrelationships between previous weight training, concurrent weight training and muscle strength and endurance during cycle ergometry elicited by functional electrical stimulation (FES). When subjects only underwent isokinetic weight training (series 1) three times per week on the quadriceps, hamstring and gluteus maximus groups for 12 weeks, strength increased linearly with time for all three muscle groups from an initial average of 17 N to 269 N at the end of training, a 15-fold increase. In the second series of experiments, different groups of subjects either underwent no strength training prior to cycle ergometry or underwent strength training of these same three muscle groups for 2 weeks, four weeks, or 6 weeks prior to cycle ergometry. Any strength training was effective in increasing endurance for cycle ergometry. However, the rate of increase in endurance during cycle ergometry with no prior strength training was only 5 min per week, whereas the rate of increase in cycle endurance during ergometry was 14.6, 25.0, and 33.3 min per week increase in endurance after strength training for 2.4 and 6 weeks, respectively. When weight training was accomplished during FES cycle ergometry (concurrently) in a third series of experiments, there was an additional increase in endurance during cycling if strength training was concurrently accomplished. With no weight training, endurance increased 23 min per week, whereas with concurrent weight training at three times per week, endurance increased during cycling by 41.6 min per week. The results of these experiments seem to show a clear advantage of weight training concurrently and before FES cycle ergometry. Results are given as mean (SD).

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Cardiovascular responses to an orthostatic challenge and electrical-stimulation-induced leg muscle contractions in individuals with paraplegia

Cited by 27 publications

References 23 publications

Orthostatic hypotension following spinal cord injury: understanding clinical pathophysiology

Orthostatic hypotension following spinal cord injury: understanding clinical pathophysiology

Electrical stimulation-evoked contractions blunt orthostatic hypotension in sub-acute spinal cord-injured individuals: two clinical case studies

The effect of previous weight training and concurrent weight training on endurance for functional electrical stimulation cycle ergometry

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