Lack of Effect of Isometric Handgrip Exercise on the Responses of the Carotid Sinus Baroreceptor Reflex in Man

1978 ◽  
Vol 55 (2) ◽  
pp. 189-194 ◽  
Author(s):  
J. Ludbrook ◽  
I. B. Faris ◽  
J. Iannos ◽  
G. G. Jamieson ◽  
W. J. Russell
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Carotid Sinus ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Baroreceptor Reflex ◽  
Transmural Pressure ◽  
Variable Pressure ◽  
Isometric Handgrip ◽  
Arterial Blood

1. The change in arterial pressure and heart rate resulting from alteration of carotid sinus transmural pressure by a median −34 mmHg and +33 mmHg by means of a variable-pressure neck chamber was tested in seven male volunteer subjects, at rest and during exertion of 35, 45 and 65% of maximum voluntary handgrip. 2. During 60 s of 35 and 45%, and during 30 s of 65%, of maximal voluntary handgrip there was virtually no alteration of the response of blood pressure to alteration in carotid sinus transmural pressure. 3. The bradycardic response to increase in carotid sinus transmural pressure was reduced at various times after the commencement of handgrip at 45 and 65% of maximum voluntary contraction. 4. It is concluded that a reduction in arterial baroreceptor reflex sensitivity does not play an important role in the initiation of the increase in arterial blood pressure and heart rate caused by isometric exercise. 5. The hypothesis is advanced that some of the cardiovascular changes in exercise may result from elevation of the central ‘set point’ for blood pressure.

Forearm endurance training attenuates sympathetic nerve response to isometric handgrip in normal humans

1992 ◽  
Vol 72 (3) ◽  
pp. 1039-1043 ◽  
Author(s):  
V. K. Somers ◽  
K. C. Leo ◽  
R. Shields ◽  
M. Clary ◽  
A. L. Mark
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Endurance Training ◽  
Sympathetic Nerve ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Isometric Handgrip ◽  
Nerve Response ◽  
The Right ◽  
Muscle Chemoreflex

Recent evidence indicates that muscle ischemia and activation of the muscle chemoreflex are the principal stimuli to sympathetic nerve activity (SNA) during isometric exercise. We postulated that physical training would decrease muscle chemoreflex stimulation during isometric exercise and thereby attenuate the SNA response to exercise. We investigated the effects of 6 wk of unilateral handgrip endurance training on the responses to isometric handgrip (IHG: 33% of maximal voluntary contraction maintained for 2 min). In eight normal subjects the right arm underwent exercise training and the left arm sham training. We measured muscle SNA (peroneal nerve), heart rate, and blood pressure during IHG before vs. after endurance training (right arm) and sham training (left arm). Maximum work to fatigue (an index of training efficacy) was increased by 1,146% in the endurance-trained arm and by only 40% in the sham-trained arm. During isometric exercise of the right arm, SNA increased by 111 +/- 27% (SE) before training and by only 38 +/- 9% after training (P less than 0.05). Endurance training did not significantly affect the heart rate and blood pressure responses to IHG. We also measured the SNA response to 2 min of forearm ischemia after IHG in five subjects. Endurance training also attenuated the SNA response to postexercise forearm ischemia (P = 0.057). Sham training did not significantly affect the SNA responses to IHG or forearm ischemia. We conclude that endurance training decreases muscle chemoreflex stimulation during isometric exercise and thereby attenuates the sympathetic nerve response to IHG.

Role of sinoaortic reflexes in hemodynamic patterns of natural defense behaviors in the cat

1981 ◽  
Vol 240 (3) ◽  
pp. H421-H429 ◽  
Author(s):  
G. Baccelli ◽  
R. Albertini ◽  
A. Del Bo ◽  
G. Mancia ◽  
A. Zanchetti
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Carotid Sinus ◽  
Emotional Behavior ◽  
Natural Defense ◽  
Arterial Blood ◽  
Hemodynamic Pattern ◽  
Before And After

To evaluate whether sinoaortic afferents contribute to the hemodynamic pattern of fighting, cardiovascular changes associated with fighting were studied in cats before and after sinoaortic denervation. Sinoaortic denervation exaggerates the decrease in heart rate, cardiac output, and arterial pressure during immobile confrontation (hissing, staring but no movement). During nonsupportive fighting (fighting with forelimbs while lying on one side) and supportive fighting ( fighting while standing on four feet) sinoaortic denervation reduces the increase in heart rate and cardiac output, minimizes the mesenteric vasoconstriction, induces a fall in arterial blood pressure, but does not affect iliac vasoconstriction or vasodilatation. The hemodynamic pattern of fighting is similarly changed by temporary inactivation of carotid sinus baroreflexes by common carotid occlusion as by chronic section of sinoaortic nerves. It is concluded that sinoaortic reflexes play an important role in the cardiovascular patterns accompanying natural fighting. They favor cardiac action and allow a marked visceral vasoconstriction to occur, thus minimizing or preventing a fall in blood pressure during emotional behavior.

Effects of a Sustained Muscular Contraction on Human Intraocular Pressure

1974 ◽  
Vol 47 (3) ◽  
pp. 249-257 ◽  
Author(s):  
D. F. Marcus ◽  
H. F. Edelhauser ◽  
M. G. Maksud ◽  
R. L. Wiley
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Intraocular Pressure ◽  
Recovery Period ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Lactate Concentration ◽  
Post Exercise ◽  
Blood Samples ◽  
Hand Grip

1. Normal subjects performed fatiguing static hand-grip contraction at tensions of 20% and 55% of their maximum voluntary contraction (MVC). Intraocular pressure (IOP) was measured by applanation tonometry before, during and after the isometric exercise. Forearm blood samples were taken from the antecubital vein in both the exercised and non-exercised arm before and 2 min post-exercise for measurement of plasma lactate, osmolality, Pv,o2, Pv,co2 and pH. 2. During hand grip the heart rate and blood pressure increased significantly, whereas the IOP remained unchanged from control in both the 20% and 55% MVC experiments. 3. In the recovery period heart rate and blood pressure returned to control values within 3 min and the IOP decreased significantly from control in both the 20% and 55% MVC experiments. 4. When an occlusion cuff was inflated on the exercising arm just before release of the 55% MVC grip, the decreased IOP could be delayed until the cuff was released. 5. Post-exercise blood samples showed elevated lactate concentrations and Pv,o2 and decreased pH in the exercised arm; however, the values remained unchanged in the non-exercised arm. The decreased IOP after exercise may be related to an increased blood lactate concentration.

Baroreflex responsiveness is maintained during isometric exercise in humans

1986 ◽  
Vol 61 (2) ◽  
pp. 797-803 ◽  
Author(s):  
T. J. Ebert
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Carotid Sinus ◽  
Maximum Voluntary Contraction ◽  
Transmural Pressure ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Baroreflex Control ◽  
Baroreflex Function ◽  
Isometric Handgrip Exercise

The simultaneous rise in heart rate and arterial pressure during isometric handgrip exercise suggests that arterial baroreflex control may be altered. We applied incremental intensities of neck suction and pressure to nine healthy young men to alter carotid sinus transmural pressure. Carotid stimuli were delivered during 1) supine control, 2) “anticipation” of beginning exercise, and 3) handgrip (20% of maximum voluntary contraction). Anticipation was a quiet period, immediately preceding the beginning of handgrip, when no muscular work was being performed. Compared with control, the R-R interval prolongation and mean arterial pressure decline provoked by carotid stimuli were decreased during the anticipation period. These data suggest that influences from higher central neural locations may alter baroreflex function. Furthermore, we derived stimulus-response curves relating carotid sinus transmural pressure to changes in R-R interval and mean arterial pressure. These curves were shifted during handgrip; however, calculated regression slopes were not changed from control. The data indicate that isometric handgrip exercise has a specific influence on human carotid baroreflex control of arterial pressure and heart period: baroreflex function curves are shifted rightward during handgrip, whereas baroreflex sensitivity is unchanged. Furthermore, central neural influences may be partially involved in these alterations.

Sympathoadrenal-circulatory regulation during sustained isometric exercise in young and older men

1991 ◽  
Vol 261 (5) ◽  
pp. R1061-R1069 ◽  
Author(s):  
J. A. Taylor ◽  
G. A. Hand ◽  
D. G. Johnson ◽  
D. R. Seals
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Vascular Resistance ◽  
Isometric Exercise ◽  
Older Men ◽  
Electromyographic Activity ◽  
Isometric Handgrip ◽  
Significant Group ◽  
Arterial Blood ◽  
Older Subjects

The aim of this study was to test the hypothesis that the arterial blood pressure, vasoconstrictor, and sympathoadrenal adjustments to sustained submaximal isometric exercise become augmented with advancing age in humans. Fourteen young (26 +/- 1 yr) and 14 older (66 +/- 1 yr) healthy males performed isometric handgrip exercise at 30% of maximal voluntary force until exhaustion (inability to maintain target force). Maximal handgrip force was quite similar in the young and older subjects (402 +/- 20 vs. 392 +/- 20 N, respectively). The two groups did not differ significantly on any variable at rest. During sustained handgrip to exhaustion, peak levels of both perceived exertion and contracting forearm electromyographic activity were similar in the young and older men, suggesting equivalent voluntary efforts. Exercise time was not different in the two groups (315 +/- 27 s in young vs. 339 +/- 17 s in older men). Throughout exercise the increases in arterial blood pressure were very similar in the young and older subjects. Heart rate increased less (P less than 0.05), but stroke volume (impedance cardiography) tended to decrease less (not significant) in the older men; thus the increases in cardiac output were not different in the two groups. During the latter portion of exercise, systemic vascular resistance tended to increase in both the young and older men, with no significant group differences. The blood flow responses in the whole calf (venous occlusion plethysmography) and the calf skin (laser-Doppler velocimetry) were similar in the young and older subjects, as were the corresponding increases in vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Sympatholytic Drugs on the Cardiovascular Response to Isometric Exercise

1981 ◽  
Vol 60 (2) ◽  
pp. 139-143 ◽  
Author(s):  
S. J. Watt ◽  
R. D. Thomas ◽  
P. W. Belfield ◽  
P. W. Goldstraw ◽  
S. H. Taylor
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Healthy Subjects ◽  
Cardiovascular Response ◽  
Pressor Response ◽  
Isometric Exercise ◽  
Systemic Blood Pressure ◽  
Isometric Handgrip ◽  
Systemic Blood ◽  
Oral Doses

1. The effects of single oral doses of various sympatholytic drugs on the heart rate and blood pressure increases during isometric handgrip contraction were studied in six healthy subjects. 2. Bethanidine reduced both the systolic and diastolic increases in pressure. Clonidine reduced the systolic but not the diastolic increase. Oxprenolol alone or in combination with phentolamine or phenyoxybenzamine failed to influence the pressor response. 3. The increase in systemic blood pressure associated with sustained contraction of voluntary muscle appears to be relatively resistant to acute sympathetic adrenoreceptor blockade in man.

Effect of Exercise on Gain of the Carotid-Sinus Reflex in Rabbits

1982 ◽  
Vol 63 (2) ◽  
pp. 115-119 ◽  
Author(s):  
I. B. Faris ◽  
G. G. Jamieson ◽  
J. Ludbrook
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Vascular Resistance ◽  
Carotid Sinus ◽  
Treadmill Exercise ◽  
Baroreceptor Reflex ◽  
Average Blood Pressure ◽  
Reflex Gain ◽  
Dynamic Gain

1. Blood pressure, heart rate and cardiac output were measured in six rabbits before, during and immediately after treadmill exercise. During the same periods the dynamic gain of the carotid-sinus baroreceptor reflex was estimated by creating a sinusoidal oscillation of carotid-distending pressure. 2. The average blood pressure did not change significantly during or after exercise, but heart rate and cardiac output rose markedly and there was a concomitant fall in systemic vascular resistance. 3. The reflex gain for blood pressure decreased by one-fifth during exercise, and the gains for heart rate and vascular resistance by two-fifths. Immediately after exercise the gains for all three variables decreased further, to between one-half and one-third of the resting values. 4. Our results indicate that during and after dynamic exercise the correction of a potential disturbance of blood pressure by the carotid-sinus baroreceptor reflex is decreased in magnitude or in speed.

Influence of muscle mass on sympathetic neural activation during isometric exercise

1989 ◽  
Vol 67 (5) ◽  
pp. 1801-1806 ◽  
Author(s):  
D. R. Seals
Keyword(s):  
Heart Rate ◽  
Muscle Mass ◽  
Muscle Sympathetic Nerve Activity ◽  
Isometric Exercise ◽  
Systolic Pressure ◽  
Exercise Heart Rate ◽  
Neural Activation ◽  
Isometric Handgrip ◽  
Inhibitory Interaction ◽  
Arterial Blood

The primary purpose of this study was to determine whether the sympathetic neural activation induced by isometric exercise is influenced by the size of the contracting muscle mass. To address this, in nine healthy subjects (aged 19-27 yr) we measured heart rate, systolic arterial blood pressure, and muscle sympathetic nerve activity in the leg (MSNA; peroneal nerve) before (control) and during 2.5 min of isometric handgrip exercise (30% of maximal voluntary force). Exercise was performed with the right and left arms separately and with both arms simultaneously (random order). During exercise, heart rate, systolic pressure, and MSNA increased above control under all conditions (P less than 0.05). For each variable, the magnitudes of the increases from control to the end of exercise were significantly greater when exercise was performed with two arms compared with either arm alone (P less than 0.05). In general, the increases in heart rate, systolic pressure, and MSNA elicited during two-arm exercise were significantly less than the simple sums of the responses evoked during exercise of each arm separately. These findings indicate that the magnitude of the sympathetic neural activation evoked during isometric exercise in humans is determined in part by the size of the active muscle mass. In addition, our results suggest that the sympathetic cardiovascular adjustments elicited during exercise of separate limbs are not simply additive but instead exhibit an inhibitory interaction (i.e., neural occlusion).

Muscle metaboreflex activation speeds the recovery of arterial blood pressure following acute hypotension in humans

2013 ◽  
Vol 304 (11) ◽  
pp. H1568-H1575 ◽  
Author(s):  
Masashi Ichinose ◽  
Kazuhito Watanabe ◽  
Naoto Fujii ◽  
Narihiko Kondo ◽  
Takeshi Nishiyasu
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Maximum Voluntary Contraction ◽  
Cardiovascular Responses ◽  
Arterial Baroreflex ◽  
Isometric Handgrip ◽  
Muscle Metaboreflex ◽  
Peripheral Vasoconstriction ◽  
Arterial Blood ◽  
Acute Hypotension

It has been suggested that the arterial baroreflex and muscle metaboreflex are both activated during heavy exercise and that they interact to modulate primary cardiovascular reflex responses. This proposed interaction and its consequences are not fully understood, however. The purpose of present study was to test our hypothesis that dynamic arterial baroreflex-mediated cardiovascular responses to acute systemic hypotension in humans are augmented when the muscle metaboreflex is active and that this results in a faster recovery of arterial blood pressure. Acute hypotension was induced nonpharmacologically in 12 healthy subjects by releasing bilateral thigh cuffs after 9 min of suprasystolic resting ischemia, with and without muscle metaboreflex activation via postexercise muscle ischemia (PEMI) after 1 min of isometric handgrip exercise at 50% maximum voluntary contraction. The thigh-cuff release evoked rapid reductions in mean arterial pressure (MAP) and increases in heart rate, cardiac output (Doppler), and total vascular conductance (TVC) under control conditions and during PEMI. The reductions in MAP from baseline were greater and the increases in TVC were smaller during PEMI than control. In addition, arterial baroreflex-mediated peripheral vasoconstriction was augmented during PEMI, as evidenced by a near doubling of the rate of recovery of MAP and TVC. These results show that when the muscle metaboreflex is activated in humans, arterial baroreflex-mediated peripheral vasoconstriction elicited in response to acute hypotension is augmented, which halves the time needed for MAP recovery. Such modulation of baroreflex function would be advantageous for maintaining an elevated arterial blood pressure during activation of the muscle metaboreflex.

Baroreflex modulation of muscle sympathetic nerve activity during posthandgrip muscle ischemia in humans

2001 ◽  
Vol 91 (4) ◽  
pp. 1679-1686 ◽  
Author(s):  
Jian Cui ◽  
Thad E. Wilson ◽  
Manabu Shibasaki ◽  
Nicole A. Hodges ◽  
Craig G. Crandall
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Isometric Handgrip ◽  
Nerve Activity ◽  
Arterial Blood ◽  
Muscle Ischemia ◽  
The Relationship

To identify whether muscle metaboreceptor stimulation alters baroreflex control of muscle sympathetic nerve activity (MSNA), MSNA, beat-by-beat arterial blood pressure (Finapres), and electrocardiogram were recorded in 11 healthy subjects in the supine position. Subjects performed 2 min of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 2.5 min of posthandgrip muscle ischemia. During muscle ischemia, blood pressure was lowered and then raised by intravenous bolus infusions of sodium nitroprusside and phenylephrine HCl, respectively. The slope of the relationship between MSNA and diastolic blood pressure was more negative ( P < 0.001) during posthandgrip muscle ischemia (−201.9 ± 20.4 units · beat−1 · mmHg−1) when compared with control conditions (−142.7 ± 17.3 units · beat−1 · mmHg−1). No significant change in the slope of the relationship between heart rate and systolic blood pressure was observed. However, both curves shifted during postexercise ischemia to accommodate the elevation in blood pressure and MSNA that occurs with this condition. These data suggest that the sensitivity of baroreflex modulation of MSNA is elevated by muscle metaboreceptor stimulation, whereas the sensitivity of baroreflex of modulate heart rate is unchanged during posthandgrip muscle ischemia.

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