Autonomic mediation of the pressor responses to isometric exercise in humans

1988 ◽  
Vol 64 (5) ◽  
pp. 2190-2196 ◽  
Author(s):  
D. R. Seals ◽  
P. B. Chase ◽  
J. A. Taylor
Keyword(s):  
Sympathetic Nerve Activity ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Nerve Activity ◽  
Pressor Responses ◽  
Isometric Handgrip Exercise ◽  
The Right ◽  
Exercise In Humans

The purpose of this study was to determine the respective contributions of tachycardia and increases in sympathetic nerve activity (SNA) in mediating the pressor responses to fatiguing vs. nonfatiguing levels of isometric handgrip exercise (IHE) in humans. We performed direct (microneurographic) measurements of muscle SNA from the right peroneal nerve in the leg and recorded arterial pressure (AP) and heart rate (HR) in eight healthy subjects before (control), during, and after 2.5 min of IHE at 15, 25, or 35% of maximal voluntary contraction (MVC). At 15% MVC, AP increased during the initial 1.5 min of IHE (7 mmHg, P less than 0.05) and remained at this level; at 25 and 35% MVC, AP increased throughout IHE (22 and 34 mmHg vs. control, respectively, P less than 0.05). HR increased during the initial 1.5 min of IHE at all three levels (5, 12, and 19 beats/min, respectively, P less than 0.05) but did not increase further over the last minute. At 15% MVC, muscle SNA did not increase above control; during 25 and 35% MVC, muscle SNA did not increase during the 1st min of IHE but increased progressively thereafter (109 and 205% vs. control, respectively, P less than 0.05). The magnitudes of the average increases in AP and muscle SNA over the last minute of IHE were directly related (r = 0.99, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Platelet ADP-Hypersensitivity by Aging and Isometric Exercise in Diabetics and its Prevention by EG-626

1977 ◽  
Author(s):  
T. Sano ◽  
T. Motomiya ◽  
Y. Itoh ◽  
N. Mashimo ◽  
H. Yamazaki ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Camp Phosphodiesterase ◽  
Minimum Effective Concentration ◽  
Isometric Handgrip Exercise ◽  
Thrombotic Tendency

The important role of platelet aggregation in the pathophysiology of diabetic vascular disease has been emphasized. The authors devised a new method to assess platelet sensitivity to aggregation performed without centrifugation (Sano et al. Thrombos. Haemostasis April '77 issue, in press). Using this technique, platelet aggregability in diabetics was assessed concerning to age and to. the effect of isometric exercise. The effect of EG-626, a potent cAMP phosphodiesterase inhibiting and thromboxane A2-antagonistic substance, administered prior to exercise was also observed.In 52 diabetics without macroangiopathy, platelet sensitivity to ADP-aggregation was assessed. The sensitivity was expressed by ‘n’ of the minimum effective concentration of serially two-fold diluted ADP, 2-n mg/ml, to give aggregation. In males, both diabetics and healthy, the sensitivity correlated significantly with age. The regression lines obtained were Y=2.15+0,13X (Y: sensitivity, X:age in years) in the diabetics and Y=6.58+0.04X in the healthy subjects respectively. The value of the slope was significantly higher in the diabetics comparing to the healthy subjects. An enhancement of the platelet sensitivity was disclosed significantly in the diabetics but not in the healthy subjects, after isometric handgrip exercise at 50% maximal voluntary contraction for 2 minutes.. This enhancement was prevented when the patients were treated orally with 300 mg of EG-626, 1.5 hours before exercise. These findings would suggest the thrombotic tendency in diabetics and anti-thrombotic effect of this compound.

Cardiopulmonary baroreflexes do not modulate exercise-induced sympathoexcitation

1988 ◽  
Vol 64 (5) ◽  
pp. 2197-2203 ◽  
Author(s):  
D. R. Seals
Keyword(s):  
Lower Body Negative Pressure ◽  
Voluntary Contraction ◽  
Voluntary Exercise ◽  
Sympathetic Outflow ◽  
Isometric Handgrip ◽  
General Hypothesis ◽  
Isometric Handgrip Exercise ◽  
Exercise Induced ◽  
The Right ◽  
Exercise In Humans

The purpose of this study was to test the general hypothesis that sympathoinhibitory cardiopulmonary baroreflexes modulate sympathetic outflow during voluntary exercise in humans. Direct (microneurographic) measurements of postganglionic sympathetic nerve activity to noncontracting muscle (MSNA) were made from the right peroneal nerve in the leg, and arterial pressure (AP) and heart rate (HR) were recorded in 10 healthy subjects before (control) and for 2.5 min during each of five interventions: 1) lower-body negative pressure at -10 mmHg (LBNP) alone, 2 and 3) isometric handgrip exercise at 15 and 30% of maximal voluntary contraction (MVC) alone, and 4 and 5) handgrip at 15 and 30% MVC performed during LBNP. During LBNP alone, which should have reduced cardiopulmonary baroreflex sympathoinhibition, AP and HR did not change from control, but MSNA increased 93 +/- 24% (P less than 0.05). Handgrip elicited contraction intensity-dependent increases in AP and HR (P less than 0.05), but MSNA increased above control only at the 30% MVC level (165 +/- 30%, P less than 0.05). The HR, AP, and MSNA responses to either level of handgrip performed during LBNP were not different from the algebraic sums of the corresponding responses to handgrip and LBNP performed separately (P greater than 0.05). Since there was no facilitation of the MSNA response to handgrip when performed during LBNP compared with algebraic sums of the separate responses, our results do not support the hypothesis that cardiopulmonary baroreflexes modulate (inhibit) sympathetic outflow during exercise in humans.

Cardiopulmonary reflexes do not modulate exercise pressor reflexes during isometric exercise in humans

1993 ◽  
Vol 74 (5) ◽  
pp. 2559-2565 ◽  
Author(s):  
J. A. Arrowood ◽  
P. K. Mohanty ◽  
C. McNamara ◽  
M. D. Thames
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Lower Body Negative Pressure ◽  
Isometric Exercise ◽  
Lower Body ◽  
Isometric Handgrip ◽  
Nerve Activity ◽  
Pressor Reflexes ◽  
The Relationship ◽  
Exercise In Humans

Previous studies that measured reflex vasoconstrictor responses during isometric exercise have suggested that these responses were modulated by arterial and cardiopulmonary baroreflexes. The purpose of these experiments was to determine forearm vasoconstrictor responses to isometric handgrip alone and during two levels of cardiopulmonary baroreceptor unloading with lower body negative pressure (-5 and -10 mmHg LBNP). Handgrip combined with -5 mmHg LBNP produced vasoconstrictor responses that were significantly greater than the algebraic sum of the separate responses to handgrip and LBNP alone, thus confirming earlier studies. However, with -10 mmHg LBNP, the vasoconstrictor responses to LBNP plus handgrip were not different from the algebraic sum of the separate response to LBNP and handgrip alone. These results indicate that when the influence of cardiac baroreceptors was reduced to a greater degree (-10 mmHg LBNP) than in previous studies, no interaction was observed, whereas with less reduction (-5 mmHg LBNP) an apparent interaction was noted. These data, together with recent studies in which sympathetic nerve activity to the lower leg was measured during similar protocols, suggest nonlinearities in the relationship between sympathetic nerve activity and vasoconstrictor responses.

scholarly journals Isometric Handgrip Exercise Training Improves Spirometric Parameters and Pulmonary Capacity

2021 ◽  
Vol 28 (3) ◽  
pp. 328-338
Author(s):  
Ogbutor Udoji Godsday ◽  
Nwangwa Eze Kingsley ◽  
Nwogueze Bartholomew Chukwuebuka ◽  
Chukwuemeka Ephraim ◽  
Ezunu Emmanuel ◽  
...  
Keyword(s):  
Pulmonary Function ◽  
Isometric Exercise ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Post Exercise ◽  
Significant Difference ◽  
Isometric Handgrip Exercise ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

Decline in normal physiological pulmonary function has been attributed to premorbid conditions such as prehypertension. Research evidence suggests that physical activity reduces age-related decline in pulmonary function and improves the efficiency of the lungs in prehypertensive patients. However, there is a scarcity of data evidence relating to isometric exercise and pulmonary function. Furthermore, the interrelationship between the intensity and duration of isometric exercise and pulmonary function in these patients is still uncertain. Therefore, this study was undertaken to investigate the effect of isometric handgrip exercise on pulmonary function capacity in adults with prehypertension. To determine the effectiveness of isometric handgrip exercise on pulmonary function capacity in adults with prehypertension. A quasi experiment using a pre- and post-exercise method was carried out in two out-patients hospital settings. The sample comprised 192 sedentary pre-hypertensive subjects, aged between 30–50 years, that were randomly distributed into three groups of 64 participants each. The subjects performed, for 24 consecutive days, an isometric handgrip exercise at 30% Maximum Voluntary Contraction (M.V.C.). At the end of the 24 days, group one (GP1) discontinued, while group two (GP2) continued the exercise protocol for another 24 consecutive days and group three (GP3) continued with the exercise protocol for another 24 consecutive days but at 50% M.V.C. Determinants of lung function (outcomes) were Forced Expiratory Volume in 1 s (FEV1), Forced Vital Capacity (FVC), FEV1/FVC Ratio and Peak Expiratory Flow Rate (PEFR). The study shows that there was no statistically significant difference in the pre- and post-exercise outcomes for FEV1, FVC, FEV1/FVC Ratio and PEFR after 24 days for group 1. In group 2, there was a statistically significant difference in the FVC [(mean = 0.12 ± 0.12), (p = 0.002)], FEV1 [(mean = 0.15 ± 0.17), (p = 0.003)] and PEF [(mean = 0.85 ± 0.35), (p = 0.001)] after 48 days. In group 3, there was a statistically significant difference (p = 0.001) in all the outcomes assessed after 48 days. There was a between groups difference in favour of group 2 compared with group 1 for outcomes of FEV1 [(mean = 0.142 ± 0.68), (p = 0.005)] and PEF [(mean = 0.83 ± 0.19), (p = 0.0031)]. There was statistically significant difference in favour of group 3 compared to group 2, by increasing the exercise intensity from 30% to 50% M.V.C., for outcomes of FVC [mean change = 0.10 ± 0.052), (p = 0.005)], FEV1/FVC [mean change = 3.18 ± 0.75), (p = 0.017)] and PEF [(mean change = 0.86 ± 0.35), (p = 0.001)] after 48 days. Isometric handgrip exercise (after 48 days at 30% to 50% M.V.C.) improves outcomes of pulmonary function capacity in adults with prehypertension. Meanwhile, duration and/or increase in intensity of the isometric effort significantly contributed to the affects attained.

Modulation of sympathetic nerve activity during posthandgrip muscle ischemia in humans

1994 ◽  
Vol 266 (1) ◽  
pp. H79-H83 ◽  
Author(s):  
C. A. Ray ◽  
N. H. Secher ◽  
A. L. Mark
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Sensory Nerve ◽  
Vascular Occlusion ◽  
Voluntary Contraction ◽  
Central Command ◽  
Isometric Handgrip ◽  
Nerve Activity ◽  
Muscle Ischemia

To evaluate modulation of muscle sympathetic nerve activity (MSNA) during posthandgrip muscle ischemia (PHGMI), subjects performed 2 min of isometric handgrip at 33% of maximal voluntary contraction (MVC) followed by 2 min of PHGMI produced by forearm vascular occlusion. The response to PHGMI was studied in the absence and again during the addition of contralateral rhythmic handgrip (RHG; 40 times/min) at 15% (n = 6) and 30% (n = 10) MVC during the second minute of the PHGMI. Additionally, to isolate the effect of central command, response to PHGMI was studied during attempted RHG after sensory nerve blockade (n = 5). RHG for 2 min at 15 and 30% MVC and attempted RHG for 2 min did not increase MSNA. Isometric handgrip elicited an 130 +/- 48% increase in MSNA (P < 0.05), which was maintained during PHGMI. RHG at 15 and 30% MVC elicited an attenuation of MSNA (-10 +/- 7% and -14 +/- 6%, respectively) when performed during the second minute of PHGMI (P < 0.05). In contrast, attempted RHG did not significantly affect MSNA during PHGMI. The findings demonstrate modulation of MSNA during activation of the muscle metaboreflex. The attenuation of metaboreceptor-mediated increases in MSNA appear to be the result of mechanosensitive muscle afferents and not central command.

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.

Sex differences in forebrain and cardiovagal responses at the onset of isometric handgrip exercise: a retrospective fMRI study

2007 ◽  
Vol 103 (4) ◽  
pp. 1402-1411 ◽  
Author(s):  
Savio W. Wong ◽  
Derek S. Kimmerly ◽  
Nicholas Massé ◽  
Ravi S. Menon ◽  
David F. Cechetto ◽  
...  
Keyword(s):  
Sex Differences ◽  
Maximal Voluntary Contraction ◽  
Cardiovascular Response ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Anterior Cingulate ◽  
Exercise Heart Rate ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Ventral Medial Prefrontal Cortex

In general, cardiac regulation is dominated by the sympathetic and parasympathetic nervous systems in men and women, respectively. Our recent study had revealed sex differences in the forebrain network associated with sympathoexcitatory response to baroreceptor unloading. The present study further examined the sex differences in forebrain modulation of cardiovagal response at the onset of isometric exercise. Forebrain activity in healthy men ( n = 8) and women ( n = 9) was measured using functional magnetic resonance imaging during 5 and 35% maximal voluntary contraction handgrip exercise. Heart rate (HR), mean arterial pressure (MAP), and muscle sympathetic nerve activity (MSNA) were collected in a separate recording session. During the exercise, HR and MAP increased progressively, while MSNA was suppressed ( P < 0.05). Relative to men, women demonstrated smaller HR (8 ± 2 vs. 18 ± 3 beats/min) and MAP (3 ± 2 vs. 11 ± 2 mmHg) responses to the 35% maximal voluntary contraction trials ( P < 0.05). Although a similar forebrain network was activated in both groups, the smaller cardiovascular response in women was reflected in a weaker insular cortex activation. Nevertheless, men did not show a stronger deactivation at the ventral medial prefrontal cortex, which has been associated with modulating cardiovagal activity. In contrast, the smaller cardiovascular response in women related to their stronger suppression of the dorsal anterior cingulate cortex activity, which has been associated with sympathetic control of the heart. Our findings revealed sex differences in both the physiological and forebrain responses to isometric exercise.

scholarly journals The Role of Central Command in the Increase in Muscle Sympathetic Nerve Activity to Contracting Muscle During High Intensity Isometric Exercise

2021 ◽  
Vol 15 ◽  
Author(s):  
Daniel Boulton ◽  
Chloe E. Taylor ◽  
Simon Green ◽  
Vaughan G. Macefield
Keyword(s):  
Sympathetic Nerve ◽  
High Intensity ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Isometric Exercise ◽  
Dependent Manner ◽  
Nerve Activity ◽  
Contracting Muscle ◽  
Tungsten Microelectrode ◽  
The Right

We previously demonstrated that muscle sympathetic nerve activity (MSNA) increases to contracting muscle as well as to non-contracting muscle, but this was only assessed during isometric exercise at ∼10% of maximum voluntary contraction (MVC). Given that high-intensity isometric contractions will release more metabolites, we tested the hypothesis that the metaboreflex is expressed in the contracting muscle during high-intensity but not low-intensity exercise. MSNA was recorded continuously via a tungsten microelectrode inserted percutaneously into the right common peroneal nerve in 12 participants, performing isometric dorsiflexion of the right ankle at 10, 20, 30, 40, and 50% MVC for 2 min. Contractions were immediately followed by 6 min of post-exercise ischemia (PEI); 6 min of recovery separated contractions. Cross-correlation analysis was performed between the negative-going sympathetic spikes of the raw neurogram and the ECG. MSNA increased as contraction intensity increased, reaching mean values (± SD) of 207 ± 210 spikes/min at 10% MVC (P = 0.04), 270 ± 189 spikes/min at 20% MVC (P &lt; 0.01), 538 ± 329 spikes/min at 30% MVC (P &lt; 0.01), 816 ± 551 spikes/min at 40% MVC (P &lt; 0.01), and 1,097 ± 782 spikes/min at 50% MVC (P &lt; 0.01). Mean arterial pressure also increased in an intensity-dependent manner from 76 ± 3 mmHg at rest to 90 ± 6 mmHg (P &lt; 0.01) during contractions of 50% MVC. At all contraction intensities, blood pressure remained elevated during PEI, but MSNA returned to pre-contraction levels, indicating that the metaboreflex does not contribute to the increase in MSNA to contracting muscle even at these high contraction intensities.

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