scholarly journals Interindividual variability in muscle sympathetic responses to static handgrip in young men: evidence for sympathetic responder types?

2018 ◽  
Vol 314 (1) ◽  
pp. R114-R121 ◽  
Author(s):  
Anthony V. Incognito ◽  
Connor J. Doherty ◽  
Jordan B. Lee ◽  
Matthew J. Burns ◽  
Philip J. Millar
Keyword(s):  
Blood Pressure ◽  
Diastolic Blood Pressure ◽  
Interindividual Variability ◽  
Muscle Sympathetic Nerve Activity ◽  
Voluntary Contraction ◽  
Response Patterns ◽  
Arterial Baroreflex ◽  
Muscle Metaboreflex ◽  
Time To Peak ◽  
Pressure Time

Negative and positive muscle sympathetic nerve activity (MSNA) responders have been observed during mental stress. We hypothesized that similar MSNA response patterns could be identified during the first minute of static handgrip and contribute to the interindividual variability throughout exercise. Supine measurements of multiunit MSNA (microneurography) and continuous blood pressure (Finometer) were recorded in 29 young healthy men during the first (HG1) and second (HG2) minute of static handgrip (30% maximal voluntary contraction) and subsequent postexercise circulatory occlusion (PECO). Responders were identified on the basis of differences from the typical error of baseline total MSNA: 7 negative, 12 positive, and 10 nonresponse patterns. Positive responders demonstrated larger total MSNA responses during HG1 ( P < 0.01) and HG2 ( P < 0.0001); however, the increases in blood pressure throughout handgrip exercise were similar between all groups, as were the changes in heart rate, stroke volume, cardiac output, total vascular conductance, and respiration (all P > 0.05). Comparing negative and positive responders, total MSNA responses were similar during PECO ( P = 0.17) but opposite from HG2 to PECO (∆40 ± 46 vs. ∆-21 ± 62%, P = 0.04). Negative responders also had a shorter time-to-peak diastolic blood pressure during HG1 (20 ± 20 vs. 44 ± 14 s, P < 0.001). Total MSNA responses during HG1 were associated with responses to PECO ( r = 0.39, P < 0.05), the change from HG2 to PECO ( r = −0.49, P < 0.01), and diastolic blood pressure time to peak ( r = 0.50, P < 0.01). Overall, MSNA response patterns during the first minute of static handgrip contribute to interindividual variability and appear to be influenced by differences in central command, muscle metaboreflex activation, and rate of loading of the arterial baroreflex.

Abstract 266: Neural Circulatory Responses to Isolated Muscle Metaboreflex Activation in Postmenopausal Women

Hypertension ◽  
2013 ◽  
Vol 62 (suppl_1) ◽  
Author(s):  
Jody L Greaney ◽  
Evan L Matthews ◽  
Paul J Fadel ◽  
William B Farquhar ◽  
Megan M Wenner
Keyword(s):  
Blood Pressure ◽  
Postmenopausal Women ◽  
Young Women ◽  
Blood Pressure Response ◽  
Muscle Sympathetic Nerve Activity ◽  
Feedback Mechanism ◽  
Voluntary Contraction ◽  
Pressure Response ◽  
Isometric Handgrip ◽  
Muscle Metaboreflex

Understanding the neural circulatory responses to exercise in postmenopausal women (PMW) is important given their greater risk for developing hypertension. During exercise, blood pressure is controlled, in part, by the exercise pressor reflex, which is a feedback mechanism originating in skeletal muscle and compromised of mechanically and metabolically sensitive afferents. A recent study reported an enhanced blood pressure response during exercise in normotensive PMW due to greater muscle metaboreflex activation, but the mechanism(s) underlying these responses are unknown. Herein, we tested the hypothesis that metaboreflex activation elicits exaggerated sympathetic nervous system responses in PMW compared to young women, contributing to the enhanced blood pressure response during exercise. Methods: Blood pressure (BP, Finometer) and muscle sympathetic nerve activity (MSNA, peroneal microneurography) were continuously measured in 7 PMW (age 59±2 years; BMI 24±1 kg/m 2 ) and 7 young women (age 23±2 years; BMI 22±2 kg/m 2 ) during 2-minutes of isometric handgrip exercise performed at 30% of maximal voluntary contraction followed by 3-minutes of forearm ischemia (post-exercise ischemia, PEI) to isolate muscle metaboreflex activation. Results: Resting mean arterial pressure (MAP) was similar between PMW (85±3 mmHg) and young women (82±2 mmHg; P>0.05). During exercise, the increase in MAP was greater in PMW (Δ18±2mmHg) compared to young women (Δ 12±2 mmHg; P<0.05), and this was maintained during PEI (Δ13±1 mmHg PMW vs. Δ 6±1 mmHg young women; P<0.05). Resting MSNA was higher in PMW (24±4 bursts/min) compared to young women (9±3 bursts/min; P<0.05). Interestingly, the increase in MSNA during exercise was comparable between groups (P>0.05), whereas during PEI, the increase in MSNA was approximately 50% greater in PMW compared to young women (Δ13±2 burst/min PMW vs. 7±2 bursts/min young women; P<0.05). Conclusions: These preliminary data suggest that compared to young women, PMW exhibit an exaggerated MSNA response to isolated muscle metaboreflex activation.

scholarly journals Transfer function characteristics of the neural and peripheral arterial baroreflex arcs at rest and during postexercise muscle ischemia in humans

2009 ◽  
Vol 296 (5) ◽  
pp. H1416-H1424 ◽  
Author(s):  
Shigehiko Ogoh ◽  
James P. Fisher ◽  
Colin N. Young ◽  
Peter B. Raven ◽  
Paul J. Fadel
Keyword(s):  
Transfer Function ◽  
Muscle Sympathetic Nerve Activity ◽  
Voluntary Contraction ◽  
Arterial Baroreflex ◽  
Isometric Handgrip ◽  
Vascular Conductance ◽  
Muscle Metaboreflex ◽  
Arterial Blood ◽  
Muscle Ischemia ◽  
Transfer Function Gain

Previous studies have demonstrated an increase in the arterial baroreflex (ABR) control of muscle sympathetic nerve activity (MSNA) during isolated activation of the muscle metaboreflex with postexercise muscle ischemia (PEMI). However, the increased ABR-MSNA control does not appear to manifest in an enhancement in the ABR control of arterial blood pressure (BP), suggesting alterations in the transduction of MSNA into a peripheral vascular response and a subsequent ABR-mediated change in BP. Thus we examined the operating gains of the neural and peripheral arcs of the ABR and their interactive relationship at rest and during muscle metaboreflex activation. In nine healthy subjects, graded isolation of the muscle metaboreflex was achieved by PEMI following isometric handgrip performed at 15% and 30% maximal voluntary contraction (MVC). To obtain the sensitivities of the ABR neural and peripheral arcs, the transfer function gain from BP to MSNA and MSNA to femoral vascular conductance, respectively, was analyzed. No changes from rest were observed in the ABR neural or peripheral arcs during PEMI after 15% MVC handgrip. However, PEMI following 30% MVC handgrip increased the low frequency (LF) transfer function gain between BP and MSNA (ABR neural arc; +58 ± 28%, P = 0.036), whereas the LF gain between MSNA and femoral vascular conductance (ABR peripheral arc) was decreased from rest (−36 ± 8%, P = 0.017). These findings suggest that during high-intensity muscle metaboreflex activation an increased ABR gain of the neural arc appears to offset an attenuation of the peripheral arc gain to help maintain the overall ABR control of systemic BP.

Forearm elevation augments sympathetic activation during handgrip exercise in humans

2002 ◽  
Vol 103 (3) ◽  
pp. 295-301 ◽  
Author(s):  
Daisaku MICHIKAMI ◽  
Atsunori KAMIYA ◽  
Qi FU ◽  
Yuki NIIMI ◽  
Satoshi IWASE ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Muscle Sympathetic Nerve Activity ◽  
Voluntary Contraction ◽  
Sympathetic Activation ◽  
Handgrip Exercise ◽  
Excitatory Effect ◽  
Muscle Metaboreflex ◽  
Forearm Exercise ◽  
Exercise In Humans

Although angina pectoris in patients with coronary heart disease often occurs when their forearms are in an elevated position for a prolonged period, and sympathetic activation is a major cause of this condition, little is known about the physiological effects of forearm elevation on sympathetic activity during forearm exercise. We hypothesized that forearm elevation augments sympathetic activation during the static handgrip exercise in humans. A total of 10 healthy male volunteers performed 2min of static handgrip exercise at 30% of maximal voluntary contraction followed by 2min of post-exercise muscle ischaemia (PEMI; specific activation of the muscle metaboreflex) with two forearm positions: the exercising forearm was elevated 50cm above the heart (forearm-elevated trial) or fixed at the level of the heart (heart-level trial). Muscle sympathetic nerve activity (MSNA), blood pressure and heart rate were monitored. MSNA increased during handgrip exercise in both forearm positions (P<0.001); the increase was 51% greater in the forearm-elevated trial (516±99 arbitrary units) than in the heart-level trial (346±44units; P<0.05). The increase in mean blood pressure was 8.4mmHg greater during exercise in the forearm-elevated trial (P<0.05), while changes in heart rate were similar in both forearm positions. The increase in MSNA during PEMI was 71% greater in the forearm-elevated trial (393±71 arbitrary units/min) than in the heart-level trial (229±29units/min; P<0.05). These results support the hypothesis that forearm elevation augments sympathetic activation during handgrip exercise. The excitatory effect of forearm elevation on exercising MSNA may be mediated primarily by increased activation of the muscle metaboreflex.

Modulation of arterial baroreflex control of muscle sympathetic nerve activity by muscle metaboreflex in humans

2004 ◽  
Vol 286 (2) ◽  
pp. H701-H707 ◽  
Author(s):  
Masashi Ichinose ◽  
Mitsuru Saito ◽  
Hiroyuki Wada ◽  
Asami Kitano ◽  
Narihiko Kondo ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Linear Relationship ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Total Activity ◽  
Arterial Baroreflex ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Muscle Metaboreflex ◽  
Burst Strength

We aimed to investigate the interaction [with respect to the regulation of muscle sympathetic nerve activity (MSNA) and blood pressure] between the arterial baroreflex and muscle metaboreflex in humans. In 10 healthy subjects who performed a 1-min sustained handgrip exercise at 50% maximal voluntary contraction followed by forearm occlusion, arterial baroreflex control of MSNA (burst incidence and strength and total activity) was evaluated by analyzing the relationship between beat-by-beat spontaneous variations in diastolic arterial blood pressure (DAP) and MSNA both during supine rest (control) and during postexercise muscle ischemia (PEMI). During PEMI (vs. control), 1) the linear relationship between burst incidence and DAP was shifted rightward with no alteration in sensitivity, 2) the linear relationship between burst strength and DAP was shifted rightward and upward with no change in sensitivity, and 3) the linear relationship between total activity and DAP was shifted to a higher blood pressure and its sensitivity was increased. The modification of the control of total activity that occurs in PEMI could be a consequence of alterations in the baroreflex control of both MSNA burst incidence and burst strength. These results suggest that the arterial baroreflex and muscle metaboreflex interact to control both the occurrence and strength of MSNA bursts.

Muscle afferent and central command contributions to the cardiovascular response to isometric exercise of postural muscle in patients with mild chronic heart failure

2001 ◽  
Vol 100 (6) ◽  
pp. 643-651 ◽  
Author(s):  
C. A. CARRINGTON ◽  
W. J. FISHER ◽  
M. K. DAVIES ◽  
M. J. WHITE
Keyword(s):  
Heart Failure ◽  
Blood Pressure ◽  
Chronic Heart Failure ◽  
Diastolic Blood Pressure ◽  
Plantar Flexion ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Triceps Surae ◽  
Control Subjects ◽  
Muscle Afferent

The roles of muscle afferent activity and central drive in controlling the compromised cardiovascular system of patients with mild chronic heart failure (CHF) during isometric exercise were examined. Blood pressure and heart rate responses were recorded in eight stable CHF patients (ejection fraction 20–40%; age 62±11 years) and in nine healthy age-matched controls during voluntary and electrically evoked isometric plantar flexion and subsequent post-exercise circulatory occlusion (PECO). During voluntary contraction, control subjects had a greater mean increase in systolic blood pressure than patients (42.4±19.2 and 23.0±10.9 mmHg respectively; P < 0.01), but this was not the case during PECO. During electrically evoked contraction, but not during PECO, the CHF group had smaller (P < 0.05) mean increases in both systolic and diastolic blood pressure than controls (13.0±5.3 compared with 25.4±14.0 mmHg and 7.6±3.0 compared with 12.9±7.2 mmHg respectively). Intra-group comparison between responses to voluntary and electrically evoked contractions revealed greater (P < 0.05) mean increases in systolic and diastolic blood pressure during the voluntary contraction in both the patients and the control subjects. These data suggest that muscle afferent drive to the pressor response from the triceps surae is low in this age group, both in control subjects and in CHF patients. Additionally, the patients may have a relatively desensitized muscle mechanoreceptor reflex.

Delayed and diminished pressor response to muscle sympathetic nerve activity in the elderly

1996 ◽  
Vol 80 (3) ◽  
pp. 869-875 ◽  
Author(s):  
Y. Sugiyama ◽  
T. Matsukawa ◽  
A. S. Shamsuzzaman ◽  
H. Okada ◽  
T. Watanabe ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Diastolic Blood Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Pressor Response ◽  
Muscle Sympathetic Nerve Activity ◽  
Pressure Rise ◽  
The Elderly ◽  
Young Group ◽  
Nerve Activity

We studied the effects of aging on alpha-receptor-mediated vasoconstrictive responses to sympathetic nerve activity in 16 healthy aged [75.8 +/- 2.7 (SE) yr] and young men (33.8 +/- 2.0 yr). Muscle sympathetic nerve activity (MSNA), heart rate, and blood pressure were analyzed during slow respiration (0.1 Hz). Peak amplitude and phase were calculated from a cosine function fitted with 0.1 Hz by using the least squares method. The latency of the pressor response to MSNA, defined as lag time from the peak of MSNA to diastolic blood pressure, was significantly longer in the aged than the young group (7.1 +/- 0.3 vs. 5.4 +/- 0.4 s; P < 0.01). The extent of pressor response to MSNA, defined as diastolic blood pressure rise in response to increase in total MSNA, was significantly lower in the aged than the young group (0.038 +/- 0.006 vs. 0.099 +/- 0.024 mmHg/unit, P < 0.001). These results suggest that alpha-receptor-mediated vasoconstrictive responses to MSNA may be attenuated in the elderly.

Sympathetic Activation due to Limb Venous Distension Is Preserved during Muscle Metaboreceptor Stimulation

2021 ◽  
Author(s):  
Jian Cui ◽  
Cheryl Blaha ◽  
Urs A. Leuenberger ◽  
Lawrence I. Sinoway
Keyword(s):  
Blood Pressure ◽  
Skeletal Muscle ◽  
Healthy Subjects ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Muscle Afferents ◽  
Sympathetic Activation ◽  
Nerve Activity ◽  
Post Exercise ◽  
Muscle Metaboreflex

Venous saline infusions in an arterially occluded forearm evokes reflex increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) in humans (venous distension reflex). It is unclear if the inputs from metabolically sensitive skeletal muscle afferents (i.e. muscle metaboreflex) would modify venous distension reflex. We hypothesized that muscle metaboreceptor stimulation might augment the venous distension reflex. BP (Finapres), heart rate (ECG), and MSNA (microneurography) were assessed in 18 young healthy subjects. In trial A, saline (5% forearm volume) was infused into the veins of an arterially occluded arm (non-handgrip trial). In trial B, subjects performed 2 min static handgrip followed by post exercise circulatory occlusion (PECO) of the arm. During PECO, saline was infused into veins of the arm (handgrip trial). In trial A, the infusion increased MSNA and BP as expected (both P < 0.001). In trial B, handgrip significantly raised MSNA, BP and venous lactic acid concentrations. Venous saline infusion during PECO further raised MSNA and BP (both P < 0.001). The changes in MSNA (D8.6 ± 1.5 to D10.6 ± 1.8 bursts/min, P = 0.258) and mean arterial pressure (P = 0.844) evoked by the infusion during PECO were not significantly different from those in the non-handgrip trial. These observations indicate that venous distension reflex responses are preserved during sympathetic activation mediated by the muscle metaboreflex.

Impact of heart failure and exercise capacity on sympathetic response to handgrip exercise

2001 ◽  
Vol 280 (3) ◽  
pp. H969-H976 ◽  
Author(s):  
Catherine F. Notarius ◽  
Deborah J. Atchison ◽  
John S. Floras
Keyword(s):  
Heart Failure ◽  
Muscle Sympathetic Nerve Activity ◽  
Normal Subjects ◽  
Peak Oxygen Uptake ◽  
Voluntary Contraction ◽  
Handgrip Exercise ◽  
Muscle Metaboreflex ◽  
Sympathetic Response ◽  
Patients With Heart Failure ◽  
Rest And Exercise

Peak oxygen uptake (V˙o 2 peak) in patients with heart failure (HF) is inversely related to muscle sympathetic nerve activity (MSNA) at rest. We hypothesized that the MSNA response to handgrip exercise is augmented in HF patients and is greatest in those with lowV˙o 2 peak. We studied 14 HF patients and 10 age-matched normal subjects during isometric [30% of maximal voluntary contraction (MVC)] and isotonic (10%, 30%, and 50% MVC) handgrip exercise that was followed by 2 min of posthandgrip ischemia (PHGI). MSNA was significantly increased during exercise in HF but not normal subjects. Both MSNA and HF levels remained significantly elevated during PHGI after 30% isometric and 50% isotonic handgrip in HF but not normal subjects. HF patients with lower V˙o 2 peak (<56% predicted; n = 8) had significantly higher MSNA during rest and exercise than patients withV˙o 2 peak > 56% predicted ( n = 6) and normal subjects. The muscle metaboreflex contributes to the greater reflex increase in MSNA during ischemic or intense nonischemic exercise in HF. This occurs at a lower threshold than normal and is a function ofV˙o 2 peak.

Effect of adenosine receptor blockade with caffeine on sympathetic response to handgrip exercise in heart failure

2001 ◽  
Vol 281 (3) ◽  
pp. H1312-H1318 ◽  
Author(s):  
C. F. Notarius ◽  
D. J. Atchison ◽  
G. A. Rongen ◽  
J. S. Floras
Keyword(s):  
Heart Failure ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Normal Subjects ◽  
Voluntary Contraction ◽  
Receptor Blockade ◽  
Handgrip Exercise ◽  
Muscle Metaboreflex ◽  
Sympathetic Response ◽  
Isotonic Exercise

Adenosine (Ado) increases muscle sympathetic nerve activity (MSNA) reflexively. Plasma Ado and MSNA are elevated in heart failure (HF). We tested the hypothesis that Ado receptor blockade by caffeine would attenuate reflex MSNA responses to handgrip (HG) and posthandgrip ischemia (PHGI) and that this action would be more prominent in HF subjects than in normal subjects. We studied 12 HF subjects and 10 age-matched normal subjects after either saline or caffeine (4 mg/kg) infusion during isometric [30% of maximal voluntary contraction (MVC)] and isotonic (10%, 30%, and 50%) HG exercise, followed by 2 min of PHGI. In normal subjects, caffeine did not block increases in MSNA during PHGI after 50% HG. In HF subjects, caffeine abolished MSNA responses to PHGI after both isometric and 50% isotonic exercise ( P < 0.05) but MSNA responses during HG were unaffected. These findings are consistent with muscle metaboreflex stimulation by endogenous Ado during ischemic or intense nonischemic HG in HF and suggest an important sympathoexcitatory role for endogenous Ado during exercise in this condition.

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.

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