Carotid baroreflex regulation of sympathetic nerve activity during dynamic exercise in humans

2001 ◽  
Vol 280 (3) ◽  
pp. H1383-H1390 ◽  
Author(s):  
P. J. Fadel ◽  
S. Ogoh ◽  
D. E. Watenpaugh ◽  
W. Wasmund ◽  
A. Olivencia-Yurvati ◽  
...  
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Dynamic Exercise ◽  
Moderate Intensity ◽  
Burst Frequency ◽  
Nerve Activity ◽  
Arm Cycling ◽  
Carotid Baroreflex ◽  
Neck Pressure

We sought to determine whether carotid baroreflex (CBR) control of muscle sympathetic nerve activity (MSNA) was altered during dynamic exercise. In five men and three women, 23.8 ± 0.7 (SE) yr of age, CBR function was evaluated at rest and during 20 min of arm cycling at 50% peak O2uptake using 5-s periods of neck pressure and neck suction. From rest to steady-state arm cycling, mean arterial pressure (MAP) was significantly increased from 90.0 ± 2.7 to 118.7 ± 3.6 mmHg and MSNA burst frequency (microneurography at the peroneal nerve) was elevated by 51 ± 14% ( P < 0.01). However, despite the marked increases in MAP and MSNA during exercise, CBR-Δ%MSNA responses elicited by the application of various levels of neck pressure and neck suction ranging from +45 to −80 Torr were not significantly different from those at rest. Furthermore, estimated baroreflex sensitivity for the control of MSNA at rest was the same as during exercise ( P = 0.74) across the range of neck chamber pressures. Thus CBR control of sympathetic nerve activity appears to be preserved during moderate-intensity dynamic exercise.

scholarly journals Influence of Sex and Age on Muscle Sympathetic Nerve Activity of Healthy Normotensive Adults

Hypertension ◽  
2020 ◽  
Vol 76 (3) ◽  
pp. 997-1005 ◽  
Author(s):  
Daniel A. Keir ◽  
Mark B. Badrov ◽  
George Tomlinson ◽  
Catherine F. Notarius ◽  
Derek S. Kimmerly ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Body Mass Index ◽  
Body Mass ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Systematic Change ◽  
Burst Frequency ◽  
Nerve Activity ◽  
Age Related

As with blood pressure, age-related changes in muscle sympathetic nerve activity (MSNA) may differ nonlinearly between sexes. Data acquired from 398 male (age: 39±17; range: 18–78 years [mean±SD]) and 260 female (age: 37±18; range: 18–81 years) normotensive healthy nonmedicated volunteers were analyzed using linear regression models with resting MSNA burst frequency as the outcome and the predictors sex, age, MSNA, blood pressure, and body mass index modelled with natural cubic splines. Age and body mass index contributed 41% and 11%, respectively, of MSNA variance in females and 23% and 1% in males. Overall, changes in MSNA with age were sigmoidal. At age 20, mean MSNA of males and females were similar, then diverged significantly, reaching in women a nadir at age 30. After 30, MSNA increased nonlinearly in both sexes. Both MSNA discharge and blood pressure were lower in females until age 50 (17±9 versus 25±10 bursts·min −1 ; P <1×10 −19 ; 106±11/66±8 versus 116±7/68±9 mm Hg; P <0.01) but converged thereafter (38±11 versus 35±12 bursts·min −1 ; P =0.17; 119±15/71±13 versus 120±13/72±9 mm Hg; P >0.56). Compared with age 30, MSNA burst frequency at age 70 was 57% higher in males but 3-fold greater in females; corresponding increases in systolic blood pressure were 1 (95% CI, −4 to 5) and 12 (95% CI, 6–16) mm Hg. Except for concordance in females beyond age 40, there was no systematic change with age in any resting MSNA-blood pressure relationship. In normotensive adults, MSNA increases after age 30, with ascendance steeper in women.

Naloxone does not affect the cardiovascular and sympathetic adjustments to static exercise in humans

1994 ◽  
Vol 77 (1) ◽  
pp. 231-235 ◽  
Author(s):  
C. A. Ray ◽  
J. A. Pawelczyk
Keyword(s):  
Heart Rate ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Static Exercise ◽  
Burst Frequency ◽  
Nerve Activity ◽  
Double Blind ◽  
Endogenous Opiates ◽  
Muscle Ischemia

Previous studies suggested that endogenous opiates may attenuate the cardiovascular and sympathetic adjustments to static exercise. We tested whether this effect originates from exercising skeletal muscle. Eight men performed 2 min of static handgrip (30% maximum) followed by 2 min of posthandgrip muscle ischemia after three interventions: 1) control, 2) intra-arterial injection of naloxone HCl (60 micrograms) or vehicle (saline) in the exercising arm, and 3) systemic infusion of naloxone (4 mg) or vehicle. Naloxone and vehicle trials were performed double blind on separate days. Preexercise baseline muscle sympathetic nerve activity (burst frequency), heart rate, and blood pressure were similar across interventions on either day. During static handgrip, control, intra-arterial, and systemic administration of vehicle and naloxone elicited similar increases in total muscle sympathetic nerve activity (58 +/- 24 vs. 68 +/- 26, 146 +/- 49 vs. 132 +/- 42, 137 +/- 54 vs. 164 +/- 44%, respectively), heart rate (9 +/- 2 vs. 8 +/- 3, 16 +/- 3 vs. 16 +/- 2, 20 +/- 4 vs. 19 +/- 3 beats/min, respectively), and mean arterial pressure (22 +/- 4 vs. 21 +/- 4, 29 +/- 5 vs. 26 +/- 3, 28 +/- 4 vs. 27 +/- 4 mmHg, respectively). Additionally, there were no differences between vehicle and naloxone trials during posthandgrip muscle ischemia. Thus, contrary to previous reports, we conclude that the endogenous opiate peptide system does not modulate cardiovascular and sympathetic responses to brief periods of static exercise or muscle ischemia in humans.

scholarly journals Validity and reliability of measuring resting muscle sympathetic nerve activity using short sampling durations in healthy humans

2016 ◽  
Vol 121 (5) ◽  
pp. 1065-1073 ◽  
Author(s):  
Karambir Notay ◽  
Jeremy D. Seed ◽  
Anthony V. Incognito ◽  
Connor J. Doherty ◽  
Massimo Nardone ◽  
...  
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Intraclass Correlation ◽  
Validity And Reliability ◽  
Burst Frequency ◽  
Nerve Activity ◽  
True Value ◽  
Sampling Duration ◽  
Resting Muscle

Resting muscle sympathetic nerve activity (MSNA) demonstrates high intraindividual reproducibility when sampled over 5–30 min epochs, although shorter sampling durations are commonly used before and during a stress to quantify sympathetic responsiveness. The purpose of the present study was to examine the intratest validity and reliability of MSNA sampled over 2 and 1 min and 30 and 15 s epoch durations. We retrospectively analyzed 68 resting fibular nerve microneurographic recordings obtained from 53 young, healthy participants (37 men; 23 ± 6 yr of age). From a stable 7-min resting baseline, MSNA (burst frequency and incidence, normalized mean burst amplitude, total burst area) was compared among each epoch duration and a standard 5-min control. Bland-Altman plots were used to determine agreement and bias. Three sequential MSNA measurements were collected using each sampling duration to calculate absolute and relative reliability (coefficients of variation and intraclass correlation coefficients). MSNA values were similar among each sampling duration and the 5-min control (all P > 0.05), highly correlated ( r = 0.69–0.93; all P < 0.001), and demonstrated no evidence of fixed bias (all P > 0.05). A consistent proportional bias ( P < 0.05) was present for MSNA burst frequency (all sampling durations) and incidence (1 min and 30 and 15 s), such that participants with low and high average MSNA underestimated and overestimated the true value, respectively. Reliability decreased progressively using the 30- and 15-s sampling durations. In conclusion, short 2 and 1 min and 30 s sampling durations can provide valid and reliable measures of MSNA, although increased sample size may be required for epochs ≤30 s, due to poorer reliability.

Sympathetic Responses to Valsalva's Manoeuvre Following Bed Rest

2003 ◽  
Vol 28 (3) ◽  
pp. 342-355 ◽  
Author(s):  
J. Kevin Shoemaker ◽  
Cynthia S. Hogeman ◽  
Lawrence I. Sinoway
Keyword(s):  
Blood Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Bed Rest ◽  
Pressure Control ◽  
Burst Frequency ◽  
Nerve Activity ◽  
Head Up Tilt ◽  
Valsalva's Manoeuvre

The purpose of this study was to examine whether 14 days of head-down tilt bed rest (HDBR) alters autonomic regulation during Valsalva's manoeuvre (VM) and if this would predict blood pressure control during a 60° head-up tilt (HUT) test. To examine autonomic control of blood pressure, we measured the changes in systolic (ΔSBP) and diastolic (ΔDBP) blood pressure between baseline and the early straining (Phase IIE) period of VM (20 sec straining to 40 mmHg; N = 7) in conjunction with changes in muscle sympathetic nerve activity (MSNA; microneurography) burst frequency (B/min) and total activity (%Δ) from baseline over the 20-sec straining period. MSNA data were successfully recorded from 6 of the 7 individuals. The averaged responses from three repeated VMs performed in the supine position were compared between the pre- and post-HDBR tests. Compared with the pre-HDBR test, a greater reduction in SBP, DBP, and MAP was observed during Phase IIE following HDBR, p < 0.05. The increase in MSNA burst frequency during straining was augmented in the post- compared with the pre-HDBR test, p < 0.0001, as was the Phase IV blood pressure overshoot, p < 0.05. Although all subjects completed the 20-min pre-HDBR tilt test without evidence of hypotension or orthostatic intolerance, the post-HDBR test was stopped early in 5 of the 7 subjects due to systolic hypotension. The responses during the VM suggest that acute autonomic adjustments to rapid blood pressure changes are preserved after bed rest. Furthermore, MSNA and blood pressure responses during VM did not predict blood pressure control during orthostasis following HDBR. Key words: muscle sympathetic nerve activity, blood pressure, orthostatic tolerance, head-up tilt

scholarly journals Effects of dynamic arm and leg exercise on muscle sympathetic nerve activity and vascular conductance in the inactive leg

2019 ◽  
Vol 127 (2) ◽  
pp. 464-472
Author(s):  
Connor J. Doherty ◽  
Trevor J. King ◽  
Anthony V. Incognito ◽  
Jordan B. Lee ◽  
Andrew D. Shepherd ◽  
...  
Keyword(s):  
Muscle Mass ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Burst Frequency ◽  
Vascular Conductance ◽  
Nerve Activity ◽  
Burst Amplitude ◽  
Leg Cycling ◽  
Concurrent Exercise

The influence of muscle sympathetic nerve activity (MSNA) responses on local vascular conductance during exercise are not well established. Variations in exercise mode and active muscle mass can produce divergent MSNA responses. Therefore, we sought to examine the effects of small- versus large-muscle mass dynamic exercise on vascular conductance and MSNA responses in the inactive limb. Thirty-five participants completed two study visits in a randomized order. During visit 1, superficial femoral artery (SFA) blood flow (Doppler ultrasound) was assessed at rest and during steady-state rhythmic handgrip (RHG; 1:1 duty cycle, 40% maximal voluntary contraction), one-leg cycling (17 ± 3% peak power output), and concurrent exercise at the same intensities. During visit 2, MSNA (contralateral fibular nerve microneurography) was acquired successfully in 12/35 participants during the same exercise modes. SFA blood flow increased during RHG ( P < 0.0001) and concurrent exercise ( P = 0.03) but not cycling ( P = 0.91). SFA vascular conductance was unchanged during RHG ( P = 0.88) but reduced similarly during concurrent and cycling exercise (both P < 0.003). RHG increased MSNA burst frequency ( P = 0.04) without altering burst amplitude ( P = 0.69) or total MSNA ( P = 0.26). In contrast, cycling and concurrent exercise had no effects on MSNA burst frequency (both P ≥ 0.10) but increased burst amplitude (both P ≤ 0.001) and total MSNA (both P ≤ 0.007). Across all exercise modes, the changes in MSNA burst amplitude and SFA vascular conductance were correlated negatively ( r = −0.43, P = 0.02). In summary, the functional vascular consequences of alterations in sympathetic outflow to skeletal muscle are most closely associated with changes in MSNA burst amplitude, but not frequency, during low-intensity dynamic exercise. NEW & NOTEWORTHY Low-intensity small- versus large-muscle mass exercise can elicit divergent effects on muscle sympathetic nerve activity (MSNA). We examined the relationships between changes in MSNA (burst frequency and amplitude) and superficial femoral artery (SFA) vascular conductance during rhythmic handgrip, one-leg cycling, and concurrent exercise in the inactive leg. Only changes in MSNA burst amplitude were inversely associated with SFA vascular conductance responses. This result highlights the functional importance of measuring MSNA burst amplitude during exercise.

scholarly journals Modulation of muscle sympathetic nerve activity to muscle heating during dynamic exercise

2009 ◽  
Vol 296 (5) ◽  
pp. R1439-R1444 ◽  
Author(s):  
Jonathan S. Cook ◽  
Chester A. Ray
Keyword(s):  
Blood Flow ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Interactive Effect ◽  
Total Activity ◽  
Muscle Temperature ◽  
Isometric Handgrip ◽  
Burst Frequency ◽  
Nerve Activity

Previous studies from our laboratory have demonstrated that altering muscle temperature of the exercising forearm can elicit changes in muscle sympathetic nerve activity (MSNA) during ischemic isometric handgrip. The purpose of the current study was to determine the interactive effect of muscle temperature and blood flow on MSNA responses during dynamic handgrip (DHG). Eight subjects performed two bouts of graded DHG to fatigue followed by 2 min of postexercise muscle ischemia (PEMI). Local heating of the forearm increased muscle temperature from 33.6 ± 0.3 to 38.3 ± 0.5°C ( P < 0.05). Mean arterial pressure and heart rate increased in a linear fashion during graded DHG ( P < 0.05) but were not affected by muscle temperature. MSNA (burst frequency and total activity) at fatigue and PEMI were elevated in all conditions ( P < 0.05). However, MSNA responses were not different between temperature conditions. To ascertain the effect of blood flow, eight additional subjects completed two trials of ischemic DHG under control or warm conditions followed by 2 min of PEMI. MSNA, expressed as burst frequency and total activity, was significantly greater in warm compared with the control trial (Δ14 ± 3 and Δ9 ± 2 bursts/30 s, and Δ1,234 ± 260 and Δ751 ± 199 units/30 s, respectively). This finding supports the concept that muscle heating sensitizes skeletal muscle afferents during muscle contractions and augments MSNA in humans. However, on the basis of these findings, we conclude that muscle blood flow modulates the effect of muscle temperature on MSNA during exercise.

Low-frequency electroacupuncture and physical exercise decrease high muscle sympathetic nerve activity in polycystic ovary syndrome

2009 ◽  
Vol 297 (2) ◽  
pp. R387-R395 ◽  
Author(s):  
Elisabet Stener-Victorin ◽  
Elizabeth Jedel ◽  
Per Olof Janson ◽  
Yrsa Bergmann Sverrisdottir
Keyword(s):  
Physical Exercise ◽  
Sympathetic Nerve ◽  
Untreated Control ◽  
Sympathetic Nerve Activity ◽  
Polycystic Ovary ◽  
Muscle Sympathetic Nerve Activity ◽  
Low Frequency ◽  
Control Group ◽  
Burst Frequency ◽  
Nerve Activity

We have recently shown that polycystic ovary syndrome (PCOS) is associated with high muscle sympathetic nerve activity (MSNA). Animal studies support the concept that low-frequency electroacupuncture (EA) and physical exercise, via stimulation of ergoreceptors and somatic afferents in the muscles, may modulate the activity of the sympathetic nervous system. The aim of the present study was to investigate the effect of these interventions on sympathetic nerve activity in women with PCOS. In a randomized controlled trial, 20 women with PCOS were randomly allocated to one of three groups: low-frequency EA ( n = 9), physical exercise ( n = 5), or untreated control ( n = 6) during 16 wk. Direct recordings of multiunit efferent postganglionic MSNA in a muscle fascicle of the peroneal nerve before and following 16 wk of treatment. Biometric, hemodynamic, endocrine, and metabolic parameters were measured. Low-frequency EA ( P = 0.036) and physical exercise ( P = 0.030) decreased MSNA burst frequency compared with the untreated control group. The low-frequency EA group reduced sagittal diameter ( P = 0.001), while the physical exercise group reduced body weight ( P = 0.004) and body mass index ( P = 0.004) compared with the untreated control group. Sagittal diameter was related to MSNA burst frequency ( Rs = 0.58, P < 0.005) in the EA group. No correlation was found for body mass index and MSNA in the exercise group. There were no differences between the groups in hemodynamic, endocrine, and metabolic variables. For the first time we demonstrate that low-frequency EA and physical exercise lowers high sympathetic nerve activity in women with PCOS. Thus, treatment with low-frequency EA or physical exercise with the aim to reduce MSNA may be of importance for women with PCOS.

Endurance exercise training is associated with elevated basal sympathetic nerve activity in healthy older humans

1994 ◽  
Vol 77 (3) ◽  
pp. 1366-1374 ◽  
Author(s):  
A. V. Ng ◽  
R. Callister ◽  
D. G. Johnson ◽  
D. R. Seals
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Acute Stress ◽  
Muscle Sympathetic Nerve Activity ◽  
Cold Pressor Test ◽  
Plasma Norepinephrine ◽  
Isometric Handgrip ◽  
Burst Frequency ◽  
Nerve Activity ◽  
Control Subjects

We tested the hypothesis that endurance training is associated with altered basal levels of muscle sympathetic nerve activity (MSNA) and responses to acute stress in healthy older adults. MSNA (peroneal microneurography) and plasma norepinephrine (NE) concentrations were measured during supine rest, a cold pressor test, and isometric handgrip (40% maximal voluntary force to exhaustion) in 16 older masters endurance athletes [10 men, 6 women; 66 +/- 1 (SE) yr] and 15 healthy normotensive untrained control subjects (9 men, 6 women; 65 +/- 1 yr). The athletes had higher levels of estimated daily energy expenditure and maximal oxygen uptake and lower levels of resting heart rate and body fat than the control subjects (all P < 0.05). MSNA during supine rest was elevated in the athletes whether expressed as burst frequency (43 +/- 2 vs. 32 +/- 3 bursts/min, respectively; P < 0.05) or burst incidence (75 +/- 4 vs. 52 +/- 5 bursts/100 heartbeats, respectively; P < 0.01). These whole group differences were due primarily to markedly higher levels of MSNA in the athletic vs. untrained women (48 +/- 4 vs. 25 +/- 3 bursts/min, 82 +/- 3 vs. 38 +/- 3 bursts/100 heartbeats, respectively, P < 0.001). In contrast, basal plasma NE concentrations were not significantly different in the athletes vs. control subjects. The MSNA and plasma NE responses to acute stress tended to be greater in the athletes. These findings indicate that vigorous regular aerobic exercise is associated with an elevated level of MSNA at rest and a tendency for an enhanced response to acute stress in healthy normotensive older humans.

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