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.

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.

Chemoreflex and metaboreflex control during static hypoxic exercise

2005 ◽  
Vol 288 (4) ◽  
pp. H1724-H1729 ◽  
Author(s):  
Anne Houssiere ◽  
Boutaina Najem ◽  
Agniezka Ciarka ◽  
Sonia Velez-Roa ◽  
Robert Naeije ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Circulatory Arrest ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Isometric Handgrip Exercise ◽  
Baseline Values ◽  
Hypoxic Exercise

To investigate the effects of muscle metaboreceptor activation during hypoxic static exercise, we recorded muscle sympathetic nerve activity (MSNA), heart rate, blood pressure, ventilation, and blood lactate in 13 healthy subjects (22 ± 2 yr) during 3 min of three randomized interventions: isocapnic hypoxia (10% O2) (chemoreflex activation), isometric handgrip exercise in normoxia (metaboreflex activation), and isometric handgrip exercise during isocapnic hypoxia (concomitant metaboreflex and chemoreflex activation). Each intervention was followed by a forearm circulatory arrest to allow persistent metaboreflex activation in the absence of exercise and chemoreflex activation. Handgrip increased blood pressure, MSNA, heart rate, ventilation, and lactate (all P < 0.001). Hypoxia without handgrip increased MSNA, heart rate, and ventilation (all P < 0.001), but it did not change blood pressure and lactate. Handgrip enhanced blood pressure, heart rate, MSNA, and ventilation responses to hypoxia (all P < 0.05). During circulatory arrest after handgrip in hypoxia, heart rate returned promptly to baseline values, whereas ventilation decreased but remained elevated ( P < 0.05). In contrast, MSNA, blood pressure, and lactate returned to baseline values during circulatory arrest after hypoxia without exercise but remained markedly increased after handgrip in hypoxia ( P < 0.05). We conclude that metaboreceptors and chemoreceptors exert differential effects on the cardiorespiratory and sympathetic responses during exercise in hypoxia.

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.

Forearm training attenuates sympathetic responses to prolonged rhythmic forearm exercise

1996 ◽  
Vol 81 (4) ◽  
pp. 1778-1784 ◽  
Author(s):  
Lawrence Sinoway ◽  
Jeffrey Shenberger ◽  
Gretchen Leaman ◽  
Robert Zelis ◽  
Kristen Gray ◽  
...  
Keyword(s):  
Heart Rate ◽  
Nervous System ◽  
Sympathetic Nervous System ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Voluntary Contraction ◽  
Nerve Activity ◽  
Sympathetic Nervous ◽  
Sympathetic Responses ◽  
Forearm Exercise

Sinoway, Lawrence, Jeffrey Shenberger, Gretchen Leaman, Robert Zelis, Kristen Gray, Robert Baily, and Urs Leuenberger.Forearm training attenuates sympathetic responses to prolonged rhythmic forearm exercise. J. Appl. Physiol. 81(4): 1778–1784, 1996.—We previously demonstrated that nonfatiguing rhythmic forearm exercise at 25% maximal voluntary contraction (12 2-s contractions/min) evokes sympathoexcitation without significant engagement of metabolite-sensitive muscle afferents (B. A. Batman, J. C. Hardy, U. A. Leuenberger, M. B. Smith, Q. X. Yang, and L. I. Sinoway. J. Appl. Physiol. 76: 1077–1081, 1994). This is in contrast to the sympathetic nervous system responses observed during fatiguing static forearm exercise where metabolite-sensitive afferents are the key determinants of sympathetic activation. In this report we examined whether forearm exercise training would attenuate sympathetic nervous system responses to rhythmic forearm exercise. We measured heart rate, mean arterial blood pressure (MAP), muscle sympathetic nerve activity (microneurography), plasma norepinephrine (NE), and NE spillover and clearance (tritiated NE kinetics) during nonfatiguing rhythmic forearm exercise before and after a 4-wk unilateral forearm training paradigm. Training had no effect on forearm mass, maximal voluntary contraction, or heart rate but did attenuate the increase in MAP (increase in MAP: from 15.2 ± 1.8 before training to 11.4 ± 1.4 mmHg after training; P < 0.017), muscle sympathetic nerve activity (increase in bursts: from 10.8 ± 1.4 before training to 6.2 ± 1.1 bursts/min after training; P < 0.030), and the NE spillover (increase in arterial spillover: from 1.3 ± 0.2 before training to 0.6 ± 0.2 nmol ⋅ min−1 ⋅ m−2after training, P < 0.014; increase in venous spillover: from 2.0 ± 0.6 before training to 1.0 ± 0.5 nmol ⋅ min−1 ⋅ m−2after training, P < 0.037) seen in response to exercise performed by the trained forearm. Thus forearm training reduces sympathetic responses during a nonfatiguing rhythmic handgrip paradigm that does not engage muscle metaboreceptors. We speculate that this effect is due to a conditioning-induced reduction in mechanically sensitive muscle afferent discharge.

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.

scholarly journals Interstitial pH, K+, lactate, and phosphate determined with MSNA during exercise in humans

2000 ◽  
Vol 278 (3) ◽  
pp. R563-R571 ◽  
Author(s):  
David A. MacLean ◽  
Virginia A. Imadojemu ◽  
Lawrence I. Sinoway
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Exercise Bout ◽  
Exercise Pressor Reflex ◽  
Pressor Reflex ◽  
Lactate Levels ◽  
First Time ◽  
Exercise In Humans

The purpose of the present study was to use the microdialysis technique to simultaneously measure the interstitial concentrations of several putative stimulators of the exercise pressor reflex during 5 min of intermittent static quadriceps exercise in humans ( n = 7). Exercise resulted in approximately a threefold ( P < 0.05) increase in muscle sympathetic nerve activity (MSNA) and 13 ± 3 beats/min ( P < 0.05) and 20 ± 2 mmHg ( P < 0.05) increases in heart rate and blood pressure, respectively. During recovery, all reflex responses quickly returned to baseline. Interstitial lactate levels were increased ( P < 0.05) from rest (1.1 ± 0.1 mM) to exercise (1.6 ± 0.2 mM) and were further increased ( P < 0.05) during recovery (2.0 ± 0.2 mM). Dialysate phosphate concentrations were 0.55 ± 0.04, 0.71 ± 0.05, and 0.48 ± 0.03 mM during rest, exercise, and recovery, respectively, and were significantly elevated during exercise. At the onset of exercise, dialysate K+ levels rose rapidly above resting values (4.2 ± 0.1 meq/l) and continued to increase during the exercise bout. After 5 min of contractions, dialysate K+ levels had peaked with an increase ( P < 0.05) of 0.6 ± 0.1 meq/l and subsequently decreased during recovery, not being different from rest after 3 min. In contrast, H+ concentrations rapidly decreased ( P < 0.05) from resting levels (69.4 ± 3.7 nM) during quadriceps exercise and continued to decrease with a mean decline ( P < 0.05) of 16.7 ± 3.8 nM being achieved after 5 min. During recovery, H+ concentrations rapidly increased and were not significantly different from baseline after 1 min. This study represents the first time that skeletal muscle interstitial pH, K+, lactate, and phosphate have been measured in conjunction with MSNA, heart rate, and blood pressure during intermittent static quadriceps exercise in humans. These data suggest that interstitial K+ and phosphate, but not lactate and H+, may contribute to the stimulation of the exercise pressor reflex.

Heart Rate and Blood Pressure Responses to Static Handgrip Exercise of Different Intensities: Reliability and Adult versus Child Differences

2002 ◽  
Vol 14 (1) ◽  
pp. 45-55 ◽  
Author(s):  
Kenneth R. Turley ◽  
D. Eric Martin ◽  
Eric D. Marvin ◽  
Kelley S. Cowley
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Maximal Voluntary Contraction ◽  
Cardiovascular Response ◽  
Isometric Exercise ◽  
Cardiovascular Responses ◽  
Voluntary Contraction ◽  
Static Exercise ◽  
Handgrip Exercise ◽  
Blood Pressure Responses

To determine the reliability of cardiovascular responses to isometric exercise of different intensities, and to compare adult versus child responses, 27 boys (7–9 years old) and 27 men (18–26 years old) performed static handgrip exercise at 10, 20, and 30% of previously determined maximal voluntary contraction (MVC) for three min each on different days, while heart rate (HR) and blood pressure (BP) were measured. HR reliability was moderately high at all intensities in both boys and men ranging from R = 0.52–0.87. BP reliability was moderate in men and boys at 30% MVC while at 10% and 20% MVC reliability was very low for boys and only moderate for men. HR response from pre- to 3-min of static exercise was not different between boys versus men at any intensity. At 30% MVC diastolic (20.2 vs. 29.3 mmHg), systolic (17.4 vs. 36.2 mmHg) and mean (19.2 vs. 31.6 mmHg) BP responses were lower in boys versus men, respectively. At 20% MVC SBP (6.8 vs. 14.3 mmHg) and MBP (8.4 vs. 12.6 mmHg) responses were lower in boys versus men, respectively. In conclusion, the reliability of cardiovascular response to isometric exercise is low at low contraction intensities and moderate at higher contraction intensities. Further, BP response in men at 30% MVC is higher than boys, while responses are similar at lower contraction intensities.

Hormonal, metabolic, and cardiovascular responses to static exercise in humans: influence of epidural anesthesia

1991 ◽  
Vol 261 (2) ◽  
pp. E214-E220 ◽  
Author(s):  
M. Kjaer ◽  
N. H. Secher ◽  
F. W. Bach ◽  
H. Galbo ◽  
D. R. Reeves ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Epidural Anesthesia ◽  
Pressor Response ◽  
Plasma Concentrations ◽  
Cardiovascular Responses ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Static Exercise ◽  
Exercise In Humans

To determine the role of reflex neural mechanisms for hormonal, metabolic, heart rate (HR), and blood pressure (MABP) changes during static exercise, seven health young males performed 10-min periods of two-legged static knee extension both during control and during epidural anesthesia. Comparisons were made at identical absolute (29 Nm) and relative [15% maximal voluntary contraction (MVC)] force. Afferent nerve blockade was verified by hypesthesia below T10-T12 and attenuated postexercise ischemic pressor response. Leg strength was reduced to 67 +/- 5% of control. At same relative force, increases in MABP and HR occurred more rapidly without than with epidural anesthesia (P less than 0.05). This difference was diminished during identical absolute force. Changes in plasma concentrations of catecholamines followed the pattern of HR and MABP responses, with differences between epidural and control experiments being most pronounced early in the work period. Plasma beta-endorphin was elevated only after control exercise. No response at 15% MVC was found for growth hormone, adrenocorticotropic hormone, insulin, glucagon, cortisol, glycerol, free fatty acids, or glucose (P greater than 0.05). In conclusion, during static exercise with large muscle groups and moderate relative force, modest changes in plasma hormones and metabolites take place. Furthermore, afferent nervous feedback from contracting muscles is important in regulation of blood pressure, heart rate, and catecholamine responses during static exercise in humans.

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