Ischemic exercise and the muscle metaboreflex

2000 ◽  
Vol 89 (4) ◽  
pp. 1432-1436 ◽  
Author(s):  
Jacob A. Cornett ◽  
Michael D. Herr ◽  
Kristen S. Gray ◽  
Michael B. Smith ◽  
Qing X. Yang ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Random Order ◽  
Muscle Afferents ◽  
Voluntary Contraction ◽  
The Other ◽  
Reflex Response ◽  
Handgrip Exercise ◽  
Muscle Metaboreflex ◽  
Effort Level ◽  
Arterial Blood

In exercising muscle, interstitial metabolites accumulate and stimulate muscle afferents. This evokes the muscle metaboreflex and raises arterial blood pressure (BP). In this report, we examined the effects of tension generation on muscle metabolites and BP during ischemic forearm exercise in humans. Heart rate (HR), BP, Pi, H2PO4 −, and pH (31P-NMR spectroscopy) data were collected in 10 normal healthy men (age 23 ± 1 yr) during rhythmic handgrip exercise. After baseline measurements, the subjects performed rhythmic handgrip for 2 min. At 2 min, a 250-mmHg occlusion cuff was inflated, and ischemic handgrip exercise was continued until near fatigue (Borg 19). Measurements were continued for an additional 30 s of ischemia. This protocol was performed at 15, 30, 45, and 60% of the subjects' maximum voluntary contraction (MVC) in random order. As tension increased, the time to fatigue decreased. In addition, mean arterial pressure and HR were higher at 60% MVC than at any of the other lower tensions. The NMR data showed significantly greater increases in H2PO4 −, Pi, and H+at 60% than at 15 and 30% MVC. Therefore, despite the subjects working to the same perceived effort level, a greater reflex response (represented by BP and HR data) was elicited at 60% MVC than at any of the other ischemic tensions. These data are consistent with the hypothesis that, as tension increases, factors aside from insufficient blood flow contribute to the work effect on muscle metabolites and the magnitude of the reflex response.

Cutaneous vascular responses to isometric handgrip exercise

1989 ◽  
Vol 66 (4) ◽  
pp. 1586-1592 ◽  
Author(s):  
W. F. Taylor ◽  
J. M. Johnson ◽  
W. A. Kosiba ◽  
C. M. Kwan
Keyword(s):  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Dynamic Exercise ◽  
Laser Doppler ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Local Skin ◽  
Vascular Responses ◽  
Arterial Blood ◽  
Isometric Handgrip Exercise

Cutaneous vascular responses to dynamic exercise have been well characterized, but it is not known whether that response pattern applies to isometric handgrip exercise. We examined cutaneous vascular responses to isometric handgrip and dynamic leg exercise in five supine men. Skin blood flow was measured by laser-Doppler velocimetry and expressed as laser-Doppler flow (LDF). Arterial blood pressure was measured noninvasively once each minute. Cutaneous vascular conductance (CVC) was calculated as LDF/mean arterial pressure. LDF and CVC responses were measured at the forearm and chest during two 3-min periods of isometric handgrip at 30% of maximum voluntary contraction and expressed as percent changes from the preexercise levels. The skin was normothermic (32 degrees C) for the first period of handgrip and was locally warmed to 39 degrees C for the second handgrip. Finally, responses were observed during 5 min of dynamic two-leg bicycle exercise (150–175 W) at a local skin temperature of 39 degrees C. Arm LDF increased 24.5 +/- 18.9% during isometric handgrip in normothermia and 64.8 +/- 14.1% during isometric handgrip at 39 degrees C (P less than 0.05). Arm CVC did not significantly change at 32 degrees C but significantly increased 18.1 +/- 6.5% during isometric handgrip at 39 degrees C (P less than 0.05). Arm LDF decreased 12.2 +/- 7.9% during dynamic exercise at 39 degrees C, whereas arm CVC fell by 35.3 +/- 4.6% (in each case P less than 0.05). Chest LDF and CVC showed similar responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventilatory responses to static handgrip exercise

1983 ◽  
Vol 54 (6) ◽  
pp. 1457-1462 ◽  
Author(s):  
S. R. Muza ◽  
L. Y. Lee ◽  
R. L. Wiley ◽  
S. McDonald ◽  
F. W. Zechman
Keyword(s):  
Time Course ◽  
Ventilatory Response ◽  
Maximum Voluntary Contraction ◽  
Muscle Afferents ◽  
Voluntary Contraction ◽  
Static Exercise ◽  
Handgrip Exercise ◽  
Co2 Partial Pressure ◽  
Ventilatory Responses ◽  
End Tidal

Previous research indicates that fatiguing static exercise causes hyperventilation and a decrease of end-tidal CO2 partial pressure PETCO2. The objectives of this study were 1) to examine the changes in pattern of breathing during static exercise, and 2) to define the isocapnic ventilatory response. Six healthy males were studied once a week at one of three levels of static handgrip exercise: 15, 25, or 30% maximum voluntary contraction (MVC) was sustained for 5 min while holding PETCO2 constant or allowing it to run free. During 25 and 30% MVC, we observed 1) progressive increases in mean tidal volume (VT), inspiratory ventilation (VI), VT/TI, heart rate (HR), and arterial BP, 2) increased breath-to-breath variability of VT, 3) no significant changes in respiratory frequency (f), and 4) progressive decreases in PETCO2. Keeping PETCO2 constant at preexercise levels did not change the pattern or magnitude of the ventilatory response to exercise. The time course and magnitude of the subjects' perceived effort resembled the time course and magnitude of the ventilatory response. The variability of VT during the response to static exercise suggests an element of control instability. The identical ventilatory responses during hypocapnic and isocapnic conditions may result from the slow response of the central chemoreceptors; an overriding influence of muscle afferents; and/or increased central command arising with fatigue.

Evaluation of muscle metaboreflex function through graded reduction in forearm blood flow during rhythmic handgrip exercise in humans

2011 ◽  
Vol 301 (2) ◽  
pp. H609-H616 ◽  
Author(s):  
Masashi Ichinose ◽  
Stephane Delliaux ◽  
Kazuhito Watanabe ◽  
Naoto Fujii ◽  
Takeshi Nishiyasu
Keyword(s):  
Blood Flow ◽  
Forearm Blood Flow ◽  
Pressor Response ◽  
Muscle Blood Flow ◽  
Voluntary Contraction ◽  
Open Loop ◽  
Handgrip Exercise ◽  
Hemodynamic Responses ◽  
Muscle Metaboreflex ◽  
Arterial Blood

Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metaboreflex. Our aim was to determine the muscle metaboreflex threshold and gain in humans by creating an open-loop relationship between active muscle blood flow and hemodynamic responses during a rhythmic handgrip exercise. Eleven healthy subjects performed the exercise at 5 or 15% of maximal voluntary contraction (MVC) in random order. During the exercise, forearm blood flow (FBF), which was continuously measured using Doppler ultrasound, was reduced in five steps by manipulating the inner pressure of an occlusion cuff on the upper arm. The FBF at each level was maintained for 3 min. The initial reductions in FBF elicited no hemodynamic changes, but once FBF fell below a threshold, mean arterial blood pressure (MAP) and heart rate (HR) increased and total vascular conductance (TVC) decreased in a linear manner. The threshold FBF during the 15% MVC trial was significantly higher than during the 5% MVC trial. The gain was then estimated as the slope of the relationship between the hemodynamic responses and FBFs below the threshold. The gains for the MAP and TVC responses did not differ between workloads, but the gain for the HR response was greater in the 15% MVC trial. Our findings thus indicate that increasing the workload shifts the threshold for the muscle metaboreflex to higher blood flows without changing the gain of the reflex for the MAP and TVC responses, whereas it enhances the gain for the HR response.

Activation of the carotid chemoreflex secondary to muscle metaboreflex stimulation in men

2014 ◽  
Vol 306 (9) ◽  
pp. R693-R700 ◽  
Author(s):  
H. Edgell ◽  
M. K. Stickland
Keyword(s):  
Nervous Activity ◽  
Random Order ◽  
Voluntary Contraction ◽  
Sympathetic Nervous Activity ◽  
Muscle Metaboreflex ◽  
Healthy Men ◽  
Sympathetic Control ◽  
Muscle Sympathetic Nervous Activity ◽  
Sympathetic Nervous ◽  
Stimulation Of

Recent work has shown that the carotid chemoreceptor (CC) contributes to sympathetic control of cardiovascular function during exercise, despite no evidence of increased circulating CC stimuli, suggesting enhanced CC activity/sensitivity. As interactions between metaboreceptors and chemoreceptors have been previously observed, the purpose of this study was to isolate the metaboreflex while acutely stimulating or inhibiting the CC to determine whether the metaboreflex increased CC activity/sensitivity. Fourteen young healthy men (height: 177.0 ± 2.1 cm, weight: 85.8 ± 5.5 kg, age: 24.6 ± 1.1 yr) performed three trials of 40% maximal voluntary contraction handgrip for 2 min, followed by 3 min of postexercise circulatory occlusion (PECO) to stimulate the metaboreflex. In random order, subjects either breathed room air, hypoxia (target SPo2 = 85%), or hyperoxia (FiO2 = 1.0) during the PECO to modulate the chemoreflex. After these trials, a resting hypoxia trial was conducted without handgrip or PECO. Ventilation (V̇e), heart rate (HR), blood pressure, and muscle sympathetic nervous activity (MSNA) data were continuously obtained. Relative to normoxic PECO, inhibition of the CC during hyperoxic PECO resulted in lower MSNA ( P = 0.038) and HR ( P = 0.021). Relative to normoxic PECO, stimulation of the CC during hypoxic PECO resulted in higher HR ( P < 0.001) and V̇e ( P < 0.001). The ventilatory and MSNA responses to hypoxic PECO were not greater than the sum of the responses to hypoxia and PECO individually, indicating that the CC are not sensitized during metaboreflex activation. These results demonstrate that stimulation of the metaboreflex activates, but does not sensitize the CC, and help explain the enhanced CC activity with exercise.

Individual differences in cardiac and vascular components of the pressor response to isometric handgrip exercise in humans

2014 ◽  
Vol 306 (2) ◽  
pp. H251-H260 ◽  
Author(s):  
Kazuhito Watanabe ◽  
Masashi Ichinose ◽  
Rei Tahara ◽  
Takeshi Nishiyasu
Keyword(s):  
Individual Differences ◽  
Arterial Pressure ◽  
Pressor Response ◽  
Voluntary Contraction ◽  
Handgrip Exercise ◽  
Isometric Handgrip ◽  
Muscle Metaboreflex ◽  
Coefficients Of Variation ◽  
Isometric Handgrip Exercise ◽  
Induced Changes

We tested the hypotheses that, in humans, changes in cardiac output (CO) and total peripheral vascular resistance (TPR) occurring in response to isometric handgrip exercise vary considerably among individuals and that those individual differences are related to differences in muscle metaboreflex and arterial baroreflex function. Thirty-nine healthy subjects performed a 1-min isometric handgrip exercise at 50% of maximal voluntary contraction. This was followed by a 4-min postexercise muscle ischemia (PEMI) period to selectively maintain activation of the muscle metaboreflex. All subjects showed increases in arterial pressure during exercise. Interindividual coefficients of variation (CVs) for the changes in CO and TPR between rest and exercise periods (CO: 95.1% and TPR: 87.8%) were more than twofold greater than CVs for changes in mean arterial pressure (39.7%). There was a negative correlation between CO and TPR responses during exercise ( r = −0.751, P < 0.01), but these CO and TPR responses correlated positively with the corresponding responses during PEMI ( r = 0.568 and 0.512, respectively, P < 0.01). The CO response during exercise did not correlate with PEMI-induced changes in an index of cardiac parasympathetic tone and cardiac baroreflex sensitivity. These findings demonstrate that the changes in CO and TPR that occur in response to isometric handgrip exercise vary considerably among individuals and that the two responses have an inverse relationship. They also suggest that individual differences in components of the pressor response are attributable in part to variations in muscle metaboreflex-mediated cardioaccelerator and vasoconstrictor responses.

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.

Slowing of carotid-cardiac baroreflex with standing and with isometric and dynamic muscle activity

1996 ◽  
Vol 271 (4) ◽  
pp. H1363-H1369 ◽  
Author(s):  
P. Sundblad ◽  
D. Linnarsson
Keyword(s):  
Muscle Activity ◽  
Sympathetic Activity ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
The Other ◽  
Sitting Position ◽  
Arm Exercise ◽  
Mean Values ◽  
Leg Exercise ◽  
Male Subjects

We hypothesized that the carotid-cardiac baroreflex becomes slowed in conditions with increased sympathetic activity. Changes in heart rate (HR) and blood pressure in response to 10-s trains of 50-mmHg pulses of neck suction (NS) were studied in six male subjects during supine rest, upright rest, isometric arm exercise at 30% of maximum voluntary contraction, and dynamic leg exercise at 100 W in the sitting position. Estimated mean carotid distending pressure increased by approximately 20 mmHg with 50-mmHg, QRS-triggered, pulsatile NS. Repeated NS sequences were performed in each condition. The amplitude of the bradycardic response was highly variable among the subjects and did not differ significantly between conditions, mean values ranging from 0.3 to 0.6 beats.min-1.mmHg-1. In supine rest, the full bradycardic response appeared within < 1 s, i.e., during or immediately after the R-R interval of the first NS pulse. In the other conditions it took significantly longer, 2-3 s or three to seven R-R intervals, for the full HR responses to develop. Our results support the notion that the carotid-cardiac baroreflex in humans becomes slowed under conditions of concurrent sympathetic stimulation.

Dynamic cerebral autoregulation during and after handgrip exercise in humans

2010 ◽  
Vol 108 (6) ◽  
pp. 1701-1705 ◽  
Author(s):  
Shigehiko Ogoh ◽  
Kohei Sato ◽  
Toshinari Akimoto ◽  
Anna Oue ◽  
Ai Hirasawa ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Cerebral Autoregulation ◽  
Valsalva Maneuver ◽  
Maximum Voluntary Contraction ◽  
Static Exercise ◽  
Handgrip Exercise ◽  
Arterial Blood ◽  
Significant Difference ◽  
Acute Hypotension ◽  
Dynamic Cerebral Autoregulation

The purpose of the present study was to examine the effect of static exercise on dynamic cerebral autoregulation (CA). In nine healthy subjects at rest before, during, and after static handgrip exercise at 30% maximum voluntary contraction, the response to an acute drop in mean arterial blood pressure and middle cerebral artery mean blood velocity was examined. Acute hypotension was induced nonpharmacologically via rapid release of bilateral thigh occlusion cuffs. Subjects were instructed to avoid executing a Valsalva maneuver during handgrip. To quantify dynamic CA, the rate of regulation (RoR) was calculated from the change in cerebral vascular conductance index during the transient fall in blood pressure. There was no significant difference in RoR between rest (mean ± SE; 0.278 ± 0.052/s), exercise (0.333 ± 0.053/s), and recovery (0.305 ± 0.059/s) conditions ( P = 0.747). In addition, there was no significant difference in the rate of absolute cerebral vasodilatory response to acute hypotension between three conditions ( P = 0.737). This finding indicates that static exercise and related elevations in blood pressure do not alter dynamic CA.

scholarly journals The activity of a single muscle sympathetic vasoconstrictor nerve unit is affected by physiological stress in humans

2006 ◽  
Vol 290 (2) ◽  
pp. H853-H860 ◽  
Author(s):  
Hisayoshi Murai ◽  
Shigeo Takata ◽  
Michiro Maruyama ◽  
Manabu Nakano ◽  
Daisuke Kobayashi ◽  
...  
Keyword(s):  
Single Unit ◽  
Physiological Stress ◽  
Valsalva Maneuver ◽  
Muscle Sympathetic Nerve Activity ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Accurate Information ◽  
Neural Firing ◽  
Handgrip Exercise ◽  
New Strategy

Recording of neural firing from single-unit muscle sympathetic nerve activity (MSNA) is a new strategy offering information about the frequency of pure sympathetic firing. However, it is uncertain whether and when single-unit MSNA would be more useful than multiunit MSNA for analysis of various physiological stresses in humans. In 15 healthy subjects, we measured single-unit and multiunit MSNA before and during handgrip exercise at 30% of maximum voluntary contraction for 3 min and during the Valsalva maneuver at 40 mmHg expiratory pressure for 15 s. Shapes of individual single-unit MSNA were proved to be consistent and suitable for further evaluation. Single-unit and multiunit MSNA exhibited similar responses during handgrip exercise. However, acceleration of neural firing determined from single-unit MSNA became steeper than multiunit MSNA during the Valsalva maneuver. During the Valsalva maneuver, unlike handgrip exercise, the distribution of multiunit burst between 0, 1, 2, 3, and 4 spikes was significantly shifted toward multiple spikes within a given burst ( P < 0.05). These results indicated that evaluation of single-unit MSNA could provide more detailed and accurate information concerning the role and responses of neuronal discharges induced by various physiological stresses in humans, especially amid intense sympathetic activity.

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.

Sign in / Sign up

Export Citation Format

Share Document