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.

Sympathetic neural discharge and vascular resistance during exercise in humans

1989 ◽  
Vol 66 (5) ◽  
pp. 2472-2478 ◽  
Author(s):  
D. R. Seals
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Vascular Resistance ◽  
Sympathetic Nerve ◽  
Muscle Sympathetic Nerve Activity ◽  
Isometric Exercise ◽  
Lower Leg ◽  
Voluntary Contraction ◽  
Isometric Handgrip ◽  
Exercise In Humans

The purpose of this study was to determine the relationship between changes in efferent muscle sympathetic nerve activity (MSNA) to the lower leg and calf vascular resistance (CVR) during isometric exercise in humans. We made intraneural (microneurographic) determinations of MSNA in the right leg (peroneal nerve) while simultaneously measuring calf blood flow to the left leg, arterial pressure, and heart rate in 10 subjects before (control), during, and after (recovery) isometric handgrip exercise performed for 2.5 min at 15, 25, and 35% of maximal voluntary contraction (MVC). Heart rate and arterial pressure increased above control within the initial 30 s of handgrip at all levels, and the magnitudes of the increases at end contraction were proportional to the intensity of the exercise. In general, neither MSNA nor CVR increased significantly above control levels during handgrip at 15% MVC. Similarly, neither variable increased above control during the initial 30 s of handgrip at 25 and 35% MVC; however, during the remainder of the contraction period, progressive, parallel increases were observed in MSNA and CVR (P less than 0.05). The correlation coefficients relating changes in MSNA to changes in CVR for the individual subjects averaged 0.63 +/- 0.07 (SE) (range 0.30–0.91) and 0.94 +/- 0.06 (range 0.80–0.99) for the 25 and 35% MVC levels, respectively. During recovery, both MSNA and CVR returned rapidly toward control levels. These findings demonstrate that muscle sympathetic nerve discharge and vascular resistance in the lower leg are tightly coupled during and after isometric arm exercise in humans. Furthermore, the exercise-induced adjustments in the two variables are both contraction intensity and time dependent.

Hyperoxia enhances metaboreflex sensitivity during static exercise in humans

2006 ◽  
Vol 291 (1) ◽  
pp. H210-H215 ◽  
Author(s):  
Anne Houssière ◽  
Boutaina Najem ◽  
Nicolas Cuylits ◽  
Sophie Cuypers ◽  
Robert Naeije ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Sympathetic Nerve ◽  
Animal Studies ◽  
Muscle Sympathetic Nerve Activity ◽  
Circulatory Arrest ◽  
Lactic Acid Production ◽  
Isometric Exercise ◽  
Lactate Production ◽  
Voluntary Contraction ◽  
Isometric Handgrip

Peripheral chemoreflex inhibition with hyperoxia decreases sympathetic nerve traffic to muscle circulation [muscle sympathetic nerve activity (MSNA)]. Hyperoxia also decreases lactate production during exercise. However, hyperoxia markedly increases the activation of sensory endings in skeletal muscle in animal studies. We tested the hypothesis that hyperoxia increases the MSNA and mean blood pressure (MBP) responses to isometric exercise. The effects of breathing 21% and 100% oxygen at rest and during isometric handgrip at 30% of maximal voluntary contraction on MSNA, heart rate (HR), MBP, blood lactate (BL), and arterial O2 saturation (SaO2) were determined in 12 healthy men. The isometric handgrips were followed by 3 min of postexercise circulatory arrest (PE-CA) to allow metaboreflex activation in the absence of other reflex mechanisms. Hyperoxia lowered resting MSNA, HR, MBP, and BL but increased SaO2 compared with normoxia (all P < 0.05). MSNA and MBP increased more when exercise was performed in hyperoxia than in normoxia (MSNA: hyperoxic exercise, 255 ± 100% vs. normoxic exercise, 211 ± 80%, P = 0.04; and MBP: hyperoxic exercise, 33 ± 9 mmHg vs. normoxic exercise, 26 ± 10 mmHg, P = 0.03). During PE-CA, MSNA and MBP remained elevated (both P < 0.05) and to a larger extent during hyperoxia than normoxia ( P < 0.05). Hyperoxia enhances the sympathetic and blood pressure (BP) reactivity to metaboreflex activation. This is due to an increase in metaboreflex sensitivity by hyperoxia that overrules the sympathoinhibitory and BP lowering effects of chemoreflex inhibition. This occurs despite a reduced lactic acid production.

Muscle sympathetic nerve responses to graded leg cycling

1993 ◽  
Vol 75 (2) ◽  
pp. 663-667 ◽  
Author(s):  
M. Saito ◽  
A. Tsukanaka ◽  
D. Yanagihara ◽  
T. Mano
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Oxygen Uptake ◽  
Sympathetic Nerve ◽  
Muscle Sympathetic Nerve Activity ◽  
Burst Frequency ◽  
Control Value ◽  
Leg Cycling ◽  
Exercise Muscle ◽  
The Right

The aim of this study was to clarify the relationship between sympathetic outflow to skeletal muscle and oxygen uptake during dynamic exercise. Muscle sympathetic nerve activity (MSNA) was recorded from the right median nerve microneurographically in eight healthy volunteers during leg cycling at four different intensities in a seated position for a 16-min bout. Work loads selected were 20, 40, 60, and 75% of maximal oxygen uptake (VO2max). Heart rate and blood pressure were measured during each exercise test. MSNA burst frequency was suppressed by 28% during cycling at 20% VO2max (23 vs. 33 bursts/min for control). Thereafter, it increased in a linear fashion with increasing work rate, with a significantly higher burst frequency during 60% VO2max than the control value. Both heart rate and mean blood pressure rose significantly during 20% VO2max from the control value and increased linearly with increased exercise intensity. During light exercise, MSNA was suppressed by arterial and cardiopulmonary baroreceptors as a result of the hemodynamic changes associated with leg muscle pumping. The baroreflex inhibition may overcome the muscle metaboreflex excitation to induce MSNA suppression during light exercise. These results suggest that during light exercise MSNA is inhibited, perhaps due to loading of the cardiopulmonary and arterial baroreflexes, and that during heavier exercise the increase in MSNA occurs as muscle metaboreflexes are activated.

Influence of Sympatholytic Drugs on the Cardiovascular Response to Isometric Exercise

1981 ◽  
Vol 60 (2) ◽  
pp. 139-143 ◽  
Author(s):  
S. J. Watt ◽  
R. D. Thomas ◽  
P. W. Belfield ◽  
P. W. Goldstraw ◽  
S. H. Taylor
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Healthy Subjects ◽  
Cardiovascular Response ◽  
Pressor Response ◽  
Isometric Exercise ◽  
Systemic Blood Pressure ◽  
Isometric Handgrip ◽  
Systemic Blood ◽  
Oral Doses

1. The effects of single oral doses of various sympatholytic drugs on the heart rate and blood pressure increases during isometric handgrip contraction were studied in six healthy subjects. 2. Bethanidine reduced both the systolic and diastolic increases in pressure. Clonidine reduced the systolic but not the diastolic increase. Oxprenolol alone or in combination with phentolamine or phenyoxybenzamine failed to influence the pressor response. 3. The increase in systemic blood pressure associated with sustained contraction of voluntary muscle appears to be relatively resistant to acute sympathetic adrenoreceptor blockade in man.

Exercise intensity influences cardiac baroreflex function at the onset of isometric exercise in humans

2007 ◽  
Vol 103 (3) ◽  
pp. 941-947 ◽  
Author(s):  
James P. Fisher ◽  
Shigehiko Ogoh ◽  
Colin N. Young ◽  
David M. Keller ◽  
Paul J. Fadel
Keyword(s):  
Blood Pressure ◽  
Exercise Intensity ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Isometric Handgrip ◽  
Baroreflex Control ◽  
Cardiac Responses ◽  
Carotid Baroreflex ◽  
Exercise Onset ◽  
Exercise In Humans

We sought to examine the influence of exercise intensity on carotid baroreflex (CBR) control of heart rate (HR) and mean arterial pressure (MAP) at the onset of exercise in humans. To accomplish this, eight subjects performed multiple 1-min bouts of isometric handgrip (HG) exercise at 15, 30, 45 and 60% maximal voluntary contraction (MVC), while breathing to a metronome set at eupneic frequency. Neck suction (NS) of −60 Torr was applied for 5 s at end expiration to stimulate the CBR at rest, at the onset of HG (<1 s), and after ∼40 s of HG. Beat-to-beat measurements of HR and MAP were recorded throughout. Cardiac responses to NS at onset of 15% (−12 ± 2 beats/min) and 30% (−10 ± 2 beats/min) MVC HG were similar to rest (−10 ± 1 beats/min). However, HR responses to NS were reduced at the onset of 45% and 60% MVC HG (−6 ± 2 and −4 ± 1 beats/min, respectively; P < 0.001). In contrast to HR, MAP responses to NS were not different from rest at exercise onset. Furthermore, both HR and MAP responses to NS applied at ∼40s of HG were similar to rest. In summary, CBR control of HR was transiently blunted at the immediate onset of high-intensity HG, whereas MAP responses were preserved demonstrating differential baroreflex control of HR and blood pressure at exercise onset. Collectively, these results suggest that carotid-cardiac baroreflex control is dynamically modulated throughout isometric exercise in humans, whereas carotid baroreflex regulation of blood pressure is well-maintained.

Baroreflex modulation of muscle sympathetic nerve activity during posthandgrip muscle ischemia in humans

2001 ◽  
Vol 91 (4) ◽  
pp. 1679-1686 ◽  
Author(s):  
Jian Cui ◽  
Thad E. Wilson ◽  
Manabu Shibasaki ◽  
Nicole A. Hodges ◽  
Craig G. Crandall
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Isometric Handgrip ◽  
Nerve Activity ◽  
Arterial Blood ◽  
Muscle Ischemia ◽  
The Relationship

To identify whether muscle metaboreceptor stimulation alters baroreflex control of muscle sympathetic nerve activity (MSNA), MSNA, beat-by-beat arterial blood pressure (Finapres), and electrocardiogram were recorded in 11 healthy subjects in the supine position. Subjects performed 2 min of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 2.5 min of posthandgrip muscle ischemia. During muscle ischemia, blood pressure was lowered and then raised by intravenous bolus infusions of sodium nitroprusside and phenylephrine HCl, respectively. The slope of the relationship between MSNA and diastolic blood pressure was more negative ( P < 0.001) during posthandgrip muscle ischemia (−201.9 ± 20.4 units · beat−1 · mmHg−1) when compared with control conditions (−142.7 ± 17.3 units · beat−1 · mmHg−1). No significant change in the slope of the relationship between heart rate and systolic blood pressure was observed. However, both curves shifted during postexercise ischemia to accommodate the elevation in blood pressure and MSNA that occurs with this condition. These data suggest that the sensitivity of baroreflex modulation of MSNA is elevated by muscle metaboreceptor stimulation, whereas the sensitivity of baroreflex of modulate heart rate is unchanged during posthandgrip muscle ischemia.

scholarly journals Whole body heat stress attenuates the pressure response to muscle metaboreceptor stimulation in humans

2016 ◽  
Vol 121 (5) ◽  
pp. 1178-1186 ◽  
Author(s):  
Jian Cui ◽  
Cheryl Blaha ◽  
Lawrence I. Sinoway
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heat Stress ◽  
Sympathetic Nerve ◽  
Muscle Sympathetic Nerve Activity ◽  
Cardiovascular Responses ◽  
Whole Body ◽  
Isometric Handgrip ◽  
Whole Body Heat Stress ◽  
Body Heat

The effects of whole body heat stress on sympathetic and cardiovascular responses to stimulation of muscle metaboreceptors and mechanoreceptors remains unclear. We examined the muscle sympathetic nerve activity (MSNA), blood pressure, and heart rate in 14 young healthy subjects during fatiguing isometric handgrip exercise, postexercise circulatory occlusion (PECO), and passive muscle stretch during PECO. The protocol was performed under normothermic and whole body heat stress (increase internal temperature ~0.6°C via a heating suit) conditions. Heat stress increased the resting MSNA and heart rate. Heat stress did not alter the mean blood pressure (MAP), heart rate, and MSNA responses (i.e., changes) to fatiguing exercise. During PECO, whole body heat stress accentuated the heart rate response [change (Δ) of 5.8 ± 1.5 to Δ10.0 ± 2.1 beats/min, P = 0.03], did not alter the MSNA response (Δ16.4 ± 2.8 to Δ17.3 ± 3.8 bursts/min, P = 0.74), and lowered the MAP response (Δ20 ± 2 to Δ12 ± 1 mmHg, P < 0.001). Under normothermic conditions, passive stretch during PECO evoked significant increases in MAP and MSNA (both P < 0.001). Of note, heat stress prevented the MAP and MSNA responses to stretch during PECO (both P > 0.05). These data suggest that whole body heat stress attenuates the pressor response due to metaboreceptor stimulation, and the sympathetic nerve response due to mechanoreceptor stimulation.

Effect of aerobic conditioning on cardiovascular response to isometric exercise

1982 ◽  
Vol 52 (5) ◽  
pp. 1257-1260 ◽  
Author(s):  
B. J. Morgan ◽  
H. L. Brammell ◽  
D. L. Sable ◽  
M. L. Morton ◽  
L. D. Horwitz
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Systolic Blood Pressure ◽  
Cardiovascular Response ◽  
Isometric Exercise ◽  
Adrenergic Blockade ◽  
Isometric Handgrip ◽  
Double Product ◽  
Beta Adrenergic ◽  
Aerobic Conditioning

The response to isometric handgrip exercise (IHE) and isometric quadriceps exercise (IQE) (30% maximum voluntary contraction held 3 min) was studied before and after 5 wk of aerobic training. Training exercises involved only the lower extremities. Seventeen healthy unconditioned males aged 21--35 yr were subjects. During training nine subjects received propranolol in doses that provided a high degree of beta-adrenergic blockade; eight received a placebo. All subjects were tested before training or drug and after training, 3--5 days off drug. With IGE after training, the placebo group had lower maximum heart rate (91 +/- 4 to 79 +/- 5 beats/min, P less than 0.05), systolic blood pressure (151 +/- 5 to 139 +/- 4 mmHg, P less than 0.05), and double product (heart rate x systolic blood pressure) (138 +/- 10 x 10(2) to 110 +/- 7 x 10(2), P less than 0.05). The response to IQE in the propranolol group was unchanged after training. Heart rate, systolic blood pressure, and double product with IHE was unchanged in either group after training. Aerobic conditioning can modify the hemodynamic response to isometric exercise. This effect is specific for the trained muscle group and is prevented by beta-adrenergic blockade.

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.

Isometric handgrip training reduces arterial pressure at rest without changes in sympathetic nerve activity

2000 ◽  
Vol 279 (1) ◽  
pp. H245-H249 ◽  
Author(s):  
Chester A. Ray ◽  
Dario I. Carrasco
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Cardiovascular Responses ◽  
Voluntary Contraction ◽  
Isometric Handgrip ◽  
Nerve Activity ◽  
Muscle Ischemia

The purpose of this study was to determine whether isometric handgrip (IHG) training reduces arterial pressure and whether reductions in muscle sympathetic nerve activity (MSNA) mediate this drop in arterial pressure. Normotensive subjects were assigned to training ( n = 9), sham training ( n = 7), or control ( n = 8) groups. The training protocol consisted of four 3-min bouts of IHG exercise at 30% of maximal voluntary contraction (MVC) separated by 5-min rest periods. Training was performed four times per week for 5 wk. Subjects' resting arterial pressure and heart rate were measured three times on 3 consecutive days before and after training, with resting MSNA (peroneal nerve) recorded on the third day. Additionally, subjects performed IHG exercise at 30% of MVC to fatigue followed by muscle ischemia. In the trained group, resting diastolic (67 ± 1 to 62 ± 1 mmHg) and mean arterial pressure (86 ± 1 to 82 ± 1 mmHg) significantly decreased, whereas systolic arterial pressure (116 ± 3 to 113 ± 2 mmHg), heart rate (67 ± 4 to 66 ± 4 beats/min), and MSNA (14 ± 2 to 15 ± 2 bursts/min) did not significantly change following training. MSNA and cardiovascular responses to exercise and postexercise muscle ischemia were unchanged by training. There were no significant changes in any variables for the sham training and control groups. The results indicate that IHG training is an effective nonpharmacological intervention in lowering arterial pressure.

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