Effect of concentric and eccentric muscle actions on muscle sympathetic nerve activity

1999 ◽  
Vol 86 (2) ◽  
pp. 558-563 ◽  
Author(s):  
Dario I. Carrasco ◽  
Michael D. Delp ◽  
Chester A. Ray
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Nerve Activity ◽  
Endurance Time ◽  
Muscle Metaboreflex ◽  
Muscle Ischemia ◽  
Muscle Actions

The purpose of this study was to determine the effects of concentric (Con) and eccentric (Ecc) muscle actions on leg muscle sympathetic nerve activity (MSNA). Two protocols were utilized. In protocol 1, eight subjects performed Con and Ecc arm curls for 2 min, with a resistance representing 50% of one-repetition maximum for Con curls. Heart rate (HR) and mean arterial pressure (MAP) were greater ( P < 0.05) during Con than during Ecc curls. Similarly, the MSNA was greater ( P < 0.05) during Con than during Ecc curls. In protocol 2, eight different subjects performed Con and Ecc arm curls to fatigue, followed by postexercise muscle ischemia, by using the same resistance as in protocol 1. Endurance time was significantly greater for Ecc than for Con curls. The increase in HR, MAP, and MSNA was greater ( P < 0.05) during Con than during Ecc curls. However, when the data were normalized as a function of endurance time, the differences in HR, MAP, and MSNA between Con and Ecc curls were no longer present. HR, MAP, and MSNA responses during postexercise muscle ischemia were similar for Con and Ecc curls. Con curls elicited greater increase ( P < 0.05) in blood lactate concentration than did Ecc curls. In summary, Con actions contribute significantly more to the increase in cardiovascular and MSNA responses during brief, submaximal exercise than do Ecc actions. However, when performed to a similar level of effort (i.e., fatigue), Con and Ecc muscle actions elicit similar cardiovascular and MSNA responses. These results indicate that the increase in MSNA during a typical bout of submaximal dynamic exercise is primarily mediated by the muscle metaboreflex, which is stimulated by metabolites produced predominantly during Con muscle action.

Modulation of sympathetic nerve activity during posthandgrip muscle ischemia in humans

1994 ◽  
Vol 266 (1) ◽  
pp. H79-H83 ◽  
Author(s):  
C. A. Ray ◽  
N. H. Secher ◽  
A. L. Mark
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Sensory Nerve ◽  
Vascular Occlusion ◽  
Voluntary Contraction ◽  
Central Command ◽  
Isometric Handgrip ◽  
Nerve Activity ◽  
Muscle Ischemia

To evaluate modulation of muscle sympathetic nerve activity (MSNA) during posthandgrip muscle ischemia (PHGMI), subjects performed 2 min of isometric handgrip at 33% of maximal voluntary contraction (MVC) followed by 2 min of PHGMI produced by forearm vascular occlusion. The response to PHGMI was studied in the absence and again during the addition of contralateral rhythmic handgrip (RHG; 40 times/min) at 15% (n = 6) and 30% (n = 10) MVC during the second minute of the PHGMI. Additionally, to isolate the effect of central command, response to PHGMI was studied during attempted RHG after sensory nerve blockade (n = 5). RHG for 2 min at 15 and 30% MVC and attempted RHG for 2 min did not increase MSNA. Isometric handgrip elicited an 130 +/- 48% increase in MSNA (P < 0.05), which was maintained during PHGMI. RHG at 15 and 30% MVC elicited an attenuation of MSNA (-10 +/- 7% and -14 +/- 6%, respectively) when performed during the second minute of PHGMI (P < 0.05). In contrast, attempted RHG did not significantly affect MSNA during PHGMI. The findings demonstrate modulation of MSNA during activation of the muscle metaboreflex. The attenuation of metaboreceptor-mediated increases in MSNA appear to be the result of mechanosensitive muscle afferents and not central command.

Muscle pump-induced inhibition of sympathetic vasomotor outflow during low-intensity leg cycling is attenuated by muscle metaboreflex activation

2020 ◽  
Vol 128 (1) ◽  
pp. 1-7
Author(s):  
Keisho Katayama ◽  
Thales C. Barbosa ◽  
Jasdeep Kaur ◽  
Benjamin E. Young ◽  
Damsara Nandadeva ◽  
...  
Keyword(s):  
Sympathetic Nerve ◽  
High Intensity ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Nerve Activity ◽  
Muscle Metaboreflex ◽  
Muscle Pump ◽  
Low Intensity ◽  
Leg Cycling ◽  
Cardiopulmonary Baroreflex

Muscle sympathetic nerve activity (MSNA) decreases during leg cycling at low intensity because of muscle pump-induced increases in venous return and loading of the cardiopulmonary baroreceptors. However, MSNA increases during leg cycling when exercise is above moderate intensity or for a long duration, suggesting that the sympathoinhibitory effect of the cardiopulmonary baroreflex can be overridden by a powerful sympathoexcitatory drive, such as the skeletal muscle metaboreflex. Therefore, we tested the hypothesis that high-intensity muscle metaboreflex activation attenuates muscle pump-induced inhibition of MSNA during leg cycling. MSNA (left radial nerve) was recorded during graded isolation of the muscle metaboreflex in the forearm with postexercise ischemia (PEI) after low (PEI-L)- and high (PEI-H)-intensity isometric handgrip exercise (20% and 40% maximum voluntary contraction, respectively). Leg cycling (15–20 W) was performed alone and during each PEI trial (PEI-L+Cycling, PEI-H+Cycling). Cycling alone induced a significant decrease in MSNA burst frequency (BF) and total activity (TA). MSNA BF and TA also decreased when cycling was performed during PEI-L. However, the magnitude of decrease in MSNA during PEI-L+Cycling [∆BF: –19 ± 2% ( P < 0.001), ∆TA: –25 ± 4% ( P < 0.001); mean ± SE] was less than that during cycling alone [∆BF: –39 ± 5% ( P = 0.003), ∆TA: –45 ± 5% ( P = 0.002)]. More importantly, MSNA did not decrease during cycling with PEI-H [∆BF: –1 ± 2% ( P = 0.845), ∆TA: +2 ± 3% ( P = 0.959)]. These results suggest that muscle pump-induced inhibition of sympathetic vasomotor outflow during low-intensity leg cycling is attenuated by muscle metaboreflex activation in an intensity-dependent manner. NEW & NOTEWORTHY There are no available data concerning the interaction between the sympathoinhibitory effect of muscle pump-induced cardiopulmonary baroreflex loading during leg cycling and the sympathoexcitatory influence of the muscle metaboreflex. In this study, muscle metaboreflex activation attenuated the inhibition of muscle sympathetic nerve activity (MSNA) during leg cycling. This may explain, in part, the response of MSNA to graded-intensity dynamic exercise in which low-intensity leg cycling inhibits MSNA whereas high-intensity exercise elicits graded sympathoexcitation.

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.

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.

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.

Augmentation of muscle sympathetic nerve activity during fatiguing isometric leg exercise

1993 ◽  
Vol 75 (1) ◽  
pp. 228-232 ◽  
Author(s):  
C. A. Ray ◽  
A. L. Mark
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Burst Frequency ◽  
Nerve Activity ◽  
Muscle Metaboreflex ◽  
Isometric Knee Extension ◽  
Leg Exercise

Recent studies have shown a lack of an increase in muscle sympathetic nerve activity (MSNA) during leg exercise. Experiments using isometric knee extension (IKE) have shown a biphasic response in MSNA with a decrease during the 1st min and a return of MSNA to control levels during the 2nd min of IKE. Moreover, MSNA was not augmented during postexercise muscle ischemia (PEMI) of the exercising leg, suggesting that the muscle metaboreflex may have not been engaged in these experiments. The purpose of the present study was 1) to examine MSNA during IKE performed to fatigue to determine whether MSNA could be increased with leg exercise and 2) to determine whether increases in MSNA during fatiguing IKE were associated with an augmented MSNA response during PEMI. IKE was initially performed to fatigue at 30% of maximal voluntary contraction in the sitting position (n = 7; trial 1). IKE elicited a marked increase in mean arterial pressure and heart rate (P < 0.01). Total MSNA (burst frequency x mean burst amplitude; units) in the contralateral leg increased 96 +/- 40% (P < 0.01) above control levels during the final 30 s of IKE (207 +/- 23 s). Subjects (n = 8) then performed IKE to fatigue followed by PEMI (trial 2). MSNA in the contralateral leg increased 107 +/- 50% (P < 0.01) above control levels during the final 30 s of IKE (169 +/- 12 s) and remained significantly elevated during PEMI (83 +/- 40% above control), indicating that the muscle metaboreflex was engaged during fatiguing IKE.(ABSTRACT TRUNCATED AT 250 WORDS)

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