Sympathetic modulation of blood flow and O2 uptake in rhythmically contracting human forearm muscles

1992 ◽  
Vol 263 (4) ◽  
pp. H1078-H1083 ◽  
Author(s):  
M. J. Joyner ◽  
L. A. Nauss ◽  
M. A. Warner ◽  
D. O. Warner
Keyword(s):  
Blood Flow ◽  
Body Position ◽  
Maximum Voluntary Contraction ◽  
Sympathetic Nerves ◽  
Work Load ◽  
Voluntary Contraction ◽  
Sympathetic Block ◽  
O2 Uptake ◽  
Fick Principle ◽  
Rhythmic Exercise

This study tested the effects of sympathetically mediated changes in blood flow to active muscles on muscle O2 uptake (VO2) in humans. Four minutes of graded (15-80% of maximum voluntary contraction, MVC) rhythmic handgrip exercise were performed. Forearm blood flow (FBF) (plethysmography) and deep vein O2 saturation were measured each minute. Forearm O2 uptake was calculated using the Fick principle. In protocol 1, exercise was performed while supine and again while upright to augment sympathetic outflow to the active muscles. Standing reduced FBF at rest from 3.6 to 2.2 ml.100 ml-1.min-1 (P < 0.05). During light exercise (15-40% MVC) FBF was unaffected by body position. Standing reduced FBF (P < 0.05) from 36.0 to 25.2 ml.100 ml-1.min-1 and forearm VO2 from 38.2 to 28.1 ml.kg-1.min-1 during the final work load. In protocol 2, exercise was performed while supine before and after local anesthetic block of the sympathetic nerves to the forearm. Sympathetic block increased FBF at rest from 3.1 to 8.9 ml.100 ml-1.min-1 (P < 0.05), and FBF was higher during all work loads At 70-80% of MVC sympathetic block increased FBF from 35.4 to 50.7 ml.100 ml-1.min-1 (P < 0.05), and forearm VO2 from 45.5 to 54.2 ml.kg-1.min-1 (P < 0.05). These results suggest that in humans sympathetic nerves modulate blood flow to active muscles during light and heavy rhythmic exercise and that this restraint of flow can limit O2 uptake in muscles performing heavy rhythmic exercise.

Near-infrared estimation of O2 supply and consumption in forearm muscles working at varying intensity

1996 ◽  
Vol 80 (4) ◽  
pp. 1279-1284 ◽  
Author(s):  
S. Homma ◽  
H. Eda ◽  
S. Ogasawara ◽  
A. Kagaya
Keyword(s):  
Blood Flow ◽  
Near Infrared ◽  
Maximum Voluntary Contraction ◽  
Venous Occlusion ◽  
Voluntary Contraction ◽  
Flow Index ◽  
O2 Consumption ◽  
Rate Of Increase ◽  
Consumption Index ◽  
O2 Supply

We estimated a blood flow index, O2 supply index, and O2 consumption index from near-infrared (NIR) signals during venous occlusion imposed at rest and immediately after handgrip exercise with loads equal to 5, 10, 15, 20, 25, and 30% of the maximum voluntary contraction. We also estimated forearm blood flow (BFfa) by strain-gauge plethysmography and forearm O2 consumption (VO2fa) by the invasive method. There was a significant correlation between the rate of increase in total hemoglobin during venous occlusion obtained from NIR signals and BFfa in each subject (r = 0.853 approximately 0.981, P < 0.001). There was also a significant correlation (r = 0.854 approximately 0.944, P < 0.001) between the O2 consumption index estimated from NIR signals and VO2fa. The mean values for O2 supply index in five subjects increased with exercise intensity, while the O2 consumption index showed no further increase about 25% of maximum voluntary contraction. We found significant positive correlations between the O2 supply index and BFfa (r = 0.986, P < 0.001) and the O2 consumption index and VO2fa (r = 0.976, P < 0.001) during exercise at 5-30% of maximum voluntary contraction. These results demonstrate that analysis of NIR signals during venous occlusion provides an advantageous method of estimation of O2 supply and consumption in working muscles during exercise of varying intensity.

Intestinal O2 uptake during sympathetic stimulation and partial arterial occlusion

1979 ◽  
Vol 236 (5) ◽  
pp. H731-H735
Author(s):  
A. P. Shepherd
Keyword(s):  
Blood Flow ◽  
Arterial Occlusion ◽  
Sympathetic Nerves ◽  
Capillary Density ◽  
Sympathetic Stimulation ◽  
O2 Uptake ◽  
Diffusion Limitations ◽  
O2 Extraction ◽  
Series Of Experiments ◽  
Through Diffusion

In isolated loops of canine small bowel perfused at constant blood flow, stimulating perivascular sympathetic nerves (8--10 Hz) depressed O2 extraction and O2 uptake. Because sympathetic stimulation also decreased 86Rb extraction, the results confirmed earlier studies indicating that sympathetic stimulation closes "precapillary sphincters" and through diffusion limitations reduces the capillary-to-cell flux of oxygen. To determine if sympathetic stimulation could lower O2 uptake under more physiologic circumstances, a second series of experiments was performed during constant arterial pressure perfusion. Sympathetic stimulation reduced blood flow by about 30% in the steady phase. Oxygen extraction did not increase appreciably, so O2 uptake was also reduced. When partial arterial occlusion was used to lower the blood flow to the level that it reached during sympathetic stimulation, large increases (37%) in O2 extraction occurred so that O2 uptake remained near control levels. The results indicate that after arterial occlusion local mechanisms maintain O2 uptake by increasing O2 extraction through capillary density increases, but that this mechanism is impaired by sympathetic stimulation.

Effects of contraction force and frequency on postexercise hyperemia in human calf muscles

1980 ◽  
Vol 49 (4) ◽  
pp. 649-654 ◽  
Author(s):  
D. Richardson ◽  
R. Shewchuk
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Calf Muscle ◽  
Contraction Force ◽  
A Value ◽  
True Blood ◽  
The Right ◽  
Human Calf

The purpose of this study was to examine the separate effects of contraction force and frequency on postexercise hyperemia in the human calf muscle. Nine male subjects were used. Each was seated in a chair with the right foot on a pedal coupled to a load cell and the knee secured. Calf muscle blood flow, measured by a Whitney gauge, was determined before and periodically after 3-pmin bouts of rhythmic isometric plantar-flexor exercise. The contraction frequency was graded from 20 to 50 to 80 contractions/min. The force per contraction was graded from 7.5 to 15 to 30% of maximum voluntary contraction (MVC) of the calf muscle. The average MCV was 502 lb. Peak postexercise blood flow (PBF) increased with either increasing frequency at a given force or increasing force at a given frequency. However, at the higher levels of exercise, PBF tended to plateau at a value of about 50 ml.min-1.100 ml-1. The plateau phase of PBF was associated with a substantial increase in the total volume of postexercise hyperemia. This appeared to be well above any repayment of a blood flow deficit. However, it is not certain that the extra volume represented the repayment of a true blood flow debt.

Effects of airflow and work load on cardiovascular drift and skin blood flow

1984 ◽  
Vol 56 (5) ◽  
pp. 1411-1417 ◽  
Author(s):  
J. D. Shaffrath ◽  
W. C. Adams
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Skin Blood Flow ◽  
Prolonged Exercise ◽  
Work Load ◽  
Progressive Increase ◽  
Cycle Ergometry ◽  
O2 Uptake ◽  
Mean Values ◽  
Cardiovascular Drift

Cardiovascular drift (CVD) can be defined as a progressive increase in heart rate (HR), decreases in stroke volume (SV) and mean arterial pressure (MAP), and a maintained cardiac output (Q) during prolonged exercise. To test the hypothesis that the magnitude of CVD would be related to changes in skin blood flow ( SkBF ), eight healthy, moderately trained males performed 70-min bouts of cycle ergometry in a 2 X 2 assortment of airflows (less than 0.2 and 4.3 m X s-1) and relative work loads (43.4% and 62.2% maximal O2 uptake). Ambient temperature and relative humidity were controlled to mean values of 24.2 +/- 0.8 degrees C and 39.5 +/- 2.4%, respectively. Q, HR, MAP, SkBF , skin and rectal temperatures, and pulmonary gas exchange were measured at 10-min intervals during exercise. Between the 10th and 70th min during exercise at the higher work load with negligible airflow, HR and SkBF increased by 21.6 beats X min-1 and 14.0 ml X 100 ml-1 X min-1, respectively, while SV and MAP decreased by 16.4 ml and 11.3 mmHg. The same work load in the presence of 4.3 m X s-1 airflow resulted in nonsignificant changes of 7.6 beats X min-1, 4.0 ml X (100 ml-1 X min)-1, -2.7 ml, and -1.7 mmHg for HR, SkBF , SV, and MAP. Since nonsignificant changes in HR, SkBF , SV, and MAP were observed at the lower work load in both airflow conditions, the results emphasize that CVD occurs only in conditions which combine high metabolic and thermal circulatory demands.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of altered arterial perfusion pressure on vascular conductance and muscle blood flow dynamic response during exercise in humans

2013 ◽  
Vol 114 (5) ◽  
pp. 620-627 ◽  
Author(s):  
Rodrigo Villar ◽  
Richard L. Hughson
Keyword(s):  
Blood Flow ◽  
Power Output ◽  
Perfusion Pressure ◽  
Body Position ◽  
Muscle Blood Flow ◽  
Plantar Flexion ◽  
Voluntary Contraction ◽  
Vascular Conductance ◽  
Arterial Perfusion ◽  
Three Body

Changes in vascular conductance (VC) are required to counter changes in muscle perfusion pressure (MPP) to maintain muscle blood flow (MBF) during exercise. We investigated the recruitment of VC as a function of peak VC measured in three body positions at two different work rates to test the hypothesis that adaptations in VC compensated changes in MPP at low-power output (LPO), but not at high-power output (HPO). Eleven healthy volunteers exercised at LPO and HPO (repeated plantar flexion contractions at 20–30% maximal voluntary contraction, respectively) in horizontal (HOR), 35° head-down tilt (HDT), and 45° head-up tilt (HUT). Muscle blood flow velocity and popliteal diameter were measured by ultrasound to determine MBF, and VC was estimated by dividing MBF flow by MPP. Peak VC was unaffected by body position. The rates of increase in MBF and VC were significantly faster in HUT and slower in HDT than HOR, and rates were faster in LPO than HPO. During LPO exercise, the increase in, and steady-state values of, MBF were less for HUT and HDT than HOR; the increase in VC was less in HUT than HOR and HDT. During HPO exercise, MBF in the HDT was reduced compared with HOR and HUT, even though VC reached 92% VC peak, which was greater than HOR, which was, in turn, greater than HUT. Reduced MBF during HPO HDT exercise had the functional consequence of a significant increase in muscle electromyographic index, revealing the effects of MPP on O2 delivery during exercise.

scholarly journals Effect of vitamin C on hyperoxia-induced vasoconstriction in exercising skeletal muscle

2014 ◽  
Vol 117 (10) ◽  
pp. 1207-1211 ◽  
Author(s):  
Sushant M. Ranadive ◽  
Michael J. Joyner ◽  
Branton G. Walker ◽  
Jennifer L. Taylor ◽  
Darren P. Casey
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Vitamin C ◽  
Muscle Blood Flow ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Ros Generation ◽  
Forearm Vascular Conductance ◽  
Forearm Exercise ◽  
Induced Changes

Hyperoxia can cause substantial reductions in peripheral and coronary blood flow at rest and during exercise, which may be caused by reactive oxygen species (ROS) generated during hyperoxia. The aim of this study was to investigate the role of ROS in hyperoxia-induced reductions in skeletal muscle blood flow during forearm exercise. We hypothesized that infusion of vitamin C would abolish the effects of hyperoxia on the forearm blood flow (FBF) responses to exercise. Twelve young healthy adults performed rhythmic forearm handgrip exercise (10% of maximum voluntary contraction for 5 min) during normoxia and hyperoxia. For each condition, two trials were conducted with intra-arterial administration of saline or vitamin C. FBF was measured using Doppler ultrasound. During hyperoxia with saline, FBF and forearm vascular conductance (FVC) were 86.3 ± 5.1 and 86.8 ± 5.2%, respectively, of the normoxic values (100%) ( P < 0.05). During vitamin C, hyperoxic FBF and FVC responses were 90.9 ± 4.2 and 90.9 ± 4.1%, respectively, of the normoxic values ( P = 0.57 and 0.59). Subjects were then divided into three subgroups based on their percent decrease in FBF (>20, 10–20, and <10%) during hyperoxia. In the subgroup that demonstrated the greatest hyperoxia-induced changes (>20%), FBF and FVC during hyperoxia were 67.1 ± 4.0 and 66.8 ± 3.6%, respectively, of the normoxic values. Vitamin C abolished these effects on FBF and FVC with values that were 102.0 ± 5.2 and 100.8 ± 6.1%, respectively. However, vitamin C had no effect in the other two subgroups. This analysis is consistent with the idea that ROS generation blunts the FBF responses to exercise in the subjects most affected by hyperoxia.

Arm blood flow at rest and during arm exercise

1991 ◽  
Vol 70 (2) ◽  
pp. 928-933 ◽  
Author(s):  
G. Ahlborg ◽  
M. Jensen-Urstad
Keyword(s):  
Blood Flow ◽  
Indocyanine Green ◽  
Work Load ◽  
Mechanical Efficiency ◽  
Dilution Method ◽  
O2 Uptake ◽  
Concentration Difference ◽  
Arm Exercise ◽  
Constant Rate ◽  
Leg Exercise

To test the applicability of a dye-dilution method to quantitate total arm blood flow at rest and during arm exercise, indocyanine green was infused at a constant rate into the brachial artery. Eight subjects performed continuous 30-min arm exercises with an increase in intensity every 10 min (30, 60, and 90 W). The loads corresponded to 29 +/- 1, 48 +/- 2, and 78 +/- 4% (means +/- SE) of the maximal O2 uptake (VO2max 2.13 +/- 0.08 l/min) during arm exercise. VO2max during arm exercise was 61 +/- 1.7% of that during leg exercise. The dye concentration was analyzed in blood samples from three arm veins, two ipsi- and one contralateral, at shoulder level. Corresponding dye concentrations in both ipsilateral veins and a stable concentration difference between ipsi- and contralateral veins were achieved. Total arm blood flow was calculated to be 0.21 +/- 0.04 l/min at rest and 2.43 +/- 0.14 l/min at 90 W. Arm O2 uptake rose from 9 +/- 2 to 323 +/- 21 ml/min. Arm blood flow and O2 uptake each correlated linearly with both work load (r = 0.98) and pulmonary O2 uptake (r greater than or equal to 0.98). Mechanical efficiency for the arm and body was 34-44 and 16-19%, respectively. We conclude that arm blood flow can be determined by continuous infusion of indocyanine green.

Forearm blood flow responses to handgripping after local neuromuscular blockade

1998 ◽  
Vol 84 (2) ◽  
pp. 754-758 ◽  
Author(s):  
Christopher K. Dyke ◽  
Niki M. Dietz ◽  
Robert L. Lennon ◽  
David O. Warner ◽  
Michael J. Joyner
Keyword(s):  
Skeletal Muscle ◽  
Heart Rate ◽  
Blood Flow ◽  
Neuromuscular Blockade ◽  
Drug Administration ◽  
Forearm Blood Flow ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Neuromuscular Blocking ◽  
Motor Nerves

Dyke, Christopher K., Niki M. Dietz, Robert L. Lennon, David O. Warner, and Michael J. Joyner. Forearm blood flow responses to handgripping after local neuromuscular blockade. J. Appl. Physiol. 84(2): 754–758, 1998.—To test the hypothesis that acetylcholine “spillover” from motor nerves contributes significantly to skeletal muscle vasodilation during exercise, we measured the forearm blood flow responses during attempted handgripping after local paralysis of the forearm with the neuromuscular-blocking drug pipecuronium. This compound blocks postsynaptic nicotinic receptors but has no impact on acetylcholine release from motor nerves. The drug was administered selectively to one forearm by using regional intravenous drug administration techniques in five subjects. Pipecuronium reduced maximum forearm grip strength from 40.0 ± 3.2 kg before treatment to 0.0 kg after treatment. By contrast, drug administration had no effect on maximum voluntary contraction in the untreated forearm (41.3 ± 3.3 vs. 41.4 ± 2.7 kg). During 2 min of attempted maximal contraction of the paralyzed forearm, the forearm blood flow increased from only 3.4 ± 0.8 to 4.8 ± 1.2 ml ⋅ 100 ml−1 ⋅ min−1( P < 0.05). Heart rate increased from 63 ± 3 to 73 ± 8 beats/min ( P > 0.05) during attempted contraction, and only three of five subjects showed obvious increases in heart rate. Mean arterial pressure increased significantly ( P < 0.05) from 102 ± 6 to 109 ± 9 mmHg during attempted contractions. When these increases in flow are considered in the context of the marked (10-fold or greater) increases in flow seen in contracting forearm skeletal muscle, it appears that acetylcholine spillover from motor nerves has, at most, a minimal impact on the hyperemic responses to contraction in humans.

scholarly journals Influence of sex and active muscle mass on renal vascular responses during static exercise

2006 ◽  
Vol 291 (1) ◽  
pp. H121-H126 ◽  
Author(s):  
Afsana Momen ◽  
Brian Handly ◽  
Allen Kunselman ◽  
Urs A. Leuenberger ◽  
Lawrence I. Sinoway
Keyword(s):  
Blood Flow ◽  
Muscle Mass ◽  
Maximum Voluntary Contraction ◽  
Duplex Ultrasound ◽  
Cardiovascular Responses ◽  
Voluntary Contraction ◽  
Static Exercise ◽  
Men And Women ◽  
Renal Vasoconstriction ◽  
Renal Vascular

During exercise, reflex renal vasoconstriction helps maintain blood pressure and redistributes blood flow to the contracting muscle. Sex and muscle mass have been shown to influence certain cardiovascular responses to exercise. Whether sex and/or muscle mass influence renal vasoconstrictor responses to exercise is unknown. We studied healthy men ( n = 10) and women ( n = 10) matched for age and body mass index during handgrip (HG, small muscle mass) and quadriceps contraction (QC, large muscle mass) as beat-to-beat changes in renal blood flow velocity (RBV; duplex ultrasound), mean arterial pressure (MAP; Finapres), and heart rate (ECG) were monitored. Renal vascular resistance (RVR) index was calculated as MAP ÷ RBV. Responses to HG vs. QC were compared in 13 subjects. We found that 1) RVR responses to short (15-s) bouts and fatiguing HG were similar in men and women (change in RVR during 15-s HG at 70% of maximum voluntary contraction = 23 ± 4 and 31 ± 4% in men and women, respectively, P = not significant); 2) post-HG circulatory responses were similar in men and women; and 3) HG and QC were similar during short (15-s) bouts (change in RVR during HG at 50% of maximum voluntary contraction = 19 ± 3 and 18 ± 5% for arm and leg, respectively, P = not significant). Our findings suggest that muscle reflex-mediated renal vasoconstriction is similar in men and women during static exercise. Moreover, muscle mass does not contribute to the magnitude of the reflex renal vasoconstrictor response seen with muscle contraction.

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