Cardiovascular Responses During Downhill Treadmill Walking at Self-Selected Intensity in Older Adults

Cardiovascular responses of older adults to downhill (DTW, –10% incline) and level treadmill walking (0%) at self-selected walking speed (SSWS) were examined. Fifteen participants (age 68 ± 4 yr, height 1.69 ± 0.08 m, body mass 74.7 ± 8.1 kg) completed two 15-min walks at their SSWS (4.6 ± 0.6 km/hr). Cardiovascular responses were estimated using an arterial-volume finger clamp and infrared plethysmography. Oxygen consumption was 25% lower during DTW and associated with lower values for stroke volume (9.9 ml/beat), cardiac output (1.0 L/min), arteriovenous oxygen difference (a-v O2 diff, 2.4 ml/L), and systolic blood pressure (10 mmHg), with no differences in heart rate or diastolic and mean arterial blood pressure. Total peripheral resistance (TPR) was higher (2.11 mmHg) during DTW. During downhill walking, an exercise performed with reduced cardiac strain, endothelial changes, and reduced metabolic demand may be responsible for the different responses in TPR and a-v O2 diff. Future work is warranted on whether downhill walking is suitable for higher risk populations.

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Oxygen Consumption, Heart Rate, Rating of Perceived Exertion, and Systolic Blood Pressure with Water Treadmill Walking

Journal of Aging and Physical Activity ◽

10.1123/japa.16.1.14 ◽

2008 ◽

Vol 16 (1) ◽

pp. 14-23 ◽

Cited By ~ 11

Author(s):

David R. Dolbow ◽

Richard S. Farley ◽

Jwa K. Kim ◽

Jennifer L. Caputo

Keyword(s):

Blood Pressure ◽

Older Adults ◽

Heart Rate ◽

Oxygen Consumption ◽

Systolic Blood Pressure ◽

Perceived Exertion ◽

Cardiovascular Responses ◽

Treadmill Walking ◽

Rating Of Perceived Exertion ◽

Water Treadmill

The purpose of this study was to examine the cardiovascular responses to water treadmill walking at 2.0 mph (3.2 km/hr), 2.5 mph (4.0 km/hr), and 3.0 mph (4.8 km/hr) in older adults. Responses to water treadmill walking in 92 °F (33 °C) water were compared with responses to land treadmill walking at 70 °F (21 °C) ambient temperature. After an accommodation period, participants performed 5-min bouts of walking at each speed on 2 occasions. Oxygen consumption (VO2), heart rate (HR), systolic blood pressure (SBP), and rating of perceived exertion (RPE) were significantly higher during therapeutic water treadmill walking than during land treadmill walking. Furthermore, VO2, HR, and RPE measures significantly increased with each speed increase during both land and water treadmill walking. SBP significantly increased with each speed during water treadmill walking but not land treadmill walking. Thus, it is imperative to monitor HR and blood pressure for safety during this mode of activity for older adults.

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Blood pressure and blood flow variation during postural change from sitting to standing: model development and validation

Journal of Applied Physiology ◽

10.1152/japplphysiol.00177.2005 ◽

2005 ◽

Vol 99 (4) ◽

pp. 1523-1537 ◽

Cited By ~ 131

Author(s):

Mette S. Olufsen ◽

Johnny T. Ottesen ◽

Hien T. Tran ◽

Laura M. Ellwein ◽

Lewis A. Lipsitz ◽

...

Keyword(s):

Blood Pressure ◽

Mathematical Model ◽

Blood Flow ◽

Young Subject ◽

Venous Blood ◽

Cardiovascular Responses ◽

Physiological Data ◽

Postural Change ◽

Metabolic Demand ◽

Arterial Blood

Short-term cardiovascular responses to postural change from sitting to standing involve complex interactions between the autonomic nervous system, which regulates blood pressure, and cerebral autoregulation, which maintains cerebral perfusion. We present a mathematical model that can predict dynamic changes in beat-to-beat arterial blood pressure and middle cerebral artery blood flow velocity during postural change from sitting to standing. Our cardiovascular model utilizes 11 compartments to describe blood pressure, blood flow, compliance, and resistance in the heart and systemic circulation. To include dynamics due to the pulsatile nature of blood pressure and blood flow, resistances in the large systemic arteries are modeled using nonlinear functions of pressure. A physiologically based submodel is used to describe effects of gravity on venous blood pooling during postural change. Two types of control mechanisms are included: 1) autonomic regulation mediated by sympathetic and parasympathetic responses, which affect heart rate, cardiac contractility, resistance, and compliance, and 2) autoregulation mediated by responses to local changes in myogenic tone, metabolic demand, and CO2 concentration, which affect cerebrovascular resistance. Finally, we formulate an inverse least-squares problem to estimate parameters and demonstrate that our mathematical model is in agreement with physiological data from a young subject during postural change from sitting to standing.

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Cardiovascular responses to oxygen inhalation after hemorrhage in anesthetized rats: hyperoxic vasoconstriction

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00381.2006 ◽

2007 ◽

Vol 292 (2) ◽

pp. H776-H785 ◽

Cited By ~ 5

Author(s):

James L. Atkins ◽

Ken B. Johnson ◽

Frederick J. Pearce

Keyword(s):

Blood Pressure ◽

Blood Pressure Response ◽

Peripheral Resistance ◽

Cardiovascular Responses ◽

Pressure Response ◽

Oxygen Inhalation ◽

Arterial Blood ◽

Anesthetized Rats ◽

Initial Care ◽

Target Pressure

Oxygen inhalation is recommended for the initial care of trauma victims. The improved survival seen in early hemorrhage is normally associated with an increase in blood pressure. Although clinical use of oxygen can occur late after hemorrhage, the effects of late administration have not been specifically examined. Anesthetized rats were studied using an isobaric hemorrhage model with target pressures of either 70 or 40 mmHg. At various times after hemorrhage, the feedback control of the blood pressure was stopped and the inspired gas was changed from room air to 100% oxygen. The results show that shortly after hemorrhage to 70 mmHg, oxygen inhalation results in an increase in mean arterial blood pressure of 60 ± 3 mmHg, which is associated with a large increase in total peripheral resistance from 0.89 ± 0.05 to 1.25 ± 0.1 peripheral resistance units. The blood pressure response is essentially unchanged with time, and it is not altered by a 10-min exposure to NG-nitro-l-arginine methyl ester. At a target pressure of 40 mmHg, the initial blood pressure response to oxygen is the same, but it gradually decreases as the animal develops a lactic acidosis. We conclude that the therapeutic value of oxygen needs to be separately evaluated for late hemorrhage.

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Prior head-down tilt does not impair the cerebrovascular response to head-up tilt

Journal of Applied Physiology ◽

10.1152/japplphysiol.00871.2014 ◽

2015 ◽

Vol 118 (11) ◽

pp. 1356-1363 ◽

Cited By ~ 4

Author(s):

Changbin Yang ◽

Yuan Gao ◽

Danielle K. Greaves ◽

Rodrigo Villar ◽

Thomas Beltrame ◽

...

Keyword(s):

Blood Pressure ◽

Cardiac Output ◽

Peripheral Resistance ◽

Resistance Index ◽

Cardiovascular Responses ◽

Mean Flow ◽

Cerebrovascular Autoregulation ◽

Arterial Blood ◽

Head Up Tilt ◽

S Period

The hypothesis that cerebrovascular autoregulation was not impaired during head-up tilt (HUT) that followed brief exposures to varying degrees of prior head-down tilt (HDT) was tested in 10 healthy young men and women. Cerebral mean flow velocity (MFV) and cardiovascular responses were measured in transitions to a 60-s period of 75° HUT that followed supine rest (control) or 15 s HDT at −10°, −25°, and −55°. During HDT, heart rate (HR) was reduced for −25° and −55°, and cardiac output was lower at −55° HDT. MFV increased during −10° HDT, but not in the other conditions even though blood pressure at the middle cerebral artery (BPMCA) increased. On the transition to HUT, HR increased only for −55° condition, but stroke volume and cardiac output transiently increased for −25° and −55°. Total peripheral resistance index decreased in proportion to the magnitude of HDT and recovered over the first 20 s of HUT. MFV was significantly less in all HDT conditions compared with the control in the first 5-s period of HUT, but it recovered quickly. An autoregulation correction index derived from MFV recovery relative to BPMCA decline revealed a delay in the first 5 s for prior HDT compared with control but then a rapid increase to briefly exceed control after −55° HDT. This study showed that cerebrovascular autoregulation is modified by but not impaired by brief HDT prior to HUT and that cerebral MFV recovered quickly and more rapidly than arterial blood pressure to protect against cerebral hypoperfusion and potential syncope.

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Cardiovascular responses to blockade of angiotensin and alpha-adrenergic receptors

AJP Renal Physiology ◽

10.1152/ajprenal.1978.235.3.f199 ◽

1978 ◽

Vol 235 (3) ◽

pp. F199-F202

Author(s):

L. J. Borucki ◽

D. Levenson ◽

N. K. Hollenberg

Keyword(s):

Blood Pressure ◽

Cardiac Output ◽

Arterial Blood Pressure ◽

Total Peripheral Resistance ◽

Peripheral Resistance ◽

Cardiovascular Responses ◽

Adrenergic Blockade ◽

Venous Tone ◽

Arterial Blood ◽

Adrenergic Blocking

Both angiotensin and alpha-adrenergic blocking agents reduce arterial blood pressure in hypovolemic states. We have compared the effects of an angiotensin antagonist (saralasin) and an alpha-adrenergic blocking agent (phenoxybenzamine) in supramaximal dosage on cardiac output, total peripheral resistance, and venous tone in rabbits rendered hypovolemic by restriction of sodium intake, supplemented by a furosemide-induced diuresis 48 h prior to study. Saralasin (10 microgram/kg per min) reduced arterial blood pressure significantly (-15 +/- 1.2 mmHg) despite an unchanged cardiac output (P less than 0.025) due to a fall in total peripheral resistance. Phenoxybenzamine (5 mg/kg) induced a much larger fall in arterial blood pressure (-28 +/- 3.6 mmHg), despite an identical reduction in total peripheral resistance, because cardiac output also fell (+/- 9 ml/kg per min). The reduction in cardiac output was associated with a significant increase in hindlimb venous distensibility (P less than 0.001) after alpha-adrenergic blockade. Saralasin, conversely, had no influence on venous tone. Adrenergic mechanisms contribute to cardiovascular homeostasis through an influence on both arteriolar and venous tone, whereas the effect of angiotensin is directed entirely to the arteriolar side of the circulation.

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Cardiovascular responses to military antishock trouser inflation during standing arm exercise

Journal of Applied Physiology ◽

10.1152/jappl.1987.63.3.1224 ◽

1987 ◽

Vol 63 (3) ◽

pp. 1224-1229 ◽

Cited By ~ 10

Author(s):

A. V. Ng ◽

P. Hanson ◽

E. A. Aaron ◽

R. B. Demment ◽

J. M. Conviser ◽

...

Keyword(s):

Blood Pressure ◽

Repeated Measures ◽

Peripheral Resistance ◽

Cardiovascular Responses ◽

Gravitational Effect ◽

Positive Pressure ◽

Arm Cranking ◽

Lower Body Positive Pressure ◽

Arterial Blood ◽

And Control

Military antishock trousers (MAST) inflated to 50 mmHg were used with 12 healthy males (mean age 28 +/- 1 yr) to determine the effects of lower-body positive pressure on cardiac output (Q), stroke volume (SV), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MABP), total peripheral resistance (TPR), and O2 uptake (VO2) during graded arm-cranking exercise. Subjects were studied while standing at rest and at 25, 50, and 75% of maximal arm-cranking VO2. At each level, rest or work was continued for 6 min with MAST inflated and for 6 min with MAST deflated. Order of inflation and deflation was alternated at each experimental rest or exercise level. Measurements were obtained during the last 2 min at each level. Repeated-measures analysis of variance revealed significant increases (P less than 0.001) in Q, SV, and MABP and a consistent decrease in HR with MAST inflation. There was no apparent change in Q/VO2 between inflated and control conditions. There was no effect of MAST inflation on VO2 or TPR. MAST inflation counteracts the gravitational effect of venous return in upright exercise, restoring central blood volume and thereby increasing Q and MABP from control. HR is decreased consequent to increased MABP through arterial baroreflexes. The associated decrease in TPR is not observed, being offset by the mechanical compression of leg vasculature with MAST inflation.

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Cardiovascular effect of V1 vasopressinergic blockade during acute hypercapnia in conscious rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1987.252.1.r127 ◽

1987 ◽

Vol 252 (1) ◽

pp. R127-R133 ◽

Cited By ~ 1

Author(s):

B. R. Walker

Keyword(s):

Blood Pressure ◽

Cardiac Output ◽

Total Peripheral Resistance ◽

Peripheral Resistance ◽

Cardiovascular Effects ◽

Cardiovascular Responses ◽

Hypercapnic Acidosis ◽

Conscious Rat ◽

Arterial Pco2 ◽

Arterial Blood

Experiments were performed to test the possible involvement of arginine vasopressin (AVP) in the systemic cardiovascular responses to acute hypercapnic acidosis in conscious chronically instrumented rats. Exposure to 6% CO2 caused arterial PCO2 to rise from 34 +/- 2 to 53 +/- 1 Torr. This level of hypercapnia was associated with a consistent bradycardia; however, cardiac output, blood pressure, and total peripheral resistance were not significantly affected. Administration of 10 micrograms/kg iv of the specific V1 vasopressinergic antagonist d(CH2)5Tyr(Me)AVP during 6% CO2 had no effect on any of the measured hemodynamic variables. Furthermore, d(CH2)5Tyr(Me)AVP also had no effect in normocapnic control animals. Exposure to a more severe level of hypercapnia (10% CO2, arterial PCO2 = 89 +/- 1 Torr) resulted in marked hemodynamic alterations. Profound bradycardia and decreased cardiac output in addition to increases in mean arterial blood pressure and total peripheral resistance were observed. V1 vasopressinergic antagonism during 10% CO2 had no effect on heart rate but greatly increased cardiac output. In addition, blood pressure fell and resistance was decreased below prehypercapnic levels. These data suggest that a number of the hemodynamic alterations associated with severe hypercapnic acidosis in the conscious rat may be mediated by the peripheral cardiovascular effects of enhanced AVP release.

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Comparison of cardiovascular response to passive tilt in young and elderly men

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y88-232 ◽

1988 ◽

Vol 66 (11) ◽

pp. 1425-1432 ◽

Cited By ~ 5

Author(s):

D. A. Cunningham ◽

R. J. Petrella ◽

D. H. Paterson ◽

P. M. Nichol

Keyword(s):

Blood Pressure ◽

Cardiac Output ◽

Cardiovascular Response ◽

Peripheral Resistance ◽

Cardiovascular Responses ◽

Left Ventricular ◽

Age Effects ◽

Hemodynamic Responses ◽

Arterial Blood ◽

Postural Changes

To test the hypothesis that altered hemodynamic responses to postural changes are associated with aging, cardiovascular responses to head-up tilt (HUT) and head-down tilt (HDT) were examined in 12 healthy young (average age, 24.6 ± 1.7 years) and 12 healthy elderly (average age, 68.6 ± 2.2 years) men. Subjects were passively tilted from supine to 30°, 60°, and 90° HUT and HDT. Responses to these perturbations were determined 5 min after tilting with measures of heart rate (HR), blood pressure (SBP, DBP), and echocardiographically determined left ventricular diameter in systole and diastole (LVIDs, LVIDd). In HUT there were no significant age effects. In both young and elderly, SBP decreased significantly (p < 0.05), and DBP and HR increased significantly. Ejection fraction (EF), mean arterial blood pressure (MABP), and rate-pressure product (RPP) were unchanged in both groups. In HDT, the hemodynamic responses of the young and elderly were in opposite directions and significant age effects were found for SBP, DBP, HR, LVIDs, EF, MABP, and RPP. In HDT, the young appear to increase cardiac output primarily due to an increase in EF and end-diastolic volume (LVIDd), while HR is unchanged and SBP is decreased. MABP is unchanged, suggesting a small decrease in total peripheral resistance. The elderly may increase cardiac output slightly, owing to an increase in LVIDd with no change in EF, and a large increase in HR. Afterload increased markedly, therefore attenuating any increase in cardiac output. These results suggest that in healthy men, the cardiovascular response to HUT is not age related, while conversely there appear to be significant differences between young and elderly in response to HDT.

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Fructose ingestion acutely elevates blood pressure in healthy young humans

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00680.2007 ◽

2008 ◽

Vol 294 (3) ◽

pp. R730-R737 ◽

Cited By ~ 128

Author(s):

Clive M. Brown ◽

Abdul G. Dulloo ◽

Gayathri Yepuri ◽

Jean-Pierre Montani

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Cardiac Output ◽

Energy Expenditure ◽

Total Peripheral Resistance ◽

Peripheral Resistance ◽

Cardiovascular Responses ◽

Health Concern ◽

Arterial Blood ◽

Glucose Ingestion

Overconsumption of fructose, particularly in the form of soft drinks, is increasingly recognized as a public health concern. The acute cardiovascular responses to ingesting fructose have not, however, been well-studied in humans. In this randomized crossover study, we compared cardiovascular autonomic regulation after ingesting water and drinks containing either glucose or fructose in 15 healthy volunteers (aged 21–33 yr). The total volume of each drink was 500 ml, and the sugar content 60 g. For 30 min before and 2 h after each drink, we recorded beat-to-beat heart rate, arterial blood pressure, and cardiac output. Energy expenditure was determined on a minute-by-minute basis. Ingesting the fructose drink significantly increased blood pressure, heart rate, and cardiac output but not total peripheral resistance. Glucose ingestion resulted in a significantly greater increase in cardiac output than fructose but no change in blood pressure and a concomitant decrease in total peripheral resistance. Ingesting glucose and fructose, but not water, significantly increased blood pressure variability and decreased cardiovagal baroreflex sensitivity. Energy expenditure increased by a similar amount after glucose and fructose ingestion, but fructose elicited a significantly greater increase in respiratory quotient. These results show that ingestion of glucose and fructose drinks is characterized by specific hemodynamic responses. In particular, fructose ingestion elicits an increase in blood pressure that is probably mediated by an increase in cardiac output without compensatory peripheral vasodilatation.

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