Cardio-Respiratory Response to Exercise in Normal Children

1971 ◽  
Vol 40 (5) ◽  
pp. 419-431 ◽  
Author(s):  
S. Godfrey ◽  
C. T. M. Davies ◽  
E. Wozniak ◽  
Carolyn A. Barnes
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Steady State ◽  
Minute Ventilation ◽  
Work Load ◽  
Normal Children ◽  
Progressive Exercise ◽  
Maximum Work ◽  
Response To Exercise ◽  
Submaximal Heart Rate

1. The results of studies during simple progressive exercise to exhaustion and steady-state submaximal exercise in 117 boys and girls aged 6–16 years are presented. 2. In the simple progressive exercise test, the highest work load achieved and the submaximal heart rate were related to size and sex. The maximum heart rate and submaximal ventilation were largely independent of size and sex. 3. Steady-state exercise was performed at one-third and two-thirds of the maximum work load achieved in the simple progressive test. The Indirect (CO2) Fick method was used to measure cardiac output. 4. At any given level of steady-state work, tidal volume, dead space, heart rate and stroke volume were closely related to size, with girls having higher heart rates and smaller stroke volumes than boys. Minute ventilation and cardiac output were virtually independent of size and sex. The cardiac output in children was the same as that in the adult for any given oxygen consumption. Blood lactate was related to size at any given work load, but was independent of size at any given fraction of the maximum working capacity.

Cardio-Respiratory Response to Treadmill Exercise in Normal Children

1971 ◽  
Vol 40 (5) ◽  
pp. 433-442 ◽  
Author(s):  
Sandra D. Anderson ◽  
S. Godfrey
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Steady State ◽  
Respiratory Exchange Ratio ◽  
Treadmill Exercise ◽  
Physical Working Capacity ◽  
Respiratory Response ◽  
Working Capacity ◽  
Normal Children ◽  
Ventilatory Responses

1. Studies have been made of the response to running on a treadmill in forty boys and girls aged 5–15 years. 2. Each child was studied at two consecutive levels of steady-state work representing about 50% and 80% of his physical working capacity. Cardiac output was measured by the Indirect (CO2) Fick method. 3. The cardiac and ventilatory responses to exercise were similar to those seen during cycling on an ergometer except that the heart rate and the respiratory exchange ratio were a little lower. Stroke volume was the same. 4. The responses of children to running and cycling are discussed and the similarity to the responses of adults is noted.

Effect of beta-adrenergic blockade during exercise on ventilation and gas exchange

1976 ◽  
Vol 41 (6) ◽  
pp. 886-892 ◽  
Author(s):  
H. V. Brown ◽  
K. Wasserman ◽  
B. J. Whipp
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Steady State ◽  
Minute Ventilation ◽  
Co2 Flux ◽  
Normal Subjects ◽  
Adrenergic Blockade ◽  
Beta Adrenergic ◽  
Co2 Output ◽  
Ventilatory Effects

The ventilatory effects of beta-adrenergic blockade during steady-state exercise were studied in eight normal subjects using intravenous propranolol hydrochloride (0.2 mg/kg). Heart rate decreased in all subjects by an average of 17%. Coincident with the phase of decreasing heart rate was a significant decrease in both minute ventilation (VE) and CO2 output (VCO2), averaging 9.6 and 9.2%, respectively. Both functions returned to prepropranolollevels after heart rate had reached its reduced steady-state value. The change in VE was significantly correlated with the change in VCO2 (r = 0.85, Pless than 0.005), and was associated with negligible changes in endtidal CO2 tensions and ventilatory equivalents for CO2. We interpret these studies as showing that the transient isocapnic hypopnea concomitant with an acute reduction in cardiac output was secondary to a transient decrease in CO2 flux (cardiac output x mixed venous CO2 content). This decrease in VE appearsto be induced by the acute decrease in cardiac output (“cardiodynamic hypopnea”), in fashion similar to the previously described cardiodynamic hyperpnea.

Dynamics of cardiac, respiratory, and metabolic function in men in response to step work load

1982 ◽  
Vol 52 (5) ◽  
pp. 1198-1208 ◽  
Author(s):  
Y. Miyamoto ◽  
T. Hiura ◽  
T. Tamura ◽  
T. Nakamura ◽  
J. Higuchi ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Time Constant ◽  
Minute Ventilation ◽  
Initial Period ◽  
Work Load ◽  
Work Intensity ◽  
Control Value ◽  
End Tidal

Stroke volume, heart rate, cardiac output, tidal volume, respiratory frequency, minute ventilation, end-tidal tensions of O2 and CO2, O2 uptake, CO2 output, and respiratory exchange ratio were measured simultaneously in healthy male volunteers before, during, and after upright bicycle exercise from 0 to 360 and 720 kpm/min. The circulatory variables were determined continuously once per 20 cardiac cycles and the respiratory variables breath by breath using separate computer-based systems in which an impedance pneumograph and an impedance cardiograph were incorporated. Stroke volume, heart rate, and cardiac output started to increase without measurable delay at the onset of exercise. Stroke volume increased by 20% from resting control value in response to the mildest exercise and essentially leveled off with a further increase in work load. Time constant for cardiac output increased with the increasing work load. Time constant for minute ventilation was much longer than that for cardiac output and independent of work intensity. A good synchronization between the ventilation and cardiac output responses at an initial period of transitions from rest to exercise and from exercise to rest seems to support the concept of cardiodynamic hyperpnea.

Autonomic regulation of heart rate response to exercise in Tibetan and Han residents of Lhasa (3,658 m)

1993 ◽  
Vol 75 (5) ◽  
pp. 1968-1973 ◽  
Author(s):  
J. Zhuang ◽  
T. Droma ◽  
J. R. Sutton ◽  
R. E. McCullough ◽  
R. G. McCullough ◽  
...  
Keyword(s):  
Heart Rate ◽  
High Altitude ◽  
Minute Ventilation ◽  
Random Order ◽  
Work Load ◽  
Cycle Ergometer ◽  
O2 Consumption ◽  
Tibet Autonomous Region ◽  
Ergometer Exercise ◽  
Response To Exercise

To test the hypothesis that native high-altitude residents have less beta-sympathetic and more parasympathetic tone than newcomers, we compared the effects of beta-sympathetic and parasympathetic blockade in 10 Tibetan and 9 Han acclimatized male residents of Lhasa, Tibet Autonomous Region, China (elevation 3,658 m). Each subject was studied during cycle ergometer exercise at 70, 132, and 191 W after placebo (normal saline), beta-sympathetic (propranolol, 0.2 mg/kg iv), or parasympathetic (atropine, 0.04 mg/kg iv) blockade in random order on different days. At rest, the fall in resting heart rate with propranolol and the rise with atropine were equal in Tibetan and Han subjects. During exercise, the fall in heart rate with propranolol relative to placebo values was greater in the Han than in the Tibetan group, whereas the rise in heart rate with atropine was greater in the Tibetans. Propranolol or atropine administration did not change minute ventilation per unit O2 consumption in either group. At the highest level of exercise on the placebo day, the Tibetans achieved a higher work load and level of O2 consumption than the Han subjects. Propranolol or atropine reduced O2 consumption and work load similarly in the two groups at the highest exercise level. The results supported our hypothesis that native Tibetan residents of high altitude exhibit more para-sympathetic and less beta-sympathetic tone during exercise. Neither relatively greater parasympathetic nor less sympathetic activation appeared implicated in the greater exercise capacity of Tibetans compared with that of acclimatized newcomer residents of high altitude.

Physiological adjustments of women to prolonged work during acute hypoxia

1980 ◽  
Vol 49 (3) ◽  
pp. 367-373 ◽  
Author(s):  
J. A. Wagner ◽  
D. S. Miles ◽  
S. M. Horvath
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Steady State ◽  
Acute Hypoxia ◽  
Pulmonary Ventilation ◽  
Work Load ◽  
Altitude Exposure ◽  
Work Duration ◽  
Physiological Adjustments ◽  
Bicycle Work

Five women (23-32 yr) performed bicycle work in a hypobaric chamber for 2 h at 41% of their respective altitude maximal oxygen uptakes (VO2) at 758, 586, 523, and 446 Torr barometric pressures (PB). Steady-state VO2 was achieved within 5 min work at all altitudes. Pulmonary ventilation (29.2 +/- 1.9 (mean +/- SE) 1/min, BTPS), respiratory rate (22 +/- 2 breaths/min), cardiac output (8.5 +/- 1.4 1/min), heart rate (115 +/- 6 beats/min), and stroke volume (75 +/- 13 ml) were similar at all altitudes, but time-related changes differed with altitude. Blood lactates did not change with work duration and were similar at 758 and 586 Torr PB but progressively elevated at 523 and 446 Torr. Blood norepinephrine, measured only at 758 and 446 Torr PB, increased with work but not altitude; epinephrine increased only at altitude. Norepinephrine levels and respiratory, cardiovascular, and thermoregulatory functions were essentially dependent on relative work load; blood lactates and epinephrine levels were not. Many physiological functions in these women performing sustained light work during acute altitude exposure were remarkably stable in contrast to previously reported studies on men.

Cardiovascular response to cycle exercise during and after pregnancy

1989 ◽  
Vol 66 (1) ◽  
pp. 336-341 ◽  
Author(s):  
S. P. Sady ◽  
M. W. Carpenter ◽  
P. D. Thompson ◽  
M. A. Sady ◽  
B. Haydon ◽  
...  
Keyword(s):  
Heart Rate ◽  
Maximal Exercise ◽  
Cardiovascular Response ◽  
Work Load ◽  
Cycle Ergometry ◽  
Maximal Heart Rate ◽  
O2 Uptake ◽  
Cycle Exercise ◽  
Vascular Beds ◽  
Response To Exercise

Our purpose was to determine if pregnancy alters the cardiovascular response to exercise. Thirty-nine women [29 +/- 4 (SD) yr], performed submaximal and maximal exercise cycle ergometry during pregnancy (antepartum, AP, 26 +/- 3 wk of gestation) and postpartum (PP, 8 +/- 2 wk). Neither maximal O2 uptake (VO2max) nor maximal heart rate (HR) was different AP and PP (VO2 = 1.91 +/- 0.32 and 1.83 +/- 0.31 l/min; HR = 182 +/- 8 and 184 +/- 7 beats/min, P greater than 0.05 for both). Cardiac output (Q, acetylene rebreathing technique) averaged 2.2 to 2.8 l/min higher AP (P less than 0.01) at rest and at each exercise work load. Increases in both HR and stroke volume (SV) contributed to the elevated Q at the lower exercise work loads, whereas an increased SV was primarily responsible for the higher Q at higher levels. The slope of the Q vs. VO2 relationship was not different AP and PP (6.15 +/- 1.32 and 6.18 +/- 1.34 l/min Q/l/min VO2, P greater than 0.05). In contrast, the arteriovenous O2 difference (a-vO2 difference) was lower at each exercise work load AP, suggesting that the higher Q AP was distributed to nonexercising vascular beds. We conclude that Q is greater and a-vO2 difference is less at all levels of exercise in pregnant subjects than in the same women postpartum but that the coupling of the increase in Q to the increase in systemic O2 demand (VO2) is not different.(ABSTRACT TRUNCATED AT 250 WORDS)

Constancy of stroke volume in ventricular responses to exertion

1959 ◽  
Vol 196 (4) ◽  
pp. 745-750 ◽  
Author(s):  
Robert F. Rushmer
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Cardiac Response ◽  
Indirect Measurements ◽  
Increase Stroke Volume ◽  
Normal Man ◽  
The Right ◽  
Response To Exercise ◽  
Indicator Dilution Techniques

Diastolic and systolic dimensions of the left ventricle and the free wall of the right ventricle in intact dogs are affected little by spontaneous exercise. The concept that stroke volume and heart rate in normal man increase by about the same relative amounts was derived from estimations of cardiac output, particularly in athletes, based upon indirect measurements using foreign gases or CO2. Data for man obtained with the modern cardiac catheterization or indicator dilution techniques confirm the impression derived from intact dogs that increased stroke volume is neither an essential nor a characteristic feature of the normal cardiac response to exercise. Stroke volume undoubtedly increases whenever cardiac output is increased with little change in heart rate (e.g. in athletes or in patients with chronic volume loads on the heart). Tachycardia produced experimentally with an artificial pacemaker in a resting dog causes a marked reduction in diastolic and systolic dimensions and in the stroke change of dimensions. The factors generally postulated to increase stroke volume during normal exercise may prevent the reduction in stroke volume accompanying tachycardia.

Effects of N2O narcosis on breathing and effort sensations during exercise and inspiratory resistive loading

1996 ◽  
Vol 81 (4) ◽  
pp. 1562-1571 ◽  
Author(s):  
D. M. Fothergill ◽  
N. A. Carlson
Keyword(s):  
Heart Rate ◽  
Steady State ◽  
Minute Ventilation ◽  
Esophageal Pressure ◽  
Incremental Exercise ◽  
Time To Exhaustion ◽  
Gas Mixture ◽  
Resistive Loading ◽  
Inspiratory Resistance ◽  
Sufficient Magnitude

Fothergill, D. M., and N. A. Carlson. Effects of N2O narcosis on breathing and effort sensations during exercise and inspiratory resistive loading. J. Appl. Physiol. 81(4): 1562–1571, 1996.—The influence of nitrous oxide (N2O) narcosis on the responses to exercise and inspiratory resistive loading was studied in thirteen male US Navy divers. Each diver performed an incremental bicycle exercise test at 1 ATA to volitional exhaustion while breathing a 23% N2O gas mixture and a nonnarcotic gas of the same [Formula: see text], density, and viscosity. The same gas mixtures were used during four subsequent 30-min steady-state submaximal exercise trials in which the subjects breathed the mixtures both with and without an inspiratory resistance (5.5 vs. 1.1 cmH2O ⋅ s ⋅ l−1at 1 l/s). Throughout each test, subjective ratings of respiratory effort (RE), leg exertion, and narcosis were obtained with a category-ratio scale. The level of narcosis was rated between slight and moderate for the N2O mixture but showed great individual variation. Perceived leg exertion and the time to exhaustion were not significantly different with the two breathing mixtures. Heart rate was unaffected by the gas mixture and inspiratory resistance at rest and during steady-state exercise but was significantly lower with the N2O mixture during incremental exercise ( P< 0.05). Despite significant increases in inspiratory occlusion pressure (13%; P < 0.05), esophageal pressure (12%; P < 0.001), expired minute ventilation (4%; P < 0.01), and the work rate of breathing (15%; P < 0.001) when the subjects breathed the N2O mixture, RE during both steady-state and incremental exercise was 25% lower with the narcotic gas than with the nonnarcotic mixture ( P < 0.05). We conclude that the narcotic-mediated changes in ventilation, heart rate, and RE induced by 23% N2O are not of sufficient magnitude to influence exercise tolerance at surface pressure. Furthermore, the load-compensating respiratory reflexes responsible for maintaining ventilation during resistive breathing are not depressed by N2O narcosis.

Cardiopulmonary response to exercise in patients with intrapulmonary vascular shunts

1993 ◽  
Vol 75 (1) ◽  
pp. 321-328 ◽  
Author(s):  
M. K. Whyte ◽  
J. M. Hughes ◽  
J. E. Jackson ◽  
A. M. Peters ◽  
S. C. Hempleman ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Oxygen Delivery ◽  
Minute Ventilation ◽  
Arterial Oxygen ◽  
Normal Range ◽  
Arterial Pco2 ◽  
Ventilatory Equivalent ◽  
Tissue Oxygen Delivery ◽  
Flow Through ◽  
Response To Exercise

The majority of patients with intrapulmonary right-to-left shunting due to pulmonary arteriovenous malformations-exhibit good maximum exercise capacity (> 70% predicted) despite profound arterial oxygen desaturation. We studied seven such patients to assess tissue oxygen delivery during steady-state exercise. From rest to exercise [50 +/- 7 (SE) W] arterial saturation fell from 80 +/- 3 to 74 +/- 3%, and mean right-to-left shunt increased slightly from 31 +/- 4 to 34 +/- 5% (P = NS). Minute ventilation was high for oxygen uptake, and the ventilatory equivalent was raised (174 +/- 19% predicted) and was correlated with shunt size (r = 0.93). The majority of the patients maintained pulmonary alveolar blood flow within the predicted range for their power output, but total cardiac output was increased to 142 +/- 11% predicted due to flow through the shunt. Consequently, on exercise, oxygen delivery per unit oxygen consumption [2.3–3.3 (normal range 1.6–2.4)] and calculated mixed venous oxygen tension (27.0 +/- 0.8 Torr) were preserved. Arterial PCO2 rose on exercise by 2.8 +/- 1.2 Torr, in proportion to the ratio of flow through the shunt to total cardiac output (r = 0.73), but remained low (33.1 +/- 1.4 Torr) in absolute terms. The high cardiac output on exercise may be facilitated by a low pulmonary vascular resistance (0.33 +/- 0.08 mmHg.1–1.min, measured at rest), which may explain why exercise performance is better in these patients than in patients with equivalent hypoxemia from other causes.

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