Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0392674 (exhaustion)
 13,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acetazolamide (A) is a potent inhibitor of carbonic anhydrase. It has been shown to be efficacious in preventing acute mountain sickness as well as decreasing the O2 desaturation that occurs during sleep in individuals with chronic mountain sickness who live at altitude. Very little data, however, are available about its effect on exercise. We studied six healthy males in a double-blind cross-over design using acetazolamide and placebo (P) during normoxic and hypoxic (fractional inspired O2 = 0.118) progressive work exercise to exhaustion on a bicycle ergometer. A metabolic acidosis was documented in all subjects on A (P less than 0.045). Before exercise, subjects on A had 2.0 and 3.5 l/min increase in minute ventilation (VE) during normoxia (P = not significant) and hypoxia (P less than 0.005), respectively, and a 2.2% increase in arterialized O2 hemoglobin saturation (SaO2) during hypoxia. During normoxic and hypoxic exercise, VE/kpm and SaO2/kpm were significantly higher while the respiratory exchange ratio (R) was significantly lower on A. These effects were greater on hypoxia. During normoxia, maximal O2 consumption (1/min) was lower on A [3.1 +/- 0.4 (A) vs. 3.8 +/- 0.2 (P), P less than 0.025] and higher during hypoxia on A[2.6 +/- 0.7 (A) vs. 2.4 +/- 0.1 (P), P less than 0.05]. The increase in exercise VE on A may result in an increased alveolar and subsequent arterial O2 tension which may be important for exercise at altitude. Carbonic anhydrase inhibition may also affect CO2 transport in the lung, which may explain the lower R.
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PMID:Effect of acetazolamide on normoxic and hypoxic exercise in humans at sea level. 666 67

Altering CO2 storage has been shown to influence lactate metabolism. However, the metabolic effects on man during physical activity have not been well documented. Subjects (n = 8) performed a progressive bicycle test (beginning at 0 and increasing 30 W every 4 min to exhaustion) on two occasions (once inspiring compressed air and once 4% CO2 and 21% O2). The work time, peak Vo2, VCO2, and HR achieved were the same in the two trials for each subject. The VI was significantly (p less than or equal to 0.05) elevated throughout the CO2 work and the recovery. The O2 debt increased from a mean of 5.87 to 7.761 with CO2, although the difference was not significant. Blood lactate was lower (p less than or equal to 0.05) from the onset of the work and throughout both the exercise and the 30 min. recovery period. Peak lactate was decreased from a mean of 9.59 to 6.99mM.1(-1). The oxygen cost of the work was not altered but the blood lactate response to the activity was significantly depressed. The reduction in lactate could be due to glycolytic inhibition and enhanced fat metabolism. The data support, but do not prove, this hypothesis.
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PMID:The effects of hypercapnia on metabolic responses to progressive exhaustive work. 677 67

The effects of the menstrual cycle on cardiorespiratory variables, blood lactate, and performance were studied in exercising females. Nine healthy subjects, 20--24 yr of age, were investigated in midfollicular and midluteal phases of the menstrual cycle at 33, 66, and 90% of maximum power output (light, heavy, and exhaustive exercise). Occurrence of ovulation was confirmed in all subjects by measurement of progesterone, which increased from 0.6 +/- 0.1 (mean +/- SE) in the follicular to 8.9 +/- 2.2 ng/ml in the luteal phase. There was no difference in heart rate (HR), ventilation, O2 uptake, or CO2 output between the two phases during light and heavy exercise, and there was no difference in HR at exhaustion. Cardiac output measured midway through light and heavy exercise periods was not affected by the phase of testing. Time for which exhaustive exercise could be maintained increased from 1.57 +/- 0.32 in the follicular to 2.97 +/- 0.63 min in the luteal phase (P less than 0.02). Blood lactate was higher in the follicular phase after heavy exercise (6.62 +/- 0.8 vs. 4.92 +/- 0.5 mmol/l) (P less than 0.05) and at exhaustion (8.12 +/- 0.9 vs. 6.76 +/- 0.6 mmol/L) (P less than 0.01). A further study showed no effect of cycle phase on lactate disappearance during exercise. We conclude that while aerobic performance and the cardiorespiratory adaptations to exercise are not influenced by the phase of the menstrual cycle, performance of high-intensity exercise is improved, and lactate production appears to be decreased in the luteal phase when estradiol and progesterone levels are elevated.
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PMID:Effects of menstrual cycle on blood lactate, O2 delivery, and performance during exercise. 679

Ventilation, heart rate, and arterial blood gas tensions were measured at rest and during incremental exercise in 10 patients with emphysema after intravenous placebo or 7 mg metoprolol. Metoprolol reduced heart rate by 14% (P less than 0.001) and ventilation by 11% (P less than 0.01), but there was no significant difference in arterial O2 or CO2 tension (Pao2 and PaCO2, respectively). Metoprolol increased the time to exhaustion on a cycle ergometer (P less than 0.05) but did not improve the 12-min walking distance. A double-blind randomized crossover comparison of 4 wk treatment with atenolol (100 mg/day), metoprolol (100 mg/day), or matched placebo was performed in 12 patients with emphysema. Both beta-adrenoceptor antagonists reduced resting heart rate by 33% (P less than 0.001) and resting minute ventilation by 11% (P less than 0.025). There was no change in resting or exercise Pao2 or Paco2. During steady-state exercise on a cycle ergometer, atenolol and metoprolol reduced ventilation by 14 and 4%, respectively. This was accompanied by 11 and 5% reductions in O2 consumption (P less than 0.05) and 13 and 6% falls in CO2 production (P less than 0.05). There were no significant changes in tests of exercise tolerance, but forced expiratory volume in 1 s and forced vital capacity were reduced during beta 1-adrenergic blockade. beta 1-Blocking drugs reduce hyperventilation in emphysema by reducing pulmonary gas exchange without a change in arterial blood gas tensions. Increased airflow obstruction prevents this reduction being of therapeutic value.
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PMID:Effect of beta-adrenergic blockade on hyperventilation and exercise tolerance in emphysema. 686 97

Twenty patients with chronic bronchitis were exercised maximally on a bicycle ergometer. At exhaustion, arterial partial pressure of O2 (Pao2) decreased and that of CO2 (Paco2) increased in 8 patients (Subgroup 1). Arterial PO2 increased and Paco2 did not change in the remaining 12 patients (Subgroup 2). Forced expiratory volume in one second was lower in Subgroup 1 than in Subgroup 2. The decrease in arterial pH and the response of cardiac output were the same in both subgroups. Mixed venous PO2 decreased to 23 mm Hg or less in all patients in Subgroup 1 and in 3 patients in Subgroup 2; it stayed above 25 mm Hg in the remaining 9 patients. Our data imply that the ventilatory response to exercise is insufficient not only in Subgroup 1 but also in Subgroup 2 where the patients failed to hyperventilate in response to exercise-induced acidosis and that an unused oxygen reserve is still present at exhaustion in some patients with chronic airflow obstruction.
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PMID:Circulatory transport of oxygen in patients with chronic airflow obstruction exercising maximally. 707 12

We compared the effects of a cardioselective beta-adrenergic blocking drug, metoprolol, with a nonselective beta-adrenergic blocker, propranolol, on the response of 10 normal men to dynamic treadmill exercise. The volunteers underwent a standard graded exercise test to exhaustion while receiving placebo; propranolol, 40 mg every 6 hours; propranolol, 80 mg every 6 hours; metoprolol, 50 mg every 6 hours; or metoprolol, 100 mg every 6 hours. The drugs were given in a double-blind fashion for 48 hours before exercise. Five days were allowed between successive drug administrations and the order of drug administration was randomized. Heart rate, arterial pressure, oxygen consumption, minute ventilation and CO2 production were monitored. Plasma drug concentrations were measured at the time of exercise. Judged by plasma levels, propranolol was about three times more potent than metoprolol in attenuating heart rate. Both drugs produced a wide variation in plasma levels after a given oral dose, and both drugs attenuated the systolic blood pressure response to exercise. Neither drug affected diastolic blood pressure or maximum oxygen consumption, maximum minute ventilation or the anaerobic threshold. We conclude that there is no evidence that the cardioselective drug metoprolol is superior to propranolol in terms of the ability to perform or respond to short-term maximal exercise. In addition, the fact that maximal oxygen consumption and the anaerobic threshold were unaffected implies that fatigue during exercise while on beta-adrenergic blocking drugs is not due to an effect of these drugs in limiting blood flow to the exercising extremities.
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PMID:The effects of a cardioselective (metoprolol) and a nonselective (propranolol) beta-adrenergic blocker on the response to dynamic exercise in normal men. 707 50

1. The effects of treadmill exercise on oxygen consumption (V02), carbon dioxide production (VCO2), arterial blood lactate concentration ([L-]a), arterial blood pH and arterial gas tensions (PaO2 and PaCO2) were measured in 3 species of lizards (Varanus salvator, V. exanthematicus, Iguana iguana) 2. Varanus salvator was exercised 45 min at an intensity which required 85% of its VO2 max. V. salvator utilized supplementary anaerobic metabolism during the first 10 min of this sustainable exercise, as evidenced by a 16 mmol/l increase in [L-]a. Respiratory exchange ratios (R, where R = VCO2/VO2) exceeded 1.2 when [L-]a and [H+]a were maximal. One half of the accumulated lactate was removed from the blood during the remainder of the 45 min exercise period, while blood pH returned to resting levels. 3. In a second set of experiments, high intensity exercise led to exhaustion after 5 to 10 min in all three species, resulting in large lactate (+ delta[L-]a = 14-20 mmol/l) and hydrogen ion (+ delta[H+]a = 23-57 nmol/l) accumulations. R values ranged from 1.2-1.8 at exhaustion. 4. Recovery from both sustainable and non-sustainable exercise was characterized as a period of rapid lactate removal. Respiratory exchange ratios were low (0.3-0.5) as metabolic CO2 was retained, replacing depleted bicarbonate stores. 5. We conclude that all three lizard species make ventilatory adjustments during and after exercise that minimize disturbances to resting hydrogen ion concentrations and acid-base balance. Varanus salvator demonstrate the ability to re-establish resting acid-base status during sustained exercise requiring 85% of their VO2,max. Changes in R appear to be a useful noninvasive indicator of net blood lactate accumulation.
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PMID:Acid-base imbalance in lizards during activity and recovery. 710 39

Six adult females with normal menstrual cycles (28-31 d in length) volunteered to exercise on a bicycle ergometer on five different days of their menstrual cycles (days 2, 8, 14, 20, and 26; day 1 = onset of menstruation). Each day the subjects exercised at a maximum work load (184.4 W) and at four submaximal exercise intensities (45.0, 83.1, 121.4 and 154.4 W). Ratings of perceived exertion (RPE) were obtained during minute 4 of each 5-min submaximal exercise bout and at exhaustion each day. Overall, RPE was linearly correlated with heart rate (r = 0.87) when all exercise intensities and cycle days were considered. There was no statistically significant (P greater than 0.05) change in RPE at any exercise intensity related to cycle day. Factors (expired ventilatory volume, respiratory frequency, tidal volume, end-tidal CO2 tension, and heart rate) that may have affected RPE, maximal aerobic power, and anaerobic threshold (AT) were also statistically unchanged because of cycle day. Anaerobic threshold averaged 68.7% of the VO2max, or 1.592 l . min for all cycle days, as determined by the total expiratory volume/oxygen uptake "break point" method of Wasserman and co-workers (18). These data support the utilization of female subjects with normal menstrual cycles in psychophysiological studies without regard to menstrual cycle phase.
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PMID:Perceived exertion and anaerobic threshold during the menstrual cycle. 710 90

The effect of work rate increase in ramp work tests was studied in six healthy subjects. Each subject exercised on a cycle ergometer with the work rate incremented by either 65.4 W . min-1 and 49.0 W . min-1 for the fast ramps or 8.2 W . min-1 and 6.1 W . min-1 for the slow ramps for male and female subjects, respectively. Gas exchange was monitored by open-circuit spirometry. Arterialized venous blood samples were obtained from a dorsal hand vein. The peak VO2 was not significantly different for fast (3218 +/- 602 ml . min-1, X +/- SD) and slow (3237 +/- 601 ml . min-1) ramp tests. Gas-exchange anaerobic threshold, determined by multi-segment linear regression of VE vs VO2, was similar for fast and slow ramp tests (1742 +/- 415 and 1925 +/- 639 ml O2 . min-1, P greater than 0.05). The VO2 at which blood lactate increased 0.5 mM above resting levels was lower (1463 +/- 259 ml . min-1, P less than 0.05) than the gas-exchange anaerobic threshold for the slow ramp test. The VO2 at which blood lactate reached 2.0 mM was greater (2383 +/- 247 ml . min-1, P less than 0.05) than the gas-exchange anaerobic threshold for the fast ramp test. In addition to these lactate differences, blood pH and HCO3- did not change in direct proportion to the lactate concentration in either test. Blood PCO2 was significantly (P less than 0.05) greater at the point of exhaustion in the fast ramp test (42.2 +/- 2.3 mmHg) than in the slow ramp test (26.7 +/- 2.1 mmHg). It is concluded that the gas-exchange anaerobic threshold can be clearly dissociated from the blood lactate threshold by altering the work rate forcing function. Other mechanisms, such as H+ efflux and CO2 storage capacity, are more likely explanations for the gas-exchange anaerobic threshold.
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PMID:Blood acid-base and lactate relationships studied by ramp work tests. 713 48

The dependence of growth formation of citric acids (citrate: isocitrate = 1:1) on oxygen parital pressure of an alkane utilising yeast Saccharomycopsis lipolytica was investigated. During growth oxygen corresponds to a Michaelis-Menten-kinetics (Ks = 2.0 . 10(-5) M). The respiration quotient RQ for a dissolved oxygen concentration in the range of 10-100% (air saturation) is 0.46 +/- +/- 0.04. The phase of product formation is characterized by 3 sections. Immediately after N-exhaustion the cell activities are the highest. They decline during the first 30 hours of production. Besides the production of reserve material in this first section the highest production rate for citrate and isocitrate is observed. The rate of citric acid production depends on the oxygen partial pressure and is governed by Michaelis-Menten-kinetics. The specific production rate and the rate of oxygen consumption correspond to KS-values of 4.0 X 10(-5) and 3.3 X 10(-5) M, respectively. The RQ-value declines to a constant value of 0.23 +/- 0.02 and is not influenced by oxygen partial pressures in the range of 10--100% (related to air saturation). During the second section cell activities remain nearly constant for about 100 h. Due to this constancy the following equation could be derived: 14 O2 + C15H32 leads to 2 C6H8O7 + 3 CO2 + 8 H2O. In the third section the cell activities decline again.
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PMID:[Effect of oxygen partial pressure on citric acid synthesis in Saccharomycopsis lipolytica using n-alkanes]. 733 71


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