SEARCH · PubMed Health

Results for “Exercise”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources

PubMed2005

The effect of exercise intensity on the response to exercise rehabilitation in patients with intermittent claudication.

PURPOSE: The purpose of this randomized trial was to compare the efficacy of a low-intensity exercise rehabilitation program vs a high-intensity program in changing physical function, peripheral circulation, and health-related quality of life in peripheral arterial disease (PAD) patients limited by intermittent claudication. METHODS: Thirty-one patients randomized to low-intensity exercise rehabilitation and 33 patients randomized to high-intensity exercise rehabilitation completed the study. The 6-month exercise rehabilitation programs consisted of intermittent treadmill walking to near maximal claudication pain 3 days per week at either 40% (low-intensity group) or 80% (high-intensity group) of maximal exercise capacity. Total work performed in the two training regimens was similar by having the patients in the low-intensity group exercise for a longer duration than patients in the high-intensity group. Measurements of physical function, peripheral circulation, and health-related quality of life were obtained on each patient before and after the rehabilitation programs. RESULTS: After the exercise rehabilitation programs, patients in the two groups had similar improvements in these measures. Initial claudication distance increased by 109% in the low-intensity group (P < .01) and by 109% in the high-intensity group (P < .01), and absolute claudication distance increased by 61% (P < 0.01) and 63% (P < .01) in the low-intensity and high-intensity groups, respectively. Furthermore, both exercise programs elicited improvements (P < .05) in peak oxygen uptake, ischemic window, and health-related quality of life. CONCLUSION: The efficacy of low-intensity exercise rehabilitation is similar to high-intensity rehabilitation in improving markers of functional independence in PAD patients limited by intermittent claudication, provided that a few additional minutes of walking is accomplished to elicit a similar volume of exercise.

Aged↗

PubMed2006

Humidity influences exercise capacity in subjects with exercise-induced bronchoconstriction (EIB).

RATIONALE: Exercise-induced bronchoconstriction (EIB) increases in cold and dry air and decreases in humid air in subjects with asthma. Few reports have reported on the effect of humid environment upon exercise capacity in subjects with EIB. OBJECTIVE: The primary aim of the present study was to examine the effect of changing the humidity of the environmental air upon exercise capacity measured by peak oxygen uptake (V O2 peak), peak ventilation (V Epeak) and peak running speed (V peak) and secondarily to assess the influence of environmental humidity upon EIB in subjects suffering from EIB. METHODS: Twenty subjects (10-45 years old, male/female:13/7) with diagnosed EIB performed exercise testing under standardised, regular environmental conditions, 20.2 degrees C (+/- 1.1) and 40% (+/- 3.3) relative humidity [mean (+/- SD)], and under standardised humid environmental conditions; 19.9 degrees C (+/- 1.0) and 95% (+/- 1.7) relative humidity in random order on separate days. Lung function was measured before and 1, 3, 6, 10 and 15 min after exercise. Heart rate (HR), oxygen uptake (V O2), respiratory gas exchange ratio (RER), breathing frequency (BF) and minute ventilation (V E) were measured during exercise. RESULTS: V O2 peak and V peak increased significantly from 40% to 95% relative humidity of the environmental air, 4.5% and 5.9%, respectively (P = 0.001). HRpeak increased significantly in the humid environment, while BF(peak) decreased significantly. RERpeak and V Epeak did not change significantly. Post-exercise reduction in FEV1 (DeltaFEV1) and FEF50 (forced expiratory flow at 50% of FVC) (DeltaFEF50) significantly decreased after exercise in a humid environment as compared to regular conditions, DeltaFEV1: 12% (7,17) vs. 24% (19,29) [mean (95% confidence intervals)], respectively, DeltaFEF50: 20% (12,29) vs. 38% (30,46), respectively (P < 0.001). CONCLUSION: Exercise capacity (V O2 peak and V peak) markedly improved during exercise in humid air in subjects with EIB, whereas EIB was reduced to the half.

Adolescent↗

PubMed2000

Maximal exercise systolic pressure, exercise training, and mortality in myocardial infarction patients.

The relation of maximal exercise systolic pressure to physical conditioning and to mortality was determined in 641 men with > or =1 myocardial infarctions. Each performed a standardized multistage exercise test before randomized assignment either to an exercise group or a control group and at scheduled periodic intervals over 3 years. This study compares 123 men with maximal exercise systolic pressures (MESP) of < or =140 mm Hg with 518 men whose maximal exercise systolic pressure was > or =140 mm Hg. At baseline, the 2 groups were comparable for age, entry time since the occurrence of the qualifying cardiac event, and reported use of antihypertensive medications. Men with low MESP used more beta blockers, had lower systolic pressure measurements at rest and by definition at maximal exercise, and lower work capacity than men with higher levels of MESP. Men with low MESP experienced: (1) no reduction in mortality with exercise conditioning (p<0.86), and (2) a significantly higher mortality rate over 3 years (p<0.003) compared with men with higher levels of MESP. The relation of a low MESP to mortality persisted: (1) whether MESP or work capacity increased from the baseline exercise test to the last performed exercise test, and (2) whether it was measured at low (<6 METs) or high (> or =6 METs) levels of work capacity. We conclude that low maximal exercise systolic blood pressure is a predictor of mortality and is associated with an ineffective training response in men with myocardial infarction.

Blood Pressure↗

PubMed2004

Exercise-induced hepatocyte growth factor production in patients after acute myocardial infarction: its relationship to exercise capacity and brain natriuretic peptide levels.

BACKGROUND: The hepatocyte growth factor (HGF) is a multifunctional cytokine with cardioprotective properties and potent myogenic activity for vascular endothelium. In patients after acute myocardial infarction, exercise training has the beneficial effects on cardiovascular adaptations. We hypothesized that exercise induces HGF production in those patients. If this hypothesis is correct, HGF production may be associated with clinical parameters of cardiovascular function. METHODS AND RESULTS: In 20 patients after acute myocardial infarction, HGF levels in the pulmonary artery (HGF(PA)) and aorta (HGF(Ao)) were determined at rest and during supine submaximal exercise, with cardiac output (CO) measured by catheterization. Exercise-induced HGF production was calculated by using the following equation: [(HGF(PA)-HGF(Ao))xCO during exercise]-[(HGF(PA)-HGF(Ao))xCO at rest]. On a separate day, peak oxygen uptake (VO2) was determined during a symptom-limited upright cardiopulmonary exercise test. Exercise increased HGF production (from 1.6 +/- 3.0 to 9.0 +/- 6.3 microg/ml, p<0.001). Exercise-induced HGF production was inversely related to peak VO2 (r=-0.664, p<0.01) and positively related to levels of brain natriuretic peptide (BNP), a biochemical marker for post-infarction ventricular remodeling (r=0.686, p<0.01). CONCLUSIONS: Exercise significantly increases HGF production. This phenomenon may play an important role in post-infarction patients, particularly with reduced exercise tolerance and elevated BNP levels.

Aged↗

PubMed1994

Using the exercise test to develop the exercise prescription in health and disease.

The objective of an exercise program for persons with or without disease should be the development or maintenance of cardiorespiratory fitness, strength and muscular endurance, and flexibility. The basic principles of prescribing exercise--frequency, intensity, and duration of training--and the mode of activity as recommended by the ACSM for healthy adults are also appropriate for persons with disease. The difference in the exercise prescription for persons with disease is the manner in which these principles are applied. Usually, the more fragile the patient, the lower the intensity of exercise and the slower the progression of training. The role of cardiopulmonary exercise testing is to determine a safe and effective level of exercise for healthy persons as well as those with disease. GXT is useful in identifying individuals with disease and in providing information regarding the level of supervision needed during exercise training. In addition, exercise testing can be used to clear a person for participation in a resistance training program. Resistance training should be integrated as part of a well-rounded program, because of the importance of maintaining strength, muscle mass, and bone mineral density. Generally, the starting intensity for persons with disease is lower, the frequency and duration higher, and the progression of exercise slower to allow a more gradual adaptation to exercise training.

Exercise↗

PubMed2003

Post-exercise vitamin C supplementation and recovery from demanding exercise.

The aim of this study was to investigate whether post-exercise vitamin C supplementation influences recovery from an unaccustomed bout of exercise. Sixteen male subjects were allocated to either a placebo (P; n=8) or vitamin C (VC) group ( n=8). Subjects performed a prolonged (90-min) intermittent shuttle-running test, and supplementation began after the cessation of exercise. Immediately after exercise the VC group consumed 200 mg of VC dissolved in a 500 ml drink, whereas the subjects in the P group consumed the drink alone. Later on the same day and then in the morning and evening of the following 2 days, subjects consumed additional identical drinks. Plasma VC concentrations in the VC group increased above those in the P group 1 h after exercise and remained above P values for the 3 days after exercise. Nevertheless, post-exercise VC supplementation was not associated with improved recovery. Post-exercise serum creatine kinase activities and myoglobin concentrations were unaffected by supplementation. Muscle soreness and the recovery of muscle function in the leg flexors and extensors were not different in VC and P groups. Furthermore, although plasma concentrations of interleukin-6 and malondialdehyde increased following exercise, there was no difference between VC and P groups. These results suggest that either free radicals are not involved in delaying the recovery process following a bout of unaccustomed exercise, or that the consumption of VC wholly after exercise is unable to deliver this antioxidant to the appropriate sites with sufficient expediency to improve recovery.

Adaptation, Physiological↗

PubMed1987

Increased removal rate of exogenous triglycerides after prolonged exercise in man: time course and effect of exercise duration.

Ten healthy young men exercised for 1.5 and 3 hours, respectively, 4 to 6 weeks apart at the same work intensity, corresponding to 77% of the individual maximal heart rate. In the fasting state 1 mL of 10% Intralipid/kg body weight was injected IV, the fractional removal rate was calculated (k2-value), and fasting lipid and apolipoprotein C-I, C-II, and CIII concentrations were determined one day before, immediately before, immediately after, and one day after the exercise: measurements were also made two and three days after the three-hour session. An increase of the k2-value was found only the day after the three-hour exercise (+66%, P less than .01), while after the 1.5-hour exercise the k2-value was not changed. One and two days after the three-hour exercise the fasting serum triglyceride concentration was significantly decreased by 33% and 16%, respectively. Serum triglyceride concentration was decreased also the day after the shorter session (-17%, P less than .05). Decreases in serum cholesterol concentrations were significant after both exercise bouts, but the significance disappeared if corrections for the changes in calculated plasma volume were made. Serum level of C apolipoproteins was decreased one day after the three-hour exercise, while it was not changed after the shorter exercise. This study shows that prolonged exercise produces an increase in the removal rate of Intralipid triglycerides from the bloodstream, that this change is related to the duration of exercise, and that some time is required following the exercise, before it is manifest.

Adult↗

PubMed1986

Exercise-induced hypertension after repair of coarctation of the aorta: arm versus leg exercise.

The etiology of exercise-induced upper limb hypertension after repair of coarctation of the aorta is unknown. We hypothesized that blood flow across the coarctation repair site is a major determinant of such exercise-induced hypertension. Because arm ergometry should produce a smaller increase in descending aortic blood flow than treadmill exercise, we compared the changes in upper limb pressure and the coarctation gradient produced by each type of exercise at equivalent levels of heart rate and peak oxygen consumption in 28 children with repaired coarctation of the aorta. The children were classified into three groups: Group I, resting gradient less than 15 mm Hg and treadmill gradient less than 20 mm Hg; Group II, resting gradient less than 15 mm Hg and treadmill gradient greater than 20 mm Hg; and Group III, resting gradient greater than or equal to 15 mm Hg. Twelve children with no heart disease served as control subjects. All children were exercised to exhaustion with 45 minutes' rest between the two exercise protocols. There were no differences in maximal heart rate and oxygen consumption between the two types of exercise. In all groups, treadmill exercise produced a larger increase in arm systolic blood pressure and arm-leg gradient than did arm exercise. With treadmill exercise coarctation Groups II and III developed a greater rise in both arm-leg gradient and arm systolic pressure than was observed in the control subjects (p less than 0.05). However, with arm exercise, Group III developed a significantly greater rise in both arm pressure and arm-leg gradient (p less than 0.05) than was observed in the control subjects.

Adolescent↗

PubMed1986

Exercise tolerance and cardiorespiratory response to exercise after the Fontan operation for tricuspid atresia or functional single ventricle.

To determine the impact of the Fontan operation on exercise tolerance and on the cardiorespiratory response to exercise, we compared the results of graded exercise to maximal effort of 81 patients with tricuspid atresia or single functional ventricle studied preoperatively with those of 29 patients studied postoperatively. Postoperatively, the values for total work performed, duration of exercise and maximal oxygen uptake increased significantly. Regardless of operative status, the maximal heart rate during exercise was reduced. The cardiac output and stroke volume response to exercise were subnormal after operation. Systemic arterial blood oxygen saturation was reduced markedly preoperatively both at rest and during exercise; postoperatively, it was significantly greater than the preoperative value but it remained slightly abnormal. The ventilatory response to exercise (respiratory rate, minute ventilation and ventilatory equivalent for oxygen) decreased toward normal after operation. Exercise tolerance and the cardiorespiratory responses to exercise improve after the Fontan operation. Formal exercise testing is essential to quantitate the degree of improvement.

Adolescent↗

PubMed1985

Effect of hand-arm exercise on venous blood constituents during leg exercise.

To test the hypothesis that ancillary arm and hand exercise would change the values of antecubital blood constituents during leg exercise, seven healthy men (19-27 yrs) performed static (10% of a maximal voluntary contraction) or dynamic (60 finger flexions/min) hand-arm exercise with one hand during submaximal leg exercise (50% V2 max) in the supine position. Venous blood was analyzed for serum Na+, K+, osmolality, albumin, total Ca2+, and glucose; blood hemoglobin, hematocrit, and lactic acid; and change in plasma volume. During leg exercise there were no significant differences in these blood constituents between right and left arms at rest. Only glucose and lactate were affected by additional arm exercise. Compared with resting arm values during leg exercise, glucose decreased from 4.7 to 4.5 mmol/l (delta = 4%, P less than 0.05) and lactate increased from 2.0 to 2.4 mmol/l (delta = 20%, P less than 0.05) during static arm exercise. With dynamic arm exercise, glucose decreased from a resting level of 4.8 to 4.7 mmol/l (delta = 2%, P less than 0.05). We conclude that additional static or dynamic hand-forearm exercise accompanying leg exercise could introduce significant errors in glucose (2%-4%) and lactic acid (6%-20%) concentrations measured in venous blood.

Adult↗

PubMed2003

Muscle interstitial potassium kinetics during intense exhaustive exercise: effect of previous arm exercise.

Interstitial K+ ([K+]i) was measured in human skeletal muscle by microdialysis during exhaustive leg exercise, with (AL) and without (L) previous intense arm exercise. In addition, the reproducibility of the [K+]i determinations was examined. Possible microdialysis-induced rupture of the sarcolemma was assessed by measurement of carnosine in the dialysate, because carnosine is only expected to be found intracellularly. Changes in [K+]i could be reproduced, when exhaustive leg exercise was performed on two different days, with a between-day difference of approximately 0.5 mM at rest and 1.5 mM at exhaustion. The time to exhaustion was shorter in AL than in L (2.7 +/- 0.3 vs. 4.0 +/- 0.3 min; P < 0.05). Furthermore, [K+]i was higher from 0 to 1.5 min of the intense leg exercise period in AL compared with L (9.2 +/- 0.7 vs. 6.4 +/- 0.9 mM; P < 0.001) and at exhaustion (11.9 +/- 0.5 vs. 10.3 +/- 0.6 mM; P < 0.05). The dialysate content of carnosine was elevated by exercise, but low-intensity exercise resulted in higher dialysate carnosine concentrations than subsequent intense exercise. Furthermore, no relationship was found between carnosine concentrations and [K+]i. Thus the present data suggest that microdialysis can be used to determine muscle [K+]i kinetics during intense exercise, when low-intensity exercise is performed before the intense exercise. The high [K+]i levels reached at exhaustion can be expected to cause fatigue, which is supported by the finding that a faster accumulation of interstitial K+, induced by prior arm exercise, was associated with a reduced time to fatigue.

Acidosis↗

PubMed2006

Influence of exercise order in a resistance-training exercise session.

The order of resistance exercises within a training session may have a vital impact on the quality of the constituent exercises performed. However, very few studies have documented the specific influence of exercise order. Therefore, the purpose of this study was to examine the effect of exercise order on back squat performance in the context of a whole-body workout. Nine resistance-trained male subjects (age: 24 +/- 4 years, body mass: 81.5 +/- 15.3 kg, resistance-training experience: 7 +/- 4 years) performed the back squat exercise (4 sets at 85% of 1 repetition maximum) on 2 separate occasions in a balanced, crossover design. During one protocol, the squat exercise was performed first (protocol A); during the other protocol, it was performed after a whole-body resistance-exercise session (protocol B). Number of repetitions, average power, and rating of perceived exertion (RPE) were collected during each set of the squat exercise. All subjects performed significantly (p < 0.01) more repetitions during set 1 when they performed protocol A (8.0 +/- 1.9 repetitions) compared with protocol B (5.4 +/- 2.7 repetitions). The average power for each set was higher during protocol B compared with protocol A. There were no significant differences in RPE values between the 2 protocols. In conclusion, performing the barbell back squat first in an exercise session allowed the completion of more total repetitions. However, this study showed that performing the squat exercise after a whole-body workout session may result in greater power output if the squat is preceded by a power exercise (i.e., hang pull). This phenomenon may have been due to postactivation potentiation.

Adult↗

PubMed1983

Hemodynamic evaluation of exercise-induced ST-segment depression and elevation in ischemic heart disease. Left ventricular cineangiography during exercise.

In order to elucidate the hemodynamic significance of exercise-induced ST-segment shifts in ischemic heart disease, left ventricular cineangiography was carried out in 41 patients at rest and during supine bicycle ergometer exercise. These patients were divided into 2 groups, that is, a normal coronary artery group (6 patients), having neither significant coronary artery stenosis nor exercise-induced ST-segment shifts, and a diseased group (35 patients) having significant coronary artery stenosis (inner-diameter stenosis greater than or equal to 75%). The latter was further divided into 3 subgroups according to exercise-induced ST-segment shifts: ST-unchanged group (17 patients), ST-depression group (11 patients) and ST-elevation group (7 patients). In the normal coronary artery and ST-unchanged groups, exercise produced an increase in left ventricular end-diastolic volume index (LVEDVI), a decrease in left ventricular end-systolic volume index (LVESVI) and increases in stroke index and ejection fraction. In the ST-depression group, the appearance or aggravation of left ventricular wall motion abnormality was induced at the site of coronary artery stenosis by exercise in 9 patients. Both LVEDVI and LVESVI increased, stroke index remained unchanged, and ejection fraction decreased during exercise. In the ST-elevation group, ST-segment elevation was induced in leads with abnormal Q waves. In 2 patients, exercise induced aggravation of wall motion abnormality at the infarctional segment. LVESVI increased, but LVEDVI showed little increase, and stroke index and ejection fraction tended to decrease during exercise. In the ST-depression group, exercise-induced left ventricular pump dysfunction was due to lowered contractility (increased LVESVI) caused by transient myocardial ischemia. In the ST-elevation group, exercise-induced pump dysfunction was mainly due to lowered contractility, and in some of them, the findings suggested that transient myocardial ischemia at or around the region of infarction might be the cause of pump dysfunction. In addition, a poor compensatory effect of the Frank-Starling mechanism seemed to play a role in the onset of such dysfunction in this group.

Adult↗

PubMed2003

Exercise-trained but not untrained rats maintain free carnitine reserves during acute exercise.

Exercise training is known to induce physiological adaptations that improve exercise performance and alter patterns of energy substrate utilization to favour fatty acid oxidation. L-Carnitine is an essential cofactor for the oxidation of fatty acids under all physiological conditions, including exercise. This study evaluated the effect of acute exercise on carnitine concentrations in tissue and serum, liver carnitine palmitoyltransferase-I activity and expression, and serum lipids in both trained and untrained rats as compared to non-exercised rats. Serum acyl- and total carnitine was significantly higher in the trained animals, whether exercised or not, suggesting an exercise-induced increase in a renal threshold for carnitine. Untrained rats had significantly higher acylcarnitine in skeletal muscle and an acyl/free carnitine ratio of 0.63 +/- 0.06 compared with 0.31 +/- 0.16 in trained animals receiving an identical acute bout of exercise, demonstrating that untrained animals utilized a significantly higher percentage of free carnitine reserves during exercise. This study suggests that free carnitine reserves may be reduced during exercise in untrained rats, an effect that has the potential to impair both carbohydrate and fat metabolism during exercise.

Adaptation, Physiological↗

PubMed1988

[Finger temperature changes during exercise as related to exercise intensity].

An approach was made to assess individual exercise tolerance using finger vasoconstrictive response as a marker for exercise intensity. Finger temperature (FIT) monitoring was used as an averaged flow sensor and was validated by finger plethysmography and laser-Doppler flowmetry. Progressive multi-stage intermittent exercise protocol (3-minute exercise period alternating with 3-minute rest period) was used to permit stable FIT values before each exercise stage. Anaerobic threshold (AT) was determined by respiratory measurements. Mean room temperature was 25.4 +/- 1.6 degrees C. The general pattern of FIT during 3-minute exercise period was as follows: at the mild exercise stage FIT decreased initially, only to rise at the latter half of exercise. As the exercise stage progressed FIT decreased throughout, and at the stage of maximal effort FIT decrease linearly (LiD). FIT decrease was abolished by the nerve block. Four groups of subjects (48 in total) were studied using the above-described exercise protocol. Group I; 6 athletes, II; 16 normal subjects, III; 8 mild cardiac and IV: 15 moderate to severe cardiac patients. Mean maximal oxygen consumption (ml/kg/min) was 70, 47, 31 and 15, and mean HR (b/min) was 188, 195, 165 and 142, respectively in group I, II, III, IV. LiD was observed in greater than 80% of all cases at the work load above 90% of peak oxygen consumption, and approximately 1.6-fold of AT in group I, II and III and 1.3-fold of AT in group IV. Correlation between plasma norepinephrine and FIT decrease was observed in normal subjects. In conclusion, FIT monitoring during treadmill exercise using intermittent protocol uncovered a work load dependent progressive vasoconstrictive response. And a linear decrease of FIT indicated an approaching maximal work load for the individual subject.

Adult↗

PubMed1996

Decreased vascular sensitivity after acute exercise and chronic exercise training in rat thoracic aorta.

The effects of acute and chronic physical exercise on the sensitivity of isolated aorta to norepinephrine were investigated. After chronic exercise, the EC50 values for norepinephrine increased 3.1-fold and 2.3-fold in endothelium-intact and in endothelium-denuded aorta, respectively. The attenuated sensitivity of aorta to norepinephrine after chronic exercise was still evident in endothelium-denuded aorta, but to a lesser extent than in endothelium-intact aorta. After acute exercise, in control rats, the EC50 values increased 7.8-fold and 5.4-fold in endothelium-intact and endothelium-denuded aorta, respectively. The attenuated sensitivity of aorta to norepinephrine after an acute exercise was still evident in endothelium-denuded aorta. In trained rats, the EC50 values increased 2.3-fold and 2.6-fold in endothelium-intact and endothelium-denuded aorta, respectively. Thus, acute exercise was less effective in trained than in control rats. No significant difference in 60 mM KCl-induced tension between control and trained rats was observed with or without endothelium after acute and chronic exercise. The results suggest that levels of endothelium-dependent releasing factor may increase in response to norepinephrine after acute and chronic exercise. In addition, the attenuated sensitivity of aorta to norepinephrine after acute and chronic exercise may also result from the change(s) in the receptor sites. However, the degree of desensitization caused by acute exercise was less in the rats adapted to chronic exercise than in the sedentary control rats.

Adrenergic alpha-Agonists↗

PubMed1997

Relationship between exercise hyperpnea, hemodynamics, and blood gases before and during glyceryl trinitrate infusion in patients with exercise-induced elevation of pulmonary artery wedge pressure.

BACKGROUND: The mechanisms underlying the excessive ventilatory response to exercise in patients with cardiac failure are still not fully understood. HYPOTHESIS: This study was undertaken to investigate the mechanisms behind exercise hyperpnea in patients with exercise-induced left ventricular dysfunction. METHODS: In 18 patients, aged 57-82 years, all with atherosclerotic lumbar aorta aneurysm and pulmonary artery wedge pressure (PAWP) > 25 mmHg during supine exercise, ventilation (V), central hemodynamics, and arterial and venous blood gases were examined during supine rest and exercise, before and during infusion of glyceryl trinitrate (GTN). RESULTS: Before GTN, exercise PAWP was 32.2 +/- 6.1 mmHg and V/V O2 was 33.8 +/- 7.7 l/l (130% of predicted). With GTN, exercise PAWP was markedly reduced to 15.3 +/- 3.8 mmHg (p < 0.001), whereas V/V O2 was only marginally reduced to 32.3 +/- 3.0 l/l (124% of predicted) (p < 0.05). Exercise physiologic dead space (VD/VT) declined from 0.31 +/- 0.16 to 0.26 +/- 0.17 (p < 0.05), while PaCO2 was reduced from 5.20 +/- 0.31 to 5.10 +/- 0.24 kPa (p < 0.05). PvO2 and cardiac output (CO), however, were unchanged below normal. CONCLUSION: The data show that exercise-induced hyperpnea was not substantially reduced by rapid normalization of PAWP and could not be related to preservation of normal PaCO2 in the presence of high VD/VT. The persistence of exercise hyperpnea and reduced PvO2 after GTN is consistent with augmented ventilatory stimuli from hypoxia-induced metabolic abnormalities in the skeletal muscles, or/and persistently reduced CO, due to changes in the integrated superior command of ventilation and circulation.

Aged↗

PubMed2001

Endothelial dysfunction and decreased exercise tolerance in interferon-alpha therapy in chronic hepatitis C: relation between exercise hyperemia and endothelial function.

BACKGROUND: We previously reported that reversible endothelial dysfunction is caused by interferon-alpha therapy (IFN) in patients with chronic hepatitis C. In experimental studies, limb blood flow during exercise is reported to be dependent on endothelium-derived nitric oxide. HYPOTHESIS: The purpose of this study was to confirm the effect of IFN on endothelial function and to investigate whether exercise hyperemia is dependent on endothelial function in humans. METHODS: We performed symptom-limited exercise treadmill testing and measured flow-mediated vasodilation (FMD, endothelium-dependent vasodilation) and sublingual glyceryl-trinitrate-induced dilation (GTN-D, 0.3 mg, endothelium-independent vasodilation) in the brachial artery by using high-resolution ultrasound in 10 patients with chronic active hepatitis C (age 53 +/- 11 years, 2 men, 8 women) before and immediately after administration of recombinant interferon 2b (10 million U/day) for 4 weeks. RESULTS: There were no significant abnormal findings in any patients in routine studies of 24-h ambulatory electrocardiogram monitoring, two-dimensional echocardiography, and exercise treadmill testing both before and after treatment. Leg fatigue and exhaustion were the reasons for termination of exercise treadmill testing in each patient. Pressure rate product was calculated at rest and peak exercise. Interferon-alpha therapy significantly (p<0.05) decreased FMD (6.8 +/- 3.1 vs. 1.9 +/- 2.6%), exercise treadmill testing tolerance time (437 +/- 89 vs. 395 +/- 62 s) and peak pressure rate product (283 +/- 41 vs. 241 +/- 47 mmHg x beats/min x 10(-2)), but not GTN-D (13.4 +/- 5.4 vs. 17.0 +/- 5.5%). The change of FMD due to IFN significantly and highly correlated with exercise treadmill testing tolerance time (r = 0.86, p<0.001), but not with change of peak pressure rate product, suggesting that FMD is more closely related to the condition of the peripheral circulation than is cardiac performance. CONCLUSION: These results suggest that IFN in patients with chronic hepatitis C impairs endothelial function and exercise tolerance, and that endothelial function might be at least partly involved in exercise hyperemia in humans.

Adult↗