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PubMed2004

[The impact of comprehensive cardiac rehabilitation in patients up to 55 years old after acute myocardial infarction treated with primary coronary intervention].

UNLABELLED: The aim of our study was to evaluate the impact of comprehensive 3-phases cardiac rehabilitation in patients aged up to 55 years after acute myocardial infarction treated with primary coronary intervention (PCI) of the infarction related artery on the cardiovascular status, modification of coronary risk factors, psychological and physical status and exercise tolerance. METHODS: Out of 106 consecutive patients aged up to 55 years with acute myocardial infarction (AMI) with ST-segment elevation, treated with primary coronary intervention (PCI) of the infarction related artery 71 patients entered the study and were randomized either to the Study Group (GB) or to the Control Group (GK). 31 patients of GB underwent 3-phases cardiac rehabilitation program and 40 patients of GK did not participate in phase III of the program. At phase I of the rehabilitation and 6 months after myocardial infarction physical examination, echocardiography and treadmill exercise test were performed. RESULTS: At 6-months follow-up chest pain and symptoms of heart failure were significantly less common (p < 0.001) and a tendency for fewer new cardiac events and re-PCI was noted in GB. Self-evaluated, significantly greater improvement in the emotional and physical status as well as in physical activity (p < 0.001) was achieved in GB. In GB better exercise tolerance on treadmill exercise test, greater improvement in left ventricular ejection fraction (p < 0.05) and contractile index (p < 0.05) on echocardiography were observed. The effects of the secondary prevention in terms of smoking cessation and obesity were not satisfactory in both groups. CONCLUSION: 3-phases comprehensive cardiac rehabilitation in patients with AMI treated with PCI of the infarction related artery improves recovery at 6-month follow-up. It has a favorable impact on the anginal and heart failure symptoms, cardiac risk factors (especially physical activity, restrictive diet), psychological and physical status. It contributes towards maintaining a further event-free period. It improves selected cardiovascular parameters such as exercise tolerance, segmental and global left ventricular function.

Adult↗

PubMed1993

The effect of obesity on ventilatory response and anaerobic threshold during exercise.

To facilitate making the physical fitness programs for obesity control, we investigated the effects of obesity on the ventilatory response during exercise and exercise tolerance. One hundred eighteen adults were divided into a normal group and fatty group by percentage of body fat. Each subject performed a submaximal exercise test under the gas-exchange measurement. The fatty group was inferior to the normal group in exercise tolerance. The respiratory mode, during exercise, in the fatty group was characterized by higher respiratory rate and less tidal volume compared with the normal group. This mode may result in increased dead space and therefore unavailable ventilation capacity. These data suggest that the characteristic respiratory mode in the fatty group was a factor in the lower exercise tolerance.

Adult↗

PubMed2001

Subacute and chronic effects of DDD pacing on left ventricular diastolic function in patients with non-obstructive hypertrophic cardiomyopathy.

The present study examined the ability of dual-chamber (DDD) pacing to improve symptoms and exercise tolerance in patients with non-obstructive hypertrophic cardiomyopathy (HNCM). Seven patients with HNCM who had failed to benefit from pharmacotherapy participated in the study. The New York Heart Association (NHYA) functional class status and exercise tolerance, which was determined by the treadmill exercise test, were recorded and an echocardiographic observation was performed before, and 1 week, 3 months and 1 year after the implantation of a permanent DDD pacemaker. The atrioventricular delay (AVd) was determined by measuring the point of peak rapid filling velocity and maximum cardiac output (CO). Two patients were not implanted with a permanent pacemaker because their CO and blood pressure decreased or because palpitation occurred during temporary pacing. The ratio between early and late peaks of flow velocity (1.56, 1.21,0.95, and 0.86 before implantation and 1 week, 3 months and 1 year after implantation, respectively); deceleration time (ms: 263.2, 217.6, 204.6, 187.0); peak filling rate (ml/s: 146.2, 204.0, 233.2, 243.6); NYHA functional class status (2.0, 1.8, 1.6, 1.4); and exercise tolerance (s: 203, 264, 403, 480) were significantly improved after implantation. However, left ventricular dimension, percent fractional shortening, ejection fraction, acceleration time and the isovolumic relaxation time were not changed significantly. In conclusion, DDD pacing improved symptoms and the NYHA functional class status, which is associated with improvement of left ventricular diastolic function. It is proposed that DDD pacing would be useful in patients not only with obstructive but also non-obstructive hypertrophic cardiomyopathy refractory to medical treatment, depending on the careful selection of subjects.

Aged↗

PubMed1991

Clenbuterol plasma concentrations after repeated oral administration and its effects on cardio-respiratory and blood lactate responses to exercise in healthy Standardbred horses.

To evaluate the effects of clenbuterol on cardio-respiratory parameters and blood lactate relation to exercise tolerance, experimental horses performed standardized exercise tests on a high-speed treadmill before and after administration of the drug. Clenbuterol was administered in feed to six healthy Standardbreds at a dose rate of 0.8 micrograms/kg b.wt twice daily for 5.5 days. Each horse was tested twice, without and with a respiratory mask, during two consecutive days. One week elapsed between the baseline tests without drug and the tests with clenbuterol treatment (each horse served as its own control). The results show an unchanged heart rate response to exercise 2 h after the last clenbuterol administration. The blood lactate response and the arterial oxygen tension during exercise did not differ before and after drug treatment. The oxygen uptake as well as pulmonary ventilation relative to the work load performed was essentially unaffected. The arterial pH during exercise was significantly increased (P less than 0.05) following clenbuterol treatment. Plasma levels of clenbuterol were maximal 2 h post-administration with values between 0.45 and 0.75 ng/ml. The plasma half-life of elimination was 10.4 h (+/- 2.25 SD). In conclusion, clenbuterol did not cause any major effects on the cardio-respiratory and blood lactate parameters studied in healthy horses performing submaximal exercise tolerance tests.

Administration, Oral↗

PubMed1998

Optimizing exercise training for subgroups of patients with chronic heart failure.

Patients with heart failure and severe left ventricular dysfunction are limited in their ability to tolerate exercise. Recent research has demonstrated that it is not a restricted cardiac output which limits exercise but an abnormality in the performance of a more peripheral component in the pathway of delivery of oxygen to the exercising muscles. Deficiencies in peripheral blood flow and skeletal muscle function and an exaggerated sensitivity to exercise-derived metabolic signals lead to early and profound exercise-induced fatigue and dyspnoea, the mechanisms of which we are only now beginning to understand. These findings raise the possibility of improving exercise tolerance by peripherally acting therapies such as exercise training of skeletal muscles in left ventricular dysfunction and chronic heart failure. Training has been shown to improve exercise tolerance at least as much as angiotensin-converting enzyme inhibitors in these syndromes; additionally, training improves ventilatory control, skeletal muscle metabolism and autonomic nervous system activity. As yet, the most appropriate forms of exercise therapy are not known nor is how best to choose the most suitable patients for this form of treatment. There is evidence that patients with at least moderate, and possibly severe but stable, heart failure can benefit from exercise rehabilitation, provided it is tailored to the capacity of the patient and certain safety considerations are taken into account.

Exercise Therapy↗

PubMed1995

Selection of medical treatment in stable angina pectoris: results of the International Multicenter Angina Exercise (IMAGE) Study.

OBJECTIVES: The present study was designed to investigate which characteristics of anginal symptoms or exercise test results could predict the favorable anti-ischemic effect of the beta-adrenergic blocking agent metoprolol and the calcium antagonist nifedipine in patients with stable angina pectoris. BACKGROUND: The characteristics of anginal symptoms and the results of exercise testing are considered of great importance for selecting medical treatment in patients with chronic stable angina pectoris. However, little information is available on how this first evaluation may be used to select the best pharmacologic approach in individual patients. METHODS: In this prospective multicenter study, 280 patients with stable angina pectoris were enrolled in 25 European centers. After baseline evaluation, consisting of an exercise test and a questionnaire investigating patients' anginal symptoms, the patients were randomly allocated to double-blind treatment for 6 weeks with either metoprolol (Controlled Release, 200 mg once daily) or nifedipine (Retard, 20 mg twice daily) according to a parallel group design. At the end of this period, exercise tests were repeated 1 to 4 h after drug intake. RESULTS: Both metoprolol and nifedipine prolonged exercise tolerance over baseline levels; the improvement was greater in the patients receiving metoprolol (p < 0.05). Multivariate analysis revealed that low exercise tolerance was the only variable associated with a more favorable effect within each treatment group. Metoprolol was more effective than nifedipine in patients with a lower exercise tolerance or with a higher rate-pressure product at rest and at ischemic threshold. None of the characteristics of anginal symptoms or exercise test results predicted a greater efficacy of nifedipine over metoprolol. CONCLUSIONS: The results of a baseline exercise test, but not the characteristics of anginal symptoms, may offer useful information for selecting medical treatment in stable angina pectoris.

Angina Pectoris↗

PubMed2005

Pulmonary hypertension and chronic obstructive pulmonary disease: a case for treatment.

Current pharmacotherapy for chronic obstructive pulmonary disease (COPD) relieves symptoms and reduces exacerbation through improving airflow limitation. Such drugs do not effectively improve exercise tolerance due in part to pulmonary hypertension associated with severe COPD, nor impact on its increased morbidity and mortality. Exercise intolerance is often improved (temporarily) by lung volume reduction surgery and pulmonary rehabilitation. Ambulatory oxygen is the most effective treatment of exercise limitation. Chronic cigarette smoking is the principal cause of COPD. An early change in smokers' lungs is pulmonary artery intimal thickening and vessel narrowing, which, as COPD develops, is correlated with both the severity of emphysema and bronchiolitis. This may be the consequence of combined smoking-induced apoptosis, inflammation, and imperfect repair. End-stage bronchiolitis and emphysema are likely to limit the effectiveness of bronchodilators and corticosteroids. There are effective treatments for idiopathic and scleroderma pulmonary arterial hypertension, which increase exercise tolerance and improve survival. Because idiopathic and COPD pulmonary hypertension share a common vascular intimal thickening, excess endothelin receptor expression, and plasma endothelin-1, an important therapeutic question to address is whether an oral endothelin-1 antagonist can improve exercise tolerance in severe COPD.

Adaptation, Physiological↗

PubMed1997

Relation of changes in left ventricular peak filling rate during exercise to exercise performance in systemic hypertension and in healed myocardial infarction.

Patients with systemic hypertension and coronary artery disease (CAD) often manifest abnormalities at rest in left ventricular (LV) diastolic function and reduced exercise tolerance. It is possible that abnormalities in filling persist during exercise and are partially related to abnormal exercise tolerance. We examined rest and exercise peak filling rate (PFR) to determine if changes in PFR during exercise influence exercise performance. We studied 20 patients with systemic hypertension who had no evidence of CAD (negative thallium-201 stress imaging) and 15 patients with prior myocardial infarction, preserved ejection fraction, and no ischemia by thallium-201 stress imaging. Results were compared with 20 normal subjects. All 55 subjects had rest and exercise radionuclide angiograms Peak workload, exercise time, and LV ejection fraction were reduced in subjects with CAD (57 +/- 24 W, 7.41 +/- 2.91 min, and 60 +/- 9%) compared with subjects with hypertension (72 +/- 21 W, 9.69 +/- 3.03 min, and 70 +/- 6%, p <0.05) and controls (80 +/- 30 W, 10.82 +/- 3.50 min, and 67 +/- 6%, p <0.05). PFR at rest was reduced in CAD subjects (2.40 +/- 0.70 end-diastolic volume per second [EDV/s]) compared with those with hypertension (2.89 +/- 0.70 EDV/s, p <0.02) and controls (3.23 +/- 0.52 EDV/s, p <0.0002). The increments in PFR during exercise were reduced in CAD patients (+1.76 +/- 0.95 EDV/s) compared with hypertensive subjects (+2.93 +/- 1.7 EDV/s) and controls (+3.22 +/- 1.4 EDV/s, p <0.05). The increment in PFR during exercise was related to exercise performance (r = 0.49, p <0.0002). These findings suggest that alterations in LV diastolic filling during exercise are important determinants of exercise performance.

Case-Control Studies↗

PubMed2005

Supplemental oxygen and heliox: 'new' tools for exercise training in chronic obstructive pulmonary disease.

PURPOSE OF REVIEW: Chronic obstructive pulmonary disease (COPD) is a condition characterized by airflow obstruction only partially reversible with usual bronchodilator therapy. Inability of gas to move freely in and out of the lungs causes dyspnea and exercise intolerance. Putative mechanisms of exercise limitation under these conditions are the occurrence of expiratory airflow limitation and dynamic lung hyperinflation developing with the increase in minute ventilation during exercise. This review will examine the results of recent studies using nonpharmacological interventions to improve exercise tolerance in COPD and their relevance to rehabilitation programs. RECENT FINDINGS: Decreasing ventilatory demands and/or gas density have been recently shown to be beneficial to improve exercise tolerance, symptoms, and quality of life. For instance, breathing supplemental oxygen was capable of reducing exercise ventilation, thus allowing expiratory flow limitation within the tidal breathing range to be minimized, and operational lung volumes to be accommodated at lower levels. As a result, dyspnea was decreased for the elastic work of breathing was decreased, and patients were able to increase exercise intensity and/or duration. Manipulating gas density has also been shown to be beneficial in relieving symptoms and improving exercise capacity, for it facilitates gas emptying during expiration. As a result, the amount of expiratory flow limitation and operational lung volumes decreased, thus ultimately leading to greater exercise tolerance. SUMMARY: Nonpharmacological interventions aimed at modifying physical gas properties appear to open new perspectives in exercise rehabilitation programs for COPD.

Administration, Inhalation↗

PubMed1993

Cardiorespiratory responses to exercise of patients with aortic stenosis, pulmonary stenosis, and ventricular septal defect.

BACKGROUND: The purpose of this study was to determine exercise tolerance and cardiac response to exercise for a large cohort of adult subjects with aortic stenosis, pulmonary stenosis, or ventricular septal defect participating in the Second Natural History Study of Congenital Heart Defects (NHS-2). METHODS AND RESULTS: Exercise testing was performed on 134 of 235 NHS-2 full participants with aortic stenosis, 195 of 331 NHS-2 full participants with pulmonary stenosis, and 324 of 594 NHS-2 full participants with ventricular septal defect. A Bruce treadmill exercise protocol was used. Mean exercise duration for patients with aortic stenosis, pulmonary stenosis, and ventricular septal defect was 86.5%, 94.2%, and 90.8% of predicted, respectively. For patients with aortic stenosis, there was a direct relation between echocardiographic Doppler maximum transaortic gradient and ST segment change during exercise. ST segment change during exercise was very uncommon for patients with pulmonary stenosis. For patients with ventricular septal defect, there was an association between arrhythmias noted during exercise and the presence of associated aortic insufficiency. CONCLUSIONS: Although exercise duration was well preserved for patients with each of the three defects, exercise tolerance was subnormal.

Adult↗

PubMed1982

Timing of operation for chronic aortic regurgitation.

Left ventricular systolic function is an important determinant of long-term prognosis in patients with chronic aortic regurgitation. Data from several centers, using invasive and noninvasive assessment of left ventricular function, indicate that long-term postoperative survival is excellent, even in symptomatic patients, if preoperative left ventricular systolic function is normal. The long-term postoperative results are significantly worse in symptomatic patients with preoperative left ventricular systolic dysfunction, many of whom appear to have irreversible left ventricular failure before the onset of symptoms and are at a risk of late postoperative death from congestive heart failure. However, within this high risk subgroup long-term prognosis is excellent for patients, despite left ventricular dysfunction, if preoperative exercise capacity is preserved. In these patients, left ventricular dysfunction is likely to be reversible after operation. Hence, all patients with left ventricular dysfunction at rest should undergo aortic valve replacement, even if severe symptoms and deterioration in exercise tolerance have not developed. Once exercise tolerance becomes limited in such patients, the likelihood of irreversible left ventricular dysfunction is increased, and long-term postoperative survival is threatened.

Aortic Valve↗

PubMed2003

Benefits of supplemental oxygen in exercise training in nonhypoxemic chronic obstructive pulmonary disease patients.

Supplemental oxygen improves exercise tolerance of normoxemic and hypoxemic chronic obstructive pulmonary disease (COPD) patients. We determined whether nonhypoxemic COPD patients undergoing exercise training while breathing supplemental oxygen achieve higher intensity and therefore improve exercise capacity more than patients breathing air. A double-blinded trial was performed involving 29 nonhypoxemic patients (67 years, exercise SaO2 > 88%) with COPD (FEV1 = 36% predicted). All exercised on cycle ergometers for 45 minutes, 3 times per week for 7 weeks at high-intensity targets. During exercise, they received oxygen (3 L/minute) (n = 14) or compressed air (3 L/minute) (n = 15). Both groups had a higher exercise tolerance after training and when breathing oxygen. However, the oxygen-trained group increased the training work rate more rapidly than the air-trained group. The mean +/- SD work rate during the last week was 62 +/- 19 W (oxygen-trained group) and 52 +/- 22 W (air-trained group) (p < 0.01). After training, endurance in constant work rate tests increased more in the oxygen-trained group (14.5 minutes) than in the air-trained group (10.5 minutes) (p < 0.05). At isotime, the breathing rate decreased four breaths per minute in the oxygen-trained group and one breath per minute in the air-trained group (p = 0.001). We conclude that supplemental oxygen provided during high-intensity training yields higher training intensity and evidence of gains in exercise tolerance in laboratory testing.

Aged↗

PubMed1993

Effect of a standardized meal on the threshold of exercise-induced myocardial ischemia in patients with stable angina.

OBJECTIVES: This study was undertaken to determine the effect of a standardized meal on the ischemic threshold and exercise capacity in a series of 20 patients with stable angina, exercise-induced ischemia and reversible exercise-induced perfusion defects. BACKGROUND: It is generally accepted that exercise tolerance in patients with angina is reduced after a meal. However, studies that have addressed this phenomenon have yielded results that are contradictory and inconclusive. METHODS: Two exercise tests using the Bruce protocol with technetium-99m (99mTc)-sestamibi were performed on consecutive days in a randomized order. One test was performed in the fasting state and the other 30 min after a 1,000-calorie meal. RESULTS: In the postprandial state, exercise time to ischemia was reduced by 20% from 248 +/- 93 s to 197 +/- 87 s (p = 0.0007), time to angina by 15% from 340 +/- 82 s to 287 +/- 94 s (p = 0.002) and exercise tolerance by 9% from 376 +/- 65 s to 344 +/- 86 s (p = 0.002). Rate-pressure products at these exercise test end points were not significantly different in the fasting and postprandial tests, and the quantitative 99mTc-sestamibi ischemia score was unchanged. CONCLUSIONS: In patients with stable angina, a 1,000-calorie meal significantly reduced time to ischemia, time to angina and exercise tolerance because of a more rapid increase in myocardial oxygen demand with exercise. The extent and severity of exercise-induced ischemia were unchanged.

Aged↗

PubMed1995

[The nifedipine withdrawal syndrome in patients with stable stenocardia of effort].

The effect of abrupt discontinuation of nifedipine (N) on exercise tolerance and myocardial ischemia was studied in 7 patients with stable angina pectoris of effort (AP). N was administered in a dose of 20 mg 4 times a day for 34 days. Exercise treadmill tests were performed before N therapy in placebo treatment, on N treatment day 1, 28, on the first day after abrupt N discontinuation and 8 days after the latter. Upon acute and regular administration N produced a significant improvement in exercise tolerance before the onset of AP, development of moderate AP and up to 1 mm depression of ST-segment. Abrupt N discontinuation resulted in substantial deterioration in exercise performance pronounced more definitely on hour 21 and 24 after the last dose intake. A substantial increase in the sum of ST-segment depression at the onset of AP and at the development of AP of moderate severity occurred on the first day of N withdrawal. 8 days after N cessation all the exercise parameters returned to the baseline levels. We conclude that abrupt cessation of regular N therapy may cause a withdrawal syndrome which manifested with a decrease in the exercise tolerance and an increase in exercise-induced myocardial ischemia.

Angina Pectoris↗

PubMed1994

Acute effects of nitrates on exercise testing in patients with syndrome X. Clinical and pathophysiological implications.

BACKGROUND: Sublingual nitrates are much more effective in relieving angina pectoris in patients with coronary artery disease than in patients with syndrome X, but it is not known whether their effect on exercise tolerance is also different in these two groups of patients. METHODS AND RESULTS: Treadmill exercise testing was performed before and after administration of sublingual isosorbide dinitrate (ISDN, 5 mg) in 18 patients with syndrome X (effort angina and normal coronaries, group X) and in 33 patients with documented coronary artery disease (group C). As a selection criterion, all patients had ST-segment depression > or = 1 mm on the control exercise test. Compared with the control test, the main differences in the two groups observed during the exercise test after administration of ISDN were (1) heart rate at 1-mm ST-segment depression was higher (126 +/- 25 versus 104 +/- 15 beats per minute [bpm], P < .01) in group C, whereas it was not different (125 +/- 15 versus 126 +/- 16 beats per minute) in group X; (2) the rate-pressure product at 1-mm ST-segment depression, the time to 1-mm ST-segment depression, and the exercise duration were significantly improved in group C (P < .01 for all) but were worsened in group X (18,047 +/- 4159 versus 20,535 +/- 4507 bpm . mm Hg, P = .014; 268 +/- 312 versus 429 +/- 214 seconds, P < .01; 494 +/- 279 versus 622 +/- 194 seconds, P = .013, respectively); (3) a normalization of the ECG (no ST-segment depression) was obtained in 10 patients (30%) of group C but in only 1 (5%) of group X (P < .01); (4) angina was prevented in 10 of 19 patients of group C but in no patient of group X (P < .01). CONCLUSIONS: In patients presenting with anginal chest pain, the effects of sublingual nitrates on exercise testing appear to be clinically useful to distinguish patients with coronary artery stenoses from patients with syndrome X. Indeed, worsening of exercise tolerance is highly predictive of normal coronary arteries. Furthermore, the failure of nitrates to improve exercise tolerance in patients with syndrome X suggests that a deficiency in coronary prearteriolar nitric oxide production is unlikely to play a key role in the pathophysiology of the syndrome.

Aged↗

PubMed2005

For gold, heart rate matters.

A 19-year-old woman presented with decreased exercise tolerance 3 years after orthotopic heart transplantation. Exercise capacity was severely reduced, with a maximal workload of 84 W, corresponding to 56% of the predicted value. After exclusion of other causes, insufficient heart rate response to exercise was considered as the major contributor to her decreased exercise tolerance. Correction of this problem with the implantation of an AAIR pacemaker dramatically improved her physical performance, allowing her to win 5 gold medals at the European Heart and Lung Transplant Games. This case report illustrates how pacemaker therapy can dramatically improve the symptoms and performance of patients with chronotropic incompetence.

Adult↗

PubMed1980

Fibrositic myofascial pain in intermittent claudication: significance of trigger areas in the calf.

To test the hypothesis of a myofascial component in intermittent claudication, 56 male patients were studied. Calf blood flow, at rest and during postischemic and postexercise hyperemia, presence of trigger areas, and exercise tolerance were evaluated and compared. The results can be summarized as follows: The exercise tolerance is reduced when trigger areas are present in the calf muscles, and the more severe the trigger areas, the lower is the exercise tolerance. Trigger areas are more severe when the hyperemic flow is more reduced. The peak flow of reactive hyperemia is also correlated to work load. Pain in intermittent claudication is a complex phenomenon. According to the aforesaid results, the severity of limb ischemia and the presence of trigger areas in the calf appear to be the major factors. Besides the two reasons already known, a third is suggested to explain calf claudication: the elective location of trigger points in the gastrocnemius muscle.

Aged↗

PubMed1998

[Gas exchange, blood acid-base balance and mechanical muscle efficiency during incremental levels of exertion in young healthy individuals].

UNLABELLED: In this study we have evaluated the changes in gas exchange variables, blood acid-base balance and the mechanical efficiency of muscle in healthy young men during an incremental exercise test. Twenty-six healthy men: age 22.1 +/- 1.4 (mean +/- SD) years, body mass 73.6 +/- 7.4 kg, height 179 +/- 8 cm, were subjects in this study. The subjects performed an incremental exercise test on a cycloergometer at a pedalling rate of 70 rev.min-1. The exercise test started at a power output of 30 W, followed by an increase of power output by 30 W every 3 minutes. Gas exchange variables were measured continuously (breath by breath). Antecubital blood samples for acid-base balance variables and plasma lactate concentration [La]pl were taken at the end of each 3-minute step. The lactate threshold (LT) in this study was defined as the highest power output above which [La]pl showed a sustained increase of > 0.5 mmol.l-1.step-1. The power output at LT amounted to 127 +/- 28 W. It corresponded to 45% of the maximal power output (MPO) reached at maximal oxygen uptake (VO2 max). The oxygen uptake at the LT amounted to 1734 +/- 282 ml.min-1 and corresponded to 48% of VO2 max (3726 +/- 363 ml.min-1). The minute ventilation at the LT amounted to 47.8 +/- 7.5 l, and its increase to the level of 125.7 +/- 19.7 l reached at the MPO was obtained mainly by intensification of breathing frequency from 23.8 +/- 3.31.min-1 to 43 +/- 5.91.min-1, for LT and MPO respectively. Analysis of the changes in PETCO2 during the incremental exercise test showed significant differences between subjects. One could recognise a group of subjects (n = 8) with high values of PETCO2 (above 45 mmHg) and a group of subjects (n = 8) with lower values of PETCO2 (below 43 mmHg). However, no significant differences in exercise tolerance, expressed by the level of MPO and maximal oxygen uptake, were found between those groups of subjects. The mechanical efficiency calculated on the basis of power output/net oxygen uptake ratio during cycling at a power output of 60 W amounted to 24.1 +/- 3.8 percent, at the LT 25.8 +/- 2.1%, whereas at the maximal power output a significant (p < 0.01) drop in muscle efficiency occurred, to the value of 23.1 +/- 1.6%. This drop in muscle efficiency occurring at the MPO may be an important factor limiting exercise tolerance when performing high power output exercise. IN CONCLUSION: The above presented data illustrate the physiological responses to incremental exercise and the level of exercise tolerance, which may serve as a reference point for the population of healthy, young physically active Polish students.

Acid-Base Equilibrium↗