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This study reports on the development and test-retest reproducibility of a modified shuttle walking and step testing protocols to assess exertional dyspnea in patients with COPD. Patients with COPD randomly performed four externally paced 3-min bouts of shuttle walking at 1.5, 2.5, 4.0 and 6.0 km x h(- 1) or stepping at constant rate of 18, 22, 26 and 32 steps x min(- 1). Walking and stepping procedures were repeated once, on a separate occasion. Ventilation, heart rate, gas exchange parameters and dyspnea Borg scores were obtained at the end of each exercise bout. Most patients completed walking or stepping at the slow and middle speed cadences but only 33% completed walking at 6.0 km x h(- 1) and 40% completed stepping at 32 steps x min(- 1). Walking and stepping at progressively faster pace caused a progressive increase in ventilation and dyspnea. Test-retest Pearson correlation coefficients for ventilation, heart rate, gas exchange parameters and dyspnea scores over the four exercise bouts, all exceeded 0.80. Intra-class correlation coefficients were at least as strong as Pearson coefficients. Bland & Altman representation showed that for repeated Borg scores, 92 and 96% of points lied within 2 SD of the mean difference between test-retest values for walking and stepping. The majority of moderate and severe COPD patients completed the 3-min shuttle waking testing at 1.5 to 4.0 km x h(- 1) and the 3-min of step testing at rates between 18 and 26 steps x min(- 1). Both field tests were highly reproducible in patients with COPD.

Some recent studies of competitive athletes have shown exercise-induced hypoxemia to begin in submaximal exercise. We examined the role of ventilatory factors in the submaximal exercise gas exchange disturbance (GED) of healthy men involved in regular work-related exercise but not in competitive activities. From the 38 national mountain rescue workers evaluated (36 +/- 1 yr), 14 were classified as GED and were compared with 14 subjects matched for age, height, weight, and maximal oxygen uptake (VO2 max; 3.61 +/- 0.12 l/min) and showing a normal response (N). Mean arterial PO2 was already lower than N (P = 0.05) at 40% VO2 max and continued to fall until VO2 max (GED: 80.2 +/- 1.6 vs. N: 91.7 +/- 1.3 Torr). A parallel upward shift in the alveolar-arterial oxygen difference vs. %VO2 max relationship was observed in GED compared with N from the onset throughout the incremental protocol. At submaximal intensities, ideal alveolar PO2, tidal volume, respiratory frequency, and dead space-to-tidal volume ratio were identical between groups. As per the higher arterial PCO2 of GED at VO2 max, subjects with an exaggerated submaximal alveolar-arterial oxygen difference also showed a relative maximal hypoventilation. Results thus suggest the existence of a common denominator that contributes to the GED of submaximal exercise and affects the maximal ventilatory response.

Objectives: The purpose of this study was to characterize peripheral flow kinetics in response to progressive discontinuous maximal exercise in 10 patients who underwent repair of coarctation of the aorta and 11 age-matched healthy adolescents., Background: An impairment of leg blood flow has been suggested on the basis of exaggerated femoral muscle lactate accumulation in patients with successful repair of coarctation. Few data are available describing blood flow kinetics of the exercising leg in such patients., Methods: Duplex ultrasound provided transcutaneous measurements of peak systolic and end-diastolic flow velocities of the femoral, humeral and renal arteries at rest and immediately after mild, moderate and maximal exercise intensities for computation of mean velocity, resistance index and femoral blood flow., Results: Femoral mean velocity and femoral blood flow increased linearly with exercise intensity in both groups, but the slope of this increase was significantly lower in patients. Similarly, humeral mean velocity increased significantly less in patients than in control subjects. Femoral resistance index sharply decreased from that at rest (patients [mean +/- SE] 1.4 +/- 0.04; control subjects 1.4 +/- 0.03) to mild exercise intensity in both groups (patients 0.69 +/- 0.03; control subjects 0.72 +/- 0.03). A further decrease was observed at maximal exercise in patients (0.60 +/- 0.04, p = 0.08) but not in control subjects (0.69 +/- 0.02)., Conclusions: These observations suggest that despite a greater exercise-induced femoral vasodilation, patients with successful correction of coarctation of the aorta demonstrate an impaired lower limb blood flow in response to strenuous dynamic exercise. In the absence of stenosis at rest, this alteration could result from exaggerated flow turbulence in the descending aorta distal to the site of correction because of loss of elasticity at the site of the resection of the coarcted segment.

Many experimental studies have utilized the activity of dopamine-beta-hydroxylase (DBH) as an index of sympathetic activity, since this enzyme is not submitted to uptake mechanisms or to enzymatic metabolism as are the circulating catecholamines norepinephrine (NE) and epinephrine (E). However, large discrepancies have been found between the results of these studies. The hypothesis which is examined in this study is that these discrepancies might arise from the different intensities in the stimuli utilized. In order to examine this possibility, plasma DBH activity was measured in seven subjects at rest and in three different conditions known to increase sympathetic activity to varying degrees, i.e., during hand-grip, standing, and supra-maximal bicycle exercise. Plasma NE and E concentrations were also measured during these stimuli. The results of this study show that DBH activity increases above resting levels only during supramaximal dynamic exercise, while plasma NE and E concentrations increase during each experimental condition. Furthermore, the increases in NE and E are related to each other and are also related to heart rate when all experimental conditions are considered. On the contrary, the variations in plasma DBH (expressed as a percentage of the resting value) are not related to other sympathetic indices or to heart rate. Since NE and E vary little from subject to subject at rest and increase discretely in response to the various stimuli, these plasma catecholamine concentrations therefore appear to represent the most accurate indices of sympathetic activity.

Plasma catecholamine concentrations at rest and in response to maximal exercise on the cycle ergometer (278 +/- 15 watts, 6 min duration) have been measured on seven young active male subjects (19 +/- 1 years old; 80 +/- 3 kg; 176 +/- 3 cm) prior to and after a eight week leg strength training program (5RM, squat and leg press exercise). Strength training resulted in a significant increase in performance on squat (103 +/- 3 to 140 +/- 5 kg) and leg press exercise (180 +/- 9 to 247 +/- 15 kg) associated with a small significant increase in lean body mass (64.5 +/- 2.2 to 66.3 +/- 2.1 kg) and no change in maximal oxygen consumption (47.5 +/- 1.3 to 46.9 +/- 1.2 ml X kg-1 X min-1). Plasma norepinephrine (NE) and epinephrine (E) concentrations (pg X mL-1) were not significantly different before and after training at rest (NE: 172 +/- 19 vs 187 +/- 30; E: 33 +/- 10 vs 76 +/- 16) or in response to maximal exercise (NE: 3976 +/- 660 vs 4163 +/- 1081; E: 1072 +/- 322 vs 1321 +/- 508). Plasma lactate concentrations during recovery were similar before and after training (147 +/- 5 vs 147 +/- 15 mg X dL-1). Under the assumption that the "central command" is reduced for a given absolute workload on the bicycle ergometer following leg strength training, these observations support the hypothesis that the sympathetic response to exercise is under the control of information from muscle chemoreceptors.

The factors associated with the exercise-induced increase in plasma atrial natriuretic peptide (ANP) have not been clearly established. Thus the purpose of the study was to further document the stimulus for the exercise-induced release of ANP and to examine the role of ANP in the control of hydromineral balance during exercise. Eight healthy male volunteers (25.1 +/- 4.5 yr) were submitted to a graded cycling exercise in both the upright and supine positions. Venous blood was sampled at rest and at the end of each 5-min work load at 40, 60, and 80% maximal oxygen uptake (Vo2max), at maximal exercise, and during recovery through an indwelling catheter for the determination of plasma vasopressin, aldosterone, catecholamines, plasma renin activity, and ANP concentrations. Results indicate a significant increase in ANP (pg/ml) from rest to maximal exercise in the upright position [rest, 21.9 +/- 10.2; 40%, 24.7 +/- 12.6; 60%, 32.4 +/- 17*; 80%, 47.8 +/- 27.7*; 100% Vo2max, 65.9 +/- 34.5* (*P less than or equal to 0.05)]. Supine concentrations were significantly higher than upright at 40 (37.9 +/- 15.2), 60 (54.0 +/- 18.8), and 80% Vo2max (68.9 +/- 16.6). Plasma ANP during maximal exercise was similar in both positions. Plasma vasopressin, aldosterone, renin activity, and catecholamines increased with increasing exercise intensity in both positions, although lower values were systematically observed in the supine position. The association of higher plasma ANP and blunted plasma vasopressin, plasma renin activity, and norepinephrine concentrations during supine exercise suggests that ANP may exert modulatory effects on the control of the hydromineral hormonal system during exercise.

Plasma norepinephrine (NE) concentration was measured by means of a sensitive radioenzymatic assay in blood collected from an antecubital vein in 10 healthy male subjects (37 +/- 2 yr, mean +/- SE). The subjects were evaluated at rest and during exercise before and after a 20-wk training program on bicycle ergometer (three 30-min sessions per week at 80% of maximal heart rate). Following the training program, maximal oxygen uptake increased significantly from 33 +/- 2 to 42 +/- 1 ml . kg-1 . min-1. Resting plasma NE remained unchanged after training (167 +/- 38 before and 185 +/- 29 pg . ml-1 after training). For a given absolute work load (735 +/- 51 kg . m. min-1) the sympathetic nervous response was lower after training as reflected by the decrease in NE concentration (1,371 +/- 286 vs. 687 +/- 64 pg . ml-1). At the same relative work load (heart rate: 158 +/- 5 before and 157 +/- 5 beats . min-1 after training) plasma NE concentration was unchanged after training (1,371 +/- 286 vs. 1,729 +/0 371 pg . ml-1). Results from the present study show that the sympathetic nervous activity is closely linked to the exercise demands and confirm earlier suggestions that it remains constant in relation to the relative work load.