Prolonged Exercise Test Research Articles

Metabolic and cardiorespiratory responses in young oarsmen during prolonged exercise tests on a rowing ergometer at power outputs corresponding to two concepts of anaerobic threshold.

A group of ten young experienced oarsmen [mean age 17.5 (SD 1.7) years, height 182.5 (SD 5.9) cm, body mass 77.0 (SEM 10.6) kg] exercised in a progressive incremental test (PIE: 50W x 3 min[-1]) on a rowing ergometer to determine the power output corresponding to the 4 mmol lactate x l(-1) anaerobic threshold (AT4) and the individual anaerobic threshold (IAT). Within 10 days they performed at random two 30-min prolonged exercise tests (PET) at power outputs corresponding to AT4 and IAT to demonstrate whether or not a steady-state blood lactate concentration [La-]b could be maintained. Oxygen uptake (VO2), heart rate (HR) and [La-]b were measured. The PIE revealed significant lower values at IAT compared to AT4 for power output (P < 0.01), HR (P < 0.01) and VO2 (P < 0.01). Coefficients of correlation between AT4 and IAT were 0.68 for power output, 0.79 for HR and 0.70 for VO2. All the subjects could complete the PET at IAT and only six out of the ten at AT4. The [La-]b at the end of PET was significantly higher at AT4 compared to IAT (P < 0.01). Similar results were found for VO2 (P < 0.01) and for HR (P < 0.01). A steady state of mean blood lactate concentration ([La-]ss was found only for the power output at IAT. From the results of this study, we concluded that both concepts of anaerobic threshold gave different information about submaximal endurance capacity. Only IAT represented on average [La-]ss. It is suggested that more research is needed to elicit optimal guidelines for the intensity of endurance training.

BRANCHED-CHAIN AMINO ACID (BCAA) SUPPLEMENTATION IMPROVES ENDURANCE CAPACITIES AND RPE 219

The purpose of this study was to investigate the effects of BCAA supplementation on endurance capacities and RPE. Total 30 female collegiate students (20.6±0.97 yr, 161.2±3.54 cm, 54.4±4.06 kg, 20.7±5.61%fat; mean±SD) volunteered as subjects. In 30 min prior to the exercise tests, subjects were orally administered either 11 g BCAA(Amino-Vital ™: 12%Bal, 14%Iso, 17%Leu) or placebo (PLAC) in a double blinded manner. Lactate threshold (LT) and onset of blood lactate accumulation(OBLA) were determined during incremental bicycle ergometer tests. Blood lactate (HLa), blood anmonia (NH3) and RPE were determined not only during incremental exercise tests, but also during prolonged exercise tests (1 hr or till exhaustion) with three different intensities (LT, n=6; 75%OBLA, n=8; 90%OBLA, n=6). Though no differences were observed for LT, significant difference (P<0.05) was noted for OBLA between BCAA (153±14.2 watt) and PLAC (135±17.5 watt) (n=10). During all prolonged exercise tests, HLa were significantly low in BCAA as compared to PLAC (P<0.05). NH3 in all tests were consistently high in BCAA when compared to PLAC(P<0.05-0.01), which may imply an increased BCAA utilization. RPEs were significantly low in BCAA as compared to PLAC (P<0.05-0.01). These results indicate that BCAA administration may improve endurance capacities and RPE during prolonged exercise of moderate intensity (from LT to 90%OBLA), despite the accumulation of anmonia.

Plasma, red cell and whole blood lactate concentrations during prolonged treadmill exercise at Vla4

SummaryThe purposes of this study were to test whether a relatively steady state with respect to the blood lactate pool can prevail during a prolonged exercise test (PET) at Vla4, to study the kinetics of the flux of lactate between plasma and cells in relation to lactate concentration [LA] and haematocrit and to test the interrelationships between plasma [PLA], whole blood [BLA] and erythrocyte lactate [ELA]. The study used 7 Standardbred trotters. In the PET they ran at their respective pre‐established Vla4 for 12 min. Before, every 2 min during and 0, 2, 5, 10 and 15 min after exercise, [PLA] and [BLA] as well as packed cell volume (PCV) were determined. [ELA] was calculated from [PLA], [BLA] and PCV. Heart rate was monitored continuously and remained at a relatively steady state of approximately 200 beats/min throughout the PET.Lactate concentrations increased exponentially during PET, [PLA] more rapidly than [BLA] and [ELA]. The diverging curves during exercise and converging declining curves after exercise suggested a delay in attainment of an equilibrium between plasma and cells. The close relationship between [PLA] and [BLA] (r = 0.98) allows derivations from regression equations. As the [LA] accumulation over time is exponential, it is likely that the increase during the first 2 min at any speed up to that causing a [BLA] of 4 mmol/l is marginal and insignificant and a submaximal incremental exercise test using 2 min step intervals could still be used for determination of Vla4.

Predictive value of the prolonged exercise test in hypokalemic paralytic attack.

Predictive value of the prolonged exercise test in hypokalemic paralytic attack.

Blood Pressure Response to Physical Exercise in Healthy Adolescents and Adolescents with Insulin-Dependent Diabetes Mellitus

1. Reference values for systolic blood pressure during exercise are provided for 88 healthy adolescents (12-22 years of age) of both sexes. Data were related to oxygen uptake, heart rate, blood lactate concentration, rate of perceived exertion, age, sex, body size and physical fitness. 2. The same variables were measured in 55 adolescents of both sexes with insulin-dependent diabetes mellitus of about 12 years duration and were analysed with respect to the healthy control group, to degree of metabolic control and to late diabetic complications. 3. In healthy adolescents the pressure response was not related to sex or age. When compared with control subjects diabetic patients had a higher diastolic blood pressure at rest and a more marked blood pressure increase, 23 versus 19 mmHg W-1 kg-1 body weight, during exercise with no sex difference. The blood pressure rise was not related to metabolic control, glomerular hyperfiltration or physical fitness. 4. Prolonged exercise tests were no more informative regarding the blood pressure response to exercise than the stepwise increased load test. Analysing the blood pressure increase versus relative work load (W/kg body weight) during exercise reveals blood pressure differences otherwise not noted. A diabetic patient with blood pressure above the 97.5% confidence limit during exercise seems to have a higher risk of developing incipient nephropathy 5 years later.

Heart Failure Therapy with Cilazapril

The efficacy and safety of cilazapril in chronic heart failure have been extensively investigated in an international clinical program in patients with underlying chronic heart failure with ischemic heart disease or dilated cardiomyopathy. Cilazapril in single doses of 1.25-5 mg produced a significant dose-dependent reduction in pulmonary capillary wedge pressure and systemic vascular resistance and a significant increase in cardiac index. In placebo-controlled studies, 1-5 mg of cilazapril once daily for 12 weeks prolonged predose exercise test duration and improved New York Heart Association classification status and signs and symptoms of chronic heart failure, including paroxysmal nocturnal dyspnea. Up to 86% of patients receiving these dosages had improvement, with only 12% of patients requiring the higher dose, 5 mg. These data indicate that cilazapril is effective when administered once daily to patients with chronic heart failure receiving concomitant therapy with digitalis and/or a diuretic. The safety of cilazapril in patients with chronic heart failure has been evaluated in 1,163 patients administered from 0.5 to 15 mg once daily for treatment periods ranging from 1 day to 57 months. Cilazapril was administered to 500 patients for at least 6 months, 264 patients for at least 1 year, and 101 patients for at least 2 years. The most frequently occurring adverse events were dizziness, coughing, dyspnea, fatigue, angina pectoris, and headache. Cilazapril was equally well tolerated by young and elderly patients. Treatment was discontinued due to adverse events in 12.9% of patients, mainly as a result of coughing (1.7%) and dizziness (1%). Forty-four patients (3.8%) died during cilazapril therapy or during a period without treatment. Of these deaths, 93% were due to cardiac causes, especially rhythm disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)

Does anaerobic threshold correlate with maximal lactate steady-state?

The aim of this study was to compare the 'anaerobic threshold' (AnT) of subjects determined during a continuous 2-min incremental exercise test until exhaustion and the 'maximal lactate steady-state' (BLaSsmax) determined during prolonged exercise at constant loads corresponding to the subjects' AnT and/or 5-25% above and below it. Seventeen subjects performed an incremental exercise test and 1-5 prolonged exercise tests on a cycle ergometer until exhaustion at intervals of 1 week, and work rates, oxygen uptake (VO2) values and brachial venous blood lactate (BLa) levels were measured. It was proposed that when exercising at a constant workload below AnT, BLa would fall after having reached its peak; at the level of AnT, BLa reaches maximal steady-state (BLaSsmax); and above AnT, BLa increases continuously. Altogether, in 34 of 45 tests with a constant workload between 80 and 125% AnT, BLa values were as expected. In those cases in which BLaSsmax was reached, BLa increased on average by 3.8 mM from resting levels. This increase was 2.0 mM greater than that seen between resting levels and AnT during incremental exercise. There was no correlation between BLa values at BLaSsmax and at AnT, both when expressed as an increase in BLa (delta BLa) and absolute BLa concentration. Altogether, 81% of the variation in BLa concentration at BLaSsmax could be explained by the subjects' age, the percentage of slow-twitch fibres and BLa levels at rest. The AnT and BLaSsmax did not differ significantly, and these values were correlated (r = 0.83). Together, AnT and age accounted for 85% of the variation seen in BLaSsmax. The BLaSsmax did not correlate with AnT when fixed at a BLa concentration of 4 mM (AnT4mM). The three hypotheses tested in this study were confirmed, and the present results demonstrate that AnT correlates with BLaSsmax. The few exceptions to anticipated BLa kinetics were small in magnitude and could be explained by physiological variations.

Effects of prolonged exercise at a similar percentage of maximal oxygen consumption in trained and untrained subjects

Six trained male cyclists and six untrained but physically active men participated in this study to test the hypothesis that the use of percentage maximal oxygen consumption (%VO2max) as a normalising independent variable is valid despite significant differences in the absolute VO2max of trained and untrained subjects. The subjects underwent an exercise test to exhaustion on a cycle ergometer to determine VO2max and lactate threshold. The subjects were grouped as trained (T) if their VO2max exceeded 60 ml.kg-1.min-1, and untrained (UT) if their VO2max was less than 50 ml.kg-1.min-1. The subjects were required to exercise on the ergometer for up to 40 min at power outputs that corresponded to approximately 50% and 70% VO2max. The allocation of each exercise session (50% or 70% VO2max) was random and each session was separated by at least 5 days. During these tests venous blood was taken 10 min before exercise (- 10 min), just prior to the commencement of exercise (0 min), after 20 min of exercise (20 min), at the end of exercise and 10 min postexercise (+ 10 min) and analysed for concentrations of cortisol, [Na+], [K+], [Cl-], glucose, free fatty acid, lactate [la-], [NH3], haemoglobin [Hb] and for packed cell volume. The oxygen consumption (VO2) and related variables were measured at two time intervals (14-15 and 34-35 min) during the prolonged exercise tests. Rectal temperature was measured throughout both exercise sessions. There was a significant interaction effect between the level of training and exercise time at 50% VO2max for heart rate (fc) and venous [la-].(ABSTRACT TRUNCATED AT 250 WORDS)

Physiologic and metabolic response to progressive and prolonged exercise in amyotrophic lateral sclerosis.

Physical work capacity in 35 ALS patients and 6 untrained controls was evaluated during progressive bicycle ergometry. In the ALS patients, maximum oxygen consumption (VO2max) and work capacity (Wmax) drop in relation to the decrease in ALS functional score. However, the oxygen cost (ml O2/kpm) of submaximal exercise was significantly increased. Prolonged submaximal exercise tests in six ALS patients and six matched untrained controls indicated that the exercise-induced increase in plasma free fatty acids, beta-hydroxybutyrate, esterified carnitine, and muscle esterified carnitine was significantly retarded in ALS patients.

Acute effects of endurance exercise on human adipose tissue metabolism

In order to study the acute effects of exercise on adipose tissue metabolism, 27 sedentary male subjects, 18 to 27 years of age, performed a prolonged aerobic exercise test. Biopsies of adipose tissue were obtained from the suprailiac fat depot before and immediately after a 90-minute period of exercise on ergocycle at an average intensity of 88% of maximal heart rate. Fat cells, isolated by collagenase digestion, were measured for their glucose conversion into triglycerides and for lipolytic activity. Adipose tissue lipoprotein lipase activity released by heparin was also determined. Mean basal and insulin-stimulated glucose conversion into triglycerides decreased significantly with exercise ( P < .05) while adipose tissue lipoprotein lipase activity increased ( P < .01). Fat cell lipolysis increased during exercise only for its epinephrine-stimulated values ( P < .05). The total amount of work performed during the test was correlated only with changes in lipoprotein lipase activity ( r = .42, P < .05). Finally, the changes induced by exercise in lipoprotein lipase activity ( r = .37, P < .05) and insulin-stimulated glucose conversion into triglycerides ( r = .61, P < .01) were positively correlated with fat cell weight. These results indicate that adipose tissue metabolic activities are selectively influenced by endurance exercise. They also suggest that these metabolic changes are not closely coupled with the amount of work performed in a prolonged exercise bout.

Plasma levels of renin, angiotensin II, and 6-ketoprostaglandin F1 alpha in endurance athletes.

Twelve male runners and 12 matched nonathletes performed a prolonged uninterrupted graded exercise test on the bicycle ergometer up to exhaustion to study blood pressure and plasma levels of renin (PRA), vasoconstrictor angiotensin II (ANG II), and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), a metabolite of the vasodilator prostacyclin. In the athletes work load was increased by 30 W/4 min, and in the control subjects the increments of work load were adjusted to their lower exercise capacity to equalize total exercise duration. Blood was drawn, and blood pressure and O2 uptake (VO2) were measured at rest and at the fourth, eighth, and last steps of exercise. Peak VO2 averaged 60 +/- 1.6 ml . min-1 . kg-1 in the runners and 46.8 +/- 1.5 in the nonathletes. To evaluate differences between athletes and controls, PRA, ANG II, and 6-keto-PGF1 alpha were first adjusted for significant confounding factors, such as age, weight, hematocrit, 24-h urinary sodium excretion, and O2 uptake. PRA was significantly lower in the athletes (F = 11.2; P less than 0.01); ANG II was not different at rest, but its rise with exercise was less steep in the runners (F = 8.2; P less than 0.01), whereas 6-keto-PGF1 alpha was not different between the groups (F = 1.3; NS). Despite the differences in PRA and ANG II, however, blood pressure was similar in athletes and nonathletes (F = 0.0; NS).

Metabolic and Cardiovascular Responses of Children during Prolonged Physical Activity

Abstract Metabolic and cardiovascular responses during 45 minutes of continuous moderate intensity exercise were investigated in 11 children, 8–11 years of age. Maximal oxygen consumption ( max) was determined by a treadmill test and was used to set the workload for the prolonged 45-minute exercise test at 50% max. Oxygen consumption, pulmonary ventilation, and central and peripheral circulatory measures were monitored for two-minute intervals at six selected points (min 4, 11, 18, 29, 36, 43) during the exercise period. Oxygen consumption during the first measurement period was 0.92 l/min and was significantly higher (p < .05) than the five subsequent time periods which averaged 0.88l/min. The respiratory exchange ratio decreased (p < .05) after the second measurement period from 0.90 to 0.86. Pulmonary ventilation did not change significantly, although breathing rate and tidal volume significantly (p < .05) increased by 9.1% and decreased by 8.3%, respectively. Changes in cardiac output, measured by the...

The prolonged exercise test.

The response to a standardized exercise test was investigated in 12 volunteers and 13 patients with aches, cramps, and pains. In men, creatine kinase (CK) levels peaked (up to 1600 mU per milliliter) between 10 and 20 hours after exercise. High levels of blood lactate during exercise were related to the intensity of work and to high levels of CK after exercise. The patients could be divided into several groups: (1) those with no change in blood metabolites (psychogenic); (2) those with a disproportionate rise in CK (metabolic myopathies); (3) those with a disproportionate rise of lactate (mitochondrial abnormalities); and (4) in one patient with exercise-related pains, subnormal elevation of fatty acid levels. The correlation of changes in blood lactate, CK, and fatty acids may be useful, whereas an isolated measurement, even if outside the normal range, is often meaningless.

Non-glucoregulatory hormones (T4, T3, rT3, TSH, testosterone) during physical exercise in juvenile type diabetics.

Non-glucoregulatory hormones (T4, T3, rT3, TSH and testosterone) were studied by radioimmunoassay in juvenile-type diabetics in moderate control and in ketosis due to insulin withdrawal and in age matched "normals" during a mild prolonged exercise test. The basal serum hormone levels revealed the following findings: Serum testosterone was markedly lower in diabetics than in normals ( 177 +/- 24 resp. 618 +/- 52 ng/dl). This is in contrast to other studies, but it may reflect decreased testicular function due to an early, clinically not apparent atherosclerotic disease. Serum T3 was significantly lower in diabetics than in normals (110 +/- 16 resp. 145 +/- 19), suggesting an early "low T3-syndrome" in juvenile-type diabetics. However, increased serum rT3 levels were not observed, and serum T4 and TSH were normal. Mild prolonged exercise had no major effects on these nonglucoregulatory hormones. In juvenile-type diabetics the degree of metabolic control had no influence on the response of the mentioned hormones. However, an increased cortisol/testosterone ratio in ketotic diabetics in the basal state with a further increase during exercise was demonstrated, indicating an aggravation of the catabolic state in these patients during exercise.