Eccentric and concentric exercises induce different adaptions in adipose tissue biology

Alterations in adipose tissue (AT) metabolism related to inflammation and adipokine's production lead to perturbations in its capacity to store lipids and release fatty acids (FA) during feeding/fasting transition or during exercise. Exercise has a beneficial effect on AT metabolism, but conventional trainings are not always suitable for patients with functional limitations. Dynamic eccentric (ECC) exercise prevents the accumulation of AT and may then overcome those limitations. Consequently, this study aimed at investigating AT's adaptations after ECC training. Nine-week-old male rats were randomly assigned to a control sedentary or three-trained groups for which treadmill slopes modulated exercise oxygen consumption (VO₂) and mechanical work (n = 15 per group): (1) + 15% uphill-concentric group (CONC), (2) - 15% downhill group (ECC15, same mechanical work as CONC) and (3) - 30% downhill group (ECC30, same VO₂, or oxygen cost as CONC). Body composition and energy expenditure (EE) were measured before and after 8 weeks of training. Subcutaneous AT was collected to study total FA profile and gene expression. Higher total EE was driven by lean mass gain in trained animals. In AT, there was a decrease in arachidonic acid with CONC or ECC15 training. Increased adiponectin, leptin, lipases, Glut4 and Igf1 mRNA levels in ECC15 group suggested major metabolic adaption in AT. In conclusion, ECC could induce beneficial modifications in AT fatty acid profile and the expression of key genes related to metabolism and insulin sensitivity.

Altered mitochondrial regulation in quadriceps muscles of patients with COPD

Evidence exists for locomotor muscle impairment in patients with chronic obstructive pulmonary disease (COPD), including fiber type alterations and reduced mitochondrial oxidative capacity. In this study high-resolution respirometry was used to quantify oxygen flux in permeabilized fibres from biopsies of the vastus lateralis muscle in patients with COPD and compared to healthy control subjects. The main findings of this study were that (i) routine state 2 respiration was higher in COPD; (ii) state 3 respiration in the presence of ADP was similar in both groups with substrate supply of electrons to complex I (COPD 38·28 ± 3·58 versus control 42·85 ± 3·10 pmol s(-1) mg tissue(-1) ), but O(2) flux with addition of succinate was lower in COPD patients (COPD 63·72 ± 6·33 versus control 95·73 ± 6·53 pmol s(-1) mg tissue(-1) ); (iii) excess capacity of cytochrome c oxidase in COPD patients was only ~50% that of control subjects. These results indicate that quadriceps muscle mitochondrial function is altered in patients with COPD. The regulatory mechanisms underlying these functional abnormalities remain to be uncovered.

Leg Muscle Blood Flow During 1 and 2-leg Knee Extension Exercise in Patients with COPD and Aged-Controls

Background: In chronic obstructive pulmonary disease (COPD), leg muscle blood flow may be compromised during dynamic exercise due to the competing influence of respiratory muscle work for available cardiac output. This study examined the flow demand limits of skeletal muscle flow in varying muscle mass recruitment. It employed one leg knee extension (1L-KE) and two-leg knee extension (2L-KE) to examine the mass-specific work rates at which peripheral circulatory function may become compromised due to elevated respiratory demands. Methods: Three male COPD patients (70 ± 5 yr; FEV1 /FVC = 42 ± 11%) and two aged-controls (74 ± 1 yr; FEV1/FVC = 76 ± 5%) completed three sets of 7-minute steady state 1L-KE and 2L-KE at 20, 40 and 65% (SS20%; SS40%; SS65%) of previously determined ergometer-specific peak power, separated by rest periods of 15 min. Leg muscle blood flow (BF) was determined using pulsed Doppler sonography of the femoral artery during incremental exercise loads and post-exercise. ECG, blood pressure, ventilatory parameters and VO2 were obtained continuously, and dye dilution cardiac output was measured at rest and during exercise. Results: Preliminary data showed that, for each exercise intensity, the required VO2 is similar in both groups. However, the workloads in COPD are between 60% and 82% of the control group workloads. During 1L-KE and 2L-KE, BF is consistently higher in COPD compared to controls. For 1L-KE, the increase in BF from rest (mean ± SD in ml/min; COPD vs controls) are SS20%: 763 ± 244 vs 105 ± 34; SS40%: 1157 ± 597 vs 310 ± 97; SS65%: 1493 ± 348 vs 424 ± 45. BF relative to workload is at least 3-fold higher in COPD compared to controls for all exercise intensities. Conclusions: These data suggest that mean muscle blood flow may not be compromised during knee-extensor exercise in COPD patients, and ongoing data will clarify whether this is a compensatory response to altered peripheral muscle metabolic function.

Test-retest Reproducibility of Constant Rate Step and Shuttle Walk Test for the Assessment of Exertional Dyspnea in patients with COPD

Background: Alternatives for laboratory exercise testing are needed to better reflect symptoms of physical activities of daily living in chronic disease. Such a tool should accurately set the exercise intensity and show good reproducibility. This study examined the reproducibility of constant rate walking (CRWT) and stepping tests (CRST) to assess exertional dyspnea in patients with COPD. Methods: Stable COPD patients (n=43; 65 ± 6.5 yr; FEV1= 49 ± 16% pred.) equipped with a portable Jaeger Oxycon Mobile® metabolic system completed both the CRWT and the CRST. Each test included four 3-min constsant rate stages separated by a 10-min rest period on two occasions separated by 7 to 14 days. For both exercise modalities the selected rates targeted intensities between 25 and 80% VO2 peak for moderately-severe COPD patients. Ventilation (VE) and gas exchange were obtained during the third minute and the Borg dyspnea score at the end of each exercise bout. Results: An equal proportion of patients (35%) completed stage 4 of the CRWT and of the CRST. The test-retest correlation coefficients for dyspnea scores ranged from 0.79 to 0.95 for stages 1 through 4 for theCRWTand from 0.88 to 0.85 for the CRST while those for VE (L·min-1) ranged from 0.95 to 0.98 and 0.91 to 0.95 respectively. Conclusion: These results show both the CRWT and the CRST to be highly reproducible for the assessment of exertional dyspnea in patients with moderate-severe COPD. However, a better linearity in VE and VO2 with exercise stages was seen for the CRST than for the CRWT since patients complied more easily to the imposed external load with stepping than with walking.

Efficiency of movement in health and chronic disease

Mechanical efficiency of movement expresses the efficacy of skeletal muscles to transform biochemical energy into "external work" or movement. In young healthy humans, the mechanical efficiency and/or the work economy of various locomotor activities such as cycling, up-hill walking or running, stair climbing or swimming varies from 5 - 9% for swimming to 20-25% for cycling ergometry or stair climbing. There are five potential steps at which an extra demand or "wasting" of energy may occur in supplying energy to the contracting muscle: a) the resting metabolism b) the cost of ventilation b) the percentage of moles of ATP produced per mole of atomic oxygen processed through the mitochondria c) the percentage of molecular ATP used by myofibrils for tension production and d) the cost of multi-segment movement coordination towards a locomotor displacement. This article presents the little evidence available on the efficiency of movement in patients with chronic diseases such as COPD and discusses the mechanisms through which chronic disease may contribute to a potential "exaggerated energy demand" or "energy wastage".

Early onset of pulmonary gas exchange disturbance during progressive exercise in healthy active men

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.

Gender differences in temperature and vascular characteristics during exercise recovery

Temperature and vascular responses during exercise recovery were examined in men and women of similar age and fitness status (VO2max: 76 +/- 5 vs 73 +/- 5 mL O2 / kg Fat Free Mass x min). Forearm blood flow (venous occlusion plethysmography; FBF), rectal (Trectal) and forearm skin (Tskin) temperatures (degree C) were measured before and every 15 min up to 105 min (t105) during recovery from a 45-min run at 75% of VO2max. Results indicate Trectal decreased to pre-exercise levels within 25 min in men but reached and remained at values lower than baseline between 60 and 105 min of recovery in women. From 90 to 105 min of recovery, Tskin was lower in women than men (t105 : 29.0 +/- 1.3 vs 30.7 +/- 1.5; p <.05). Recovery FBF (mL/100mL x min) was higher in men than women from the start (6.2 +/- 1.9 vs 4.9 +/- 1.9) to the end of recovery (t105 = 1.7 +/- 0.6 vs 2.6 +/- 1.1) (p <.05). Heat flux calculated at the forearm was higher in women and increased throughout the last hour of recovery (p <.05). Further investigations are needed to examine mechanisms underlying failure of post-exercise core and skin temperatures in women to stabilize at pre-exercise levels.

Resetting of the cardiopulmonary baroreflex 10 years after surgical repair of coarctation of the aorta

OBJECTIVE

To characterise cardiopulmonary baroreflex responses and examine the effects of a 45 minute cycling bout late after successful repair of coarctation of the aorta.

SUBJECTS

10 young adults (mean (SEM) age 18.1 (2.6 years)) operated on for coarctation of the aorta 12.7 (3.5) years earlier, and 10 healthy controls.

DESIGN

Forearm blood flow (venous occlusion plethysmography) and vascular resistance, left ventricular internal diastolic diameter, and central venous pressure estimated from an antecubital vein were measured in the supine position at baseline and during five minute applications of lower body negative pressure (LBNP) at -15 mm Hg (LBNP(-15)) and -40 mm Hg (LBNP(-40)). Venous samples were obtained at baseline and during LBNP(-40) for noradrenaline (norepinephrine), adrenaline (epinephrine), renin activity, and aldosterone. The tests were repeated after 45 minutes of moderate exercise.

RESULTS

Baseline heart rate (78 (9) v 64 (6) beats/min), echocardiographic cardiac output (6.9 (1.1) v 5.0 (0.2) l/min), shortening fraction (41.7 (1.8)% v 33.3 (1.3)%), and forearm blood flow (3.4 (0.4) v 2.3 (0.3) ml/100 g/min) were higher in the coarctation group than in the controls (p < 0.05). Changes in forearm blood flow and forearm vascular resistance from baseline to LBNP(-40) were similar in both groups, but the relation between forearm vascular resistance and estimated central venous pressure or left ventricular internal diastolic diameter was shifted downward in the coarctation group. Plasma adrenaline was increased in the coarctation group (baseline: 3.2 (0.6) v 2.4 (0.3) pmol/l in controls; LBNP(-40): 687 (151) v 332 (42) pmol/l) (p < 0.05). Both groups showed a similar downward displacement of forearm vascular resistance (p < 0.05) after exercise.

CONCLUSIONS

There appears to be resetting of the cardiopulmonary baroreflex to a lower forearm vascular resistance in young adults operated on for coarctation of the aorta, associated with hyperdynamic left ventricular function. Raised circulating adrenaline could contribute to the lower forearm vascular resistance.

Cardiorespiratory interactions during resistive load breathing

The addition to the respiratory system of a resistive load results in breathing pattern changes and in negative intrathoracic pressure increases. The aim of this study was to use resistive load breathing as a stimulus to the cardiorespiratory interaction and to examine the extent of the changes in heart rate variability (HRV) and respiratory sinus arrhythmia (RSA) in relation to the breathing pattern changes. HRV and RSA were studied in seven healthy subjects where four resistive loads were applied in a random order during the breath and 8-min recording made in each condition. The HRV spectral power components were computed from the R-R interval sequences, and the RSA amplitude and phase were computed from the sinusoid fitting the instantaneous heart rate within each breath. Adding resistive loads resulted in 1) increasing respiratory period, 2) unchanging heart rate, and 3) increasing HRV and changing RSA characteristics. HRV and RSA characteristics are linearly correlated to the respiratory period. These modifications appear to be linked to load-induced changes in the respiratory period in each individual, because HRV and RSA characteristics are similar at a respiratory period obtained either by loading or by imposed frequency breathing. The present results are discussed with regard to the importance of the breathing cycle duration in these cardiorespiratory interactions, suggesting that these interactions may depend on the time necessary for activation and dissipation of neurotransmitters involved in RSA.

New statistical method for detection and quantification of respiratory sinus arrhythmia

A statistical method with the advantages of 1) enabling graphical representation of within-respiratory cycle heart rate variations, 2) detecting the presence of respiratory sinus arrhythmia (RSA) in a moving window, and 3) providing breath-by-breath RSA amplitude and phase obtained from the fitting of a sinusoid to the instantaneous relative heart rate is presented.

Low intensity exercise and varying proportions of dietary glucose and fat modify milk and mammary gland compositions and pup growth

Exercise during pregnancy or lactation may create a competition for glucose between the exercising muscle and either the developing fetus or the lactating mammary gland. To test these two hypotheses, pregnant rats were randomly assigned to isoenergetic diets with varying levels of glucose (20, 40 or 60% by weight) and fat (30, 22 or 14%, respectively, by weight) and were rested (R) or exercised (E) on a motorized treadmill at 20 m/min, 60 min/d (low intensity), 7 d/wk throughout pregnancy and lactation. Main effects and selected interactions of diet and exercise during pregnancy and diet, exercise and litter size during lactation were tested using 3 x 2 and 3 x 2 x 2 factorial designs, respectively. Neither diet nor exercise affected pregnancy outcomes. In contrast, during lactation, milk and mammary gland compositions and pup growth were altered. Exercise produced higher milk protein concentrations (40% glucose diet) and lower milk lactose concentrations (20% glucose diet). Exercise also lowered mammary gland fat content and produced higher milk fat concentrations. The 60% glucose diet resulted in the highest milk fat concentrations, but pups of dams fed the 40% diet were heavier on lactation d 15 than pups of dams fed the 60% diet. Taken together, these results support the claim of decreased availability of glucose to the mammary gland for lactose synthesis during chronic low intensity exercise. Additionally, the best lactation performance was not supported by a high carbohydrate (60% glucose), lower fat (14%) intake. A more moderate carbohydrate (40% glucose), higher fat (22%) intake promoted greater pup weights at weaning, suggesting an overlooked role for macronutrient composition in optimizing lactation performance.

In vivo hypoxic exposure impairs metabolic adaptations to a 48 hour fast in rats

Hypoxia is well known to affect carbohydrate metabolism through its action on liver function and thus on glucose homeostasis. The aim of this study was to examine the carbohydrate, lipid and protein metabolic responses to 48 h of hypoxia, as well as the hormonal adaptations using both normoxic controls and hypoxic animals in the fasted state to standardize for the marked hypophagia observed in response to hypoxia. Hypoxia exposure (inspiratory oxygen fraction (FI,O2) = 0.1) resulted in a greater weight loss (-23 +/- 3.6% versus -16 +/- 2% in controls, p<0.001). Hypoxia plus fasting led to a significant increase in plasma glucose, lactate, insulin and catecholamine concentrations, while the increase in free fatty acid and beta-hydroxybutyrate was abolished. Changes in plasma amino acid patterns were not affected by hypoxia. Liver glycogen depletion was significantly less pronounced in the hypoxic group, while phosphoenolpyruvate carboxykinase (a key enzyme of liver gluconeogenesis) activity and transcription enhancements were abolished by hypoxia. Overall, hypoxic exposure in rats fasted for 48 h resulted in a unique pattern that differed from responses to injury or fasting per se. Oxygen seems to play a central role in the metabolic adaptation to fasting, from gene expression to weight loss. Since hypoxaemia associated with fasting has detrimental effects on nutritional balance, the present observations may be clinically relevant in the setting of acute exacerbation with hypoxaemia for chronic respiratory disease.

Influence of the postoperative period and surgical procedure on ambulatory blood pressure-determination of hypertension load after successful surgical repair of coarctation of the aorta

AIMS

This study quantified hypertension load using 24-h ambulatory blood pressure monitoring after successful repair of coarctation of the aorta less than (1) or more than 10 years previously (2) and examined the influence of the surgical procedure (anastomosis or subclavian flap).

METHODS AND RESULTS

Ambulatory blood pressure recordings were obtained using an Accutracker II monitor every 30 min during the day and hourly, at night. Day and night systolic and diastolic values were higher in coarctation of the aorta than in controls: (day: systolic blood pressure/diastolic blood pressure: 133/71 +/- 6/4 vs 115/66 +/- 3/2 night: systolic blood pressure/diastolic blood pressure: 117/61 +/- 4/4 vs 107/57 +/- 3/2 mmHg, P < 0.01) and at all times, were higher in coarctation of the aorta (2) than in coarctation of the aorta (1). Clinical daytime systolic hypertension was observed in 20% of recordings from coarctation of the aorta (1) and 49% from coarctation of the aorta (2) while diastolic hypertension was not observed. However, systolic blood pressure and diastolic blood pressure responses to daily activities were significantly higher in coarctation of the aorta than in controls and this was more marked in coarctation of the aorta (2) than in coarctation of the aorta (1). Type of surgery did not affect either hypertension prevalence or blood pressure reactivity.

CONCLUSIONS

These observations indicate exaggerated systolic blood pressure and diastolic blood pressure reactivity after repair of coarctation of the aorta, the prevalence of systolic hypertension doubling 10 years after surgery.

Effects of indomethacin and polyunsaturated fatty acid diet on exercise-induced hypoxaemia in master athletes

We have previously reported a reduction in exercise-induced hypoxaemia following polyunsaturated fatty acid supplementation (PUFA). Although this might have been explained by increases in membrane fluidity, a clear explanation could not be provided due to potentially confounding influences of series-2 prosta- glandin mediated effects resulting from PUFA. In this investigation, ten master athletes [mean age 48.1 (SEM 6) years, maximal oxygen uptake (VO2max) 3.39 (SEM 0.21) l x min(-1)] completed a maximal cycling test (Ctrl) which was repeated after the administration of 150 mg of indomethacin to inhibit prostaglandin synthesis, both before and after 6 weeks of 3.66-g PUFA x day(-1). Cardiorespiratory parameters were obtained simultaneously with brachial arterial blood sampling for partial pressure of oxygen in arterial blood (PaO2), partial pressure of carbon dioxide in arterial blood (PaCO2), pH, oxygen saturation in arterial blood and lactate concentration determinations. A significant decrease in PaO2 (mmHg) from rest [93 (SEM 1.5)] was observed for exercise intensities of more than 40% VO2max in Ctrl reaching 75.9 (SEM 2.1) at VO2max. PUFA resulted in a 5.0 (SEM 0.68) mmHg upward shift (P < 0.05) in the PaO2-oxygen uptake relationship, reducing the difference in partial pressure of oxygen between alveolar air and arterial blood (P(A-a)O2) at VO2max [Ctrl 36 (SEM 1.6) vs PUFA 33 (SEM 2.2) mmHg] while PaCO2, remained unchanged. Indomethacin had no effect on either PaO2, ideal partial pressure of oxygen in alveolar gas or P(A-a)O2 in either Ctrl or after PUFA. In contrast, the fall in pH was significantly reduced after indomethacin while VCO2, PaCO2 and lactacidaemia remained unchanged. These observations confirm an effect of PUFA on exercise PaO2 behaviour which does not appear to be mediated by the influence of a series-2 prostaglandin.

Cardiovascular responses to dynamic submaximal exercise in children previously treated with anthracycline

This study assessed the long-term (5-year) outcome of pediatric low-dose anthracycline therapy on the circulatory response to moderate exercise. Thirteen patients (13 +/- 4 years old) and 15 age-matched control subjects completed a maximal cycle ergometer protocol as well as two 5-minute cycling tests at 33% and 66% maximal oxygen uptake (V(O2)max) for determination of cardiac index (carbon dioxide rebreathing). V(O2)max was lower in patients than in control subjects (1.3 +/- 0.5 L/min vs 2.3 +/- 0.6 L/min) (p< 0.05). Smaller relative increases in cardiac index for similar increases in relative exercise intensities were found in patients (33% V(O2)max, 73% vs 116%; 66% V(O2)max, 115% vs 192%), as a result of smaller increases in stroke index from rest (33% V(O2)max, 33% vs 54%; 66% V(O2)max, 33% vs 69%; p< 0.05). Similarly, despite normal resting systolic function, patients exhibited a lower stroke index and higher heart rate for any given value of oxygen uptake (milliliters per minute per square meter). Children who had survived cancer exhibited stroke index impairment during exercise similar in intensity to that of recreational activities or play, attesting to a limited inotropic reserve.

Exercise-induced oxyhemoglobin desaturation and pulmonary diffusing capacity during high-intensity exercise

The purpose of this investigation was to examine if exercise-induced arterial oxyhemoglobin desaturation selectively observed in highly trained endurance athletes could be related to differences in the pulmonary diffusing capacity (DL) measured during exercise. The DL of 24 male endurance athletes was measured using a 3-s breath-hold carbon monoxide procedure (to give DLCO) at rest as well as during cycling at 60% and 90% of these previously determined VO2max. Oxyhemoglobin saturation (SaO2%) was monitored throughout both exercise protocols using an Ohmeda Biox II oximeter. Exercise-induced oxyhemoglobin desaturation (DS) (SaO2% < 91% at VO2max) was observed in 13 subjects [88.2 (0.6)%] but not in the other 11 nondesaturation subjects [NDS: 92.9 (0.4)%] (P < or = 0.05), although VO2max was not significantly different between the groups [DS: 4.34 (0.65) l/min vs NDS: 4.1 (0.49) l/min]. At rest, no differences in either DLCO [ml CO.mmHg-1.min-1: 41.7 (1.7) (DS) vs 41.1 (1.8) (NDS)], DLCO/VA [8.2 (0.4) (DS) vs 7.3 (0.9) (NDS)], MVV [l/min: 196.0 (10.4) (DS) vs 182.0 (9.9) (NDS)] or FEV1/FVC [86.3 (2.2) (DS) vs 82.9 (4.7) (NDS)] were found between groups (P > or = 0.05). However, VE/VO2 at VO2max was lower in the DS group [33.0 (1.1)] compared to the NDS group [36.8 (1.5)] (P < or = 0.05). Exercise DLCO (ml CO.mmHg-1.min-1) was not different between groups at either 60% VO2max [DS: 55.1 (1.4) vs NDS: 57.2 (2.1)] or at 90% VO2max [DS: 61.0 (1.8) vs NDS: 61.4 (2.9)]. A significant relationship (r = 0.698) was calculated to occur between SaO2% and VE/VO2 during maximal exercise. The present findings indicate that the exercise-induced oxyhemoglobin desaturation seen during submaximal and near-maximal exercise is not related to differences in DL, although during maximal exercise SaO2 may be limited by a relatively lower exercise ventilation.

[Cardiac output evaluation during exercise in children treated with atrial surgery for transposition of great vessels]

The long-term physiopathological consequences of atrial surgery (Senning or Mustard procedures) for transposition of the great vessels with respect to exercise capacity are not well known. We measured the cardiac index by the technique of CO2 rebreathing at two submaximal levels of exercise corresponding to a stable oxygen consumption of 20 (E20) and 30 (E30) ml/min/kg in 7 patients successfully operated for transposition of the great vessels and in 7 control children paired for age, gender and body surface area. Despite an identical chronotropic response to exercise in the two groups, the increase in cardiac index was not as great in the children operated for transposition (from 6.86 +/- 0.51 to 7.71 +/- 0.78 l/min/m2) as in the control population (from 7.71 +/- 0.78 to 10.2 +/- 0.51 l/min/m2; p < 0.02). The stroke volume index was therefore significantly lower in the transposition group at both levels of exercise (52 +/- 3.2 vs 63 +/- 4.1 ml/m2; p < 0.04 at E20; and 46.4 +/- 4.3 vs 66 +/- 5.1 ml/m2 at E30). The main cause of this reduction of the stroke volume index is probably a lack of adaptation of right ventricular systolic function on exercise but it is not possible to exclude diastolic dysfunction due to reduce compliance secondary to the intraatrial patch. The conditions of preload are in fact instrumental in increasing stroke volume index at submaximal exercise levels.

Cardiac output response to dynamic exercise after atrial switch repair for transposition of the great arteries

Results from this study showed that patients who underwent successful operation for transposition of the great arteries had no appropriate increase in stroke volume in response to exercise of a nature similar to common recreational activities. The impairment, most likely due to disturbances in both venous return and ventricular systolic function, is compensated for by an increase in peripheral oxygen extraction; however, this increase may not be adequate with maturation or during prolonged exercise when cardiovascular constraints are more important.

Peripheral blood flow responses to exercise after successful correction of coarctation of the aorta

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.

Exercise-induced hypoxaemia in master athletes: effects of a polyunsaturated fatty acid diet

Exercise-induced hypoxaemia (EIH) has been associated with an oxygen diffusion limitation. Because polyunsaturated fatty acids (PUFA) administration can modify cell membrane fluidity, we hypothesized that the importance of EIH could be reduced after a 6-week PUFA diet. Resting pulmonary functions and a maximal cycling test were performed before and after the diet, in eight master athletes -48 (SD 6 years)-. The partial pressure of O2 in arterial blood (PaO2), alveolar ventilation (VA) and ideal alveolar-arterial oxygen partial pressure difference (P(Ai-a) O2) were obtained at each exercise intensity. The extent of EIH at maximal exercise was significantly lower after PUFA [PaO2-17.2 (SEM 1.9) vs -12.9 (SEM 2.2)]. Before PUFA, VA accounted for 50% of the variance in the fall in P (Ai-a) for intensities below 80% maximal oxygen uptake (VO2max) and P(Ai-a)O2 for 60% between 70% and 100% VO2max. After PUFA, the reduction in EIH was highly correlated (r2 = 0.85; P < 0.001) to resulting changes in P(Ai-a)O2 and resting pulmonary diffusing capacity (DLCO)/VA but not with changes in ideal alveolar partial pressure of oxygen. The improvement in EIH following PUFA could be related to an increase in alveolar-arterial oxygen conductance following improved pulmonary diffusion.

Exercise-induced cardiac hypertrophy. Fact or fallacy?

After a century of research reports, the notion of exercise-induced cardiac hypertrophy is still an expected adaptation to regular exercise training. Experimental evidence reported both in animals and in humans over the past 3 decades suggests, however, that this conclusion may not be totally warranted. Data from 20 years of echocardiographic investigations of athletes and nonathletes indicate that differences in cardiac dimensions are not very large. Cross-sectional comparisons of over 1000 athletes and roughly 800 control individuals indicate an average difference of 1.6 mm in left ventricular (LV) wall thickness and of 5.3 mm in end-diastolic diameter. Differences reported after training programmes lasting 4 to 52 weeks are even smaller, with average increases of 0.3 mm in LV wall thickness and only 2.1mm in end-diastolic diameter. This article reviews data from animal and human studies concerning cardiac morphology and exercise training to show that the traditional interpretation of the literature has failed to take into account several methodological considerations or factors that may act as confounders in the interpretation of data. Results from animal studies indicate that the observation of cardiac hypertrophy is equivocal at best. In many reports the reported changes in heart size are not significant, and in instances where significant changes are reported these may be seen to be confounded by a number of factors. For example, in rats the reported training-induced hypertrophy may be related to gender differences in the responsiveness of cardiac dimensions or body and/or organ growth rather than to true heart hypertrophy. Furthermore, the interpretation of results from training studies in rats has often been based on the assumption that the metabolic, haemodynamic and thermoregulatory requirements of swimming and running exercise in rats are similar, which may in fact not be the case. In addition, the use of the heart weight/body weight ratio as an index of cardiac hypertrophy, although widespread in animal studies, is open to criticism owing to failure to control for concurrent changes in body weight. Several methodological considerations and factors confounding the outcome of exercise training in humans have also been omitted when interpreting echocardiographic cross-sectional and longitudinal findings. For example, in adult echocardiography the practical resolution of the echocardiographic technique amounts to roughly 2.2mm. It follows, therefore, that unless differences of changes in cardiac dimensions exceed the limit of resolution they are meaningless although statistically significant.(ABSTRACT TRUNCATED AT 400 WORDS)

Fluid-regulating and sympathoadrenal hormonal responses to peak exercise following cardiac transplantation

Orthotopic heart transplantation results in cardiac denervation that can disrupt the normal regulation of hydromineral balance. This study compared the exercise-induced variations in plasma osmolality; atrial natriuretic peptide (ANP), arginine vasopressin (AVP), norepinephrine (NE), epinephrine (E), and dopamine (DA) concentrations; and plasma renin activity (PRA) of six cardiac transplant recipients (HTX) and six healthy age-matched controls (C) submitted to graded upright maximal cycling. Venous blood samples were obtained at rest, at submaximal (70% O2 uptake) and peak exercise, and after 10 and 30 min of sitting recovery. Peak O2 uptake was not different between groups despite lower maximal heart rate in HTX (136 +/- 6 vs. 183 +/- 9 beats/min). Baseline plasma ANP and PRA were higher in HTX (203 +/- 55 pg/ml and 29.9 +/- 7.4 ng.ml-1 x h-1) than in C (71 +/- 17 pg/ml and 5.4 +/- 0.96 ng.ml-1 x h-1); AVP was lower in HTX than in C (1.1 +/- 0.3 vs. 3.2 +/- 0.8 pg/ml; P < 0.05); and circulating E, NE, and DA were not different between groups. Exercise resulted in more marked increases in HTX than in C for ANP (300 vs. 100%), AVP (2,000 vs. 300%), NE (860 vs. 500%), and DA (611 vs. 187%) but not for PRA and a higher E response in C than in HTX (455 vs. 1,258%). These observations confirm that the potential for ANP release to central volume loading is independent of intact cardiac innervation. The exaggerated AVP response in HTX could, however, reflect the absence of inhibitory influences consecutive to denervation.(ABSTRACT TRUNCATED AT 250 WORDS)

A test for the measurement of pulmonary diffusion capacity during high-intensity exercise

The most commonly used technique for the measurement of pulmonary diffusing capacity (DL) is the single-breath hold technique requiring a 10-s breath-hold after the maximal inspiration of carbon monoxide (0.3% CO) and helium (10% He). To measure pulmonary diffusing capacity in our experiments, we had the added advantage of the use of the Gould Pulmonary Function Laboratory that automates the collection and recording of data and the calibration of equipment for each test. However, this technique, DL(CO), is difficult to use during exercise of moderate or elevated intensity because of the lengthy breath-hold. Thus, the purpose of the present study was to compare DL(CO) with 3-s and 5-s breath-holds to a 10-s breath-hold at rest and during moderate and intense exercise in 14 subjects. As expected, an increase in the DL(CO) was observed during moderate and intense exercise when compared to resting values (45.7 +/- 10.0 and 53.0 +/- 7.6 vs 32.1 +/- 7.7 ml CO min-1 mmHg-1). No difference was observed between values for DL(CO) measured at varying breath-hold times at rest (3 s: 32.9 +/- 7.4; 5 s: 32.0 +/- 7.5; 10 s: 31.4 +/- 8.2 ml CO min-1 mmHg-1) or during moderate exercise (3 s: 45.9 +/- 10.1; 5 s: 45.9 +/- 10.6; 10 s: 45.2 +/- 10.4 ml CO min-1 mmHg-1) or intense exercise (3 s: 52.1 +/- 8.3; 5 s: 54.3 +/- 9.3; 10 s: 52.6 +/- 5.2 ml CO min-1 mmHg-1). Reliability coefficients indicated that the use of a 3-s breath-hold was appropriate.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased plasma atriopeptin response to volume-overloading maneuvers and exercise after atriopulmonary anastomosis of Fontan

Atriopulmonary anastomosis results in a chronic right atrial pressure-volume overload. Water and salt retention is a frequent clinical observation in patients after atriopulmonary anastomosis. The purpose of this study was to examine if this could be related to an inability to increase already elevated circulating atriopeptin (ANP) in response to central volume-overloading conditions. Eighteen patients (mean age 16 +/- 6 years) with an atriopulmonary anastomosis underwent routine cardiac catheterization during which a 5-minute head-down 10 degrees tilt was performed. Peripheral venous and right atrial blood samples were obtained under basal conditions, and after tilting and angiography for determination of ANP concentrations. At a different time, circulating ANP levels were measured during a maximal graded exercise protocol. Increased circulating ANP concentrations were found under basal conditions (114 +/- 10 pg/ml). Tilting and cardioangiography resulted in significant increases in mean atrial pressure (basal: 12 +/- 0.7 mm Hg; tilt: 13.4 +/- 0.63 mm Hg; after angiography: 15.8 +/- 0.8 mm Hg), but not in atrial or peripheral ANP. Compared with the expected threefold increase in plasma ANP induced by maximal exercise in healthy control subjects, only a slight (0.25-fold) increase was found in patients. These observations suggest a reduced stimulus-release response after atriopulmonary anastomosis, which could be related to a loss of atrial stretch receptor sensitivity, achievement of the limit for maximal right atrial secretion, or an alteration in right atrial compliance, or a combination.

Comparison of cardiac output determinants in response to upright and supine exercise in patients with cystic fibrosis

This study characterizes cardiac output response to progressive submaximal upright cycling in CF patients. Thirty-one CF patients as well as 11 aged-matched CF control subjects completed cardiac output determinations (CO2-rebreathing) at rest, and at submaximal exercise corresponding to 30, 50 and 75 percent VO2max, in both upright and supine positions. The VO2max was similar in three of four groups, but lower in those with severe CF. The cardiac output generally increased with exercise intensity in both positions, except in severe CF. The change from upright to supine posture resulted in a significant increase in SI at rest and for every submaximal exercise in control subjects, but not CF patients. These observations may suggest that the abnormal cardiac output response observed in severe CF could be related to a potential limitation in ventricular diastolic reserve found in all CF patients independent of disease severity which becomes more apparent under increased ventricular preload.

A simple and disposable sweat collector

Apart from in cystic fibrosis, where sweat analysis provides valuable diagnostic information, sweat yields remain an overlooked biological fluid. Technical problems (dilution, condensation, contamination, evaporation, etc.) linked to currently available collection procedures are of concern and thwart their use. To overcome some of these technical difficulties, an original sweat-collection technique is described. A collection capsule is created inside a flexible, adhesive and disposable anchoring membrane pasted onto the skin. A fluid-tight window is positioned in the upper part of the pocket and gives access to its content. Through the collection window, complete emptying of the sweat collector can be achieved repeatedly by suction using a vacutainer tube inserted in a tube holder equipped with a long dull needle. With prior addition of a suitable marker, fractional samplings can also be performed using a precision micropipette. This collecting method allows for kinetic studies on sweat rate and sweat content. The limited bias-inducing manipulations linked to the described technique, coupled with the ease of performing kinetic studies on sweat volume and content, make this original tool a reliable and accurate sweat-collection technique.

Plasma atriopeptin response to prolonged cycling in humans

The exercise-induced increase in plasma atriopeptin (ANP) has been related to exercise intensity. The independent effect of duration on the ANP response to dynamic exercise remains incompletely documented. The purpose of this study was to describe the time course of plasma ANP concentration during a 90-min cycling exercise protocol and to examine this in light of concurrent variations in plasma arginine vasopressin (AVP), aldosterone (ALD), and catecholamine (norepinephrine and epinephrine) concentrations as well as plasma renin activity (PRA). Seven male and four female healthy college students (23 +/- 2 yr) completed a prolonged exercise protocol on a cycle ergometer at an intensity of 67% of maximal O2 uptake. Venous blood was sampled through an indwelling catheter at rest, after 15, 30, 45, 60, and 90 min of exercise, and after 30 min of passive upright recovery. Results (means +/- SE) indicate an increase in ANP from rest (22 +/- 2.6 pg/ml) at 15 min of exercise (45.3 +/- 7.4 pg/ml) with a further increase at 30 min (59.4 +/- 9.8 pg/ml) and a leveling-off thereafter until completion of the exercise protocol (51.7 +/- 10.7 pg/ml). In plasma ALD and PRA, a significant increase was found from rest (ALD, 21.4 +/- 6.4 ng/dl), PRA, 2.5 +/- 0.5 ng.ml-1.h-1 after 30 min of cycling, which continued to increase until completion of the exercise (ALD 46.6 +/- 8.7 ng/dl, PRA 9.5 +/- 0.9 ng.ml-1.h-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolactinotrophic effect of endogenous and exogenous heat loads in human male adults

Factors associated with heat-induced increase in blood prolactin (PRL) were investigated. Ten male volunteers (23.7 +/- 2.2 yr) were exposed to exogenous heating (head-out immersion) in 41 degrees C water (control 37 degrees C) for 30 min with and without face fanning and cooling. In seven of the subjects, endogenous heating was produced by a 45-min exercise in a warm environment (41 degrees C; control 10 degrees C) with and without selective face fanning. Venous blood was collected before and after each trial; blood hormones were analyzed by radioimmunologic techniques. Heat loading, whether exogenous or endogenous in origin, induced significant increases in blood PRL, beta-endorphin, and vasoactive intestinal peptide (VIP) levels. Blood thyrotropin (TSH) level decreased significantly during water immersion and more significantly with face cooling. From measurement in peripheral blood, the differential beta-endorphin, VIP, and TSH responses to selective face ventilation during exogenous and endogenous heat exposures suggest that blood PRL released in heat derives from secretory stimuli that are independent of these prolactinotropic factors.

Contribution of hGH20K variant to blood hGH response in sauna and exercise

Exercise-induced increases in blood somatotropin (hGH) have always been considered in terms of quantity of the circulating molecules. Knowing that the hypophysis can release several GH species, we investigated the differential release in blood of total hGH (hGHT) and the main hGH variant (hGH20K) molecules in six trained male swimmers exposed to three different conditions known to favor GH release in blood: 45 min--70% maximum oxygen uptake (VO2max) bicycling and swimming, and 20 min of sauna bathing. Based on the binding specificity of hGH antibodies, hGH20K was isolated then assayed using the Nichols immunoradiometric assay system. All three experimental conditions produced significant (P less than 0.001) elevations in blood hGHT and hGH20K. In all three cases, mean blood hGH20K contribution to blood hGHT was relatively constant (11.9, SE 0.7%). Rises in rectal temperature were not statistically related to the changes in blood hGHT. This demonstration of a relatively constant elevation in hGH20K during bicycling, swimming, and sauna bathing can hardly explain the large differences in blood hGHT responses reported in literature under similar conditions.

Comparison of cardiovascular adjustments to exercise in adolescents 8 to 15 years of age after correction of tetralogy of fallot, ventricular septal defect or atrial septal defect

Surgical correction of tetralogy of Fallot (TF) has generally been associated with a reduced maximal exercise tolerance, possibly related to the ventriculotomy inherent to the intracardiac repair procedure. This study documents the exercise hemodynamics of a group of patients operated on for TF who showed similar clinical and functional characteristics, and compares these responses to those of age-matched patients operated on for an isolated ventricular septal defect (VSD) or atrial septal defect (ASD) in an attempt to better understand the role of the ventriculotomy in the exercise limitation. Thirty patients, ages 12 to 19 years, operated on before 5 years of age for complete repair of TF (n = 13), VSD (n = 7) or ASD (n = 10) and 10 age-matched control subjects underwent a progressive maximal cycling test to determine the maximal oxygen uptake (VO2 max), and completed submaximal cycling at intensities of 33 and 66% VO2 max, respectively, to determine the cardiac output (CO2-rebreathing). No significant differences in VO2 max were observed (TF = 37.6 +/- 10; VDS = 34.0 +/- 9.2; ASD = 36.5 +/- 7; controls = 41.3 +/- 6.0 ml/kg/min). The maximal heart rate, however, remained lower in all patient groups in comparison with control subjects (p less than or equal to 0.05) (TF = 178 +/- 14; VSD = 172 +/- 17; ASD = 179 +/- 16; controls = 191 +/- 12 beats/min).(ABSTRACT TRUNCATED AT 250 WORDS)

[A comparison of cyclists' time records according to altitude and materials used]

The purpose of this study was to re-assess the energy cost of track cycling in order (a) to compare the one-hour world records at sea-level and altitude with classical bicycles or with modern bicycles including aerodynamic components, and (b) to estimate the optimal altitude to set a new one-hour world record. Energy cost of track cycling with a classical or aerodynamic bicycle was estimated according to the equation developed by di Prampero et al. (1979) using data from Davies (1980) for the rolling resistance coefficient and from Gross et al. (1983) for the aerodynamic resistance coefficient for each type of bicycle. When compared to the classical track-bicycle, and to the bicycle studied by di Prampero et al. (1979), the aerodynamic track-bicycle reduces the resistance coefficient by 11.7 and 16.9% respectively. According to these estimations the cyclists sustain 87-95% of maximal aerobic power over one hour, which is a likely value for a 60 min exercise period for top-level athletes. When the reduction of air density and of maximal aerobic power with altitude are taken into account, equivalences between performances achieved at different altitudes and with the two types of track-bicycles, can be computed. The best overall performance appears to be the current one-hour record at sea-level using an aerodynamic bicycle (Moser: 50.644 km.h-1). This performance is equivalent to 53.5 km.h-1 in Mexico City (2230 m), 54.4 km.h-1 in La Paz (3417 m) and 54.5 km.h-1 at 3843 m (472 mmHg), which would be the optimal altitude to set the record.

Plasma atrial natriuretic peptide during brief upright and supine exercise in humans

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.

Exercise after surgical repair of congenital cardiac lesions

Congenital heart defects arise in approximately 1% of all live births, independent of ethnic and geographical considerations. With the development of new surgical procedures and current technologies a large number of these heart lesions can be surgically corrected in infancy. In the majority of cases patients evaluated some 10 to 20 years after surgery are asymptomatic and can lead a normal life. Despite their satisfactory clinical outcome patients may, nevertheless, show an abnormal pattern of physiological responses when submitted to dynamic exercise. This paper reviews the scientific literature concerning the exercise capabilities and the cardiorespiratory adjustments to exercise in patients surgically corrected for 4 of the most common congenital heart lesions: isolated atrial septal defect, isolated ventricular septal defects, pulmonary stenosis and tetralogy of Fallot. The maximal exercise tolerance of postoperative congenital heart defect patients may usually be related to: (a) the age of the patients at the time of surgery; (b) the severity of the lesions remaining after surgery; and (c) the age of the patients at the time of investigation. Although normal maximal exercise capabilities may be found in a good number of patients operated for either of the 4 lesions considered, this does not imply normal exercise haemodynamics. A general observation made in these 4 groups of patients is that of a subnormal exercise cardiac output which may or may not be fully compensated by an increase in peripheral oxygen extraction. The limitation in exercising cardiac output may, in turn, be attributed to either a subnormal stroke volume or a limitation in the chronotropic response to exercise or a combination of both factors. Residual pulmonary stenosis, increased pulmonary vascular resistance, increased myocardial stiffness are all factors that may contribute to the cardiac output limitation. A thorough explanation of underlying causes for the abnormal haemodynamic response to exercise, however, still remains to be provided.

The aerobic demand of backstroke swimming, and its relation to body size, stroke technique, and performance

Few studies have examined the aerobic demand of backstroke swimming, and its relation to body morphology, technique, or performance. The aims of this study were thus to: i) describe the aerobic demand of backstroke swimming in proficient swimmers at high velocities; ii) assess the effects of body size and stroke technique on submaximal and maximal O2 costs, and; iii) test for a relationship between submaximal O2 costs and maximal performance. Sixteen male competitive swimmers were tested during backstroke swimming at velocities from 1.0 to 1.4 m.s-1. Results showed that VO2 increased linearly with velocity (m.s-1) following the equation VO2 = 6.28v - 3.81 (r = 0.77, SEE/Y = 14.9%). VO2 was also related to the subjects' body mass, height, and armspan. Longer distances per stroke were associated with lower O2 costs, and better maximal performances. A significant relation was found between VO2 at 1.1 m.s-1, adjusted for body mass, and 400 m performance (r = -0.78). Submaximal VO2 was also related to reported times for 100 m and 200 m races. Multiple correlation analyses indicated that VO2 at 1.1 m.s-1 and VO2max accounted for up to 78% of the variance in maximal performances. These results suggest that the assessment of submaximal and maximal VO2 during backstroke swimming may be of value in the training and testing programs of competitive swimmers.

Echocardiographic assessment of left ventricular performance before and after marathon running

Echocardiography was used to indirectly assess the effects of marathon running on myocardial performance. Thirteen marathon runners (mean +/- SEM:30 +/- 1.6 years) were submitted to a resting echocardiographic examination before racing and during early recovery from marathon racing. Indices of left ventricular performance were computed from M-mode recordings of left ventricular dimensions and aortic valve motions. Comparison of basal and post-marathon indices of left ventricular performance showed no significant differences in either pre-ejection period (PEP), left ventricular ejection index (LVEI), fractional shortening (% delta D), ejection fraction (EF), or mean rate of circumferential fiber shortening (mVcf). Cardiac output (Qc) computed from left ventricular end-diastolic (LVEDV) and end-systolic volumes (LVESV) were significantly higher following marathon running (4.9 +/- 0.4 to 6.7 +/- 0.7 L/min) because of a marked increase in resting heart rate (HR) (58 +/- 3 to 76 +/- 3 bpm). A significant decrease in systolic blood pressure (118 +/- 4 to 108 +/- 3 mm Hg), associated with a slight reduction in calculated total peripheral resistance was also observed after the race. These circulatory adjustments probably reflect thermoregulatory activity that allows a greater blood flow to the skin for heat dissipation, as well as persistence of reactive muscle hyperemia. Echocardiographic evidence suggests that marathon running does not lead to marked impairments in left ventricular performance. However, the absence of change in the end-systolic volume, despite a marked reduction in cardiac afterload, may suggest a slight alteration in contractility that could not be detected with the use of echocardiography.

Sympathetic response to maximal bicycle exercise before and after leg strength training

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.

Plasma norepinephrine, epinephrine, and dopamine beta-hydroxylase activity during exercise in man

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.

Left ventricular dimensions following training in young and middle-aged men

To document the effects of endurance training upon left ventricular dimensions, an echocardiographic examination was performed on 11 young (19 +/- 1 years) and 13 middle-aged (40 +/- 3 years) subjects before and after a 20-week endurance training program. The maximal working capacity was increased by 28% and 27% in young and in middle-aged subjects, respectively. Following training, the left ventricular posterior wall and septal thickness in diastole were unchanged both in young (10.1 +/- 0.2 mm and 9.0 +/- 0.2 mm, pre-; 10.1 +/- 0.2 mm and 9.3 +/- 0.3 mm, post-) and in middle-aged subjects (10.0 +/- 0.3 mm and 10.2 +/- 0.3 mm, pre-; 9.7 +/- 0.2 mm and 10.1 +/- 0.2 mm, post-); the left ventricular end-diastolic internal diameter was unchanged in middle-aged subjects (47.8 +/- 0.9 mm, pre-; 48.1 +/- 1.0 mm, post-) but was significantly increased in young subjects (47.8 +/- 1.0 mm, pre-; 49.9 +/- 1.0 mm, post-) (P less than 0.05). These data could suggest that the left ventricular adaptation to training decreases with age. However, the decrease in resting heart rate observed in young subjects (68 +/- 3 to 60 +/- 2 beats X min-1) (P less than 0.05) but not in middle-aged subjects (63 +/- 3 and 65 +/- 3 beats X min-1) could also increase diastolic filling time and explain the small left ventricular end-diastolic enlargement found in the young subjects.

Plasma norepinephrine response to exercise before and after training in humans

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.

Echocardiography and the Athlete's Heart

In brief: Echocardiographic studies permit direct, accurate measurements of the ventricular wall thickness and cavity diameter. The authors review several of these studies, which show that elite athletes' left ventricles are larger than those of sedentary persons. Left ventricular wall thickness is greater in athletes excelling in sports involving static exercise, whereas those in endurance sports have larger ventricular cavities. These differences in cardiac dimensions may be the result of genetic makeup, prolonged and strenuous training, or a combination of both. Studies of short-term training showed only minor or no changes in left ventricular morphology, although significant improvements in performance and aerobic capacity were reported.

Electro- and echocardiographic study of the left ventricle in man after training

Fourteen sedentary middle-aged men underwent a chest X-ray, a 12 lead ECG, a VCG, and an echocardiographic examination prior to and following 5 months of training a moderately severe intensity, on a cycle ergometer. No modification in the X-ray cardiac profile was observed following training. Some electrocardiographic (R wave amplitude in V5 and V6 and Sokolow index: SV1 + RV5 or V6) and vectorcardiographic (maximal QRS vector amplitude, maximal spatial QRS vector, and R wave amplitude) indices of left ventricular hypertrophy were slightly but significantly increased following training. The echocardiographic measurements in diastole (septal and posterior wall thickness, left ventricular internal diameter, and left ventricular mass) were unchanged after training. Results suggest that electrical changes may not provide adequate indications of left ventricular morphological modifications. The lack of echocardiographic evidences of left ventricular hypertrophy suggest that: (1) training does not necessarily induce left ventricular hypertrophy; (2) the large heart sometimes observed in athletes may be the result of a genetic factor or of a prolonged and very intensive training pursued since a very young age, over a number of years; and (3) left ventricular enlargement probably plays a minor role in the increase in aerobic capacity following training.