RESUMO
This study examined the relationships between plasma and saliva adrenocortical hormones in response to long-duration submaximal exercise. In nine healthy, physically active, female volunteers, blood and saliva samples were taken at rest and every 30 min during a 120-min cycling trial at 50-55% VO(2max) for cortisol and dehydroepiandrosterone (DHEA) analysis. Correlation analysis revealed a moderate but significant relationship between plasma and saliva cortisol (r = 0.35, P < 0.02) and plasma and saliva DHEA (r = 0.47, P < 0.001) during the submaximal exercise. When expressed in percent of resting values, the correlations between the plasma and saliva concentrations were higher for both hormones during the exercise (cortisol: r = 0.72; DHEA: r = 0.68, P < 0.001). The results thus suggest that, even under prolonged exercise conditions, non-invasive saliva samples may offer a practical approach to assessing pituitary-adrenal function, especially when compared with individual basal values.
Assuntos
Desidroepiandrosterona/análise , Desidroepiandrosterona/sangue , Exercício Físico/fisiologia , Hidrocortisona/análise , Hidrocortisona/sangue , Saliva/química , Ciclismo , Feminino , Humanos , Adulto JovemRESUMO
BACKGROUND: Given the high correlation between the serum and saliva hormone values demonstrated at rest, saliva provides a convenient non-invasive way to determine dehydroepiandrosterone (DHEA) and cortisol concentrations. However, to our knowledge, pituitary adrenal recovery following short-term suppression with corticosteroids has never been investigated in saliva. The aim of this study was therefore to examine how steroid hormone concentrations in saliva are influenced by short-term corticosteroid administration. MATERIALS AND METHODS: We studied saliva DHEA and cortisol concentrations before, during (day 1-day 7) and following (day 8-day 16) the administration of oral therapeutic doses of prednisone (50 mg daily for 1 week) in 11 healthy recreationally trained women. RESULTS: Mean saliva DHEA and cortisol concentrations decreased immediately after the start of prednisone treatment (P < 0.05). Three days after concluding prednisone administration, both saliva DHEA and cortisol had returned to pretreatment levels. CONCLUSIONS: These data are consistent with previous studies on blood samples and suggest that non-invasive saliva samples may offer a practical approach to assessing pituitary-adrenal function continuously during and after short-term corticosteroid therapy.
Assuntos
Desidroepiandrosterona/metabolismo , Glucocorticoides/administração & dosagem , Hidrocortisona/metabolismo , Prednisona/administração & dosagem , Saliva/metabolismo , Adulto , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Adulto JovemRESUMO
In order to test the hypothesis that salbutamol would change substrate oxidation during submaximal exercise, eight recreationally trained men twice performed 1 h at 60% VO(2) peak after ingestion of placebo or 4 mg of salbutamol. Gas exchange was monitored and blood samples were collected during exercise for GH, ACTH, insulin, and blood glucose and lactate determination. With salbutamol versus placebo, there was no significant difference in total energy expenditure and substrate oxidation, but the substrate oxidation balance was significantly modified after 40 min of exercise. ACTH was significantly decreased with salbutamol during the last 10 min of exercise, whereas no difference was found between the two treatments in the other hormonal and metabolic parameters. The theory that the ergogenic effect of salbutamol results from a change in substrate oxidation has little support during relatively short term endurance exercise, but it is conceivable that longer exercise duration can generate positive findings.
Assuntos
Albuterol/farmacologia , Oxirredução/efeitos dos fármacos , Resistência Física/efeitos dos fármacos , Resistência Física/fisiologia , Hormônio Adrenocorticotrópico/sangue , Glicemia , Exercício Físico/fisiologia , Hormônio do Crescimento/sangue , Humanos , Insulina/sangue , Ácido Láctico/sangue , Masculino , Esforço Físico/efeitos dos fármacos , Esforço Físico/fisiologia , Fatores de Tempo , Adulto JovemRESUMO
In order to test the hypothesis that short-term corticoid intake alters food intake, body composition and adipokines secretion in healthy volunteers with regular sport practice, nutrient intake was assessed in eight male athletes with and without prednisolone (PRED, 60 mg/day for 1 week) ingestion in a random, double blind, crossover design. Body weight, body composition, adipokines (i.e., leptin, adiponectin and TNF-alpha), insulin and blood glucose were determined before and at the end of each treatment. PRED did not induce any significant change in body weight, body composition or food intake. Insulin and TNF-alpha were not significantly altered with PRED compared to placebo but blood glucose, leptin and adiponectin concentrations at rest appear significantly increased after PRED treatment (P < 0.05). Our data show that 1 week glucocorticoid treatment does not promote obesity in recreationally trained men but further studies are necessary to understand its effects on the metabolically active hormones, leptin and adiponectin.
Assuntos
Adiponectina/sangue , Ingestão de Alimentos/efeitos dos fármacos , Leptina/sangue , Prednisolona/farmacologia , Fator de Necrose Tumoral alfa/sangue , Glicemia , Composição Corporal/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Estudos Cross-Over , Método Duplo-Cego , Humanos , Insulina/sangue , Masculino , Distribuição Aleatória , Adulto JovemRESUMO
OBJECTIVE: To investigate the effects of short-term prednisolone ingestion combined with intense training on exercise performance, hormonal (adrenocorticotrophic hormone (ACTH), prolactin, luteinising hormone (LH), growth hormone (GH), thyroid-stimulating hormone (TSH), dehydroepiandrosterone (DHEA), testosterone, insulin) and metabolic parameters (blood glucose, lactate, bicarbonate, pH). METHODS: Eight male recreational athletes completed four cycling trials at 70-75% peak O(2) consumption until exhaustion just before (1) and after (2) either oral placebo or prednisolone (60 mg/day for 1 week) treatment coupled with standardised physical training (2 hours/day), according to a double-blind and randomised protocol. Blood samples were collected at rest, during exercise and passive recovery for the hormonal and metabolic determinations. RESULTS: Time of cycling was not significantly changed after placebo but significantly increased (p<0.05) after prednisolone administration (50.4 (6.2) min for placebo 1, 64.0 (9.1) min for placebo 2, 56.1 (9.1) min for prednisolone 1 and 107.0 (20.7) min for prednisolone 2). There was no significant difference in any measured parameters after the week of training with placebo but a decrease in ACTH, DHEA, PRL, GH, TSH and testosterone was seen with prednisolone treatment during the experiment (p<0.05). No significant change in basal, exercise or recovery LH, insulin, lactate, pH or bicarbonate was found between the two treatment, but blood glucose was significantly higher under prednisolone (p<0.05) at all time points. CONCLUSION: Short-term glucocorticoid administration induced a marked improvement in endurance performance. Further studies are needed to determine whether these results obtained in recreational male athletes maintaining a rigorous training schedule are gender-dependent and applicable to elite athletes.
Assuntos
Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Glucocorticoides/farmacologia , Hormônios/metabolismo , Prednisolona/farmacologia , Glicemia/metabolismo , Estudos Cross-Over , Método Duplo-Cego , Humanos , Masculino , Consumo de Oxigênio/efeitos dos fármacos , Consumo de Oxigênio/fisiologia , Fatores de Tempo , Adulto JovemRESUMO
We examined the hypothesis that acute therapeutic glucocorticoid intake could change the contribution of fat and carbohydrate (CHO) in energy production during exercise. Nine healthy recreationally-trained male subjects twice performed submaximal exercise (60 min at 60 % VO2max) after ingestion of placebo (Pla) or 20 mg of prednisolone (Pred), according to a double blind and randomized protocol. Respiratory exchange was monitored during exercise and blood samples were collected at rest, every 10 min during exercise and after 5, 10, and 20 min of passive recovery. Pred intake significantly increased total energy expenditure during exercise, but CHO oxidation was lower and fat oxidation higher after Pred vs. Pla. ACTH and IL-6 concentrations were significantly decreased with Pred during exercise, whereas no variations were found in GH, insulin, blood glucose, and lactate between the 2 treatments. In conclusion, it appears that acute prednisolone systemic administration does reduce total carbohydrate oxidation during submaximal exercise. Further studies are necessary to clarify the mechanisms involved and to determine whether this modification in the substrate oxidation balance under glucocorticoid administration in recreationally-trained male subjects could result in a competitive advantage in elite athletes.
Assuntos
Metabolismo Energético/efeitos dos fármacos , Exercício Físico/fisiologia , Glucocorticoides/farmacologia , Prednisolona/farmacologia , Hormônio Adrenocorticotrópico/sangue , Hormônio Adrenocorticotrópico/efeitos dos fármacos , Adulto , Glicemia/efeitos dos fármacos , Metabolismo dos Carboidratos/efeitos dos fármacos , Estudos Cross-Over , Método Duplo-Cego , Gorduras/metabolismo , Hormônio do Crescimento/sangue , Humanos , Insulina/sangue , Interleucina-6/sangue , Ácido Láctico/sangue , Masculino , Pessoa de Meia-Idade , OxirreduçãoRESUMO
OBJECTIVE: To examine whether acute glucocorticoid (GC) intake alters performance and selected hormonal and metabolic variables during submaximal exercise. METHODS: In total, 14 recreational male athletes completed two cycling trials at 70-75% maximum O(2) uptake starting 3 h after an ingestion of either a lactose placebo or oral GC (20 mg of prednisolone) and continuing until exhaustion, according to a double-blind randomised protocol. Blood samples were collected at rest, after 10, 20, 30 minutes, and at exhaustion and recovery for measurement of growth hormone (GH), adrenocorticotropic hormone (ACTH), dehydroepiandrosterone (DHEA), prolactin, insulin, blood glucose, lactate and interleukin (IL)-6 determination. RESULTS: Cycling duration was not significantly changed after GC or placebo administration (55.9 (5.2) v 48.8 (2.9) minutes, respectively). A decrease in ACTH and DHEA (p<0.01) was observed with GC during all of the experiments and in IL-6 after exhaustion (p<0.05). No change in basal, exercise or recovery GH, prolactin, insulin or lactate was found between the two treatments but blood glucose was significantly higher with GC (p<0.05) at any time point. CONCLUSION: From these data, acute systemic GC administration does seem to alter some metabolic markers but did not influence performance during submaximal exercise.
Assuntos
Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Metabolismo Energético/efeitos dos fármacos , Glucocorticoides/farmacologia , Resistência Física/efeitos dos fármacos , Prednisolona/farmacologia , Adulto , Método Duplo-Cego , Metabolismo Energético/fisiologia , Exercício Físico/fisiologia , Glucocorticoides/administração & dosagem , Humanos , Masculino , Resistência Física/fisiologia , Esforço Físico/efeitos dos fármacos , Esforço Físico/fisiologia , Prednisolona/administração & dosagemRESUMO
To study the effects of a therapeutical dose of corticosteroid alone or associated with beta-2 agonist on performance and substrate response during intense submaximal exercise, seven healthy moderately trained male volunteers participated in the double-blind randomized cross-over study. An intense endurance exercise test to exhaustion was performed after ingestion of placebo (Pla), 20 mg prednisolone (Pred), and 20 mg prednisolone plus 4 mg salbutamol (Pred-Sal). Blood samples were collected at rest, after 5, 10 min of exercise, at exhaustion, and after 5 (r5), 10 (r10), and 20 (r20) min of passive recovery for ACTH, growth hormone, insulin, blood glucose, and lactate measurements. There were no significant differences in exercise time to exhaustion between the three treatments (Pla: 21.5 +/- 2.9; Pred: 22.0 +/- 2.5; Pred-Sal: 24.2 +/- 2.8 min). ACTH was significantly lowered after Pred and Pred-Sal vs. Pla from the start of exercise to the end of the experiment (p < 0.05). Pred and Pred-Sal increased resting and recovery (r10 and r20) significantly but not exercise blood glucose values. There were no significant differences in growth hormone concentrations between the three treatments whereas insulin was significantly higher at rest, during exercise, and at r20 after Pred-Sal administration vs. Pred and Pla (p < 0.05). Pred and Pred-Sal showed no significant effect on blood lactate compared with Pla treatment. These preliminary results do not support the hypothesis that acute oral therapeutic corticosteroid intake alone or associated with beta-2 mimetic improves performance during intense submaximal exercise, but further studies are necessary with tests of longer duration.
Assuntos
Agonistas Adrenérgicos beta/farmacologia , Albuterol/farmacologia , Exercício Físico/fisiologia , Glucocorticoides/farmacologia , Prednisolona/farmacologia , Hormônio Adrenocorticotrópico/sangue , Adulto , Glicemia/metabolismo , Método Duplo-Cego , Interações Medicamentosas , Hormônio do Crescimento/sangue , Humanos , Insulina/sangue , Ácido Láctico/sangue , MasculinoRESUMO
OBJECTIVE: To test the hypothesis that chronic salbutamol intake improves performance during supramaximal exercise and to estimate the effects of this treatment on body composition, bone mass, and metabolic indices in healthy women. METHODS: Fourteen female volunteers (seven sedentary and seven recreationally trained) performed a 30 second Wingate test with and without salbutamol ingestion (12 mg/day for four weeks) in a random, double blind, crossover design. Blood samples were collected at rest, at the end of the test, and during passive recovery for lactate measurement. Body composition and bone mass were determined by dual energy x ray absorptiometry. RESULTS: Peak power appeared significantly earlier and was significantly (p<0.05) increased after salbutamol intake in all subjects. There was no difference in total work performed and fatigue indices with salbutamol compared with placebo. No significant alterations in lean or fat body mass and bone variables were observed with salbutamol treatment in either trained or untrained subjects during the trial. In contrast, blood lactate was significantly (p<0.05) increased during the recovery period after salbutamol ingestion compared with placebo. CONCLUSION: As in men, chronic administration of therapeutic concentrations of salbutamol did not induce an anabolic effect in women but increased maximal anaerobic power. Further studies are necessary to clarify the mechanisms involved.
Assuntos
Agonistas Adrenérgicos beta/administração & dosagem , Albuterol/administração & dosagem , Exercício Físico/fisiologia , Adulto , Limiar Anaeróbio/efeitos dos fármacos , Composição Corporal/efeitos dos fármacos , Índice de Massa Corporal , Densidade Óssea/efeitos dos fármacos , Estudos Cross-Over , Método Duplo-Cego , Teste de Esforço/métodos , Feminino , Humanos , Ácido Láctico/sangueRESUMO
AIM: It is well established that altering O2 delivering to contracting skeletal muscle affects human performance. In this respect, a reduced O2 supply (e.g., hypoxia) increases the rate of muscle fatigue. This study aimed to determine the effects of moderate hypoxia and exercise intensity on oxygen uptake (VO2) and cardiac output (CO) kinetics during moderate [below the ventilatory threshold (VT)] and heavy (above VT) constant work rate cycling exercises. METHODS: Eight trained males (age, mean+/-SD, 22+/-3 years; height 182+/-5 cm; body mass 71+/-12 kg) performed at the same relative intensity in normoxic (FIO2=0.21) and hypoxic (FIO2=0.13) conditions moderate and heavy exercises during which pulmonary gas exchange was determined breath-by-breath and CO was monitored beat-by-beat with Doppler echocardiography. RESULTS: The rate of increase (t63%, corresponding to time constant and time delay of a monoexponential response) in CO was significantly faster than that of VO2 in 3 out of 4 experimental conditions (p<0.05). Moreover VO2 kinetics were significantly slowed by hypoxia and speeded by exercise intensity, while CO responses were unaffected by such conditions. A slowed CO response was apparent in hypoxia compared to normoxia (p>0.05) in heavy exercise. CONCLUSIONS: These results suggest an absence of coupling between CO and VO2 kinetics, and that cardiorespiratory O2 delivery is likely different at exercise onset as a function of exercise intensity and FIO2.
Assuntos
Ciclismo/fisiologia , Hipóxia/fisiopatologia , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia , Adulto , Limiar Anaeróbio/fisiologia , Análise de Variância , Débito Cardíaco , Ecocardiografia Doppler , Humanos , Análise dos Mínimos Quadrados , Masculino , Fadiga Muscular/fisiologia , Troca Gasosa Pulmonar/fisiologiaRESUMO
To investigate the impact of acute salbutamol intake on performance and selected hormonal and metabolic variables during supramaximal exercise, 13 recreational male athletes performed two 30-second Wingate tests after either placebo (PLA, lactose) or salbutamol (SAL, 4 mg) oral administration, according to a double-blind and randomized protocol. Blood samples collected at rest, end of the Wingate test, recovery (5, 10, 15 min) were tested for growth hormone (GH), insulin (INS), blood glucose (GLU), and lactate determination. We found the peak and mean power performed significantly increased after SAL vs. PLA (PPSAL: 896 +/- 46; PPPLA: 819 +/- 57 W; MPSAL: 585 +/- 27; MPPLA: 534 +/- 35 W, p < 0.05), whereas no change was observed in the fatigue index. Blood glucose and INS were significantly increased by SAL at rest, at the end of the Wingate test, and during the 5 first minutes of recovery (p < 0.05). Plasma GH was significantly decreased by SAL (p < 0.05) during the recovery whereas end-exercise and recovery blood lactate tended but were not significantly increased after SAL vs. PLA. From these data, acute salbutamol intake at therapeutical dosage did appear to improve peak power and mean power during a supramaximal exercise, but the mechanisms involved need further investigation.
Assuntos
Agonistas Adrenérgicos beta/administração & dosagem , Albuterol/administração & dosagem , Teste de Esforço/efeitos dos fármacos , Exercício Físico/fisiologia , Administração Oral , Adulto , Limiar Anaeróbio/efeitos dos fármacos , Glicemia/efeitos dos fármacos , Glicemia/metabolismo , Relação Dose-Resposta a Droga , Método Duplo-Cego , Hormônio do Crescimento Humano/sangue , Humanos , Insulina/sangue , Ácido Láctico/sangue , Masculino , Descanso/fisiologia , Levantamento de Peso/fisiologiaRESUMO
The effects of a chronic salbutamol intake (SAL, 12 mg/d during 3 weeks) on changes in body composition, metabolic indices and performance during a 30-second Wingate test were determined in 8 strength-trained male athletes (T) and 7 sedentary male (UT) subjects, according to a double-blind, randomized, cross-over protocol. Blood samples were collected both at rest, at the end of the test, and during passive recovery (5 min, 10 min, 15 min) for leptin (at rest), and blood lactate measurements. No significant changes in lean body mass, fat mass, and leptin were observed with SAL treatment in either group during the trial. Peak power was significantly increased (p < 0.05) after SAL intake in all subjects (T: 11.9 %; UT: 8.3 %) with a decrease in time to peak power with SAL compared to placebo (PLA) (p < 0.05). There was no change in total work performed and in fatigue indices with SAL compared to PLA. Blood lactate was significantly increased after SAL vs. PLA during the recovery (p < 0.05) in all subjects. The data demonstrate that the chronic administration of therapeutic levels of salbutamol increases maximal anaerobic power in man, irrespective of the subjects' training status. This study also rules out any implication of an anabolic effect in this improvement in performance during supramaximal exercise. Further studies are necessary to clarify the mechanisms involved.
Assuntos
Agonistas Adrenérgicos beta/administração & dosagem , Albuterol/administração & dosagem , Teste de Esforço/efeitos dos fármacos , Exercício Físico/fisiologia , Administração Oral , Adulto , Composição Corporal/efeitos dos fármacos , Composição Corporal/fisiologia , Estudos Cross-Over , Relação Dose-Resposta a Droga , Método Duplo-Cego , Humanos , Ácido Láctico/sangue , Leptina/sangue , Masculino , Descanso/fisiologia , Levantamento de Peso/fisiologiaRESUMO
This study examined the influence of moderate hypoxia on the oxygen uptake (V.O(2)) kinetic response (primary time constant and slow component amplitude) during moderate and heavy cycle exercise in twenty-seven male subjects with various training status. Nine endurance trained (21.5 +/- 2.6 yr), nine sprint trained (22.9 +/- 5.7 yr), and nine untrained controls (24.0 +/- 4.4 yr) completed incremental tests to exhaustion in normoxia (inspired gas concentration or FIO (2) = 21 % O(2)) and hypoxia (FIO (2) = 13 % O(2)) to establish the FIO (2)-specific ventilatory threshold (VT) and maximal VO(2). Subsequently, the subjects performed repeated constant work rate cycling exercises during 7 min at moderate intensity (80 % of FIO (2)-specific VT) and heavy intensity (midway between the FIO (2) specific VT and maximal VO(2)). Pulmonary gas exchange was measured breath-by-breath during all exercise sessions. For both moderate and heavy intensities, the time constant of the primary VO(2) component was significantly (p < 0.05) slowed by approximately 25 to 30 % in hypoxia compared to normoxia to the same extent in the three groups. Hypoxia produced a more important decrease in the amplitude of the slow component in endurance athletes (- 36 %) than in sprinters (- 30 %) and controls (- 12 %). These results suggest that both primary and slow components of VO(2) kinetics during the adjustment to moderate- and heavy-intensity exercise are sensitive to hypoxia while training status tended to modulate partly the slow component amplitude.
Assuntos
Exercício Físico/fisiologia , Hipóxia/fisiopatologia , Consumo de Oxigênio/fisiologia , Educação Física e Treinamento , Adulto , Estudos Transversais , Frequência Cardíaca/fisiologia , Humanos , Cinética , Masculino , Corrida/fisiologiaRESUMO
Little attention has been paid to children with respect to factors controlling maximal oxygen uptake (V.O (2max)). This study was therefore specifically designed to examine the potential relationships between cardiac size, diastolic function and O (2) carrying capacity with maximal aerobic capacity. Specifically, body size indices (body surface area, lean body mass), resting left ventricular dimensions and filling characteristics, blood haemoglobin concentration as well as V.O (2max) established during a maximal cycle exercise test were assessed in a large cohort (n = 142) of healthy 10 - 11 year old boys and girls. Results were compared between groups of low (< 50, L), moderate (50 - 60, M) and high (> 60, H) V.O (2max) (ml . min (-1) . kg (-1) of lean body mass). Moreover, potential contributors to V.O (2max) variance were investigated using univariate and multivariate regression analyses over the overall population. The major results show no differences between the 3 groups for all diastolic and systolic function indices as well as blood haemoglobin and systemic vascular resistances (used as an index of afterload). None of these variables emerged from regression analyses as potential predictors of V.O (2max.) After accounting for body size variation, heart dimensions, and especially left ventricular internal dimensions, differed between H and M and L and were associated with higher cardiac filling and subsequently stroke volume. Strong relationships between V.O (2max) and heart dimensions were noticed, due primarily but not exclusively to the influence of body size. After adjusting for lean body mass, end-diastolic diameter contributed modestly (8 %) but significantly to V.O (2max) variance, which is biologically meaningful.
Assuntos
Exercício Físico/fisiologia , Ventrículos do Coração/anatomia & histologia , Consumo de Oxigênio , Volume Sistólico , Antropometria , Tamanho Corporal , Criança , Diástole , Feminino , Humanos , Masculino , Resistência FísicaRESUMO
BACKGROUND: The aim of the present study was to determine in healthy children the effect of a well-controlled endurance training programme on cardiac function at maximal exercise and to define whether gender affects the training-induced cardiovascular response. The contribution of factors potentially involved in those adaptations such as cardiac dimensions and diastolic and systolic function was also investigated. METHODS: Thirty-five l0-11-year-old children took part in this study: 19 children (10 girls and nine boys) were assigned to participate in a 13-week endurance training programme (3 x 1 h week-1, intensity: > 80% HR max), and 16 (seven girls and nine boys) served as a control group. A resting echocardiographic evaluation and a maximal upright cycle test, including measurement of stroke volume (SV), cardiac output (Q) and blood pressure, were performed in all children before and after the study period. RESULTS: The training programme led to a rise in maximal O2 uptake (VO2max), brought about however, only by an increase in SVmax in both genders. Moreover, the boys increased their VO2max to a greater extent than the girls (boys: +15%; girls: +8%) only because of a higher SVmax improvement (boys: +15%; girls: +11%). No alterations were noticed in the SV pattern from rest to maximal exercise, indicating that the increase in SVrest was a key factor in the improvement of SVmax and thus VO2max. Regarding resting echocardiographic data, an increase in the left ventricular end-diastolic diameter, concomitant with an improvement in diastolic function, was observed after training and constituted an essential element in the rise in VO2max after training in these children. Moreover, during maximal exercise, a decrease in systemic vascular resistances, probably indicating peripheral cardiovascular adaptive changes, might also play an important role in the increase in VO2max. CONCLUSION: Whatever gender, aerobic training increases VO2max in children, mediated by an improvement in SVmax only. Similar mechanisms, including loading conditions and cardiac morphology, seem to be involved in both genders in order to explain such an improvement.
Assuntos
Fenômenos Fisiológicos Cardiovasculares , Exercício Físico/fisiologia , Resistência Física/fisiologia , Sexo , Pressão Sanguínea/fisiologia , Criança , Ecocardiografia Doppler/métodos , Teste de Esforço/métodos , Feminino , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Volume Sistólico/fisiologiaRESUMO
UNLABELLED: The aim of this study was to examine the effect of two endurance training regimens of varying duration and frequency on maximal oxygen uptake (VO2max) of prepubertal boys and girls. The subjects consisted of 84 prepubertal children, aged 10-11 y. Two groups, EG1 (n = 36) and EG2 (n = 20), were involved in a 13 wk endurance training programme (intensity: higher than 80% of maximal heart rate for both groups; frequency: 3 and 2 sessions per week: duration: 25-35 min and 15-20 min per session in the target zone, for EG1 and EG2, respectively). Another group of 28 children served as a control group. Each subject performed a continuous and progressive exercise test to exhaustion on a cycle ergometer to evaluate VO2max before and after the 13 wk study period. The main findings of this study were: (i) there was no improvement in VO2max after a training programme with the following characteristics: 2 sessions per week with 15-20 min of exercise performed at an intensity higher than 80% of maximal heart rate; (ii) a VO2max enhancement (on average +7%) was seen only in children who participated in a training programme organized on the basis of three sessions per week during which exercise intensities higher than 80% of maximal heart rate were sustained for at least 25 min per session; and (iii) there was no gender difference in the training response. CONCLUSION: It appeared from this longitudinal study that only a programme with continuous activity, organized on the basis of three sessions per week, with 25-35 min at an intensity higher than 80% of maximal heart rate at each session, enhanced VO2max in prepubertal boys and girls.
Assuntos
Metabolismo Energético , Exercício Físico/fisiologia , Frequência Cardíaca , Consumo de Oxigênio , Criança , Teste de Esforço , Feminino , Humanos , Masculino , Resistência Física , Aptidão Física , Fatores de TempoRESUMO
The aim of this study was to compare resting, relative submaximal (at the same percentage of maximal oxygen uptake) and maximal cardiovascular responses to progressive cycle exercise in pre-pubertal children and young adults with similar aerobic aptitude. Fourteen healthy children (7 girls and 7 boys) with a mean age of 10.8 yr and 16 healthy young adults (8 women and 8 men) with a mean age of 22.4 yr underwent a progressive cycle test until exhaustion with estimation of stroke volume and cardiac output by Doppler echocardiography. Submaximal responses were evaluated at similar exercise intensities (around 40, 60 and 80 % of maximal oxygen uptake). Mean submaximal and maximal oxygen uptake were not significantly different between the children and the adults. As expected, the adults demonstrated larger absolute values of stroke volume and cardiac output at all levels of intensity but when related to body surface area, the differences disappeared. The relationships between cardiac output and oxygen uptake calculated from comparable submaximal intensities were similar (slopes and intercepts) in the children and the adults. According to these results, it seems that the lower cardiovascular responses to exercise in children may be attributed to their smaller heart size.
Assuntos
Adaptação Fisiológica/fisiologia , Ciclismo/fisiologia , Exercício Físico/fisiologia , Adulto , Aorta/diagnóstico por imagem , Criança , Ecocardiografia Doppler , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Valores de Referência , Descanso/fisiologia , Volume Sistólico/fisiologiaRESUMO
Stroke volume (SV) response to exercise depends on changes in cardiac filling, intrinsic myocardial contractility and left ventricular afterload. The aim of the present study was to identify whether these variables are influenced by endurance training in pre-pubertal children during a maximal cycle test. SV, cardiac output (Doppler echocardiography), left ventricular dimensions (time-movement echocardiography) as well as arterial pressure and systemic vascular resistances were assessed in 10 child cyclists (VO2max: 58.5 +/- 4.4 mL min-1 kg-1) and 13 untrained children (UTC) (VO2max: 45.9 +/- 6.7 mL min-1 kg-1). All variables were measured at the end of the resting period, during the final minute of each workload and during the last minute of the progressive maximal aerobic test. At rest and during exercise, stroke index was significantly higher in the child cyclists than in UTC. However, the SV patterns were strictly similar for both groups. Moreover, the patterns of diastolic and systolic left ventricular dimensions, and the pattern of systemic vascular resistance of the child cyclists mimicked those of the UTC. SV patterns, as well as their underlying mechanisms, were not altered by endurance training in children. This result implied that the higher maximal SV obtained in child cyclists depended on factors influencing resting SV, such as cardiac hypertrophy, augmented myocardium relaxation properties or expanded blood volume.
Assuntos
Adaptação Fisiológica , Fenômenos Fisiológicos Cardiovasculares , Exercício Físico/fisiologia , Resistência Física/fisiologia , Ciclismo , Pressão Sanguínea , Peso Corporal , Criança , Frequência Cardíaca , Humanos , Masculino , Volume Sistólico , Função Ventricular EsquerdaRESUMO
The aim of this study was to examine reproducibility of stroke volume and cardiac output measurements by Doppler echocardiography during submaximal and maximal exercise in adults and children. Fourteen healthy children (8 girls and 6 boys aged 10.9 +/- 0.9yr) and eleven healthy young adults (1 female and 10 males aged 22.3 +/- 3.8 yr) underwent a progressive maximal upright cycle test until exhaustion with estimation of stroke volume and cardiac output by Doppler echocardiography on two separate occasions (one week apart). Maximal oxygen uptake and maximal heart rate were not significantly different between both tests in the children and adults indicating that similar exhaustive efforts were achieved at each test. No significant differences for mean values of stroke volume and cardiac output were observed at rest in the children and whatever the exercise intensity in the children and adults. No significant differences were observed between values of root mean square (precision and precision of error) in both groups. Thus we demonstrated that stroke volume and cardiac output values obtained by Doppler echocardiography at rest and during submaximal and maximal exercise were reproducible on test-retest measurements in children and adults.
Assuntos
Débito Cardíaco , Ecocardiografia Doppler/normas , Exercício Físico/fisiologia , Adolescente , Adulto , Criança , Feminino , Frequência Cardíaca , Humanos , Masculino , Consumo de Oxigênio , Reprodutibilidade dos Testes , Descanso/fisiologia , Volume SistólicoRESUMO
The aim of the present study was to investigate the gender effect of an endurance training programme on the maximal oxygen uptake (VO2max) of prepubertal children. The subjects comprised eighty-five 10-11-y-old prepubertal children: 35 (17 girls, 18 boys; EG) were involved in a 13-wk running training programme and 50 (22 girls, 28 boys; CG) served as a control group. Each subject carried out a continuous and progressive cycle ergometer test before and after the 13-wk study period under the same conditions and procedures. Oxygen consumption, carbon dioxide, ventilation and heart rate (HR) were continuously monitored during the test. The training programme consisted of interval and continuous long-distance running (frequency: 3 times a week, duration: 1 h per session, intensity: higher than 80% of maximal HR). V02max significantly increased after the training programme for EG (before = 42.3 +/- 7.7, after = 45.3 +/- 7.5 ml x min(-1) x kg(-1), p < 0.01), while no alterations were noticed for CG (before = 43.1 +/- 6.7, after = 42.6 +/- 7.6 ml x min(-1) x kg(-1), p < 0.01). Such an increase was higher in the girls (+9.1%) than the boys (+4.6%). The lower initial fitness of the girls could explain this, however, because a significant relationship was found between the percentage of VO2max increase after training and the initial VO2max. The present longitudinal study shows that maximal oxygen uptake can increase in prepubertal children after an aerobic training programme and that such an increase is of the same order in boys and girls when the initial aerobic fitness is taken into account.