다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Quasi-experimentation - design and analysis issues for field settings - cook,td, campbell,dt

argument is often, if not acrimonious, at least heated. It gives an impression of the fluidity of opinion on many fundamental ideas under discussion and of the urgency with which cardiac cyanosis in the newborn is regarded. When Dr. William Muscott says that the earliest he has operated for pulmonary stenosis is on an infant 3 days old, and Sir Russell Brock agrees that the earlier in the first month that operation is undertaken the better, and when Dr. Varco asks Dr. Senning 'so far as I know they have never yet catheterized any child intrauterine in Sweden, but they have done it through the delivery canal sometimes-would you tell us the indications of the Scandinavian group for catheterization in the immediate newborn period?', one is indeed being kept up with the times. But that was two years ago and already some of the questions then debated have since been answered. This beautifully printed and well-illustrated stiff paperbacked volume is, and will for a few years yet remain, an invaluable companion to a full-scale textbook on congenital heart disease.

Growth at Adolescence.

High-intensity interval training (HIT), in a variety of forms, is today one of the most effective means of improving cardiorespiratory and metabolic function and, in turn, the physical performance of athletes. HIT involves repeated short-to-long bouts of rather high-intensity exercise interspersed with recovery periods. For team and racquet sport players, the inclusion of sprints and all-out efforts into HIT programmes has also been shown to be an effective practice. It is believed that an optimal stimulus to elicit both maximal cardiovascular and peripheral adaptations is one where athletes spend at least several minutes per session in their 'red zone,' which generally means reaching at least 90% of their maximal oxygen uptake (VO2max). While use of HIT is not the only approach to improve physiological parameters and performance, there has been a growth in interest by the sport science community for characterizing training protocols that allow athletes to maintain long periods of time above 90% of VO2max (T@VO2max). In addition to T@VO2max, other physiological variables should also be considered to fully characterize the training stimulus when programming HIT, including cardiovascular work, anaerobic glycolytic energy contribution and acute neuromuscular load and musculoskeletal strain. Prescription for HIT consists of the manipulation of up to nine variables, which include the work interval intensity and duration, relief interval intensity and duration, exercise modality, number of repetitions, number of series, as well as the between-series recovery duration and intensity. The manipulation of any of these variables can affect the acute physiological responses to HIT. This article is Part I of a subsequent II-part review and will discuss the different aspects of HIT programming, from work/relief interval manipulation to the selection of exercise mode, using different examples of training cycles from different sports, with continued reference to T@VO2max and cardiovascular responses. Additional programming and periodization considerations will also be discussed with respect to other variables such as anaerobic glycolytic system contribution (as inferred from blood lactate accumulation), neuromuscular load and musculoskeletal strain (Part II).

High-intensity interval training, solutions to the programming puzzle: Part I: cardiopulmonary emphasis.

Principles of exercise testing and interpretation

Objectives This study tested the hypotheses that (1) secondary criteria (respiratory exchange ratio (RER), heart rate, blood [lactate]) traditionally used to verify the determination of maximum oxygen uptake (VO 2max ) in children can result in the acceptance of a ‘submaximal’ VO 2max or falsely reject a ‘true’ VO 2max and (2) the VO 2peak recorded during a ramp test in children is comparable to the VO 2peak achieved during supramaximal testing. Methods Thirteen children (9–10 years) completed a ramp cycle test to exhaustion to determine their VO 2peak . After 15 min of recovery, the participants performed a supramaximal cycle test to exhaustion at 105% of their ramp test peak power. Results Compared with the VO 2peak during the ramp test, a significantly lower VO 2 was recorded at a RER of 1.00 (1.293 litre/min (SD 0.265) vs 1.681 litre/min (SD 0.295), p 2peak that was not significantly different from the ramp test (1.615 litre/min (SD 0.307) vs 1.690 litre/min (SD 0.284), p=0.090, respectively). Conclusions The use of secondary criteria to verify a maximal effort in young people during ramp cycling exercise may result in the acceptance of a submaximal VO 2max . As supramaximal testing elicits a VO 2peak similar to the ramp protocol, thus satisfying the plateau criterion, the use of such tests is recommended as the appropriate method of confirming a ‘true’ VO 2max with children. Keywords Children, Aerobic Fitness, Fitness Testing, Supramaximal Exercise.

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Establishing maximal oxygen uptake in young people during a ramp cycle test to exhaustion

Endurance training consists of a structured exercise programme that is sustained for a sufficient length of time with sufficient intensity and frequency to induce an improvement in aerobic fitness. Elite young athletes generally have higher peak oxygen uptakes (peak VO₂) than their untrained peers largely due to their greater maximal stroke volumes. Trained young athletes have faster VO₂ kinetic responses to step changes in exercise intensity but whether this is due to enhanced oxygen delivery or increased oxygen utilization by the muscles remains to be explored. Blood lactate accumulation in young athletes during submaximal exercise is lower than in untrained youth and this appears to be due to enhanced oxidative function in the active muscles. No well-designed, longitudinal endurance training studies of elite young athletes have been published. Even in the general paediatric population peak VO₂ is the only component of aerobic fitness on which there are sufficient data to examine dose-response effects of endurance training. The existence of a maturational threshold below which children are not trainable remains to be proven. The magnitude of training responses is independent of sex. Pre-training peak VO₂ has a moderate but significant inverse relationship with post-training peak VO₂ which suggests that elite young athletes are likely to experience smaller increases in peak VO₂ with further endurance training than untrained youth. Empirical evidence strongly indicates that both trained and untrained young people can benefit from endurance training but the relative intensity of exercise required for optimum benefits is higher than that recommended for adults.

Endurance training and elite young athletes.

High-intensity interval training (HIIT) improves traditional cardiovascular disease (CVD) risk factors in adolescents, but no study has identified the influence of HIIT on endothelial and autonomic function in this group. Thirteen 13- to 14-yr-old adolescents (6 girls) completed six HIIT sessions over 2 wk. Each training session consisted of eight to ten 1-min repetitions of cycling at 90% peak power interspersed with 75 s of unloaded cycling. Traditional (triglycerides, cholesterol, glucose, insulin, and blood pressure) and novel [flow-mediated dilation (FMD), heart rate variability (HRV)] CVD risk factors were assessed in a fasted and postprandial state before (PRE), 1 day after (POST-1D), and 3 days after (POST-3D) training. Aerobic fitness was determined PRE and POST-3D. Two weeks of HIIT had no effect on aerobic fitness or traditional CVD risk factors determined in the fasted or postprandial state (P > 0.15). Compared with PRE, fasted FMD was improved POST-1D [P = 0.003, effect size (ES) = 0.70] but not POST-3D (P = 0.32, ES = 0.22). Fasted FMD was greater POST-1D compared with POST-3D (P = 0.04, ES = 0.48). Compared with PRE, postprandial FMD was greater POST-1D (P 0.32 for all). Two weeks of HIIT enhanced endothelial function and HRV without improvements in traditional CVD risk factors. However, most of this favorable adaptation was lost POST-3D, suggesting that regularly performing high-intensity exercise is needed to maintain these benefits.

Two weeks of high-intensity interval training improves novel but not traditional cardiovascular disease risk factors in adolescents.

The pulmonary oxygen uptake (pVO2) kinetic response at the onset of exercise provides a noninvasive window into the metabolic activity of the muscle and a valuable means of increasing our understanding of developmental muscle metabolism. However, to date only limited research has been devoted to investigating the pVO2 kinetic response during exercise in children and adolescents. From the rigorous studies that have been conducted, both age- and sex-related differences have been identified. Specifically, children display a faster exponential rise in the phase II pVO2 kinetics, which are purported to reflect the rise in muscle O2 consumption, during moderate, heavy and very heavy intensity exercise compared with adults. Furthermore, for heavy and very heavy exercise, the O2 cost of exercise is higher for the exponential phase and the magnitude of the pVO2 slow component is smaller in young children. Sex-related differences have been identified during heavy, but not moderate exercise, with prepubertal boys displaying a faster exponential phase II pVO2 kinetic response and a smaller pVO2 slow component compared with prepubertal girls. The mechanisms underlying these differences are currently poorly understood, and form the basis for future research in this area. However, it is hypothesized that an age-related modulation of the muscle phosphate feedback controllers to signal an increased rate of oxidative phosphorylation and/or altered muscle fiber type recruitment strategies have the potential to play an important role. Overall, the data support the view that at the onset of exercise children have an enhanced potential for oxidative metabolism in the myocyte compared with adults.

Oxygen uptake kinetics in children and adolescents: a review.

Aim To provide an evidence-based review of muscle metabolism changes with sex-, age- and maturation with reference to the development of youth sport performance. Methods A narrative review of data from both invasive and non-invasive studies, from 1970 to 2015, founded on personal databases supported with computer searches of PubMed and Google Scholar. Results Youth sport performance is underpinned by sex-, age- and maturation-related changes in muscle metabolism. Investigations of muscle size, structure and metabolism; substrate utilisation; pulmonary oxygen uptake kinetics; muscle phosphocreatine kinetics; peak anaerobic and aerobic performance; and fatigue resistance; determined using a range of conventional and emerging techniques present a consistent picture. Age-related changes have been consistently documented but specific and independent maturation-related effects on muscle metabolism during exercise have proved elusive to establish. Children are better equipped for exercise supported primarily by oxidative metabolism than by anaerobic metabolism. Sexual dimorphism is apparent in several physiological variables underpinning youth sport performance. As young people mature there is a progressive but asynchronous transition into an adult metabolic profile. Conclusions The application of recent developments in technology to the laboratory study of the exercising child and adolescent has both supplemented existing knowledge and provided novel insights into developmental exercise physiology. A sound foundation of laboratory-based knowledge has been established but the lack of rigorously designed child-specific and sport-specific testing environments has clouded the interpretation of the data in real life situations. The primary challenge remains the translation of laboratory research into the optimisation of youth sports participation and performance.

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Alan R. Barker

Papers

Establishing maximal oxygen uptake in young people during a ramp cycle test to exhaustion

Endurance training and elite young athletes.

Two weeks of high-intensity interval training improves novel but not traditional cardiovascular disease risk factors in adolescents.

Oxygen uptake kinetics in children and adolescents: a review.

Muscle metabolism changes with age and maturation: How do they relate to youth sport performance?