Cardiopulmonary exercise testing on adaptive equipment in children and adults with Friedreich ataxia.

INTRODUCTION/AIMS: Traditional exercise is often difficult for individuals with Friedreich ataxia (FRDA), and evidence is limited regarding how to measure exercise performance in this population. We evaluated the feasibility, reliability, and natural history of adaptive cardiopulmonary exercise test (CPET) performance in children and adults with FRDA. METHODS: Participants underwent CPET on either an arm cycle ergometer (ACE) or recumbent leg cycle ergometer (RLCE) at up to four visits (baseline, 2 weeks, 4 weeks, and 1 year). Maximum work, oxygen consumption (peak VO2), oxygen (O2) pulse, and anaerobic threshold (AT) were measured in those who reached maximal volition. Test-retest reliability was assessed with intraclass coefficients, and longitudinal change was assessed using regression analysis. RESULTS: In our cohort (N = 23), median age was 18 years (interquartile range [IQR], 14-23), median age of FRDA onset was 8 years (IQR 6-13), median Friedreich Ataxia Rating Scale score was 58 (IQR 54-62), and GAA repeat length on the shorter FXN allele (GAA1) was 766 (IQR, 650-900). Twenty-one (91%) completed a maximal CPET (n = 8, ACE and n = 13, RLCE). Age, sex, and GAA1 repeat length were each associated with peak VO2. Preliminary estimates demonstrated reasonable agreement between visits 2 and 3 for peak work by both ACE and RLCE, and for peak VO2, O2 pulse, and AT by RLCE. We did not detect significant performance changes over 1 year. DISCUSSION: Adaptive CPET is feasible in FRDA, a relevant clinical trial outcome for interventions that impact exercise performance and will increase access to participation as well as generalizability of findings.

The Fontan Udenafil Exercise Longitudinal Trial: Subgroup Analysis.

The Pediatric Heart Network's Fontan Udenafil Exercise Longitudinal (FUEL) Trial (Mezzion Pharma Co. Ltd., NCT02741115) demonstrated improvements in some measures of exercise capacity and in the myocardial performance index following 6 months of treatment with udenafil (87.5 mg twice daily). In this post hoc analysis, we evaluate whether subgroups within the population experienced a differential effect on exercise performance in response to treatment. The effect of udenafil on exercise was evaluated within subgroups defined by baseline characteristics, including peak oxygen consumption (VO2), serum brain-type natriuretic peptide level, weight, race, gender, and ventricular morphology. Differences among subgroups were evaluated using ANCOVA modeling with fixed factors for treatment arm and subgroup and the interaction between treatment arm and subgroup. Within-subgroup analyses demonstrated trends toward quantitative improvements in peak VO2, work rate at the ventilatory anaerobic threshold (VAT), VO2 at VAT, and ventilatory efficiency (VE/VCO2) for those randomized to udenafil compared to placebo in nearly all subgroups. There was no identified differential response to udenafil based on baseline peak VO2, baseline BNP level, weight, race and ethnicity, gender, or ventricular morphology, although participants in the lowest tertile of baseline peak VO2 trended toward larger improvements. The absence of a differential response across subgroups in response to treatment with udenafil suggests that the treatment benefit may not be restricted to specific sub-populations. Further work is warranted to confirm the potential benefit of udenafil and to evaluate the long-term tolerability and safety of treatment and to determine the impact of udenafil on the development of other morbidities related to the Fontan circulation.Trial Registration NCT0274115.

Peak Work Rate Increases With Lower Extremity-Focused Exercise Training in Adolescents With Fontan Circulation.

Background Skeletal muscle deficits are associated with worse exercise performance in the Fontan circulation and may be improved by exercise training. We aimed to assess the change in leg lean mass (a marker of skeletal muscle), exercise performance, and functional health status after a lower extremity-focused exercise intervention in adolescents with Fontan circulation. Methods and Results Densitometry for measurement of leg lean mass, cardiopulmonary exercise test, exercise cardiac magnetic resonance, peripheral vascular testing, physical activity questionnaire, and quality of life assessment were performed at baseline and after a 24-week, hybrid center- and home-based training program. Leg lean mass Z-scores were generated, and exercise parameters were expressed as percentage expected based on reference data. The effect of training was assessed by paired t-tests and simple linear regression. Twenty participants (15.6±1.7 years, 50% male) demonstrated low baseline leg lean mass Z-scores with no significant improvement with training (-1.38±1.02 pre versus -1.31±1.06 post, P=0.33). Maximum and percent predicted work increased from 121.9±29.8 (0.66±0.12) to 131.3±35.1 (0.70±0.15) watts (P=0.02). Peak respiratory exchange ratio increased (1.19±0.02 versus 1.25±0.01, P=0.02) but percent predicted oxygen consumption was unchanged, suggesting higher anaerobic activity after training. Physical activity questionnaire score positively associated with peak work at baseline (ß=18.13 [95% CI, 0.83-35.44], R2=0.21; P=0.04) but physical activity questionnaire, quality of life scores, exercise cardiac magnetic resonance performance, and peripheral vascular function were unchanged with training. Conclusions Peak work rate and anaerobic activity increased with lower extremity-focused training in adolescents with Fontan circulation. Larger studies should test the impact of these changes on functional status and quality of life.

Skeletal muscle deficits are associated with worse exercise performance in pediatric pulmonary hypertension.

Background: Skeletal muscle deficits are associated with worse exercise performance in adults with pulmonary hypertension (PH) but the impact is poorly understood in pediatric PH. Objective: To study muscle deficits, physical inactivity, and performance on cardiopulmonary exercise test (CPET) and exercise cardiac magnetic resonance (eCMR) in pediatric PH. Methods: Youth 8-18 years participated in a prospective, cross-sectional study including densitometry (DXA) for measurement of leg lean mass Z-score (LLMZ), handheld dynamometer with generation of dominant and non-dominant handgrip Z-scores, Physical Activity Questionnaire (PAQ), CPET, and optional eCMR. CPET parameters were expressed relative to published reference values. CMR protocol included ventricular volumes and indexed systemic flow at rest and just after supine ergometer exercise. Relationships between LLMZ, PAQ score, and exercise performance were assessed by Pearson correlation and multiple linear regression. Results: There were 25 participants (13.7 ± 2.8 years, 56% female, 64% PH Group 1, 60% functional class I); 12 (48%) performed both CPET and eCMR. Mean LLMZ (-0.96 ± 1.14) was associated with PAQ score (r = 50, p = 0.01) and with peak oxygen consumption (VO2) (r = 0.74, p = < 0.001), VO2 at anaerobic threshold (r = 0.65, p < 0.001), and peak work rate (r = 0.64, p < 0.01). Higher handgrip Z-scores were associated with better CPET and eCMR performance. On regression analysis, LLMZ and PAQ score were positively associated with peak VO2, while handgrip Z-score and PAQ score were positively associated with peak work rate. Conclusion: Muscle mass and strength are positively associated with exercise performance in pediatric PH. Future studies should determine the effect of rehabilitation programs on muscle properties and exercise performance.

Safety and Feasibility of Exercise Rehabilitation in Children with Ventricular Assist Devices.

Children with advanced heart failure may require ventricular assist devices (VAD) while awaiting heart transplantation. Currently, no data exist regarding the safety of exercise rehabilitation (ER) in children on VAD support. The purpose of this study was to determine the safety and feasibility of ER in children on VAD support awaiting heart transplantation. Eligible patients underwent VAD placement between 1998 and 2019; both inpatient and outpatient participants were included. After VAD implantation and when ambulatory, patients were enrolled in ER. Exercise sessions were scheduled three times a week and consisted of aerobic and musculoskeletal conditioning. A total of 29 patients (59% male, mean age 14 ± 3.2 years) were included with a median VAD duration of 120 ± 109 days. Cardiac diagnoses included cardiomyopathy (81%) and congenital heart disease (19%). VAD type included pulsatile (59%) and continuous-flow devices (41%). Eight hundred and sixty-four (85%) ER sessions were successfully completed and began at a mean of 49 days (range 19-108) after VAD implant. No adverse events, including episodes of hypotension, significant complex arrhythmia, or VAD malfunction occurred during exercise testing or ER, and no sessions were discontinued prematurely. Pediatric patients on VAD support can safely participate in ER with relatively high compliance, and sessions can be implemented early after VAD implantation. Given the safety profile, ER in pediatric VAD recipients, which is a modifiable pre-transplant risk factor that may improve functional capacity, warrants further study as a potential modality to improve post-transplant outcomes.

Observation of Aerosol Generation by Human Subjects During Cardiopulmonary Exercise Testing Using a High-Powered Laser Technique: A Pilot Project.

Purpose: Human respiratory aerosols may have important implications for transmission of pathogens. The study of aerosol production during vigorous breathing activities such as exercise is limited. In particular, data on aerosol production during cardiopulmonary exercise testing (CPET) are lacking. Methods: In this pilot project, we used a high-powered, pulsed Nd:YAG laser to illuminate a region of interest in front of two healthy adult subjects during CPET. Subjects exercised to the point of respiratory compensation. Images were captured with a high-speed, high-resolution camera to determine net exhaled particle (NEP) counts at different phases of CPET, including resting breathing, submaximal exercise, peak exercise, and active recovery. Experiments were performed with the room ventilation activated. Results: Net exhaled particle counts remained relatively constant until late/peak exercise when they decreased prior to rebounding into recovery. NEP counts at resting breathing were higher than those reported using other methods of measurement. Exhaled particles were in the submicron size range. Conclusion: Our method of aerosol particle quantification enables measurement of significant quantities of ultrafine particles and dynamic assessment of aerosol production during CPET. The unique pattern of aerosol production observed during submaximal and peak exercise suggests that extension of results from resting breathing to CPET may not be appropriate.

Increasing Pump Speed During Exercise Training Improves Exercise Capacity in Children with Ventricular Assist Devices.

Exercise rehabilitation during pediatric ventricular assist device (VAD) support aims to improve musculoskeletal strengthening while awaiting heart transplantation (HT). This study aimed to determine whether increasing VAD pump speed during exercise testing and training improves exercise capacity. A single-center cohort study was performed comparing changes in exercise capacity on serial cardiopulmonary exercise testing (CPET) after exercise training at a fixed VAD pump speed (historical cohort from 2014 to 2017) compared with a prospective cohort (2017-2019) who underwent increasing pump speed during exercise training. All children were supported with intracorporeal continuous-flow VAD. Four subjects (13 ± 2.8 years) were included in the historical cohort, and 6 subjects (14 ± 1.7 years) were enrolled in the prospective cohort. Ninety percent had dilated cardiomyopathy, and one had single ventricle Fontan physiology. Baseline maximal oxygen consumption (VO2) was 19 ± 6.3 ml/kg/min. After exercise training with increased pump speed, there was substantial improvement in aerobic capacity (maximal VO2 increased 42% vs. decreased 3%, respectively) and working capacity (maximal work increased 49% vs. 13%, respectively) compared with fixed pump speed. There were no adverse events reported in either the fixed or increased pump speed cohorts. Increasing VAD pump speed during exercise training results in substantial improvement in both physical working and aerobic capacity compared a fixed pump speed in children on VAD support regardless of single or biventricular ventricle physiology. Further study of a larger cohort is needed to validate these findings to improve the approach to pediatric cardiac rehabilitation in this population.

Normative Values for Cardiopulmonary Exercise Stress Testing Using Ramp Cycle Ergometry in Children and Adolescents.

OBJECTIVES: To provide sex, age, and race specific reference values for ramp cycle ergometer cardiopulmonary exercise test (CPET) in children in the US. STUDY DESIGN: Retrospective review was conducted of all cardiopulmonary CPET data from our Exercise Physiology Laboratory on healthy children and adolescents (6-18 years) with body mass index between the 5th and 95th percentiles and structurally normal hearts who performed a ramp cycle ergometry stress test between 1999 and 2015. Twenty-eight exercise variables were included: peak oxygen consumption, oxygen consumption at ventilatory anaerobic threshold, peak work rate, resting and peak heart rate and blood pressure, resting pulmonary function testing, and ventilatory responses to progressive exercise using breath-by-breath gas exchange. Owing to the nonlinear association between CPET results and age, fractional polynomials were used in the mixed-effects regression models to describe the sex- and age-specific normative values with 95% CIs, after adjusting for race and body mass index. RESULTS: We analyzed data on 1829 children (average age, 13.6 ± 2.6 years; 52% male). After 12 years of age, males generally had higher peak values for aerobic capacity and work rate. There were progressive increases with age for both sexes in resting pulmonary function and ventilatory response to exercise, peak aerobic and work rate, and oxygen pulse. Notably, there was an age-related decrease in ventilatory equivalents of oxygen and carbon dioxide at the ventilatory anaerobic threshold. CONCLUSIONS: Future research using prospective, inclusive, and statistically planned cohorts with standardized laboratory approaches and confirmed interoperability should be considered as a focus for validating normative pediatric CPET values in the future.

End-Organ Function and Exercise Performance in Patients With Fontan Circulation: What Characterizes the High Performers?

Background The physiologic hallmarks of the Fontan circulation-chronically elevated central venous pressures and low cardiac output-have significant effects not only on cardiovascular status but also impact other organ systems. Exercise capacity is limited in many and declines with age, accelerating in adolescence, but with wide variability. We explore the relationship between exercise performance and end-organ function in outpatient subjects with a Fontan circulation. Methods and Results This is a cross-sectional analysis of subject end-organ characterization from our outpatient Fontan circulation clinic with peak oxygen consumption (peak Vo2) at cardiopulmonary exercise testing as the primary outcome. We perform linear regression to assess associations between clinical characteristics and peak Vo2 as well as the magnitude of the association of clinical characteristics with peak Vo2. Of 265 subjects age 12.8 (9.5-16.4) years, there is a negative correlation between age and peak Vo2 (-0.49, P<0.001). Of those undergoing ramp cycle exercise testing, 34% perform above 80% predicted peak Vo2. Variables positively associated with peak Vo2 and their effect size include vitamin D sufficiency (+3.00, P=0.020) and absolute lymphocyte count (+0.23, P=0.005). Status as overweight/obese (-3.91, P=0.003) and hemoglobin (-0.77, P=0.003) are negatively associated. Neither ventricular morphology, timing of Fontan palliation, nor Fontan circulation type affect peak Vo2. Conclusions Higher peak Vo2 in those with a Fontan circulation is associated with younger age, vitamin D sufficiency, absence of overweight/obese, lower hemoglobin, and a healthier hepatic profile. Whether exercise training or other initiatives can modify organ characteristics in those with a Fontan circulation is worthy of exploration.

Cardiopulmonary Rehabilitation in Pediatric Patients With Congenital and Acquired Heart Disease.

BACKGROUND: Heart disease in children and adolescents is common, approaching 1.0% of the population. In those patients with complex physiology and severe cardiac dysfunction, the inability to participate in physical activity results in significant obstacles to normal acts of daily living and significantly diminished quality of life. Attempts to study the practicality and benefits of cardiopulmonary rehabilitation (CR) programs in this population have been hampered by the heterogeneity of lesions, lack of facilities, and trained personnel to supervise these types of programs. Although there are numerous articles on CR in children with cardiac disease, all suffer from the same basic problems of small sample size, short duration of study, and heterogeneous study populations. PURPOSE: The purpose of this review was to first evaluate the current rehabilitation literature on both congenital cardiac defects and acquired abnormalities-in this latter group placing a significant emphasis on cardiomyopathies, as well as the special populations in the peri-transplant period and/or mechanical circulatory support. Second, we discussed what is known about practical approaches to CR for the various types of pediatric-specific cardiac conditions. This limited data will be supplemented by the current approach of our institution to CR in these populations with the understanding that this is by no means a consensus approach to these patients. Finally, we summarized research goals for this growing group of patients. CONCLUSION: Cardiopulmonary rehabilitation in pediatric congenital and acquired heart disease is currently a field in its infancy. Significant strides have been made for complex heart disease and impaired myocardial function. Current research holds the promise for the development of programs that are practical, scalable, and can be implemented in most clinical sites within the foreseeable future.

Results of the FUEL Trial.

BACKGROUND: The Fontan operation creates a total cavopulmonary connection, a circulation in which the importance of pulmonary vascular resistance is magnified. Over time, this circulation leads to deterioration of cardiovascular efficiency associated with a decline in exercise performance. Rigorous clinical trials aimed at improving physiology and guiding pharmacotherapy are lacking. METHODS: The FUEL trial (Fontan Udenafil Exercise Longitudinal) was a phase III clinical trial conducted at 30 centers. Participants were randomly assigned udenafil, 87.5 mg twice daily, or placebo in a 1:1 ratio. The primary outcome was the between-group difference in change in oxygen consumption at peak exercise. Secondary outcomes included between-group differences in changes in submaximal exercise at the ventilatory anaerobic threshold, the myocardial performance index, the natural log of the reactive hyperemia index, and serum brain-type natriuretic peptide. RESULTS: Between 2017 and 2019, 30 clinical sites in North America and the Republic of Korea randomly assigned 400 participants with Fontan physiology. The mean age at randomization was 15.5±2 years; 60% of participants were male, and 81% were white. All 400 participants were included in the primary analysis with imputation of the 26-week end point for 21 participants with missing data (11 randomly assigned to udenafil and 10 to placebo). Among randomly assigned participants, peak oxygen consumption increased by 44±245 mL/min (2.8%) in the udenafil group and declined by 3.7±228 mL/min (-0.2%) in the placebo group (P=0.071). Analysis at ventilatory anaerobic threshold demonstrated improvements in the udenafil group versus the placebo group in oxygen consumption (+33±185 [3.2%] versus -9±193 [-0.9%] mL/min, P=0.012), ventilatory equivalents of carbon dioxide (-0.8 versus -0.06, P=0.014), and work rate (+3.8 versus +0.34 W, P=0.021). There was no difference in change of myocardial performance index, the natural log of the reactive hyperemia index, or serum brain-type natriuretic peptide level. CONCLUSIONS: In the FUEL trial, treatment with udenafil (87.5 mg twice daily) was not associated with an improvement in oxygen consumption at peak exercise but was associated with improvements in multiple measures of exercise performance at the ventilatory anaerobic threshold. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02741115.

Safety, pharmacodynamics, and potential benefit of omaveloxolone in Friedreich ataxia.

Objective: Previous studies have demonstrated that suppression of Nrf2 in Friedreich ataxia tissues contributes to excess oxidative stress, mitochondrial dysfunction, and reduced ATP production. Omaveloxolone, an Nrf2 activator and NF-kB suppressor, targets dysfunctional inflammatory, metabolic, and bioenergetic pathways. The dose-ranging portion of this Phase 2 study assessed the safety, pharmacodynamics, and potential benefit of omaveloxolone in Friedreich ataxia patients (NCT02255435). Methods: Sixty-nine Friedreich ataxia patients were randomized 3:1 to either omaveloxolone or placebo administered once daily for 12 weeks. Patients were randomized in cohorts of eight patients, at dose levels of 2.5-300 mg/day. Results: Omaveloxolone was well tolerated, and adverse events were generally mild. Optimal pharmacodynamic changes (noted by changes in ferritin and GGT) were observed at doses of 80 and 160 mg/day. No significant changes were observed in the primary outcome, peak work load in maximal exercise testing (0.9 ± 2.9 W, placebo corrected). At the 160 mg/day dose, omaveloxolone improved the secondary outcome of the mFARS by 3.8 points versus baseline (P = 0.0001) and by 2.3 points versus placebo (P = 0.06). Omaveloxolone produced greater improvements in mFARS in patients that did not have musculoskeletal foot deformity (pes cavus). In patients without this foot deformity, omaveloxolone improved mFARS by 6.0 points from baseline (P < 0.0001) and by 4.4 points versus placebo (P = 0.01) at the 160 mg/day. Interpretation: Treatment of Friedreich ataxia patients with omaveloxolone at the optimal dose level of 160 mg/day appears to improve neurological function. Therefore, omaveloxolone treatment is being examined in greater detail at 150 mg/day for Friedreich ataxia.

Association of Habitual Activity and Body Mass Index in Survivors of Congenital Heart Surgery: A Study of Children and Adolescents With Tetralogy of Fallot, Transposition of the Great Arteries, and Fontan Palliation.

BACKGROUND: Obesity is associated with increased lifelong morbidity and reduced life span and is increasingly prevalent in the congenital heart disease population. Habitual exercise is an important aspect of a healthy lifestyle and primary prevention of obesity in the general population. The association between habitual activity and body mass index (BMI) has not been studied in children with congenital heart disease. METHODS: A cross-sectional analysis of two previously collected cohorts was performed, including participants 8 to 18 years old with tetralogy of Fallot, transposition of the great arteries, and single ventricle heart disease after a Fontan operation. The association between BMI and duration of habitual exercise (measured by questionnaire) was studied. Secondary analyses assessing the effect of other possible factors for BMI were performed. RESULTS: In total, 172 participants were studied (45% Tetralogy of Fallot, 12% transposition of the great arteries, and 43% Fontan). Median BMI was 18.2, and 29% of the participants were obese or overweight. Median habitual exercise was 5.9 h/wk. Thirty-eight percent of participants reported having their activity restricted by their cardiologist. Increasing exercise duration was associated with lower BMI ( P = .01) in univariate analysis. In secondary analyses, restriction to mild exertion and participation in low-intensity exercise were both associated with increased BMI. CONCLUSION: Increased habitual activity was associated with lower BMI, emphasizing the potential role of recreational sport in the health of children with congenital heart disease.

Longitudinal changes in adolescents with TOF: implications for care.

BACKGROUND: We sought to identify predictors of change in right ventricular function and exercise capacity in adolescents following repair for tetralogy of Fallot. METHODS AND RESULTS: We performed a longitudinal study with serial cardiac magnetic resonance imaging and/or exercise stress tests. Patients with interim intervention on the pulmonary valve were excluded. Paired t-test was used to detect longitudinal changes and multivariable regression models were built to identify predictors of change. Initial and follow up magnetic resonance and exercise stress test studies were available for 65 and 63 subjects, respectively. Age at initial testing was 11.7 ± 2.7 years. Average follow up time was 4.5 ± 1.8 (magnetic resonance) and 4.0 ± 1.6 (exercise test) years. There was a significant increase in right ventricular end diastolic and systolic volume (119 ± 34 to 128 ± 35 ml/m2, P = 0.006; 49 ± 20 to 56 ± 23 ml/m2, P = 0.001, respectively), and a decrease in right ventricular ejection fraction (60 ± 7 to 56 ± 8%, P = 0.001), with no significant change in pulmonary regurgitant fraction or right ventricular cardiac index. Predictors of right ventricular dilation over time included: time elapsed from surgical repair, severity of pulmonary insufficiency and right ventricular dilation at the initial magnetic resonance imaging. Of those, time elapsed from surgical repair had the most significant effect. There was no change in exercise capacity. DISCUSSION: In the adolescent with tetralogy of Fallot, longer time from surgery, more pulmonary insufficiency and greater right ventricular dilation at initial magnetic resonance imaging are associated with progressive right ventricular dilation. These results suggest early monitoring with magnetic resonance imaging might identify those at highest risk for progressive disease.

Tricuspid annular plane systolic excursion correlates with exercise capacity in a cohort of patients with hypoplastic left heart syndrome after Fontan operation.

OBJECTIVE: Tricuspid annular plane systolic excursion (TAPSE) is a reproducible measure of right ventricular systolic function. We sought to determine the reliability of TAPSE measurements, to evaluate TAPSE in patients with hypoplastic left heart syndrome (HLHS) relative to normal values, and to correlate values of TAPSE with measures of exercise performance. DESIGN: Tricuspid annular plane systolic excursion measurements were performed off-line in the cohort of patients with single right ventricle anatomy who had been enrolled in the Sildenafil After Fontan Operation clinical trial. These values were converted to z-scores using age-specific means and standard deviations according to published reference values. Reproducibility of measurements was assessed using the coefficient of variation between two readers. Comparisons between echo measurements and exercise outcomes were assessed using Pearson correlation coefficients. RESULTS: Forty-four echocardiograms from 11 subjects were included in this analysis. The median age of included subjects was 13 years (range 12-17). The coefficient of variation for TAPSE measurements was 5.0%. TAPSE was significantly diminished relative to reference values, with a median z-score of -7.6. TAPSE values correlated with both maximal oxygen consumption (R=.64; P=.033) and oxygen consumption at the anaerobic threshold (R=.73, P=.017). CONCLUSIONS: In this small sample of children with HLHS, TAPSE was reproducible, substantially lower than reference values, and correlated well with measures of exercise performance. Further studies are needed to evaluate these findings in a larger cohort and in a longitudinal manner.

Posicionamiento sobre el entrenamiento de fuerza en jóvenes. Consenso Internacional de 2014 / Position statement on youth resistance training: the 2014 International Consensus

El manuscrito actual es la traducción del Posicionamiento sobre el Entrenamiento de Fuerza para Jóvenes: el Consenso Internacional de 2014. El consenso original es a su vez una adaptación del posicionamiento de la United Kingdom Strength and Conditioning Association. Ha sido revisado y respaldado por organizaciones profesionales relevantes en los campos de la medicina del deporte, la ciencia de la actividad física y la pediatría. Los autores de este articulo fueron seleccionados entre los campos de la ciencia del ejercicio pediátrico, la medicina pediátrica, la educación física, la preparación física y la medicina del deporte. El manuscrito fue publicado originalmente en el British Journal of Sports Medicine y representa el documento final ratificado oficialmente a nivel ejecutivo por cada organización que lo respalda. Para enlazar con la versión original del manuscrito en ingles diríjanse a: http://bjsm.bmj.com/content/early/2013/09/20/bjsports-2013-092952.full

The current manuscript is a translation of the Position statement on youth resistance training: the 2014 International Consensus. The original manuscript was adapted from the oficial position statement of the UK Strength and Conditioning Association on youth resistance training. It was subsequently reviewed and endorsed by leading professional organisations within the fields of sports medicine, exercise science and paediatrics. The authorship team for this article was selected from the fields of paediatric exercise science, paediatric medicine, physical education, strength and conditioning and sports medicine

Position statement on youth resistance training: the 2014 International Consensus.

The current manuscript has been adapted from the official position statement of the UK Strength and Conditioning Association on youth resistance training. It has subsequently been reviewed and endorsed by leading professional organisations within the fields of sports medicine, exercise science and paediatrics. The authorship team for this article was selected from the fields of paediatric exercise science, paediatric medicine, physical education, strength and conditioning and sports medicine.

Elevated left ventricular outflow tract velocities on exercise stress echocardiography may be a normal physiologic response in healthy youth.

BACKGROUND: Children with heart disease are at risk for sudden death during exercise, yet decisions regarding sports participation are often based on resting data. Acceleration across the left ventricular outflow tract (LVOT) assessed on stress echocardiography may suggest a diagnosis of hypertrophic cardiomyopathy in patients in whom it is not otherwise obvious. However, the range of peak velocities across the LVOT in healthy youth is unknown. The aim of this study was to describe LVOT velocities with maximal exercise in this age group. METHODS: Subjects up to 18 years old were prospectively enrolled if they had normal results on resting echocardiography and were undergoing exercise testing for other reasons. Subjects with significant comorbidities, suspected cardiomyopathy, or family histories of cardiomyopathy were excluded. Peak LVOT velocities were measured in the upright position using continuous-wave Doppler immediately after maximal exercise. RESULTS: Fifty subjects (mean age, 13.8 ± 2.8 years) were included. Twenty-eight (56%) were male, and 40 (80%) were Caucasian. The median peak LVOT velocity measured immediately after exercise was 2.5 m/sec (range, 1.3-5.9 m/sec). Sixteen subjects (32%) developed peak LVOT velocities of ≥3 m/sec. Twelve of the 16 (75%) with elevated velocities had a dynamic outflow tract Doppler pattern, of whom eight had evidence of intracavitary narrowing on two-dimensional echocardiography. CONCLUSIONS: The development of significant exercise-induced LVOT velocities may be a normal physiologic finding in healthy youth. The measurement of LVOT velocities alone with maximal exercise may not help distinguish patients with hypertrophic cardiomyopathy from healthy children.

Exercise capacity in the Fontan circulation.

The Fontan operation can create a stable circulation from childhood through early adulthood. However, the absence of a sub-pulmonary pumping chamber leads to a physiology in which exercise capacity is limited and decreases with age starting in adolescence. The limitation in exercise capacity is more pronounced at peak levels of exercise, but is still present during more modest levels of activity. The underlying causes of exercise impairment relate to both central cardiovascular factors (oxygen delivery) and peripheral factors (oxygen extraction). Interventions to improve cardiac preload and to improve lean muscle mass may help to improve exercise capacity and, perhaps, will alter the "natural history" of the progressive decline.