Cardiorespiratory Fitness In Youth Research Articles

Adolescent Cardiorespiratory Fitness and Future Work Ability

Although research indicates that low fitness in youth is associated with a higher risk of chronic disability in men, the association of fitness in adolescence with work ability in working men and women remains unknown. To examine the associations of adolescent health-related physical fitness with future work ability. This 45-year observational cohort study, conducted in Finland, examined the direct and indirect longitudinal associations of objectively measured health-related fitness in adolescence (in 1976) with self-reported work ability and sickness absence in early middle age (in 2001) and the Work Ability Index in late middle age (in 2021). A countrywide stratified random baseline sample included fitness measurements for cardiorespiratory fitness (CRF) (running 1.5 km for girls and 2 km for boys), musculoskeletal fitness (MF; standing broad jump and sit-ups for both sexes, pull-ups for boys, and flexed-arm hang for girls), and height and weight, from which body mass index (BMI) was calculated. Structural equation modeling-based path analysis, adjusted for age and sex at baseline and for educational level, work-related physical strain, and leisure-time physical activity in late middle age, was conducted. Data analysis was performed from January to July 2023. Self-reported work ability was measured with structured questions in early middle age and with the validated Work Ability Index in late middle age. The final sample from longitudinal analyses (1207 individuals; 579 [48%] male individuals) consisted of participants with fitness measurement from age 12 to 19 years, and work ability assessment from age 37 to 44 years and/or age 57 to 64 years. Higher adolescent CRF was associated with higher work ability (839 participants; β = 0.12; 95% CI, 0.01 to 0.22; P = .03) and lower sickness absence (834 participants; β = -0.07; 95% CI, -0.12 to -0.02; P = .004) in early middle age and, indirectly, mediated by work ability in early middle age, with a higher work ability at the end of working age (603 participants; β = 0.04; 95% CI, 0.001 to 0.08; P = .04). The results remained consistent in both sexes and after adjustment for the confounders. Neither MF nor BMI was associated with work ability (MF, 1192 participants; β = -0.07; 95% CI, -0.17 to 0.03; BMI, 1207 participants, β = 0.09; 95% CI, -0.004 to 0.19) or sickness absence (MF, 1185 participants, β = 0.02; 95% CI, -0.03 to 0.06; BMI, 1202 participants, β = -0.03; 95% CI, -0.09 to 0.03) in early middle age or with late middle age work ability, mediated by work ability in early middle age (MF, 603 participants, β = -0.02; 95% CI, -0.06 to 0.01; BMI, 603 participants, β = 0.03; 95% CI, -0.004 to 0.07). These findings suggest that low CRF in youth is associated with poor work ability at the middle and end of working life, which highlights the informative and prognostic value of CRF assessment early in youth. Enhancing CRF in the first decades of life might contribute to better work capacity and productivity in the labor force, which would have implications for health, quality of life, society, and the economy.

FMUPorto - Summaries and comments

a - Cardiac sequelae in athletes following COVID-19 vaccination evidence and misinformation b - Associations between cardiorespiratory fitness in youth and the incidence of site-specific cancer in men: a cohort study with register linkage

The impact of cardiorespiratory fitness and physical workload on disability pension–a cohort study of Swedish men

ObjectiveUnderstanding the impact of physical capacity in combination with high physical workload could be beneficial for the prevention of health-related exits from work. Therefore, the aim of this study was to investigate the separate and combined effects of low cardiorespiratory fitness and high physical workload on disability pension (DP) due to any cause, musculoskeletal disorders (MSD), and cardiovascular diseases (CVD).MethodsA total of 279 353 men born between 1951 and 1961 were followed regarding DP between 2006 and 2020, ages 45–64. Cardiorespiratory fitness was assessed during military conscription, using an ergometer bicycle test. Physical workload was based on a job-exposure matrix (JEM) linked to occupational title in 2005. Cox regression models estimated separate and combined associations with DP.ResultsLow cardiorespiratory fitness and high physical workload were associated with increased risk of DP. For all cause DP, the fully adjusted hazard ratio and 95% confidence interval for those with low cardiorespiratory fitness was 1.38 (1.32–1.46) and for those with high physical workload 1.48 (1.39–1.57). For all cause and MSD DP, but not for CVD DP, the combination of low cardiorespiratory fitness and high physical workload resulted in higher risks than when adding the effect of the single exposures.ConclusionBoth low cardiorespiratory fitness in youth and later exposure to high physical workload were associated with an increased risk of DP, where workers with the combination of both low cardiorespiratory fitness and a high physical workload had the highest risks (all-cause and MSD DP).

Latent class analysis identifies a promising combination of Supplemental Nutrition Assistance Program-Education interventions for improving student cardiorespiratory fitness

ObjectiveTo inform Supplemental Nutrition Assistance Program Education (SNAP-Ed) and other school-based interventions aiming to improve youth cardiorespiratory fitness, this study aimed to identify which SNAP-Ed school-based physical activity intervention combinations were associated with better student cardiorespiratory fitness. MethodsThis study, utilizing cross-sectional secondary data, included 5th and 7th grade students who attended SNAP-Ed-eligible public schools in California (n = 442,743 students; 4271 schools) and had complete 2016–17 state-mandated fitness test results. Latent class analysis was used to identify underlying school-based intervention combinations. Propensity score methods were used to ensure comparability of intervention and comparison schools, by calculating inverse probability weights. Multilevel models, using those inverse probability weights, assessed the associations between the identified intervention combinations and student cardiorespiratory fitness, as measured by VO2max. The models were adjusted for school-level variables (urbanicity, percent of students eligible for free- or reduced-price meals, total enrollment, and school type), child-level variables (age, gender, and race/ethnicity), and for clustering of students within schools. ResultsWe found that students attending schools with interventions focusing on comprehensive policy changes along with improving opportunities for physical activity had, on average, 1.17 mL/kg/min (95% CI: 0.72, 1.62) greater VO2max than students attending schools without any intervention. They also had statistically significantly greater VO2max compared to students attending schools with any other type of intervention combination. ConclusionOur results suggest that comprehensive school-based physical activity interventions that include policy changes along with improving physical activity opportunities may be the most effective approach for improving fitness and may warrant prioritization in SNAP-Ed efforts.

Associations between cardiorespiratory fitness in youth and the incidence of site-specific cancer in men: a cohort study with register linkage

ObjectivesTo assess the associations between cardiorespiratory fitness (CRF) in young men and the incidence of site-specific cancer.MethodsA Swedish population-based cohort study with register linkage of men who underwent military conscription...

Heart Rate Variability and Cardiorespiratory Fitness in Youth Populations: The Impact of Heart Rate on Data Analysis.

The positive association between heart rate variability and cardiorespiratory fitness in youth populations is unclear. In this regard, several methodological aspects related to heart rate variability analysis could partially explain the disagreement between studies. To the best of the authors' knowledge, the influence of the heart rate on data analysis is unclear. In the present short communication, we discuss the impact of the heart rate on the associations between heart rate variability and cardiorespiratory fitness in youth. In addition, we proposed some aspects that should be considered for statistical analyses when the relationship between heart rate variability and cardiorespiratory fitness is studied. Finally, we should acknowledge that these recommendations may be applicable for other health-related outcomes different than cardiorespiratory fitness (e.g., inflammatory markers, cognition, cardiovascular disease status).

Toward exercise as medicine for adolescents with bipolar disorder (TEAM-BD): A feasibility study

ObjectivesBipolar disorder (BD) is associated with decreased cardiorespiratory fitness (CRF) and exercise. Despite the potential benefits for physical and mental health, there is a gap in knowledge regarding treatments targeting improved CRF for BD. This treatment development and feasibility study sought to bridge the knowledge-to-action gap in this area. MethodsTwenty youth with BD, 18.0 ± 2.3 years old, enrolled in an exercise behavior change counselling (BCC) intervention targeting improved CRF. The 12-week active intervention included four in-person sessions, augmented by phone/texting sessions on intervening weeks. Optional modules included exercise coaching, family involvement, and peer support. Booster phone/texting sessions occurred at weeks 16 and 20. Participants completed CRF testing at weeks 0, 2, 8, 12, and 24. ResultsSeventy percent of participants (14/20) completed all study visits and measures. In the overall enrolled sample, 82% of CRF tests were completed (range 0–5 of 5). There were no significant changes in subjective (via self-report) and objective (via Fitbit) measures of physical activity or in CRF, though CRF testing was consistently associated with acute post-exercise improvement in mood. Most participants reported being very satisfied with the intervention following the 12-week active intervention (13/14) and at week 24 (12/14). Therapist fidelity to the BCC manual was high. ConclusionGood attendance and study adherence provides preliminary evidence of the feasibility and acceptability of a behavioral intervention targeting CRF in youth with BD. Future studies refining the current intervention are warranted toward a goal of demonstrating improved CRF in a randomized controlled trial.

Traditional and New Perspectives on Youth Cardiorespiratory Fitness.

ABSTRACTPurposeThis study aimed to review traditional and new perspectives in the interpretation of the development of youth cardiorespiratory fitness (CRF).MethodsWe analyzed data from (i) the literature which for 80 yr has been traditionally based on interpretations of peak oxygen uptake (V˙O2) in ratio with body mass (BM) and (ii) recent multilevel allometric models founded on 994 (475 from girls) determinations of 10- to 16-yr-olds’ peak V˙O2 with measures of age, maturity status, and morphological covariates (BM and fat-free mass), and from 10 to 13 yr, 110 peak V˙O2 determinations of maximum cardiovascular covariates (stroke volume, cardiac output, and arteriovenous oxygen difference).ResultsThe application of ratio scaling of physiological variables requires satisfying specific statistical assumptions that are seldom met. In direct conflict with the ratio-scaled data interpretation of CRF, multilevel allometric modeling shows that with BM controlled, peak V˙O2 increases with age but the effect is smaller in girls than boys. Maturity status exerts a positive effect on peak V˙O2, in addition to those of age and BM. Changes in maximum cardiovascular covariates contribute to explaining the development of CRF, but fat-free mass (as a surrogate for active muscle mass) is the most powerful single influence. With age, maturity status, morphological covariates, and maximum cardiovascular covariates controlled, there remains an unexplained ~4% to ~9% sex difference in peak V˙O2.ConclusionsThe traditional interpretation of peak V˙O2 in ratio with BM is fallacious and leads to spurious correlations with other health-related variables. Studies of the development of CRF require analyses of sex-specific, concurrent changes in age- and maturation-driven morphological and maximum cardiovascular covariates. Multilevel allometric modeling provides a rigorous, flexible, and sensitive method of data analysis.

Cardiorespiratory Fitness in Youth: An Important Marker of Health: A Scientific Statement From the American Heart Association.

Cardiorespiratory fitness (CRF) refers to the capacity of the circulatory and respiratory systems to supply oxygen to skeletal muscle mitochondria for energy production needed during physical activity. CRF is an important marker of physical and mental health and academic achievement in youth. However, only 40% of US youth are currently believed to have healthy CRF. In this statement, we review the physiological principles that determine CRF, the tools that are available to assess CRF, the modifiable and nonmodifiable factors influencing CRF, the association of CRF with markers of health in otherwise healthy youth, and the temporal trends in CRF both in the United States and internationally. Development of a cost-effective CRF measurement process that could readily be incorporated into office visits and in field settings to screen all youth periodically could help identify those at increased risk.

Skeletal Muscle Mass Is Linked to Cardiorespiratory Fitness in Youth.

Cardiorespiratory fitness (CRF) measured by oxygen consumption (V˙O2) during exercise is an important marker of health. The traditional method of indexing V˙O2 to total body mass is suboptimal because skeletal muscle mass (SMM), rather than fat and extracellular fluid, is the main contributor to CRF. The traditional estimating equations for peak V˙O2 in youth do not account for this. Bioelectric impedance analysis (BIA) is a noninvasive method to accurately measure body composition. The objectives of this study were to 1) examine the relationship of body composition indices and peak V˙O2 in healthy children, adolescents, and young adults, and 2) derive an optimized estimating equation incorporating BIA and compare its performance with traditional estimating equations. A retrospective, cross-sectional, single-center study of patients <21 yr old referred for exercise testing who did not have underlying cardiovascular disease. All patients underwent BIA immediately before exercise testing. Univariable and multivariable linear regression models were constructed and tested for model performance. A total of 165 young healthy people (mean age 14 yr, 48% male) were studied. There was a strong and linear relationship between peak V˙O2 and SMM (R = 0.79). The sex difference in SMM explained the most variability in CRF between boys and girls. A generalized equation using SMM (peak V˙O2 = 302 - (23.7 × age) - (50.3 × [female = 1, male = 0]) + (81.8 × SMM)) had superior performance (R = 0.80) compared with estimating equations currently used in clinical practice (R = 0.67). SMM is a stronger correlate of CRF than is total body mass in youth and may be a better scaling variable to estimate expected peak V˙O2.

Youth cardiorespiratory fitness: evidence, myths and misconceptions.

Rigorously determined peak oxygen uptake is internationally recognized as the criterion measure of youth cardiorespiratory fitness. The assessment and interpretation of children’s and adolescents’ peak oxygen uptake and the relationship of the measure with other health-related variables are well documented. There has been a recent resurgence of interest in the prediction of peak oxygen uptake from field performance tests in young people. However, coupled with ratio-scaling of data and the raising of clinical red flags, these practices risk clouding our understanding of youth cardiorespiratory fitness and its relationship with current and future health. We believe these methods have the potential to mislead clinical practice and misguide recommendations for the promotion of youth cardiovascular health. We discuss relevant scientific evidence and interpretations that have emerged from predicting youth cardiorespiratory fitness from performance test scores. We argue that children deserve to have health care founded on evidence-based science and not on myths and misconceptions.

Area-level Socioeconomic Environment and Cardiorespiratory Fitness in Youth.

Cardiorespiratory fitness is one of the most important markers of cardiometabolic health and is a strong predictor of cardiovascular disease and all-cause mortality across the lifespan. However, little is known regarding the relationship of area-level socioeconomic environment on cardiorespiratory fitness during childhood and adolescence. To examine the relationship between area-level socioeconomic environment and cardiorespiratory fitness in a diverse sample of school-age youth; and to determine the extent to which grade level, sex, race/ethnicity, and student poverty status moderate this relationship. South Carolina FitnessGram data for school year 2015 to 2016 were obtained for 44,078 youth. Cardiorespiratory fitness was determined using Progressive Aerobic Cardiovascular Endurance Run or 1-mile run/walk test. Area-level socioeconomic environment was expressed as a composite index score at the census tract level using data from the American Community Survey. Multilevel logistic regression analyses were conducted, controlling for individual-level characteristics and nesting within schools and districts. Interaction terms were then introduced to the model to examine their effect of multiple sociodemographic moderators. Approximately half of the sample had inadequate cardiorespiratory fitness for health. The odds of achieving the Healthy Fitness Zone for cardiorespiratory fitness decreased by approximately 25% to 34% with increasing deprivation of the area-level socioeconomic environment, after controlling for covariates. The association between area-level socioeconomic environment and cardiorespiratory fitness also varied significantly by sex, grade level, and race/ethnicity subgroups. Cardiorespiratory fitness was positively associated with area-level socioeconomic environment; however, the relationship varied by demographic characteristics. These results highlight the importance of examining the influence of area-level socioeconomic environment on health across the life span. Additional research is needed to explore how area-level socioeconomic environment may impact evidence-based efforts to improve youth cardiorespiratory fitness levels.

Fact and Fiction in youth Cardiorespiratory Fitness

Cardiorespiratory fitness (CRF) reflects the integrated ability to deliver oxygen from the atmosphere to the skeletal muscles and to utilize it to generate energy to support muscle activity during exercise. Peak oxygen uptake (VO2) is internationally recognized as the criterion measure of youth CRF. It is well-documented that in youth peak VO2 increases with sex-specific, concurrent changes in a range of age- and maturity status-driven morphological and physiological covariates with the timing and tempo of changes specific to individuals. However, a recent resurgence of interest in predicting peak VO2 from field test performances and the persistence of fallacious interpretations of peak VO2 in 1:1 ratio with body mass have obfuscated general understanding of the development of CRF. Moreover, as spurious relationships arise when ratio-scaled data are correlated with health-related variables the use of this scaling technique has confounded the relationship of youth CRF with indicators of current and future health. This paper reviews the extant evidence and concludes that the interpretation of youth CRF and the promotion of young people’s health and well-being should be founded on scientific facts and not on fictions based on flawed methodology and specious interpretation of data.

Lower Performance in the Six-Minute Walk Test in Obese Youth With Cardiometabolic Risk Clustering.

Background: Physical fitness is an important index of health. Our aim was to assess whether cardiorespiratory and/or musculoskeletal components of physical fitness were associated with cardiometabolic risk clustering in obese youth, using adapted and validated field tests.Methods: We evaluated 252 children and adolescents (132 males, 120 females), mean age 10.9 ± 1.9 years with primary obesity. All subjects performed the six-minute walk test (6MWT) for assessing aerobic fitness, the standing broad jump, and the 30 s-chair stand tests for lower-body muscular strength, and the handgrip test for upper body isometric strength. Cardiometabolic risk (CMR) clustering was defined as having two or more of the following risk factors: high SBP and/or DBP, impaired fasting glucose, high triglycerides (TGs), and low HDL-Cholesterol.Results: CMR clustering was found in 44 (17.5%) obese youth. Youth with CMR clustering had a lower cardiorespiratory fitness, as assessed by 6MWT, compared to those without CMR clustering. On the contrary, no difference was found with respect to musculoskeletal fitness. The six-minute walk (6MW) distance was negatively associated with sedentary time, controlling for age and height. CMR factors clustering was significantly associated with BMI standard deviation score (SDS) and negatively with 6MW distance: for each 10-m increase in the 6MW distance, a reduction of about 9% in the prevalence of CMR clustering was expected.Conclusions: A lower performance in the 6MWT may be considered as an additional trait of CMR clustering in obese youth. The 6MWT may represent a valuable, simple and low cost test to estimate the cardiorespiratory fitness in youth with obesity.

Biological and environmental determinants of 12-minute run performance in youth

Background: The 12-minute run is a commonly used indicator of cardiorespiratory fitness in youth. Variation in growth and maturity status as potential correlates of test performance has not been systematically addressed.Aim: To evaluate biological and environmental determinants of 12-minute run performance in Portuguese youth aged 7–17 years.Subjects and methods: Mixed-longitudinal samples of 187 boys and 142 girls were surveyed in 1996, 1997 and 1998. The 12-minute run was the indicator of cardiorespiratory fitness. Height, body mass and five skinfolds were measured and skeletal maturity was assessed. Physical activity, socioeconomic status and area of residence were obtained with a questionnaire. Multi-level modelling was used for the analysis.Results: Chronological age and sum of five skinfolds were significant predictors of 12-minute run performance. Older boys and girls ran longer distances than younger peers, while high levels of subcutaneous fat were associated with shorter running distances. Rural boys were more proficient in the 12-minute run than urban peers. Skeletal maturity, height, body mass index, physical activity and socioeconomic status were not significant predictors of 12-minute run performances.Conclusions: Age and sum of skinfolds in both sexes and rural residence in boys are significant predictors of 12-minute run performance in Portuguese youth.

Cumulative incidence of youth obesity is associated with low cardiorespiratory fitness levels and with maternal overweight

Abstract This longitudinal study evaluated the association between the incidence of youth overweight/obesity (Ow/Ob) and low levels of cardiorespiratory fitness (CRF) over 4 years and youths' and their parents' demographic and nutritional characteristics. The randomized sample comprised 398 youth, aged 7-17 years at baseline, from a city in southern Brazil. Subjects were classified as being Ow/Ob according to international body mass index (BMI) parameters. Parental weight and height were determined by direct questioning. Youth CRF was measured by a 9-minute walk-and-run test. The cumulative incidences of Ow/Ob and of low CRF levels were 25.1% and 20.5%, respectively. Relative to other youth, youth who were classified as "unhealthy" at baseline (with respect to CRF) and by the fourth year were more likely to be classified as Ow/Ob (relative risks: 1.12 and 1.10, respectively). Youth whose mothers were categorized as Ow/Ob were at higher risk of being classified as Ow/Ob than youth whose mothers had normal BMIs (relative risks: 1.19 at baseline and 1.20 in the fourth year). The incidence of Ow/Ob among the former youth was associated with low CRF levels and with maternal Ob.

Outdoor Time Is Associated with Physical Activity, Sedentary Time, and Cardiorespiratory Fitness in Youth

To determine whether time spent outdoors was associated with increased moderate-to-vigorous physical activity (MVPA) and related health benefits in youth. We performed a cross-sectional study of 306 youth aged 13.6 ± 1.4 years. The exposure of interest was self-reported time spent outdoors after school, stratified into three categories: none, some, and most/all of the time. The main outcome of interest was accelerometer-derived MVPA (Actical: 1500 to >6500 counts/min). Secondary outcomes included sedentary behavior, cardiorespiratory fitness, overweight status, and blood pressure. Among the 306 youth studied, those who reported spending most/all of their after-school time outdoors (n = 120) participated in more MVPA (61.0 ± 24.3 vs 39.9 ± 19.1 min/day; adjusted P < .001), were more likely to achieve the recommended minimum 60 min/day of MVPA (aOR 2.8; 95% CI, 1.3-6.4), spent less time in sedentary activities (539 ± 97 min/day vs 610 ± 146 min/day; adjusted P < .001), and had higher cardiorespiratory fitness (49 ± 5 vs 45 ± 6 mL/kg/min; adjusted P < .001) than youth who reported no time outdoors (n = 52). No differences in overweight/obesity or blood pressure were observed across the groups. Time spent outdoors is positively associated with MVPA and cardiorespiratory fitness in youth and negatively associated with sedentary behavior. Experimental trials are needed to determine whether strategies designed to increase time spent outdoors exert a positive influence on physical activity and fitness levels in youth.

Independent and Combined Association of Muscle Strength and Cardiorespiratory Fitness in Youth With Insulin Resistance and β-Cell Function in Young Adulthood

OBJECTIVETo examine the independent and combined association of isometric muscle strength of the abdomen and back and cardiorespiratory fitness (CRF) in youth with indices of glucose metabolism in young adulthood among boys and girls from the European Youth Heart Study.RESEARCH DESIGN AND METHODSWe used data from a population-based prospective cohort study among youth followed up for up to 12 years (n = 317). In youth, maximal voluntary contractions during isometric back extension and abdominal flexion were determined using a strain-gauge dynamometer and CRF was obtained from a maximal cycle ergometer test. Insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR]) and β-cell function (homeostasis model assessment of β-cell function [HOMA-B]) were estimated from fasting serum insulin and glucose that were obtained in youth and at follow-up in young adulthood.RESULTSFor each 1-SD difference in isometric muscle strength (0.16 N/kg) in youth, fasting insulin, HOMA-IR, and HOMA-B in young adulthood changed by −11.3% (95% CI −17.0 to −5.2), −12.2% (−18.2 to −5.7), and −8.9% (−14.4 to −3.0), respectively, in young adulthood after adjustment for CRF and personal lifestyle and demographic factors. Results for CRF were very similar in magnitude, and the magnitude of associations for both exposures was unchanged with additional adjustment for general or abdominal adiposity in youth. Combined associations of muscle strength and CRF with fasting insulin, HOMA-IR, and HOMA-B were additive, and adolescents in the highest sex-specific tertile for both isometric muscle strength and CRF had the lowest levels of these glucose metabolism outcomes.CONCLUSIONSIncreasing muscle strength and CRF should be targets in youth primordial prevention strategies of insulin resistance and β-cell dysfunction.

Reproducibility and Validity of the 10-Meter Shuttle Ride Test in Wheelchair-Using Children and Adolescents With Cerebral Palsy

For children with cerebral palsy (CP) who are able to walk or run, the 10-m shuttle run test is currently the test of choice to assess cardiorespiratory fitness. This test, however, has not yet been examined in wheelchair-using youth with CP. The purpose of this study was to investigate the test-retest reproducibility and validity of the 10-m shuttle ride test (SRiT) in youth with CP. Repeated measurements of the SRiT were obtained. Twenty-three individuals with spastic CP (18 boys, 5 girls; mean age=13.3 years, SD=3.6 years) using a manual wheelchair for at least part of the day participated in this study. During the study, all participants performed one graded arm exercise test (GAET) and 2 identical SRiTs within 2 weeks. Peak oxygen uptake (Vo2peak), peak heart rate (HRpeak), and respiratory exchange ratio (RER) were recorded. Intraclass correlation coefficients (2,1), the smallest detectable difference, and the limits of agreement (LOA) were calculated. The association between the results of the SRiT and GAET was tested using Pearson correlation coefficients. Intraclass correlation coefficients (.99, 95% confidence interval=.98-1.00) for all variables indicated highly acceptable reproducibility. The LOA analysis revealed satisfactory levels of agreement. The SRiT variables demonstrated strong, significant positive correlations for Vo2peak values obtained during the SRiT and the GAET (r=.84, P<.01). Although the GAET is considered the gold standard, the cardiorespiratory demand during the GAET was significantly lower compared with during the SRiT. Future studies should determine whether the GAET can still be accepted as the gold standard for upper-extremity exercise. The SRiT is a reproducible and valid test for measuring cardiorespiratory fitness in youth with spastic CP who self-propel a manual wheelchair.

Independence of physical activity and screen time as predictors of cardiorespiratory fitness in youth

Screen time (ST) is associated with physical activity (PA) levels. We aimed to investigate the relationship between ST and fitness. We assessed fitness and daily ST in 7,466 10-16-y-old schoolchildren from the east of England. The differences in fitness between ST groups, and the association between ST and fitness were assessed. ST was negatively associated with fitness in boys of all ages (P < 0.001) and girls in grades 6-9 (P < 0.005). Boys were less likely to be fit if they reported >2 h/d ST (odds ratio (OR): 0.70, 95% confidence interval (CI): 0.58-0.85) or >4 h/d (OR: 0.45, 95% CI: 0.35-0.57) ST, as were girls reporting >4 h/d ST (OR: 0.58, 95% CI: 0.43-0.78). Controlling for PA levels attenuated these odds in boys reporting >2 h/d ST (OR: 0.81, 95% CI: 0.66-0.91) or >4 h/d ST (OR: 0.65, 95% CI: 0.50-0.84) and in girls reporting >4 h/d ST (OR: 0.68, 95% CI: 0.50-0.93). These first data from English children show a negative association between ST and fitness in youth. Of note, very high levels of daily ST (>4 h) are associated with poor fitness. Some of the associations were mediated by PA levels. Our data support international recommendations to limit ST to <2 h/d; we believe such guidance should be issued in the United Kingdom.