Influence of cardiac functional capacity on gender differences in maximal oxygen uptake in children

Longitudinal development and tracking of cardiorespiratory fitness from childhood to adolescence

BACKGROUND

Cardiorespiratory fitness (CRF) is an important indicator of health in childhood and adolescence but longitudinal studies on the development and tracking of CRF from childhood to adolescence are scarce.

OBJECTIVES

The objectives of this study were (1) to assess longitudinal development and track CRF over 10 years from childhood to adolescence, and (2) to examine potential sex differences in the development and tracking of CRF during this period.

METHODS

Participants were Icelandic children born in 1999, measured at the age of 7 (n = 190, 106 girls), 9 (n = 163, 95 girls), 15 (n = 239, 134 girls), and 17 (n = 202, 119 girls). CRF was assessed with a maximal cycle ergometer test and expressed as maximal power output (Max W) and maximal power output relative to lean mass (W/kgLM). Multilevel regression models were used to study the longitudinal development of CRF, and tracking was assessed with Spearman's rank correlation, logistic regression, and the percentage of participants remaining in low, moderate, or high CRF categories between measurements.

RESULTS

Max W and W/kgLM increased for both boys and girls up to age 15. Max W plateaued for both boys and girls while W/kgLM plateaued for girls but declined for boys from age 15 to 17. Boys had higher Max W than girls from age 15 and higher W/kgLM from age 9. CRF tracked at low to moderate levels from childhood to adolescence and at high levels in adolescence, with higher values observed for boys than girls.

CONCLUSIONS

Age 15 was a critical time point in the development of CRF, with values starting to plateau for girls and decline for boys. The results support early intervention for improved CRF in later years, with interventions targeting all children, regardless of their CRF level.

Reference Values for Cardiorespiratory Fitness in Patients Aged 6 to 18 Years

OBJECTIVE

To develop reference values for cardiorespiratory fitness, as quantified by peak oxygen uptake (VO2peak) and treadmill time, in patients aged 6 through 18 years referred for cardiopulmonary exercise testing (CPET).

STUDY DESIGN

We reviewed a clinical pediatric CPET database for fitness data in children aged 6-18 years with no underlying heart disease. CPET was obtained via the Bruce protocol utilizing objectively confirmed maximal effort via respiratory exchange ratio. Fitness data (VO2peak and treadmill test duration) were analyzed to determine age- and sex-specific reference values for this pediatric cohort.

RESULTS

Data from 2025 pediatric CPETs (53.2% female) were included in the analyses. VO2peak increased with age in males, but not females. Treadmill test duration increased with age in both males and females. Fitness was generally higher in males when compared with females in the same age groups.

CONCLUSIONS

Our study provides extensive reference values for both VO2peak and total treadmill test time via the Bruce protocol for a pediatric population without known cardiac disease. Furthermore, the inclusion of objectively confirmed maximal exercise effort increases confidence in these findings compared with prior studies in this area. Clinicians performing CPET in pediatric populations can utilize these reference values to characterize test results according to representative peer data.

Open field stress testing: finally an optimal method in young children? Reference values for mobile cardiopulmonary exercise testing in healthy children aged 4-8 years

INTRODUCTION

Cardiopulmonary exercise testing represents the diagnostic tool for determining cardiopulmonary function. Especially in small children, exercise testing is extremely challenging. To address this problem, field testing has been implemented using small mobile devices. This study aims at using this protocol for developing normal values for cardiopulmonary exercise testing in very young children.

MATERIAL AND METHODS

Healthy children aged 4-8 years were recruited. All children were tested according to an outdoor protocol, in which they were instructed to walk, then run slowly, then a little harder and at last run at full speed. Each step lasted for 2 minutes, except the last step, in which the children were instructed to maintain as long as possible.

RESULTS

A total of 104 children (64 female/35 male, mean age 6.6 years) performed outdoor cardiopulmonary exercise testing using a mobile device. Almost all tests were completed successfully (95%). Despite a predominance of female study subjects, anthropometric values did not differ between boys and girls. V̇O₂peak/kg, respiratory exchange ratio, VT1, heart rate at VT1, and time of exercise were also comparable between sexes. Generally, a tendency of higher maximal oxygen uptake could be observed in older children.

CONCLUSION

Open field mobile cardiopulmonary exercise testing represents a novel approach in very young children. In this study, we were able to determine normal values of maximal oxygen uptake and OUES/kg for 4-8-year-old children. The method is easy to achieve and safe.

Effects of Sex, Training, and Maturity Status on the Cardiopulmonary and Muscle Deoxygenation Responses during Incremental Ramp Exercise

Whilst participation in regular exercise and sport has generally increased over recent decades globally, fundamental questions remain regarding the influence of growth, maturation, and sex on the magnitude of training response throughout adolescence. Trained (108 participants, 43 girls; age: 14.3 ± 1.8 years) and untrained (108 participants, 43 girls; age: 14.7 ± 1.7 years) adolescents completed an incremental ramp test to exhaustion during which breath by gas exchange, beat-by-beat heart rate (HR), stroke volume (SV) and cardiac output (Q·) and muscle deoxygenation were assessed. Device-based physical activity was also assessed over seven consecutive days. Boys, irrespective of training status, had a significantly higher absolute (2.65 ± 0.70 L min−1 vs. 2.01 ± 0.45 L min−1, p < 0.01) and allometrically scaled (183.8 ± 31.4 mL·kg−b min−1 vs. 146.5 ± 28.5 mL·kg−b min−1, p < 0.01) peak oxygen uptake (V·O2) than girls. There were no sex differences in peak HR, SV or Q· but boys had a higher muscle deoxygenation plateau when expressed against absolute work rate and V·O2 (p < 0.05). Muscle deoxygenation appears to be more important in determining the sex differences in peak V·O2 in youth. Future research should examine the effects of sex on the response to different training methodologies in youth.

A Combined Analysis of Peak and Submaximal Exercise Parameters in Delineating Underlying Mechanisms of Sex Differences in Healthy Adolescents

Peak exercise parameters are considered the gold standard to quantify cardiac reserve in cardiopulmonary exercise testing (CPET). We studied whether submaximal parameters would add additional values in analyzing sex differences in CPET. We reviewed CPET of age-matched healthy male and female adolescents by cycle ergometer. Besides peak parameters, submaximal CPET parameters, including ventilatory anaerobic threshold (VAT), oxygen uptake efficiency slope (OUES), and submaximal slopes of Δoxygen consumption (ΔVO2)/Δwork rate (ΔWR), Δheart rate (ΔHR)/ΔWR, ΔVO2/ΔHR, and Δminute ventilation (ΔVE)/ΔCO2 production (ΔVCO2), were obtained. We studied 35 male and 40 female healthy adolescents. Peak VO2 (pVO2), peak oxygen pulse (pOP), and VAT were significantly lower in females than males (1.9 ± 0.4 vs. 2.5 ± 0.6 L/min; 10 ± 2.0 vs. 13.2 ± 3.5 ml/beat; 1.23 ± 0.3 vs. 1.52 ± 0.5 L/min, respectively, all p < 0.005). Females showed significantly lower pVO2, VAT, and OUES with the same body weight than males, implying higher skeletal muscle mass in males. When simultaneously examining ΔHR/ΔWR and pOP, females showed higher dependency on increases in HR than in stroke volume. Females demonstrated significantly lower pOP with the same levels of ΔVO2/ΔHR, suggesting more limited exercise persistence than males under an anaerobic condition at peak exercise. Oxygen uptake efficiency in relation to peak VE was significantly higher in males. There was no sex difference in either ΔVO2/ΔWR or ΔVE/ΔVCO2. Combinational assessment of peak and submaximal CPET parameters delineates the multiple mechanisms that contribute to the sex differences in exercise performance.

Influence of Insulin Application Time and High-Intensity Intermittent Exercise on Hypoglycemic Risk in Adolescents With Type 1 Diabetes

PURPOSE

The study analyzed the influence of exercise on hypoglycemia episodes postexercise and in the subsequent 24 hours in children and adolescents with type 1 diabetes.

METHODS

Thirty young people performed the same protocol of physical exercises for 1 hour (Ex1h) and 2 hours (Ex2h) after the administration of insulin. They performed 30 minutes of exercise on a cycle ergometer with a load of 60% of maximal oxygen uptake, interspersed with maximum intensity sprints lasting 10 seconds every 5 minutes.

RESULTS

Regarding the occurrence of hypoglycemia, in the 8 hours following the exercises, there was no occurrence in Ex1h (χ2 = 0.001; P = .0001) and a greater proportion for Ex2h (n = 71 episodes, 53.8%), while Ex1h had a higher number of nocturnal hypoglycemic episodes (n = 60, 71.4%) compared with Ex2h (n = 31, 23.1%, χ2 = 49.521, P = .0001), Ex1h triggered a lower number of hypoglycemia (n = 84) than Ex2h (n = 134, χ2 = 11.504, P = .001). There was a greater reduction in the average amount of fast-acting insulin administered the day after Ex1h compared with Ex2h (P = .031).

CONCLUSIONS

Intermittent exercise performed 1 hour after insulin administration shows a lower risk of hypoglycemia within 8 hours after exercise, as well as a reduction in insulin the following day.

Cardiac Autonomic Modulation of Heart Rate Recovery in Children with Spina Bifida

We aimed to analyse cardiac autonomic control by assessing the post-exercise heart rate recovery (HRR) and physical fitness in children and adolescents with spina bifida (SB), compared to participants with typical development. A total of 124 participants, 42 with spina bifida (SB group) and 82 typical developmental controls (CO group) performed the arm cranking exercise test with a gas analysis system. HRR was determined at the first (HRR_1) and second (HRR_2) minute at recovery phase. Data are shown as [mean difference (95% CI)]. The SB group showed reduced HR reserve [14.5 (7.1-22.0) bmp, P<0.01], slower HRR_1 [12.4 (7.4-17.5) bpm, P<0.01] and HRR_2 [16.3 (10.6-21.9) bpm; P<0.01], lower VO2peak [VO2peak relative: 7.3 (4.2-10.3) mL·min-1·kg-1, P<0.01; VO2peak absolute: 0.42 (0.30-0.54) L·min-1, P<0.01], and lower O2 pulse [2.5 (1.8-3.2) mL·bpm, P<0.01] and ventilatory responses [13.5 (8.8-18.1) L·min-1, P<0.01] than the CO group. VE/VO2 was not different between groups [-2.82 (-5.77- -0.12); P=0.06], but the VE/VCO2 [-2.59 (-4.40-0.78); P<0.01] and the values of the anaerobic threshold corrected by body mass [-3.2 (-5.8- -0.6) mL·min-1·kg-1, P=0.01] were higher in the SB group than in the CO group. We concluded that children and adolescents with SB have reduced physical fitness and a slower HRR response after maximal effort.

Relating cardiorespiratory responses to work rate during incremental ramp exercise on treadmill in children and adolescents: sex and age differences

PURPOSE

Evaluation of cardiopulmonary exercise testing (CPET) slopes such as [Formula: see text] (cardiac/skeletal muscle function) and [Formula: see text] (O2 delivery/utilization), using treadmill protocols is limited because the difficulties in measuring the total work rate ([Formula: see text]). To overcome this limitation, we proposed a new method in quantifying [Formula: see text] to determine CPET slopes.

METHODS

CPET's were performed by healthy patients, (n = 674, 9-18 year) 300 female (F) and 374 male (M), using an incremental ramp protocol on a treadmill. For this protocol, a quantitative relationship based on biomechanical principles of human locomotion, was used to quantify the [Formula: see text] of the subject. CPET slopes were determined by linear regression of the data recorded until the gas exchange threshold occurred.

RESULTS

The method to estimate [Formula: see text] was substantiated by verifying that: [Formula: see text] for treadmill exercise corresponded to an efficiency of muscular work similar to that of cycle ergometer; [Formula: see text] (mL min-1 W-1) was invariant with age and greater in M than F older than 12 years old (13-14 years: 9.6 ± 1.5(F) vs. 10.5 ± 1.8(M); 15-16 years: 9.7 ± 1.7(F) vs. 10.6 ± 2.2(M); 17-18 years: 9.6 ± 1.7(F) vs. 11.0 ± 2.3(M), p < 0.05); similar to cycle ergometer exercise, [Formula: see text] was inversely related to body weight (BW) (r = 0.71) or [Formula: see text] (r = 0.66) and [Formula: see text] was not related to BW (r = - 0.01), but had a weak relationship with [Formula: see text] (r = 0.28).

CONCLUSION

The proposed approach can be used to estimate [Formula: see text] and quantify CPET slopes derived from incremental ramp protocols at submaximal exercise intensities using the treadmill, like the cycle ergometer, to infer cardiovascular and metabolic function in both healthy and diseased states.

25-Hydroxyvitamin D and Cardiorespiratory Fitness in Prepubertal Overweight and Obese Children

Childhood obesity has become a major global health problem. Vitamin D deficiency and poor cardiorespiratory fitness are highly prevalent in children with overweight or obesity, but little is known about their relationships. In this study, we aimed to analyze the relationship between serum 25-hydroxyvitamin D (25(OH)D) and cardiorespiratory fitness parameters in prepubertal obese and overweight children. A cross-sectional design with a sample of 57 prepubertal children, aged 9–11 years, with overweight or obesity was used. The fasting concentration of 25(OH)D was analyzed with a chemiluminescent microparticle immunoassay. Fat and lean body masses were determined by using DXA. Maximal oxygen uptake (VO_2max) was measured with the maximal treadmill test. A total of 68.4% of the sample had sufficient levels of 25(OH)D. As expected, their cardiorespiratory fitness was poor compared with that of normal-weight children, but 60% of the group exceeded the median obesity-specific reference values. No differences were found between the sexes for relative VO_2max or 25(OH)D levels. Moreover, no correlations were found between 25(OH)D and body composition or cardiorespiratory parameters for sex or vitamin D groups. Vitamin D status seems not to be directly related to body composition or cardiorespiratory fitness in prepubertal overweight or obese children.

Physical fitness and cognitive function among school-aged children in selected basic schools in the Ho Municipality of Ghana

Physical fitness is thought to promote cognitive function. Evidence about this is however lacking in the Ghanaian context. This study aimed to investigate the association between physical fitness and cognitive function among basic school children aged 8–13 years. A cross-sectional study involving 591 school children, recruited from 12 randomly selected public and private basic schools was conducted. Physical fitness tests were done using a five-test battery (Fifty metre run, handgrip strength, sit-up, flexibility and standing board jump) following standardized procedures. Cognitive function test using the Raven's Coloured Progressive Matrices (RCPM) were carried out. More girls (55%), children from 8-13 years old (49.1%) and public school children (66.1%) participated in the study. For fitness, boys performed better than girls in sit ups 3.4 ± 2.2 (mean ± SD), p = 0.012, handgrip 4.3 ± 2.0, p = 0.001 and overall fitness 4.3 ± 2.0, p = 0.007. Children in public schools performed significantly better in forward jump (p < 0.001) while those in private schools did better in 50m run (p < 0.001). For cognition, 46.1% of participants had less than 50% of the total score. Cognitive test score varied for forward jump and handgrip alone and not for sit ups, 50m run and overall score. Mean forward jump score was lowest in poor cognition group (4.9 ± 2.3), followed by good (5.3 ± 2.2) and highest among excellent (5.5 ± 2.3, p = 0.044) cognition group. Similar observation was made for handgrip. Cognition score and hand grip strength were positively but weakly correlated. (r = 0.132, p = 0.026). Although handgrip strength (measuring muscular strength) was significantly associated with cognitive function, this study found no significant association between overall physical fitness and cognitive function. These results indicate that only some components of physical fitness may be associated with cognitive function. This study is however correlational and one cannot infer causality.

Correlations Between Red Blood Cells' Variables, Cardio-Pysiological and Anthropological Variables in Young Athletes

AIM

The aim of this study was to determine and analyse the relations between anthropometric parameters, red blood cells' (RBC) variables and cardio-physiological parameters in healthy and physically active children and adolescents.

MATERIAL AND METHODS

In this study 625 subjects, (410 males and 215 females; age span 8 to 18 years) underwent body composition analysis (Matiegka method), blood analysis and ergometry testing (Bruce protocol).

RESULTS

In both groups, body height and weight were positively correlated with RBC variables. In female group almost all correlations between RBC variables and body components were insignificant. In boys all absolute body mass components showed positive correlations with RBC variables with notice that body fat mass had lowest correlation coefficient. Body fat percent (BF %) did not show any correlation with RBC variables in both gender groups. In boys BF % had moderate negative correlation with aerobic performance: exercise time (ET) and VO2max (rs = -0.41 and rs = -0.39). Lean body components showed weak positive correlations with ET and VO2max. RBC count did not show significant correlation with any cardio-physiological parameter in both groups. Haematocrit and haemoglobin showed weak positive correlations with VO2 max and general endurance (exercise time). In girls all correlations between cardio-physiological and RBC variables were insignificant. The relationship between all body components and all cardio-physiological variables in girls were statistically insignificant.

CONCLUSIONS

Our findings revealed that there are some expected positive correlations between lean body mass components, aerobic performance and RBC variables in boys, while in girls such relations were not noticed.

Relationship between breakfast consumption, BMI status and physical fitness of Ghanaian school-aged children

BACKGROUND

Good nutrition and physical activity of school-aged children are important for ensuring optimum growth and reducing obesity. This present study assessed associations between breakfast consumption, BMI-for-Age (BMI) and physical fitness in a cross-section of school-aged children attending government-owned primary schools in Kumasi, Ghana.

METHOD

The sample consisted of 438 pupils (boys = 213; girls = 225; mean age 11.1 ± 1.1), attending 10 randomly selected schools. Weight (kg), height (cm) and Mid Upper Arm Circumference (MUAC) were measured for each participant, and BMI-for-age z-scores determined using the World Health Organisation (WHO) anthroplus software. Participants were stratified into thinness, normal weight, overweight/obese using WHO cut offs. Physical fitness was assessed using forward jump, left and right handgrips, flexibility, sit-ups and 50 metre run following standard procedures and converted to scores of 1 to 10 following Japanese standards, based on which percentiles were derived. Total fitness score for each pupil was computed by adding all scores. A questionnaire was used to assess meal intake patterns.

RESULTS

The mean BMI-for-age z-score for participants was - 0.24 ± 0.99. Thinness, normal weight and overweight/obesity were 2.7, 86.5, and 10.5% respectively among the pupils. Overweight was higher in girls (14.2%) compared to boys (4.2%), p = 0.003. Similarly, mean MUAC was significantly (p = 0.021) higher in the girls (22.0 ± 3.2 cm) than the boys (20.7 ± 7.3 cm). For physical fitness, the girls scored higher in forward jump (p < 0.0001), 50-m run (p = 0.002) and overall fitness score than the boys (21.0 ± 6.2 versus 19.2 ± 8.3, p = 0.012). However, a larger proportion of boys performed excellently and poorly than girls (p = 0.019). A positive correlation was observed between BMI z-score and hand grip (r = 0.21, p < 0.001), while sit up (r = - 0.11, p = 0.018) showed a negative correlation with BMI z-score. No other fitness test varied by BMI. Overweight children performed best in handgrip. Majority of children said they engaged in exercise (89.9%) and consumed breakfast (78.9%). Breakfast consumption was not associated with BMI z-score (x2 0.0359, p = 0.549) but non-breakfast consumers performed better in 50 m run compared to consumers (7.0 seconds ± 2.3 vrs 6.3 seconds ± 2.5, p = 0.022). Children who reported to exercise were physically fitter than those who did not.

CONCLUSION

Underweight levels were low while overweight was over 10% in these children. Girls were more than 3 times affected by overweight than boys, and were also physically fitter than boys. Breakfast consumption was not related to weight or fitness.

Multilevel allometric modelling of maximum cardiac output, maximum arteriovenous oxygen difference, and peak oxygen uptake in 11-13-year-olds

PURPOSES

To investigate longitudinally (1) the contribution of morphological covariates to explaining the development of maximum cardiac output ([Formula: see text] max) and maximum arteriovenous oxygen difference (a-vO2 diff max), (2) sex differences in [Formula: see text] max and a-vO2 diff max once age, maturity status, and morphological covariates have been controlled for, and, (3) the contribution of concurrent changes in morphological and cardiovascular covariates to explaining the sex-specific development of peak oxygen uptake ([Formula: see text]).

METHODS

Fifty-one (32 boys) 11-13-year-olds had their peak [Formula: see text], maximum heart rate (HR max), [Formula: see text] max, and a-vO2 diff max determined during treadmill running on three annual occasions. The data were analysed using multilevel allometric modelling.

RESULTS

There were no sex differences in HR max which was not significantly (p > 0.05) correlated with age, morphological variables, or peak [Formula: see text]. The best-fit models for [Formula: see text] max and a-vO2 diff max were with fat-free mass (FFM) as covariate with age, maturity status, and haemoglobin concentration not significant (p > 0.05). FFM was the dominant influence on the development of peak [Formula: see text]. With FFM controlled for, the introduction of either [Formula: see text] max or a-vO2 diff max to multilevel models of peak [Formula: see text] resulted in significant (p < 0.05) additional contributions to explaining the sex difference.

CONCLUSIONS

(1) With FFM controlled for, there were no sex differences in [Formula: see text] max or a-vO2 diff max, (2) FFM was the dominant influence on the development of peak [Formula: see text], and (3) with FFM and either [Formula: see text] max or a-vO2 diff max controlled for, there remained an unresolved sex difference of ~ 4% in peak [Formula: see text].

Differences among Saudi and Expatriate Students: Body Composition Indices, Sitting Time Associated with Media Use and Physical Activity Pattern

Background: Being overweight at a young age is a predictor of developing obesity and related complications later in adulthood, posing a high risk to public health. Various ethnic subgroups have been identified as having a higher prevalence of overweight or obese. Saudi Arabia is one of the fastest-growing economies in the world, where the expatriate population comprises 33% of its total population. The objective of this study was to investigate differences in body composition indices, sitting time associated with media use, and physical activity pattern among a sample of local and expatriate school students in Saudi Arabia. Methods: 500 students (aged 8-18 years) from various schools were invited to participate in this study. Body weight, waist circumference (WC) and height were measured using a portable digital metric scale, standard measuring tape and wall mounted tape respectively. Participants and their parents were jointly asked to report the average time that the participant spent sitting using media (watching TV, playing video games, and using the internet and other screen-based devices etc.) per day. The pattern of physical activity among participants was measured using a short form of the International Physical Activity Questionnaire (IPAQ). Basal metabolic rate (BMR) and total daily energy expenditure (TEE) were estimated from body weight, height, age, sex and physical activity, according to the Harris-Benedict equation. Results: Data from 450 (90%) of the participants were used for analysis. The mean age of the participants was 14.55 ± 1.74 years. Body mass index (BMI), WC, waist to height ratio (WHtR), BMR and TEE differed significantly among the participants. Physical fitness score negatively correlated with BMI and WC, while sitting time associated with media use positively correlated with BMI, WC, WHtR and physical fitness score, among both Saudi and expatriate participants. Conclusions: Body composition indices and sitting time associated with media use were higher among Saudi boys and expatriate girls. Expatriate boys and girls were reported to be physically more active than their Saudi counterparts. BMR and TEE were higher among expatriate boys and Saudi girls. Although this study provides useful information about the association of body composition indices, sitting time associated with media use, and physical activity pattern among local and expatriate school students in SA, similar studies involving a larger study sample, with equal gender representation, are further required to determine various factors associated with this link.

Relative Age Effect of Sport Academy Adolescents, a Physiological Evaluation

The relationship between birth quarter distribution and physiological characteristics related to athletic skills, in adolescent sport academy students has not been fully investigated. In a cross-sectional study, we recruited 86 boys and 52 girls aged 12–14 years during their first term at a sport academy school. We measured body size, cardiac size, pulmonary function, body composition, lower body power, cardiorespiratory fitness parameters, and running endurance by standard methods and analyzed these estimates in relation to birth quarter by ANOVA. Birth quarter distribution in our cohort was compared with birth quarter distribution in the same ages in the whole of Sweden and analyzed by logistic regression. The academy had an overrepresentation of students born in the first quartile of the year compared to those born in the last quartile (odds ratio 2.3 (95% CI: 1.1–4.7)). When comparing the physiological characteristics between birth quarters, uniformity is prominent since out of 26 performed physiological and anthropometric tests only four showed statistically significant group differences. We thus believe that the selection process to the sport academy favours athletes with higher chronological age, i.e., a so-called relative age effect is present.

Multilevel allometric modelling of maximal stroke volume and peak oxygen uptake in 11-13-year-olds

PURPOSE

To investigate (1) whether maximal stroke volume (SVmax) occurs at submaximal exercise intensities, (2) sex differences in SVmax once fat-free mass (FFM) has been controlled for, and, (3) the contribution of concurrent changes in FFM and SVmax to the sex-specific development of peak oxygen uptake [Formula: see text].

METHODS

The peak [Formula: see text] s of 61 (34 boys) 11-12-year-olds were determined and their SV determined during treadmill running at 2.28 and 2.50 m s-1 using carbon dioxide rebreathing. The SVmax and peak [Formula: see text] of 51 (32 boys) students who volunteered to be tested treadmill running at 2.50 m s-1 on three annual occasions were investigated using multilevel allometric modelling. The models were founded on 111 (71 from boys) determinations of SVmax, FFM, and peak [Formula: see text].

RESULTS

Progressive increases in treadmill running speed resulted in significant (p < 0.01) increases in [Formula: see text], but SV levelled-off with nonsignificant (p > 0.05) changes within ~ 2-3%. In the multilevel models, SVmax increased proportionally to FFM0.72 and with FFM controlled for, there were no significant (p > 0.05) sex differences. Peak [Formula: see text] increased with FFM but after adjusting for FFM0.98, a significant (p < 0.05) sex difference in peak [Formula: see text] remained. Introducing SVmax to the multilevel model revealed a significant (p < 0.05), but small additional effect of SVmax on peak [Formula: see text].

CONCLUSIONS

Fat-free mass explained sex differences in SVmax, but with FFM controlled for, there was still a ~ 5% sex difference in peak [Formula: see text]. SVmax made a modest additional contribution to explain the development of peak [Formula: see text] but there remained an unresolved sex difference of ~ 4%.

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.

Sex-Specific Longitudinal Modeling of Youth Peak Oxygen Uptake

Purpose: To investigate peak oxygen uptake ( V˙O2 ) in relation to sex, age, body mass, fat-free mass (FFM), maturity, and overweight status. Methods: Multiplicative, allometric models of 10- to 18-year-olds were founded on 1057 determinations of peak V˙O2 supported by anthropometry and estimates of maturity status. Results: Baseline models with body mass controlled for showed age to exert a positive effect on peak V˙O2 , with negative estimates for age², sex, and a sex-by-age interaction. Sex-specific models showed maturity status to have a positive effect on peak V˙O2 in addition to the effects of age and body mass. Introducing skinfold thicknesses to provide, with body mass, a surrogate for FFM explained maturity effects and yielded a significantly (P < .05) better statistical fit in all models compared with those based on FFM estimated from youth-specific skinfold equations. With girls only, the introduction of overweight, defined by body mass index, resulted in a small but significant (P < .05) negative effect, with an age-by-overweight status interaction. Conclusions: FFM has a powerful influence on peak V˙O2 in both sexes. Interpretation of the development of youth aerobic fitness and its application to health should reflect the sex- and maturity-associated variation in FFM.

Development of peak oxygen uptake from 11-16 years determined using both treadmill and cycle ergometry

PURPOSES

To investigate the development of peak oxygen uptake ([Formula: see text]) assessed on both a treadmill and a cycle ergometer in relation with sex and concurrent changes in age, body mass, fat-free mass (FFM), and maturity status and to evaluate currently proposed 'clinical red flags' or health-related cut-points for peak [Formula: see text].

METHODS

Multiplicative multilevel modelling, which enables the effects of variables to be partitioned concurrently within an allometric framework, was used to analyze the peak [Formula: see text]s of 138 (72 boys) students initially aged 11-14 years and tested on three annual occasions. Models were founded on 640 (340 from boys) determinations of peak [Formula: see text], supported by anthropometric measures and maturity status.

RESULTS

Mean peak [Formula: see text]s were 11-14% higher on a treadmill. The data did not meet the statistical assumptions underpinning ratio scaling of peak [Formula: see text] with body mass. With body mass appropriately controlled for boys' peak [Formula: see text]s were higher than girls' values and the difference increased with age. The development of peak [Formula: see text] was sex-specific, but within sex models were similar on both ergometers with FFM the dominant anthropometric factor.

CONCLUSIONS

Data should not be pooled for analysis but data from either ergometer can be used independently to interpret the development of peak [Formula: see text] in youth. On both ergometers and in both sexes, FFM is the most powerful morphological influence on the development of peak [Formula: see text]. 'Clinical red flags' or health-related cut-points proposed without consideration of exercise mode and founded on peak [Formula: see text] in ratio with body mass are fallacious.

Relationship Between Obesity, Physical Activity, and Cardiorespiratory Fitness Levels in Children and Adolescents in Bosnia and Herzegovina: An Analysis of Gender Differences

This study aimed to examine: (i) the level of physical activity (PA), obesity indices and cardiorespiratory fitness (CRF) among boys and girls in primary school, and (ii) to determine the association of obesity indices and PA with CRF for the total number of participants, and then separately for boys and girls. 753 sixth to ninth grade girls and boys aged 10-14 years took part in this cross-sectional study. The PA was assessed by the "Physical Activity Questionnaire - Children" and CRF was assessed by the Maximal multistage a 20 m shuttle run test. Body mass index (BMI), waist circumferences (WC), and waist to height ratio (WHtR) were considered as obesity indices. Multiple linear regression analyses were performed to explore correlates of CRF. The results obtained showed the prevalence of general overweight and obesity was 25.5% in our sample which was lower than that in the regional estimate (e.g., ∼28%) for Eastern Europe. Among all participants, CRF was associated with male sex, older age, a lower WC percentile, higher WHtR, and higher level of PA. The model accounted for 24% of the variance. CRF was associated with older age and higher level of PA among girls and boys. Lower WC percentile was a significant determinant of CRF among boys. In conclusion, general overweight/obesity was not independently associated with CRF. Those with better CRF were more likely to be male and older, had a higher level of PA and lower central adiposity. These findings emphasize the importance of supporting school age children to take a part in programmed physical activity regardless of their body composition.

Validation of the Modified Shuttle Test to Predict Peak Oxygen Uptake in Youth Asthma Patients Under Regular Treatment

Background: Oxygen uptake (VO₂) evaluations by cardiopulmonary exercise test is expensive and time-consuming. Estimating VO₂ based on a field test would be an alternative.

Objective: To develop and validate an equation to predict VO_2peak based on the modified shuttle test (MST).

Methods: Cross sectional study, with 97 children and adolescents with asthma. Participants were divided in two groups: the equation group (EG), to construct the equation model of VO_2peak, and the cross-validation group (VG). Each subject performed the MST twice using a portable gas analyzer. The peak VO_2peak during MST was used in the equation model. The patients’ height, weight, gender, and distance walked (DW) during MST were tested as independent variables.

Results: The final model [-0.457 + (gender × 0.139) + (weight × 0.025) + (DW × 0.002)] explained 87% of VO_2peak variation. The VO_2peak predicted was similar to VO_2peak measured by gas analyzer (1.9 ± 0.5 L/min and 2.0 ± 0.5 L/min, respectively) (p = 0.67), and presented significant ICC 0.91 (IC95% 0.77 to 0.96); p < 0.001. The Bland–Altman analysis showed low bias (-0.15 L/min) and limits of agreement (-0.65 to 0.35 L/min). There was no difference in DW between EG (760 ± 209 m) and VG (731 ± 180 m), p = 0.51.

Conclusion: The developed equation adequately predicts VO_2peak in pediatric patients with asthma.

Top 10 Research Questions Related to Youth Aerobic Fitness

Peak oxygen uptake ([Formula: see text]₂) is internationally recognized as the criterion measure of youth aerobic fitness, but despite pediatric data being available for almost 80 years, its measurement and interpretation in relation to growth, maturation, and health remain controversial. The trainability of youth aerobic fitness continues to be hotly debated, and causal mechanisms of training-induced changes and their modulation by chronological age, biological maturation, and sex are still to be resolved. The daily physical activity of youth is characterized by intermittent bouts and rapid changes in intensity, but physical activity of the intensity and duration required to determine peak [Formula: see text]₂ is rarely (if ever) experienced by most youth. In this context, it may therefore be the transient kinetics of pulmonary [Formula: see text]₂ that best reflect youth aerobic fitness. There are remarkably few rigorous studies of youth pulmonary [Formula: see text]₂ kinetics at the onset of exercise in different intensity domains, and the influence of chronological age, biological maturation, and sex during step changes in exercise intensity are not confidently documented. Understanding the trainability of the parameters of youth pulmonary [Formula: see text]₂ kinetics is primarily based on a few comparative studies of athletes and nonathletes. The underlying mechanisms of changes due to training require further exploration. The aims of the present article are therefore to provide a brief overview of aerobic fitness during growth and maturation, increase awareness of current controversies in its assessment and interpretation, identify gaps in knowledge, raise 10 relevant research questions, and indicate potential areas for future research.

Aerobic Function and Muscle Deoxygenation Dynamics during Ramp Exercise in Children

PURPOSE

This study aimed to characterize changes in deoxyhemoglobin ([HHb]) response dynamics in boys and girls during ramp incremental exercise to investigate whether the reduced peak oxygen uptake (peak V˙O2) in girls is associated with poorer matching of muscle O2 delivery to muscle O2 utilization, as evidenced by a more rapid increase in [HHb].

METHODS

Fifty-two children (31 boys, 9.9 ± 0.6 yr, 1.38 ± 0.07 m, 31.70 ± 5.78 kg) completed ramp incremental exercise on a cycle ergometer during which pulmonary gas exchange and muscle oxygenation parameters were measured.

RESULTS

When muscle [HHb] was expressed against absolute work rate and V˙O2, girls had an earlier change in [HHb], as evidenced by the lower c/d parameter (girls, 54 ± 20 W, vs boys, 67 ± 19 W, P = 0.023; girls, 0.82 ± 0.28 L·min(-1), vs boys, 0.95 ± 0.19 L·min(-1), P = 0.055) and plateau (girls, 85 ± 12 W, vs boys, 99 ± 18 W, P = 0.031; girls, 1.02 ± 0.25 L·min(-1), vs boys, 1.22 ± 0.28 L·min(-1), P = 0.014). However, when expressed against relative work rate or V˙O2, there were no sex differences in ([HHb]) response dynamics (all P > 0.20). Significant correlations were observed between absolute and fat-free mass normalized peak V˙O2 and the HHb c/d and plateau parameters when expressed against absolute work rate or V˙O2. Furthermore, when entered into a multiple regression model, the [HHb] plateau against absolute V˙O2 contributed 12% of the variance in peak V˙O2 after adjusting for fat-free mass, gas exchange threshold, and body fatness (model R2 = 0.81, P < 0.001).

CONCLUSIONS

The sex difference in peak V˙O2 in 9- to 10-yr-old children is, in part, related to sex-specific changes in muscle O2 extraction dynamics during incremental exercise.

Effects of sitting time associated with media consumption on physical activity patterns and daily energy expenditure of Saudi school students

[Purpose] This study was performed to assess the effect of daily sitting time during media consumption on physical fitness, total energy expenditure (TEE), and body composition indices of Saudi school children. [Subjects and Methods] A total of 180 healthy Saudi school students (8-18 years) were included in this study. Sitting time, total energy expenditure, and levels of physical activity were evaluated with pre-validated internet based questionnaires. Body composition indices were evaluated using anthropometric analysis. [Results] Out of the studied participants, only 22.2% of students were physically inactive. Children with moderate and active physical scores demonstrated less sedentary behavior (TV viewing and computer usage), lower body composition values (BMI, WC, WHtR), and higher TEE than sedentary or mild activity level participants. Boys showed higher fitness scores and less sedentary behavior than girls. Media sitting time among the studied subjects correlated negatively with physical scores and positively with body composition. [Conclusion] The data presented here suggests that poor physical fitness, lower TEE, and longer sitting times differentially influence normal body composition indices among school children which may lead to overweight or obese individuals. Thus, decreasing sitting time during media consumption and enhancing physical activity may play a pivotal role in preventing obesity in young children.

Sex differences in congenital heart defects and genetically induced arrhythmias

Sex medicine can be applied to define the effect of male or female sex-associated differences on the prevalence of congenital heart defects (CHDs), on clinical manifestation of the latter, on means of dealing with the defects and facing consequent surgical treatment, as well as on the success of surgery. The widespread use of modern databases has undoubtedly enhanced the possibility of these observations compared to the past, when findings were limited to case series from single cardiology or paediatric heart surgery units. The aim of the present review is to assess all publications present in the literature on sex differences and CHD, placing particular emphasis on both contradictory aspects and less acknowledged issues. Furthermore, a section of the review is devoted to the effect of sex differences on cardiac arrhythmias, particularly the largely genetically predetermined electrophysiological differences observed between men and women.

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

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.

Longitudinal differences in aerobic capacity between children with sickle cell anemia and matched controls

BACKGROUND

The purpose of this study was to compare longitudinal trajectories of maximal aerobic capacity in children with sickle cell anemia (SCA) and matched healthy controls, and explore whether these trajectories were associated with selected physiologic variables.

PROCEDURE

Children with SCA (n = 33) and healthy controls (n = 30) matched at baseline for race, sex, Tanner stage, height, and weight completed three consecutive annual fitness assessments (VO2peak ). Data were compared between the groups at each time point and within groups over time. Change in VO2peak between the two groups over time was assessed using a linear mixed model with age, sex, fat-free mass (FFM), Tanner stage, and hemoglobin (Hgb) concentration as covariates.

RESULTS

At baseline, children with SCA had significantly lower Hgb concentration (8.9 vs. 13.7 g/dL, P < 0.001) and relative VO2peak (24.2 vs. 27.9 ml/kg/min, P = 0.006) than healthy controls. Over time, children with SCA had smaller increases than healthy controls in VO2peak (-0.1 and +4.9 ml/kg/min, P < 0.001), Tanner stage at year 2 (15% and 66% Tanner 4, P < 0.001), and FFM (+4.0 and +6.8 kg, P = 0.02). Changes in Hgb concentration did not differ between groups (+0.03 and +0.09 g/dL, P = 1.0). After adjusting for age, sex, Tanner stage, FFM, and Hgb concentration the differences in change in VO2peak over time remained significant (P < 0.001).

CONCLUSION

Children with SCA demonstrate lower relative VO2peak compared to healthy children and the difference increases over time. The difference in VO2peak trajectories between the two groups during puberty remains significant after adjusting for age, sex, FFM, Tanner stage, and Hgb concentration.

Health-related fitness profiles in adolescents with complex congenital heart disease

PURPOSE

This study investigates whether subgroups of different health-related fitness (HrF) profiles exist among girls and boys with complex congenital heart disease (ConHD) and how these are associated with lifestyle behaviors.

METHODS

We measured the cardiorespiratory fitness, muscle strength, and body composition of 158 adolescents aged 13-16 years with previous surgery for a complex ConHD. Data on lifestyle behaviors were collected concomitantly between October 2010 and April 2013. A cluster analysis was conducted to identify profiles with similar HrF. For comparisons between clusters, multivariate analyses of covariance were used to test the differences in lifestyle behaviors.

RESULTS

Three distinct profiles were formed: (1) Robust (43, 27%; 20 girls and 23 boys); (2) Moderately Robust (85, 54%; 37 girls and 48 boys); and (3) Less robust (30, 19%; 9 girls and 21 boys). The participants in the Robust clusters reported leading a physically active lifestyle and participants in the Less robust cluster reported leading a sedentary lifestyle. Diagnoses were evenly distributed between clusters.

CONCLUSIONS

The cluster analysis attributed some of the variability in cardiorespiratory fitness among adolescents with complex ConHD to lifestyle behaviors and physical activity. Profiling of HrF offers a valuable new option in the management of person-centered health promotion.

Cardiorespiratory fitness in children: a simple screening test for population studies

Cardiorespiratory fitness is one measure of body functions, and its assessment should play an important role in the activities associated with the promotion of physical activity as an important component of a healthy lifestyle. This study aimed to develop a reference system of the mean post-exercise heart rate (HRmean post-ex) after a 3-min step test for use in screening the cardiorespiratory fitness of 6- to 12-year-old children. The study included 14,501 children ages 6-12 years from primary schools in Gdansk. The participants were subjected to the 3-min Kasch Pulse Recovery Test (KPR Test). The reference range for the classification of cardiorespiratory fitness was developed on the basis of the age-specific percentile distribution of HRmean post-ex in 6- to 9- and 10- to 12-year-old children. This study showed that the 3-min KPR Test is easy to perform and well tolerated by school-age children. As such, it can constitute a useful tool for health promoters and educators. The presented age- and gender-specific reference range of HRmean post-ex enables the assessment and monitoring of submaximal exercise-induced changes in the cardiovascular system and, consequently, the physical fitness of a given individual.

Fitness level and body composition indices: cross-sectional study among Malaysian adolescent

BACKGROUND

The importance of fitness level on the well-being of children and adolescent has long been recognised. The aim of this study was to investigate the fitness level of school-going Malaysian adolescent, and its association with body composition indices.

METHODS

1071 healthy secondary school students participated in the fitness assessment for the Malaysian Health and Adolescents Longitudinal Research Team (MyHEART) study. Body composition indices such as body mass index for age, waist circumference and waist height ratio were measured. Fitness level was assessed with Modified Harvard Step Test. Physical Fitness Score was calculated using total time of step test exercise and resting heart rates. Fitness levels were divided into 3 categories - unacceptable, marginally acceptable, and acceptable. Partial correlation analysis was used to determine the association between fitness score and body composition, by controlling age, gender, locality, ethnicity, smoking status and sexual maturation. Multiple regression analysis was conducted to determine which body composition was the strongest predictor for fitness.

RESULTS

43.3% of the participants were categorised into the unacceptable fitness group, 47.1% were considered marginally acceptable, and 9.6% were acceptable. There was a significant moderate inverse association (p < 0.001) between body composition with fitness score (r = -0.360, -0.413 and -0.403 for body mass index for age, waist circumference and waist height ratio, respectively). Waist circumference was the strongest and significant predictor for fitness (ß = -0.318, p = 0.002).

CONCLUSION

Only 9.6% of the students were fit. There was also an inverse association between body composition and fitness score among apparently healthy adolescents, with waist circumference indicated as the strongest predictor. The low fitness level among the Malaysian adolescent should necessitate the value of healthy lifestyle starting at a young age.

Cardiorespiratory fitness, respiratory function and hemodynamic responses to maximal cycle ergometer exercise test in girls and boys aged 9-11 years: the PANIC Study

PURPOSE

We aimed to provide comprehensive data on and reference values for cardiorespiratory fitness, respiratory function and hemodynamic responses during and after maximal cycle ergometer test in children.

METHODS

The participants were a population sample of 140 children (69 girls) aged 9-11 years. Heart rate (HR) and systolic blood pressure (SBP) were measured from pre-exercise rest to the end of recovery. Respiratory gases were measured directly by the breath-by-breath method. Peak workload, HR changes, peak oxygen uptake (VO2), peak oxygen pulse (O2 pulse), peak respiratory exchange ratio (RER) and the lowest ratio of ventilation and carbon dioxide output (VE/VCO2) during the exercise test in girls and boys were presented according to their distributions in 5 categories.

RESULTS

HR decreased more during 4-min recovery in boys than in girls (76 vs. 67 beats/min, p < 0.001), whereas SBP decrease was similar in boys and girls (30 vs. 22 mmHg, p = 0.66). Boys had a higher peak VO2 per weight [51.9 vs. 47.6 ml/kg/min, p < 0.001] and per lean mass [67.3 vs. 63.0 ml/kg/min, p < 0.001] than girls. Peak O2 pulse per lean mass was higher in boys than in girls (0.34 vs. 0.31 ml/kg/beat, p < 0.001). There was no difference in the lowest VE/VCO2 during the test between boys and girls (28 vs. 29, p = 0.18).

CONCLUSIONS

The indicators of cardiorespiratory fitness were better in boys than in girls. These data enable the evaluation of cardiorespiratory function during and after maximal exercise test and the detection of children with abnormal values.

Obesity and its impact on the respiratory system

Obesity has complex and incompletely understood effects upon the respiratory system in childhood, which differs in some aspects to those seen in adults. There is increasing evidence that excess adiposity will impact negatively upon static and dynamic respiratory function as measured through lung volumes, lung compartment mechanics, measures of airway function and exercise capability to varying degrees. Further information is needed to better understand the effects in children, and the importance of onset and duration of obesity on subsequent outcomes. Consensus about how best to express adiposity is also an essential part of this process and fat distribution is another important factor. From a clinical standpoint this creates challenges in distinguishing a deconditioned obese young person from a non-atopic asthmatic because of symptom overlap and lung function testing results, including responses seen during airway challenges. There is evidence to support the role of weight loss in achieving normalisation of lung function parameters, but as always with obesity there are enormous challenges in realising this goal for many subjects.

Effects of obstructive sleep apnea and obesity on exercise function in children

STUDY OBJECTIVES

Evaluate the relative contributions of weight status and obstructive sleep apnea (OSA) to cardiopulmonary exercise responses in children.

DESIGN

Prospective, cross-sectional study. Participants underwent anthropometric measurements, overnight polysomnography, spirometry, cardiopulmonary exercise function testing on a cycle ergometer, and cardiac doppler imaging. OSA was defined as ≥ 1 obstructive apnea or hypopnea per hour of sleep (OAHI). The effect of OSA on exercise function was evaluated after the parameters were corrected for body mass index (BMI) z-scores. Similarly, the effect of obesity on exercise function was examined when the variables were adjusted for OAHI.

SETTING

Tertiary pediatric hospital.

PARTICIPANTS

Healthy weight and obese children, aged 7-12 y.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Seventy-one children were studied. In comparison with weight-matched children without OSA, children with OSA had a lower cardiac output, stroke volume index, heart rate, and oxygen consumption (VO2 peak) at peak exercise capacity. After adjusting for BMI z-score, children with OSA had 1.5 L/min (95% confidence interval -2.3 to -0.6 L/min; P = 0.001) lower cardiac output at peak exercise capacity, but minute ventilation and ventilatory responses to exercise were not affected. Obesity was only associated with physical deconditioning. Cardiac dysfunction was associated with the frequency of respiratory-related arousals, the severity of hypoxia, and heart rate during sleep.

CONCLUSIONS

Children with OSA are exercise limited due to a reduced cardiac output and VO2 peak at peak exercise capacity, independent of their weight status. Comorbid OSA can further decrease exercise performance in obese children.

Insomnia symptoms and cardiorespiratory fitness in healthy individuals: the Nord-Trøndelag Health Study (HUNT)

STUDY OBJECTIVES

Previous studies have found an inverse association between insomnia and self-reported physical activity, but it is not clear whether insomnia is associated with cardiorespiratory fitness. Our aim was to investigate different insomnia symptoms in relation to the gold standard measure of cardiorespiratory fitness, i.e., peak oxygen uptake (VO(2peak)).

DESIGN

Cross-sectional population study.

SETTING

Nord-Trøndelag County, Norway.

PARTICIPANTS

The group comprised 3,489 men and women who were free from cardiovascular or pulmonary diseases, cancer, and sarcoidosis and who did not use antihypertensive medication. They were included in the fully adjusted model when assessing all insomnia symptoms simultaneously.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

For insomnia, the participants reported how often they had experienced sleep problems during the past 3 months, including difficulties falling asleep at night, repeated awakenings during the night, early awakenings without being able to go back to sleep, and daytime sleepiness. Response options were "never/almost never," "sometimes" or "several times a wk." To measure cardiorespiratory fitness, the participants were asked to walk or run on a treadmill with increasing speed and/or incline until exhaustion, and VO(2peak) was recorded. We found a modest inverse and graded association of the insomnia symptoms with VO(2peak). The association was independent of self-reported physical activity and was apparent for all insomnia symptoms except for early awakenings. We found a dose-response relation for a cumulative combination of insomnia symptoms and VO(2peak) for experiencing zero, one to two, or three to four symptoms (P for trend < 0.001).

CONCLUSIONS

We found a modest inverse association of insomnia with VO(2peak) independent of the conventional cardiovascular risk factors and self-reported physical activity.

Sex differences in response to maximal exercise stress test in trained adolescents

Background

Sex comparisons between girls and boys in response to exercise in trained adolescents are missing and we investigated similarities and differences as a basis for clinical interpretation and guidance.

Methods

A total of 24 adolescent females and 27 adolescent males aged 13–19 years underwent a maximal bicycle exercise stress test with measurement of cardiovascular variables, cardiac output, lung volumes, metabolic factors/lactate concentrations and breath-by-breath monitoring of ventilation, and determination of peak VO₂.

Results

Maximum heart rate was similar in females (191 ± 9 bpm) and males (194 ± 7 bpm), cardiac index at maximum exercise was lower in females (7.0 ± 1.0 l/min/m²) than in males (8.3 ± 1.4 l/min/m², P < 0.05). Metabolic responses and RQ at maximum exercise were similar (females: 1.04 ± 0.06 vs. males: 1.05 ± 0.05). Peak VO₂ was lower in females (2.37 ± 0.34 l/min) than in males (3.38 ± 0.49 l/min, P < 0.05). When peak VO₂ was normalized to leg muscle mass sex differences disappeared (females: 161 ± 21 ml/min/kg vs. males: 170 ± 23 ml/min/kg). The increase in cardiac index during exercise is the key factor responsible for the greater peak VO₂ in adolescent boys compared to girls.

Conclusions

Differences in peak VO₂ in adolescent boys and girls disappear when peak VO₂ is normalized to estimated leg muscle mass and therefore provide a tool to conduct individual and intersex comparisons of fitness when evaluating adolescent athletes in aerobic sports.

Cardiopulmonary assessment in primary ciliary dyskinesia

BACKGROUND

Primary ciliary dyskinesia (PCD) is a rare, usually autosomal recessive disorder of ciliary dysfunction associated with lung involvement, which has a great impact on health. There is limited information concerning the aerobic fitness of children and adolescents with PCD. The aim of this study was to assess cardiopulmonary functional capacity and its relationship with pulmonary function and physical activity (PA) levels in patients with PCD.

DESIGN

Ten patients with PCD (age 13·2 ± 2·8 years) underwent spirometry and cardiopulmonary exercise testing. PA was investigated through a questionnaire. Eight age- and body mass index-matched healthy children were enrolled as controls. Main variables were forced expiratory volume at 1 s, peak oxygen uptake (VO(2peak) ) and time spent in PA.

RESULTS

Forty per cent of patients with PCD had impaired lung function as expressed by FEV(1) < 85% predicted. Only patients with impaired lung function exhibited reduced VO(2peak) (18·1 ± 7·9 mL/kg/min). Time spent in total daily PA was slightly lower in patients than controls, with no difference between patients with normal or reduced lung function. In multiple regression models, male gender (β = 0·518, P = 0·018), age (β = 0·752, P = 0·035) and time spent in vigorous PA (β = 0·353, P = 0·049) were independent predictors of aerobic fitness.

CONCLUSIONS

Assessment of resting pulmonary function and cardiopulmonary functional capacity could contribute to the evaluation of pulmonary impairment in PCD. Given the benefit of physical exercise on airway clearance and on general health and quality of life, patients with PCD should be encouraged to adopt an active lifestyle.

Lower cardiorespiratory fitness in children with Type 1 diabetes

AIMS

The present study aimed to compare cardiorespiratory fitness levels in children with and without Type 1 diabetes. In addition, the relationship between cardiorespiratory fitness and a range of physical and clinical factors was investigated.

METHODS

Eighty-eight children with Type 1 diabetes aged 5-14 years completed a submaximal step test of cardiorespiratory fitness. Sixty-two of these children were successfully matched to control subjects without diabetes based on age, sex and anthropometrics for comparison. In addition, the relationship between cardiorespiratory fitness and a range of physical and clinical variables was assessed in the children with diabetes.

RESULTS

The heart rate response to exercise was higher in children with Type 1 diabetes, indicating reduced cardiorespiratory fitness levels compared with control subjects. Both gender and glycaemic control (HbA(1c) ) were significantly associated with cardiorespiratory fitness, with female sex and poorer glycaemic control associated with reduced fitness.

CONCLUSIONS

Future research should investigate whether the reduced fitness in children with Type 1 diabetes is attributable to lower physical activity levels, or physiological changes resulting from the diabetes pathology itself.

Myocardial function and aerobic fitness in adolescent females

A recent report indicated that variations in myocardial functional (systolic and diastolic) responses to exercise do not contribute to inter-individual differences in aerobic fitness (peak VO(2)) among young males. This study was designed to investigate the same question among adolescent females. Thirteen highly fit adolescent football (soccer) players (peak VO(2) 43.5 ± 3.4 ml kg(-1) min(-1)) and nine untrained girls (peak VO(2) 36.0 ± 5.1 ml kg(-1) min(-1)) matched for age underwent a progressive cycle exercise test to exhaustion. Cardiac variables were measured by standard echocardiographic techniques. Maximal stroke index was greater in the high-fit group (50 ± 5 vs. 41 ± 4 ml m(-2)), but no significant group differences were observed in maximal heart rate or arterial venous oxygen difference. Increases in markers of both systolic (ejection rate, tissue Doppler S') and diastolic (tissue Doppler E', mitral E velocity) myocardial functions at rest and during the acute bout of exercise were similar in the two groups. This study suggests that among healthy adolescent females, like young males, myocardial systolic and diastolic functional capacities do not contribute to inter-individual variability in physiologic aerobic fitness.

Objectively assessed physical activity and aerobic fitness in a population-based sample of Norwegian 9- and 15-year-olds

The present study described current physical activity, determined compliance with physical activity guidelines and assessed aerobic fitness in a nationally representative sample of 9- and 15-year-olds in Norway. In 2005-2006, 2299 children and adolescents were randomly recruited. The participation rate was 89% and 74% among the 9- and 15-year-olds, respectively. Physical activity was assessed objectively by accelerometry, and aerobic fitness was measured directly as peak oxygen uptake during a cycle ergometry test. Boys were more physically active than girls, and 9-year-olds were substantially more active than 15-year-olds. Physical activity was higher during weekdays than weekends, and 9-year-olds were most active during spring. While four out of five children met current physical activity guidelines, only half of the adolescents did. The mean (SD) values for peak VO2 were: 9-year-old boys, 48.2 (7.1) mL/min/kg; 9-year-old girls, 42.9 (6.7) mL/min/kg; and 15-year-old girls 41.1 (6.0) mL/min/kg and 15-year-old boys 51.9 (8.0) mL/min/kg. Because of the high participation rate, this study provides a good description of the physical activity and aerobic fitness in the young population. Finally, girls and adolescents seem appropriate targets when promoting physical activity in order to increase the proportion meeting the recommendations.

Sex difference in peak oxygen uptake in prepubertal children

Prepubertal boys' greater aerobic fitness (peak V O(2)) has been attributed to their larger lean body mass (LBM); this bestowing a greater heart size and consequent larger maximum cardiac output. No difference in peak arterio-venous (A-VO(2)) difference is thought to exist. However other work indicates that boys' aerobic fitness remains 5% higher even after controlling for differences in LBM. Consequently the purpose of this study was to investigate whether peak V O(2), heart size, peak cardiac output and peak A-VO(2) difference would be comparable between a group of boys and girls with a similar LBM. A group of 9 prepubertal boys and 9 prepubertal girls with a similar mean LBM (27.0+/-1.4 boys vs. 27.0+/-2.0 kg girls) were selected. Left ventricular mass (LVM) and end diastolic volume (LVEDV) were measured using cardiac magnetic resonance imaging. Peak V O(2) was determined on a cycle ergometer following an incremental exercise protocol to exhaustion, and cardiac output was recorded using thoracic bioimpedance. Boys' peak V O(2) (1.41+/-0.18 L min(-1) vs. 1.23+/-0.08 L min(-1)) and A-VO(2) difference (14.8+/-2.1 mL 100mL(-1) vs. 12.6+/-1.6 mL 100mL(-1)) were significantly (p<0.05) higher than girls' values, but there were no significant sex differences in peak cardiac output (10.0+/-1.4 L min(-1) vs. 9.9+/-1.40 L min(-1)), LVM (97+/-13g vs. 93+/-20g) or LVEDV (77+/-8 mL vs. 70+/-13 mL). Central factors of heart size and peak cardiac output are proportional to the LBM of the individual and sex independent. Sex differences in peripheral factors such as muscle fibre type profile, may affect A-VO(2) difference and underlie prepubertal boys' higher peak V O(2).

Perfil lipídico, de aptidão cardiorrespiratória, e de composição corporal de uma amostra de dscolares de 8ª série de Canoas/RS

Atualmente as doenças cardiovasculares (DC) são as principais causas de morte no mundo, sendo compostas por uma série de fatores de risco que parecem ter sua origem durante os anos da infância e adolescência. Desta forma, diagnósticos precoces dos fatores de risco para DC devem ser realizados com freqüência já na população jovem. Frente a este quadro, o objetivo deste estudo foi descrever o perfil lipídico (PL), de aptidão cardiorrespiratória (ApC), e de composição corporal (CC) de escolares de 13-14 anos, e comparar cada uma das variáveis entre os sexos. Para tanto, foi selecionada de forma não aleatória voluntária uma amostra de 41 escolares (21 meninos e 20 meninas) da 8ª série de uma escola privada de Canoas/RS. O perfil lípidico (triglicerídeos-TRI, colesterol total-CT, HDL e LDL) dos escolares procedeu-se através da técnica padrão em um laboratório de análises clínicas. A ApC foi avaliada a partir do teste de corrida/caminhada de 9 minutos (PROESP-BR, 2002). A CC foi determinada pelo IMC e pelo somatório de dobras cutâneas tricipital e subescapular (S D.C.). Para a análise dos dados foi utilizada a estatística descritiva, sendo que para a análise por critérios foram utilizados os critérios sugeridos pelo AHA (NHI PARENT’S GUIDE, 1993), para o PL, e para ApC e CC foram utilizados os critérios sugeridos pelo PROESP-BR (2002). Os resultados apontaram que em termos de análise de tendência central, o PL, a ApC e a CC demonstraram resultados considerados normais. Todavia, quando a análise foi feita a partir dos critérios, foram detectados alguns casos fora da faixa considerada normal para os níveis lipídicos (TRI-4,9%, CT-12,2%, HDL-36,6% e LDL-4,9%), e uma ocorrência bastante elevada fora da faixa recomendada para a ApC (61%) e para a CC (IMC-17,1% e S D.C.-48,8%). Os resultados demonstram ainda haver diferenças entre os sexos nos valores médios de ApC e IMC, a favor dos meninos, e na S D.C. e HDL a favor das meninas. Com relação às distribuições nas faixas recomendadas para cada variável, não houve associações com os sexos. Os resultados obtidos são preocupantes, e demonstram, mesmo em uma amostra pequena, a existência de todos os fatores de risco analisados para DC nos escolares.

State of the Art Reviews: Development of Fitness in Children: The Influence of Gender and Physical Activity

The influences of gender and physical activity on the development of fitness are reviewed from early childhood to late adolescence. Changes in parameters of fitness prior to puberty are driven predominantly by neuroendocrine-mediated factors, although physical activity level may be influenced largely by sociocultural factors prior to and following puberty. Thus, it is still unclear to what extent environment versus genetics accounts for gender differences in fitness. Future studies need to account for all factors known to explain gender differences in fitness to better differentiate intrinsic versus environmental causes. Consequently, one must consider if and to what extent a gender comparison study actually reveals true, inherent gender differences compared with sociocultural and/or cultural influences. Nevertheless, differences in fitness between girls and boys that are influenced by sociocultural factors should be considered when devising programs to promote physical activity and enhance fitness in youth. Fundamentally, the role of parents and primary caregivers in modeling physical activity and influencing the fitness level of their child cannot be overestimated.

Aptidão cardiorrespiratória de adolescentes de Florianópolis, SC

Níveis adequados de aptidão cardiorrespiratória durante a adolescência estão diretamente relacionados a um estilo de vida saudável na fase adulta. Este estudo objetivou identificar o comportamento da aptidão cardiorrespiratória durante a adolescência e descrever a prevalência de adolescentes que atenderam e não atenderam o critério recomendado para a saúde por sexo, idade e nível socioeconômico (NSE). A amostra foi composta de 963 adolescentes (513 moças e 450 rapazes), com idades de 10 a 15 anos. Na coleta de dados, foi aplicado um questionário para obtenção do NSE (A + B, C, D + E). Para análise da aptidão cardiorrespiratória, foi realizado o teste PACER (Progressive Aerobic Cardiovascular Endurance Run). Consideraram-se como parâmetros de desempenho cardiorrespiratório o número de voltas realizadas e o consumo máximo de oxigênio - VO2max (ml/kg/min). Na análise estatística, foram utilizadas médias e desvios padrões, análise de variância two-way com teste post-hoc de Tukey, e teste qui-quadrado (p < 0,05). Enquanto o número de voltas aumentou dos 10 aos 15 anos, o VO2max diminuiu, não havendo diferenças entre os sexos. Os escolares dos NSE menos favorecidos (D + E) obtiveram menor aptidão do que os demais. Identificou-se que 68% dos rapazes e 37,8% das moças não atingiram o mínimo proposto para a saúde. Verificou-se uma maior proporção de adolescentes dos NSE D + E que não atendeu o critério recomendado. Estes achados demonstram que, aproximadamente, dois terços dos rapazes e um terço das moças apresentaram baixa aptidão cardiorrespiratória. Os adolescentes de NSE menos favorecidos foram os que apresentaram menores níveis de aptidão cardiorrespiratória.

Do racehorses and Greyhound dogs exhibit a gender difference in running speed?

At any level of competition, men run faster than women. Consequently, a male speed advantage is often presumed for other species. This assumption was tested in two animals bred for speed: horses and dogs. Results from Thoroughbred (TB), Standardbred (STB) and Greyhound (GH) races were analysed by ANOVA to compare the speeds of victorious males, neutered males (TB and STB only) and females. Separate analyses were run for shorter (TB: ≤ 1609 m, GH: 503 m) and longer (TB: >1609 m, GH: 603.5 m) TB and GH races. All STB races (trotters and pacers) were 1609 m. In TB races, intact males were 0.7% faster than females at ≤ 1609 m (n = 305; P < 0.01) and 1.4% faster at >1609 m (n = 194; P < 0.01). The speed of neutered males was equivalent to that of females at both distances. Gender accounted for 3.8 and 10.7% of the variance in speed at short and long distances, respectively. In STB pacers, intact males were 1.5% faster than females and gender accounted for 10.1% of the variance in speed (n = 96; P < 0.01). Gender was not a significant predictor of STB trotter (n = 95) or GH speed at 503 m (n = 146) or 603.5 m (n = 23). In conclusion, gender has a significant effect on speed of TBs and STB pacers. Although the effect size is small, it may be significant for racing; in a 7 furlong (1408 m) TB race, the 0.7% difference translates to an advantage of several lengths.