Alanine aminotransferase cutoffs for the pediatric fatty liver disease: Major impact of the reference population

OBJECTIVES AND STUDY

The often-recommended alanine aminotransferase (ALT) cutoffs (girls 21 U/l, boys 25 U/l) are based on a NHANES cohort. A novel concept of metabolic dysfunction associated steatotic liver disease (MASLD) emphasizes the role of ALT. We tested the prevalence of increased ALT and MASLD in children with overweight or obesity applying population-based and NHANES-based cut-offs.

METHODS

Six- to seventeen-year-old children underwent data collection in a prospective Physical Activity and Nutrition in Children (PANIC) study. ALT 95th percentiles were calculated from 1167 separate measurements considering various confounders. Test cohort comprised 1044 children with overweight/obesity.

RESULTS

ALT values increased at puberty onset (p = 0.031) and correlated negatively with age in girls (r = -0.222, p < 0.001). Particularly overall and central obesity increased ALT, whereas underweight or metabolic abnormalities had smaller effect. After applying the tested exclusions, the age-related ALT 95th percentiles were 24-29 U/l for girls and 29-32 U/l for boys. In 6-8-year-old children with overweight/obesity, the prevalence of increased ALT and MASLD were 21.6% and 2.4% with age-specific PANIC cutoffs. In older children, when NHANES-based cutoffs were used, there was a trend for higher prevalence of increased ALT and MASLD in all age groups for both sexes, reaching significance for increased ALT in 12-16-year-old boys (NHANES 63.5%, 95% confidence interval [CI]: 56.4%-70.0% vs. PANIC 47.1%, 95% CI [40.1%-54.2%]) and 9-11-year-old girls (60.0% [49.4%-69.8%] vs. 31.8% [22.8%-42.3%]), respectively. Increased ALT/MASLD were more common in boys than in girls, and in boys these increased with age, whereas in girls these peaked at age 9-12 years.

CONCLUSION

A reference population impacts on the prevalence of increased ALT and MASLD. Considering this help optimizing screening while avoiding unnecessary investigations and surveillance. The prospective part of this study is registered in clinicaltrials.gov; identifier NCT01803776.

Cross-sectional and longitudinal associations between the 24-hour movement behaviours, including muscle and bone strengthening activity, with bone and lean mass from childhood to adolescence

BACKGROUND

This study aimed to assess whether moderate-to-vigorous physical activity (MVPA), sport and exercise as a proxy measure of muscle and bone strengthening activity, sedentary behaviour, and sleep were associated with total-body-less-head (TBLH) bone mineral content (BMC) and TBLH lean mass cross-sectionally and longitudinally from age 6 to 9 years and age 9 to 11 years to age 15 to 17 years.

METHODS

We used longitudinal data from a population sample of Finnish children from the Physical Activity and Nutrition in Children study (age 6 to 9 years: n = 478, 229 females; age 9 to 11 years: n = 384, 197 females; age 15 to 17 years: n = 222, 103 females). Linear regression analysed the cross-sectional and longitudinal associations between accelerometer-assessed MVPA, sedentary time and sleep, and questionnaire-assessed sport and exercise participation and screen time with dual-energy X-ray absorptiometry-assessed TBLH BMC and lean mass.

RESULTS

In females, MVPA at age 6 to 9 years was positively associated with TBLH BMC at age 15 to 17 years (β = 0.008, p = 0.010). Sport and exercise at age 9 to 11 years was positively associated with TBLH BMC (β = 0.020, p = 0.002) and lean mass (β = 0.343, p = 0.040) at age 15 to 17 years. MVPA at age 9 to 11 years was positively associated with TBLH lean mass (β = 0.272, p = 0.004) at age 15 to 17 years. In males, sleep at age 6 to 9 years was positively associated with TBLH lean mass (β = 0.382, p = 0.003) at age 15 to 17 years. Sport and exercise at age 9 to 11 years was positively associated with TBLH BMC (β = 0.027, p = 0.012) and lean mass (β = 0.721, p < 0.001) at age 15 to 17 years.

CONCLUSIONS

Promoting engagement in the 24-hour movement behaviours in childhood, particularly sport and exercise to strengthen muscle and bone, is important in supporting bone and lean mass development in adolescence.

TRIAL REGISTRATION

NCT01803776; first trial registration date: 04/03/2013.

Physical activity volume and intensity distribution in relation to bone, lean and fat mass in children

Considering physical activity (PA) volume and intensity may provide novel insights into the relationships of PA with bone, lean, and fat mass. This study aimed to assess the associations of PA volume, PA intensity distribution, including moderate-to-vigorous PA (MVPA) with total-body-less-head bone mineral content (BMC), lean, and fat mass in children. A population sample of 290 Finnish children (158 females) aged 9-11 years from the Physical Activity and Nutrition in Children (PANIC) Study was studied. PA, including MVPA, was assessed with a combined heart rate and movement sensor, and the uniaxial acceleration was used to calculate average-acceleration (a proxy metric for PA volume) and intensity-gradient (reflective of PA intensity distribution). Linear regression analyzed the associations of PA volume, PA intensity and MVPA with BMC, lean mass, and fat mass assessed by dual-energy X-ray absorptiometry. PA volume was positively associated with BMC in females (unstandardised regression coefficient [ß] = 0.26) and males (ß = 0.47), and positively associated with lean (ß = 7.33) and negatively associated with fat mass in males (ß = -20.62). PA intensity was negatively associated with BMC in males (ß = -0.13). MVPA was positively associated with lean mass in females and males (ß = 0.007 to 0.012), and negatively associated with fat mass in females and males (ß = -0.030 to -0.029). PA volume may be important for improving BMC in females and males, and increasing lean and reducing fat mass in males, whereas MVPA may be important for favorable lean and fat outcomes in both sexes.

Sources of vitamin D and determinants of serum 25-hydroxyvitamin D in Finnish adolescents

PURPOSE

To study the intake and sources of vitamin D and determinants of serum 25-hydroxyvitamin D (S-25(OH)D) in Finnish adolescents.

METHODS

We studied 265 adolescents (117 girls) aged 15-17 years attending 8-year examinations of the PANIC Study, assessed diet using food records and other lifestyle factors by questionnaires, and analyzed S-25(OH)D by chemiluminescence immunoassay and determinants of S-25(OH)D using multivariate linear regression.

RESULTS

Mean (standard deviation) of total vitamin D intake from food and supplements was 19.2 (13.1) µg/d, and that of dietary vitamin D intake was 9.9 (5.4) µg/d. Milk fortified with vitamin D was the main dietary source of vitamin D, providing 45% of daily intake. Altogether, 29% of the adolescents used no vitamin D supplements and 25% did not meet the recommended total vitamin D intake of 10 µg/d. Mean (standard deviation) of S-25(OH)D was 62.0 (18.8) nmol/l, and S-25(OH)D was < 50 nmol/l in 29.5% of the adolescents. Vitamin D intake from supplements was the main determinant of S-25(OH)D (β = 0.465, p < 0.001), followed by consumption of milk products (β = 0.251, p < 0.001), consumption of meat products (β = 0.179, p = 0.002), travels to sunny countries (β = 0.178, p = 0.002), and average daylight time (β = 0.162, p = 0.004).

CONCLUSION

Most of the adolescents had vitamin D intake at the recommended level, although a fourth did not meet the recommended total vitamin D intake of 10 µg/d and almost a third had S-25(OH)D < 50 nmol/l. More attention should be paid to the sufficient intake of vitamin D in adolescents who do not use vitamin D supplements or fortified milk products.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01803776, registered March 3, 2013.

The Mediating Role of Endocrine Factors in the Positive Relationship Between Fat Mass and Bone Mineral Content in Children Aged 9-11 Years: The Physical Activity and Nutrition in Children Study

INTRODUCTION

We aimed to investigate whether the relationship between fat mass and bone mineral content (BMC) is mediated by insulin, leptin, adiponectin, dehydroepiandrosterone sulphate, testosterone and estradiol in children aged 9-11 years.

MATERIALS AND METHODS

We utilised cross-sectional data from the Physical Activity and Nutrition in Children study (n = 230 to 396; 112 to 203 girls). Fat mass and BMC were assessed with dual-energy X-ray absorptiometry. Endocrine factors were assessed from fasted blood samples. We applied the novel 4-way decomposition method to analyse associations between fat mass, endocrine factors, and BMC.

RESULTS

Fat mass was positively associated with BMC in girls (ß = 0.007 to 0.015, 95% confidence interval (CI) 0.005 to 0.020) and boys (ß = 0.009 to 0.015, 95% CI 0.005 to 0.019). The relationship between fat mass and BMC was mediated by free leptin index in girls (ß = -0.025, 95% CI -0.039 to -0.010) and boys (ß = -0.014, 95% CI -0.027 to -0.001). The relationship between fat mass and BMC was partially explained by mediated interaction between fat mass and free leptin index in boys (ß = -0.009, 95% CI -0.013 to -0.004) and by interaction between fat mass and adiponectin in girls (ß = -0.003, 95% CI -0.006 to -0.000).

CONCLUSION

At greater levels of adiponectin and free leptin index, the fat mass and BMC relationship becomes less positive in girls and boys respectively. The positive association between fat mass with BMC was largely not explained by the endocrine factors we assessed.

CLINICAL TRIAL REGISTRATION

[https://clinicaltrials.gov/ct2/show/NCT01803776], identifier NCT01803776.

The independent and interactive associations of physical activity intensity and vitamin D status with bone mineral density in prepubertal children: the PANIC Study

It is unclear how physical activity intensity and vitamin D status are related to bone health in prepubertal children. We found positive associations between vitamin D status and moderate-to-vigorous physical activity with bone in boys and girls. This highlights the importance of lifestyle factors for skeletal health prepuberty.

INTRODUCTION

The sex-specific independent and interactive associations of physical activity (PA) intensity and serum 25-hydroxyvitamin D (25(OH)D) levels with areal bone mineral density (aBMD) were investigated in prepubertal children.

METHODS

The participants were 366 prepubertal Finnish children (190 boys, 176 girls) aged 6-8 years. Linear regression analysed the associations of sedentary time (ST), light PA (LPA), moderate PA (MPA), moderate-to-vigorous PA (MVPA) and vigorous PA (VPA) measured by accelerometery, and serum 25(OH)D with total body less head (TBLH) and lower-limb aBMD, measured by dual-energy X-ray absorptiometry.

RESULTS

There was no interaction between PA intensity or serum 25(OH)D and sex with aBMD. MPA and MVPA were positively associated with TBLH and lower-limb aBMD (β = 0.11, 95% CI 0.02-0.20, p = 0.01). Serum 25(OH)D was positively associated with TBLH and lower-limb aBMD (β = 0.09, 95% CI 0.01-0.18, p = 0.03). There were no interactions between PA intensity and serum 25(OH)D with aBMD.

CONCLUSION

Vitamin D status, MPA and MVPA levels in active prepubertal children were positively associated with aBMD. The influence of MVPA is due to the MPA component, though our findings regarding the role of VPA should be interpreted with caution, as shorter accelerometer epochs are needed to more accurately assess VPA. This study adds evidence to the promotion of MPA and behaviours to encourage optimal vitamin D status in supporting skeletal health in childhood, though these need not be used in conjunction to be beneficial, and a sex-specific approach is not necessary in prepubertal children.

TRIAL REGISTRATION NUMBER

NCT01803776 . Date of registration: 4/03/2013.

A 2 year physical activity and dietary intervention attenuates the increase in insulin resistance in a general population of children: the PANIC study

AIMS/HYPOTHESIS

We studied for the first time the long-term effects of a combined physical activity and dietary intervention on insulin resistance and fasting plasma glucose in a general population of predominantly normal-weight children.

METHODS

We carried out a 2 year non-randomised controlled trial in a population sample of 504 children aged 6-9 years at baseline. The children were allocated to a combined physical activity and dietary intervention group (306 children at baseline, 261 children at 2-year follow-up) or a control group (198 children, 177 children) without blinding. We measured fasting insulin and fasting glucose, calculated HOMA-IR, assessed physical activity and sedentary time by combined heart rate and body movement monitoring, assessed dietary factors by a 4 day food record, used the Finnish Children Healthy Eating Index (FCHEI) as a measure of overall diet quality, and measured body fat percentage (BF%) and lean body mass by dual-energy x-ray absorptiometry. The intervention effects on insulin, glucose and HOMA-IR were analysed using the intention-to-treat principle and linear mixed-effects models after adjustment for sex, age at baseline, and pubertal status at baseline and 2 year follow-up. The measures of physical activity, sedentary time, diet and body composition at baseline and 2 year follow-up were entered one-by-one as covariates into the models to study whether changes in these variables might partly explain the observed intervention effects.

RESULTS

Compared with the control group, fasting insulin increased 4.65 pmol/l less (absolute change +8.96 vs +13.61 pmol/l) and HOMA-IR increased 0.18 units less (+0.31 vs +0.49 units) over 2 years in the combined physical activity and dietary intervention group. The intervention effects on fasting insulin (regression coefficient β for intervention effect -0.33 [95% CI -0.62, -0.04], p = 0.026) and HOMA-IR (β for intervention effect -0.084 [95% CI -0.156, -0.012], p = 0.023) were statistically significant after adjustment for sex, age at baseline, and pubertal status at baseline and 2 year follow-up. The intervention had no effect on fasting glucose, BF% or lean body mass. Changes in total physical activity energy expenditure, light physical activity, moderate-to-vigorous physical activity, total sedentary time, the reported consumption of high-fat (≥60%) vegetable oil-based spreads, and FCHEI, but not a change in BF% or lean body mass, partly explained the intervention effects on fasting insulin and HOMA-IR.

CONCLUSIONS/INTERPRETATION

The combined physical activity and dietary intervention attenuated the increase in insulin resistance over 2 years in a general population of predominantly normal-weight children. This beneficial effect was partly mediated by changes in physical activity, sedentary time and diet but not changes in body composition.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01803776 Graphical abstract.

The effects of a 2-year physical activity and dietary intervention on plasma lipid concentrations in children: the PANIC Study

PURPOSE

We studied the effects of a physical activity and dietary intervention on plasma lipids in a general population of children. We also investigated how lifestyle changes contributed to the intervention effects.

METHODS

We carried out a 2-year controlled, non-randomized lifestyle intervention study among 504 mainly prepubertal children aged 6-9 years at baseline. We assigned 306 children to the intervention group and 198 children to the control group. We assessed plasma concentrations of total, LDL, HDL, and VLDL cholesterol, triglycerides, HDL triglycerides, and VLDL triglycerides. We evaluated the consumption of foods using 4-day food records and physical activity using a movement and heart rate sensor. We analyzed data using linear mixed-effect models adjusted for age at baseline, sex, and pubertal stage at both time points. Furthermore, specific lifestyle variables were entered in these models.

RESULTS

Plasma LDL cholesterol decreased in the intervention group but did not change in the control group ( - 0.05 vs. 0.00 mmol/L, regression coefficient (β) =  - 0.0385, p = 0.040 for group*time interaction). This effect was mainly explained by the changes in the consumption of high-fat vegetable oil-based spreads (β =  - 0.0203, + 47% change in β) and butter-based spreads (β =  - 0.0294, + 30% change in β), moderate-to-vigorous physical activity (β =  - 0.0268, + 30% change in β), light physical activity (β =  - 0.0274, + 29% change in β) and sedentary time (β =  - 0.0270, + 30% change in β). The intervention had no effect on other plasma lipids.

CONCLUSION

Lifestyle intervention resulted a small decrease in plasma LDL cholesterol concentration in children. The effect was explained by changes in quality and quantity of dietary fat and physical activity.

CLINICAL TRIAL REGISTRY NUMBER

NCT01803776, ClinicalTrials.gov.

Longitudinal Associations of Fitness, Motor Competence, and Adiposity with Cognition

PURPOSE

The purpose of this study was to investigate the longitudinal associations of cardiorespiratory fitness (CRF), motor competence (MC), and body fat percentage (BF%) with cognition in children.

METHODS

Altogether, 371 children (188 boys and 183 girls) 6-9 yr of age at baseline participated in this 2-yr follow-up study. We assessed CRF by maximal cycle ergometer test, computed the MC score from the z-scores of the 50-m shuttle run, static balance, and box and block test results, measured BF% by dual-energy x-ray absorptiometry, and assessed cognition using the Raven's Coloured Progressive Matrices (RCPM) score. The associations were studied by linear regression analysis and repeated-measures ANCOVA.

RESULTS

In boys, a higher MC score (β = -0.161, 95% confidence interval [CI] = -0.314 to -0.009), a shorter 50-m shuttle run test duration (β = 0.152, 95% CI = 0.007-0.296), and a higher number of cubes moved in the Box and block test (β = -0.161, 95% CI = -0.309 to -0.013) at baseline were associated with a smaller increase in the RCPM score during follow-up. These associations were largely explained by the RCPM score at baseline. However, boys in the highest third (mean difference = 2.5, 95% CI for difference = 0.66-4.33) and the middle third (mean difference = 2.1, 95% CI for difference = 0.39-3.82) of the MC score at baseline had a higher RCPM score over the 2-yr follow-up than boys in the lowest third. CRF, MC, or adiposity was not associated with the RCPM score in girls. Changes in CRF, MC, or BF% were not associated with changes in cognition.

CONCLUSIONS

Higher MC at baseline predicted better cognition during the first two school years in boys but not in girls. CRF or adiposity was not associated with cognition in boys or girls.

Serum 25-Hydroxyvitamin D, Plasma Lipids, and Associated Gene Variants in Prepubertal Children

CONTEXT

The associations of serum 25-hydroxyvitamin D [25(OH)D] with plasma lipids remain controversial in children.

OBJECTIVE

To examine the associations and interactions of 25(OH)D and related gene variants with lipids in children.

DESIGN

Cross-sectional.

SETTING

Kuopio, Finland.

PARTICIPANTS

Population sample of 419 prepubertal white children aged 6 to 8 years.

MAIN OUTCOME MEASURES

25(OH)D, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides.

RESULTS

Serum 25(OH)D was negatively associated with total cholesterol (β = -0.141, P = 0.004), LDL cholesterol (β = -0.112, P = 0.023), HDL cholesterol (β = -0.150, P = 0.002), and triglycerides (β = -0.104, P = 0.035) adjusted for age and sex. Associations of 25(OH)D with total cholesterol, LDL cholesterol, and HDL cholesterol remained after adjustment for adiposity, physical activity, sedentary behavior, diet, daylight time, and parental education. Children in the highest quartile of 25(OH)D had the lowest total cholesterol (P = 0.022) and LDL cholesterol (P = 0.026) adjusted for age and sex. Cytochrome P450 family 2 subfamily R member 1 (CYP2R1) rs12794714, CYP2R1 rs10741657, and vitamin D binding protein (DBP) rs2282679 were associated with 25(OH)D adjusted for age and sex. CYP2R1 rs12794714 was associated with total cholesterol and LDL cholesterol and C10orf88 rs6599638 with HDL cholesterol adjusted for age, sex, and 25(OH)D. The gene variants did not explain or modify the associations of 25(OH)D with lipids.

CONCLUSIONS

25(OH)D was independently and inversely associated with total cholesterol, LDL cholesterol, and HDL cholesterol. CYP2R1 rs12794714, CYP2R1 rs10741657, and DBP rs2282679 were associated with 25(OH)D. CYP2R1 rs12794714 was associated with total cholesterol and LDL cholesterol and chromosome 10 open reading frame 88 (C10orf88) rs6599638 with HDL cholesterol independent of 25(OH)D. None of the gene variants modified the associations of 25(OH)D with lipids. Further studies are needed to detect the mechanisms for the associations of 25(OH)D with lipids.

Body fat mass, lean body mass and associated biomarkers as determinants of bone mineral density in children 6-8years of age - The Physical Activity and Nutrition in Children (PANIC) study

Lean body mass (LM) has been positively associated with bone mineral density (BMD) in children and adolescents, but the relationship between body fat mass (FM) and BMD remains controversial. Several biomarkers secreted by adipose tissue, skeletal muscle, or bone may affect bone metabolism and BMD. We investigated the associations of LM, FM, and such biomarkers with BMD in children. We studied a population sample of 472 prepubertal Finnish children (227 girls, 245 boys) aged 6-8years. We assessed BMD, LM, and FM using whole-body dual-energy x-ray absorptiometry and analysed several biomarkers from fasting blood samples. We studied the associations of LM, FM, and the biomarkers with BMD of the whole body excluding the head using linear regression analysis. LM (standardized regression coefficient β=0.708, p<0.001), FM (β=0.358, p<0.001), and irisin (β=0.079, p=0.048) were positive correlates for BMD adjusted for age, sex, and height in all children. These associations remained statistically significant after further adjustment for LM or FM. The positive associations of dehydroepiandrosterone sulphate (DHEAS), insulin, homeostatic model assessment for insulin resistance (HOMA-IR), leptin, free leptin index, and high-sensitivity C-reactive protein and the negative association of leptin receptor with BMD were explained by FM. The positive associations of DHEAS and HOMA-IR with BMD were also explained by LM. Serum 25-hydroxyvitamin D was a positive correlate for BMD adjusted for age, sex, and height and after further adjustment for FM but not for LM. LM and FM were positive correlates for BMD also in girls and boys separately. In girls, insulin, HOMA-IR, leptin, and free leptin index were positively and leptin receptor was negatively associated with BMD adjusted for age, height, and LM. After adjustment for age, height, and FM, none of the biomarkers was associated with BMD. In boys, leptin and free leptin index were positively and leptin receptor was negatively associated with BMD adjusted for age, height, and LM. After adjustment for age, height and FM, 25(OH)D was positively and IGF-1 and leptin were negatively associated with BMD. FM strongly modified the association between leptin and BMD. LM but also FM were strong, independent positive correlates for BMD in all children, girls, and boys. Irisin was positively and independently associated with BMD in all children. The associations of other biomarkers with BMD were explained by LM or FM.

Food sources of energy and nutrients in Finnish girls and boys 6-8 years of age - the PANIC study

Background

Data on food sources of nutrients are needed to improve strategies to enhance nutrient intake among girls and boys in Western countries.

Objective

To identify major food sources of energy, energy nutrients, dietary fibre, and micronutrients, and to study gender differences in these food sources among children.

Design

We assessed food consumption and nutrient intake using 4-day food records in a population sample of Finnish girls (n=213) and boys (n=217) aged 6–8 years from the Physical Activity and Nutrition in Children Study. We calculated the percentual contribution of 55 food groups for energy and nutrient intake using the population proportion method.

Results

Low-fibre grain products, skimmed milk, and high-fibre bread provided almost 23% of total energy intake. Skimmed milk was the top source of protein (18% of total intake), vitamin D (32%), potassium (20%), calcium (39%), magnesium (17%), and zinc (16%). Vegetable oils (15%) and high-fat vegetable oil–based spreads (14%) were the top sources of polyunsaturated fat. High-fibre bread was the top source of fibre (27%) and iron (12%). Non-root vegetables were the top source of folate (14%) and vitamin C (22%). Sugar-sweetened beverages provided 21% of sucrose intake. Pork was a more important source of protein and sausage was a more important source of total fat and monounsaturated fat in boys than in girls. Vegetable oils provided a higher proportion of unsaturated fat and vitamin E among boys, whereas high-fat vegetable oil–based spreads provided a higher proportion of these nutrients among girls.

Conclusion

Commonly recommended foods, such as skimmed milk, high-fibre grain products, vegetables, vegetable oil, and vegetable oil–based spreads, were important sources of several nutrients, whereas sugar-sweetened beverages provided the majority of sucrose intake among children. This knowledge can be used in improving health among children by dietary interventions, nutrition education, and health policy decision making.

Comparison between parameters from maximal cycle ergometer test first without respiratory gas analysis and thereafter with respiratory gas analysis among healthy prepubertal children

It is important to distinguish true and clinically relevant changes and methodological noise from measure to measure. In the clinical practice, maximal cycle ergometer tests are typically performed first without respiratory gas analysis and thereafter, if needed, with respiratory gas analysis. Therefore, we report a comparison of parameters from maximal cycle ergometer exercise tests that were done first without respiratory gas analysis and thereafter with it in 38 prepubertal and healthy children (20 girls, 18 boys). The Bland-Altman method was used to assess agreement in maximal workload (WMAX), heart rate (HR), and systolic blood pressure (SBP) between rest and maximum. Girls achieved higher WMAX in the exercise tests with respiratory gas analysis compared with exercise tests without respiratory gas analysis (p = 0.016), whereas WMAX was similar in the tests among boys. Maximal HR (proportional offset, -1%; coefficients of variation, 3.3%) and highest SBP (proportional offset, 3%; coefficients of variation, 10.6%) were similar in the tests among children. Precision and agreement for HR improved and precision for SBP worsened with increasing exercise intensity. Heteroscedasticity was not observed for WMAX, HR, or SBP. We conclude that maximal cycle ergometer tests without and with respiratory gas analysis can be used consecutively because measurement of respiratory gases did not impair performance or have a significant effect on the maximality of the exercise tests. Our results suggest that similar references can be used for children who accept or refuse using a mask during a maximal exercise test.

Cardiovascular fitness and haemodynamic responses to maximal cycle ergometer exercise test in children 6-8 years of age

We investigated cardiovascular fitness and haemodynamic responses to maximal cycle ergometer exercise test in children. The participants were a population sample of 425 children (204 girls, 221 boys) aged 6-8 years. Heart rate (HR) and systolic blood pressure (SBP) were measured from the beginning of pre-exercise rest to the end of recovery period. We provided reference values for peak workload and changes in HR and SBP during and after maximal exercise test in girls and boys. Girls had a lower cardiovascular fitness, indicated by peak workload per body weight [mean (2 s) 2.7 (0.9) vs. 3.1 (1.0) W · kg(-1), P < 0.001] and lean mass [mean (2 s) 3.5 (0.9) vs. 3.8 (1.0) W · kg(-1), P < 0.001] than boys. Plateau or decline in SBP close to the end of the test was found in about third of children and was considered a normal SBP response. Girls had a slower HR decrease within 2 min after the test than boys [mean (2 s) 53 (18) vs. 59 (22) beats · min(-1), P < 0.001]. The results are useful for physicians and exercise physiologists to evaluate cardiovascular fitness and haemodynamic responses to exercise in children and to detect children with low exercise tolerance or abnormal haemodynamic responses to exercise.