Adapting the "Chester step test" to predict peak oxygen uptake in children.

AIM OF THE STUDY: Maximal exercise testing may be difficult to perform in clinical practice, especially in obese children who have low cardiorespiratory fitness and exercise tolerance. We aimed to elaborate a model predicting peak oxygen consumption (VO2) in lean and obese children with use of the submaximal Chester step test. METHODS: We performed a maximal step test, which consisted of 2-minute stages with increasing intensity to exhaustion, in 169 lean and obese children (age range: 7-16 years). VO2 was measured with indirect calorimetry. A statistical Tobit model was used to predict VO2 from age, gender, body mass index (BMI) z-score and intensity levels. Estimated VO2peak was then determined from the heart rate-VO2 linear relationship extrapolated to maximal heart rate (220 minus age, in beats.min-1). RESULTS: VO2 (ml/kg/min) can be predicted using the following equation: VO2 = 22.82 - [0.68*BMI z-score] - [0.46*age (years)] - [0.93*gender (male = 0; female = 1)] + [4.07*intensity level (stage 1, 2, 3 etc.)] - [0.24*BMI z-score *intensity level] - [0.34*gender*intensity level]. VO2 was lower in participants with high BMI z-scores and in female subjects. CONCLUSION: The Chester step test can assess cardiorespiratory fitness in lean and obese children in clinical settings. Our adapted equation allows the Chester step test to be used to estimate peak aerobic capacity in children.

Physical activity increases bone mineral density in children with type 1 diabetes.

INTRODUCTION: Osteoporosis is a growing health problem in patients with type 1 diabetes mellitus (T1DM). The aim of this study was to determine the effects of a 9-month weight-bearing physical activity program on bone mineral density (BMD) and bone biomarkers in T1DM compared with healthy children. METHODS: This was a randomized controlled trial including 27 diabetic and 32 healthy children (mean age = 10.5 ± 2.5 yr). Both T1DM and healthy participants were randomized to either an exercise or a control group (i.e., four groups). At baseline and 9 months, total body (TB), lumbar spine (LS2-LS4), femoral neck, and greater trochanter areal BMD (aBMD) and serum bone biomarkers (osteocalcin, type 1 collagen cross-linking) were measured. The intervention consisted of two 90-min sessions per week of weight-bearing physical activity (ball games, jumping, rope skipping, and gymnastics). RESULTS: Baseline variables were similar among groups. At 9 months, changes in TB (T1DM = 0.035 ± 0.022 g·cm(-2), healthy = 0.031 ± 0.017 g·cm(-2)) and LS2-LS4 (T1DM = 0.046 ± 0.038 g·cm(-2), healthy = 0.063 ± 0.034 g·cm(-2)) aBMD were statistically significant in the intervention groups and of similar magnitude between T1DM and healthy subjects. The level of type 1 collagen cross-linking (T1DM = -0.12 ± 0.32 ng·mL(-1), healthy = -0.36 ± 0.11 ng·mL(-1)) decreased in the intervention groups but was not associated with TB aBMD changes. CONCLUSIONS: Regular weight-bearing physical activity (180 min·wk(-1), including ball games, jumping activities, and gymnastics) improves total and LS2-LS4 bone mineral accretion in children with T1DM, in a similar magnitude to healthy subjects. We conclude that children with T1DM should be encouraged to practice regular physical activity to enhance peak bone mass and prevent osteoporosis later in life.