An exploratory study of cardiac function and oxygen uptake during cycle ergometry in overweight children

The Effect of Body Mass Index on Acute Cardiometabolic Responses to Graded Exercise Testing in Children: A Narrative Review

Although the beneficial role of exercise for health is widely recognized, it is not clear to what extent the acute physiological responses (e.g., heart rate (HR) and oxygen uptake (VO₂)) to a graded exercise test are influenced by nutritional status (i.e., overweight vs. normal-weight). Therefore, the main objectives of the present narrative review were to examine the effect of nutritional status on acute HR, and VO₂ responses of children to exercise testing. For this purpose, we examined existing literature using PubMed, ISI, Scopus, and Google Scholar search engines. Compared with their normal-body mass index (BMI) peers, a trend of higher HRrest, higher HR during submaximal exercise testing, and lower HRmax was observed among overweight and obese children (according to BMI). Independent from exercise mode (walking, running, cycling, or stepping), exercise testing was metabolically more demanding (i.e., higher VO₂) for obese and overweight children than for their normal-weight peers. Considering these cardiometabolic differences according to BMI in children might help exercise specialists to evaluate the outcome of a graded exercise test (GXT) (e.g., VO2max, HRmax) and to prescribe optimal exercise intensity in the context of development of exercise programs for the management of body mass.

Sex differences in pulmonary oxygen uptake kinetics in obese adolescents

OBJECTIVE

To determine whether sex differences exist in the pulmonary oxygen uptake (VO2) uptake on-kinetic response to moderate exercise in obese adolescents. We also examined whether a relationship existed between the VO2 on-transient response to moderate intensity exercise, steady-state VO2, and peak VO2 between obese male and female adolescents.

STUDY DESIGN

Male (n = 12) and female (n = 28) adolescents completed a graded exercise test to exhaustion on a treadmill. Data from the initial 4 minutes of treadmill walking were used to determine the time constant.

RESULTS

The time constant was significantly different (P = .001) between obese male and female adolescents (15.17 ± 8.45 seconds vs 23.07 ± 8.91 seconds, respectively). No significant relationships were observed between the time constant and variables of interest in either sex.

CONCLUSIONS

Sex differences exist in VO2 uptake on-kinetics during moderate exercise in obese adolescents, indicating an enhanced potential for male subjects to deliver and/or use oxygen. It may be advantageous for female subjects to engage in a longer warm-up period before the initiation of an exercise regimen to prevent an early termination of the exercise session.

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.