Ventilatory anaerobic threshold in healthy children

Summary

The ventilatory anaerobic threshold (VAT) during graded exercise was defined as the oxygen uptake ($\dot V_{{\text{O}}_{\text{2}} }$) immediately below the exercise intensity at which pulmonary ventilation increased disproportionally relative to $\dot V_{{\text{O}}_{\text{2}} }$. Since VAT is considered to be a sensitive and noninvasive measure for evaluating cardiorespiratoy endurance performance, the purpose of the present study was to determine normal values in children. We examined 257 healthy children (140 boys and 117 girls) varying in age from 5.7 to 18.5 years, during treadmill exercise. The data were analyzed in relation to sex and age. In boys the lowest $\dot V_{{\text{O}}_{{\text{2max}}} }$ (ml · min⁻¹ · kg⁻¹) was found in the youngest age group (5–6 year). In girls, on the other hand, no significant increase occurred with age. For VAT, expressed as ml O₂ · min⁻¹ · kg⁻¹ or as a percent of $\dot V_{{\text{O}}_{{\text{2max}}} }$ a significant decrease was found in boys and girls with age. This suggests an increase in lactacid anaerobic capacity during growth. In contrast to observations in adults, only low correlations were found between $\dot V_{{\text{O}}_{{\text{2max}}} }$ and VAT (r=0.28 in boys and r=0.52 in girls), which suggests that the development of the underlying physiological mechanism does not occur at the same rate in growing children. These data provide normal values for VAT that can be used for clinical exercise testing in the pediatric age group.