Original Research Can the Point of Deflection From Linearity of Heart Rate Determine Ventilatory Threshold in Children?

Whether the point of deflection from linearity of heart rate (HRD) coincides with ventilatory threshold (VT) has not been extensively examined in children. The purpose of this study was to assess the relationship between the VO₂ measured at VT and the VO₂ measured at HRD. Twenty-two boys with a mean age of 10.7 years ( ± 1.0) performed a graded exercise test to determine VT, HRD, and VO₂max. There was no significant difference between mean VO₂ (ml/kg/min) at VT and at HRD (33.5 ± 3.5 vs. 34.1 ± 4.4; p>0.05). Linear regression analysis revealed a correlation of r=0.76 (p<0.01) between the VO₂ measured at VT and the VO₂ measured at HRD. These results indicate that HRD may be an accurate predictor of VT in most but not all children, and caution should be used when interpreting the significance of HRD.