Heart Rate Recovery Responses to Graded Exercise Testing in Healthy-Weight versus Obese Boys and Girls

Abstract

Heart rate recovery responses (HRRec) to graded exercise tests often serve as a surrogate measure of aerobic fitness. In young children, protocol specific and maturational sex differences in HRRec have been reported; however the impact of obesity status on HRRec has not been extensively explored. PURPOSE:To determine if differences in the absolute and relative HRRec exist in healthy-weight (HW) and obese (OB) boys and girls; and to determine the relationship between HRRec and VO2 peak measures (ml· kg-1· min-1) following maximal treadmill graded exercise testing (GXT). METHODS: Peak VO2 and peak heart rate were determined as the average of the last 30 sec of a multistage GXT. Absolute (bpm) and relative (%) HRRec, were subsequently calculated using the difference between peak heart rate and the post 1 min recovery in the 7-11 yr old HW boys (n=15), HW girls (n=7), OB boys (n=8), and OB girls (n=5). ANOVA and correlation analyses were used to determine significant (p<0.05) mean differences and relationships. RESULTS: The absolute HRRec of the OB boys (24.6 ± 8.4 bpm) were significantly less than OB girls (39.2 ± 11.3 bpm), HW boys (38.5 ± 17.0 bpm), and the HW girls (38.6 ± 9.2 bpm). The relative HRRec of the OB boys (13.5 ± 4.7%) were significantly less than HW boys (19.2 ± 8.9%) and HW girls (19.7 ± 4.8%). The mean VO2 peak between all boys (35.6 ± 10.7) and girls (33.9 ± 6.2) did not significantly differ; however the VO2 peak of the HW children (39.7 ± 8.0) was significantly greater than the OB children (27.1 ± 5.3). The VO2 peak of the HW boys (40.8 ± 8.8) was significantly greater than OB boys (25.8 ± 6.2) and OB girls (29.3 ± 2.8). The VO2 peak of the HW girls (37.2 ± 5.9) was significantly greater than the OB girls and OB boys. The VO2 peak for the entire group was significantly correlated with absolute HRRec (r=0.50) and relative HRRec (r=0.41).The VO2 peak for all boys was significantly correlated with absolute HRRec (r=0.64) and relative HRRec (r=0.52). The VO2 peak for the HW boys was significantly correlated to the absolute HRRec (r=0.56). CONCLUSIONS: HRRec to high intensity exercise in young children have not previously demonstrated sex differences. Our results indicate that obesity status may strongly influence HRRec, particularly in boys. HRRec may provide useful information relating to the cardiorespiratory fitness measures in children.