Chronotropic Index And Heart Rate Recovery After Exercise In Adolescentes With Down Syndrome

Abstract

Individuals with Down syndrome (DS) have a reduced heart rate (HR) response to exercise which is the main contributor to low cardiorespiratory fitness in this population. A previous study has shown delayed heart rate recovery (HHR) in adults with DS performing exercise testing, however there is still a gap regarding the HRR response and chronotropic index in adolescents with DS. PURPOSE: To evaluate heart rate reponse treadmill exercise test and its impact on exercise in adolescents with DS compared to non-DS. METHODS: Eleven adolescents with DS (7 girls, 4 boys; age 14.1 ± 1.04 years) and 10 non-DS (6 girls, 4 boys; age 13.7 ± 1.2 years) performed peak treadmill test with heart rate measurements. HRR was defined as the reduction in heart rate from the rate at peak exercise to the rate at 1 and 2 minutes after the cessation of exercise. Chronotropic index was calculated by a formula [(peak HR – resting HR) / (220–age – resting HR)] *100. For comparisons between groups, the independent t test was used. RESULTS: Compared to control group, adolescents with DS presented lower peak HR, loading time (s) and distance (m) (p < 0.05). In contrast, adolescents with DS had resting HR values similar to those non-DS. Participants with DS showed slower HRR than non-DS at 1 minute (DS: 21.1 ± 6.95 beats / min; controls: 47.1 ± 6.99 beats / min) and 2 minutes (DS: 28.5 ± 7.38 beats / min; controls: 49.4 ± 6.39 beats / min) of recovery (p <0,05). In addition, adolescents with DS have a lower CI (0.84 ± 0.09 vs 0.66 ± 0.09, p = 0.0001) when compared to their peers. CONCLUSION: Adolescents with DS had attenuated post-exercise HRR that may be related to lower chronotropic response at peak intensities.