Impact of obesity and Down syndrome on peak heart rate and aerobic capacity in youth and adults.

Individuals with Down syndrome (DS) exhibit reduced aerobic capacity with reduced peak heart rate (HR). This condition is often coexistent with higher level of obesity compared to individuals without DS. The purpose of this study is to investigate the effects of obesity and Down syndrome (DS) on peak heart rate (HR) and peak oxygen consumption (VO) in children and adults both with and without intellectual disabilities (ID)s. VO and HR from individualized treadmill tests on 654 individuals were analyzed. Body mass index was used to categorize individuals' weight status using standard cut-offs. DS groups had the lowest HR (167bpm±14, p<0.05) compared to individuals with (183bpm±12) without ID (187bpm±12). Obesity did not affect HR among adults and children with DS. VO was lower among individuals with DS (25.2mL/kg/min±6.3, p<0.05) when compared individuals with (37.0mL/kg/min±10.5) and without ID (36.1mL/kg/min±10.4). Obese adults with DS had lower VO (24.3mL/kg/min±6.9, p=0.001) compared to the normal weight (26.7±7.1mL/kg/min) and overweight groups (27.0mL/kg/min±6.1) with DS. Conversely, in children, obesity level did not impact VO in individuals with DS. Our results suggest that DS attenuates both VO and HR, regardless of obesity status and age group. However, obesity was associated with lower VO in all adults, but not in children with DS.