Baynard, T., Pitetti, K. H., Guerra, M., Unnithan, V. B., & Fernhall, B. (2008). Age-related changes in aerobic capacity in individuals with mental retardation: A 20-yr review. Medicine & Science in Sports & Exercise, 40(11), 1984-1989.

PURPOSE:
VO2peak (the plateau of oxygen consumption during an exercise test where oxygen consumption will plateau and CO2 uptake will be greater than O2) and maximum heart rate are important determining factors in establishing aerobic power. Individuals with Down syndrome tend to have a lower aerobic power when compared to their peers without disabilities. This study sought to determine the patterns of VO2peak and maximum heart rate with age in those with Down syndrome compared to those with mental retardation and also to people without disabilities.

PARTICIPANTS:
The study consisted of 635 individuals -180 with mental retardation, but not Down syndrome, 133 with Down syndrome, and 322 people without disabiities. Participants' ages ranged from 9 to 45 years old.

METHOD:
All participants were made familiar with the treadmill and equipment before testing began. Data was collected at 5 sites between 1985 and 2005. Individuals with mental retardation (with and without Down syndrome) began with a 4-minute warm-up on the treadmill, with a grade increase of 2.5% for every 4 minutes; when 7.5% was reached, grade increase by 2.5% every 2 minutes until exhaustion. This was the same protocol for the participants without disabilities; however, they began at a faster pace. Peak effort was determined when the individual could no longer maintain speed, their respiratory exchange was >1.0, or heart rate and oxygen uptake had reached a plateau.

RESULTS:
It was found that those with Down syndrome had an overall lower VO2peak than the other 2 groups. VO2peak also increased from the youngest age group until the age range of 16-21, when it began to plateau. Peak heart rate was greatest in the youngest age group and decreased with age among all three groups. Participants with Down syndrome had the lowest peak heart rate among any age group. Body Mass Index (BMI) also increased in all groups with age. Those with Down syndrome had the highest BMI in all age groups.

DISCUSSION:
This study shows that those with mental retardation and without Down syndrome and non-disabled participants were similar in their age-related changes, while those with Down syndrome were found to have the lowest VO2peak and HR at any age. One reason those with Down syndrome have lower aerobic power is because of reduced physical activity.