The purpose of this study is to determine if an acute bout of removal of exercise reduces enothelial function and glycemic control in an active, older adult population; and whether a 3 day return to exercise restores this response. Glycemic control is the blood glucose response following the consumption of a meal. It is an indicator of insulin resistance (or type 2 diabetes) and impaired glycemic control has been suggested to lead to cardiovascular disease. Endothelial function has been shown to be improved by chronic or acute increases in physical activity. Both of these have been shown to be impaired to acute bouts of inactivity in young populations; however the impact of acute inactivity in older adults is less understood. In this proposal the investigators will examine 1)how quickly impairments in glycemic control occur to acute physical inactivity in older adults who exercise, 2) how quickly impairments in endothelial function occur to acute inactivity in older adults who exercise, and 3) whether 3 days of a return to exercise restores these responses.

Inclusion Criteria:

1. 55 years and older, 18-40 years old
2. Healthy, physically active, performing at least 90 min/week of physical activity
3. Free of physical limitations that may interfere with alterations in daily physical activity levels

Exclusion Criteria:

1. Physician diagnosed HIV, hepatitis, or tuberculosis.
2. Body weight change of greater than 5% within the previous 2 months
3. Smoking within the previous 2 months.
4. Taking medications that alter blood glucose levels