Age and Attenuated Exercise Hyperemia: Partitioning the Contributors

Abstract

The influence of age on the central and peripheral contributors to exercise induced hyperemia is unclear. PURPOSE: Utilizing a reductionist approach, we compared the peripheral and central responses to passive limb movement (exercise without an increase in metabolism) in 11 old (68±7 years of age) and 10 young (25±3 years of age) healthy subjects. METHODS: Cardiac output (CO), heart rate (HR), stroke volume (SV), mean arterial pressure (MAP), and femoral blood flow of the passively moved leg were evaluated second by second during 3 min of passive knee extension at a rate of 1 Hz. RESULTS: In the older subjects CO, SV, HR, and femoral blood flow increased by 15%, 7%, 8% and 97% respectively. The young subjects displayed similar increases in CO, SV, and HR (15%, 6%, and 12% respectively). However, the young subjects displayed a greater increase in femoral blood flow (136%) compared to the older subjects. The difference with age in the hyperemic response to the passive leg movement with age can be explained by a greater increase in antegrade blood flow (103%) and smaller increase in retrograde blood flow (165%) in the young compared to the old subjects (74% and 204% respectively). CONCLUSIONS: Thus, in agreement with previous reports of attenuated exercise induced hyperemia with age, it appears that the difference is unrelated to central responses to limb movement, is peripheral in nature, and is not dependent upon metabolism. Funding: NIH PO1 HL-091830