The effects of aging and activity on muscle blood flow

Abstract

Background: Our purpose was to determine if aging had an influence on muscle blood flow independent of habitual physical activity levels.

Methods: Blood flow was measured in the femoral artery by Doppler ultrasound after cuff occlusion of 10 minutes. Active and inactive older subjects (73 +/- 7 years) were compared to active and inactive young subjects (26 +/- 6 years).

Results: Peak blood flow capacity when normalized to lean muscle mass was related to activity level (p < 0.001), but not to age. Specifically, the young active group had higher peak blood flows than the young inactive (p = 0.031) or older inactive (p = 0.005) groups. Resting blood flow and conductance were not significantly different between groups. Mean arterial pressure was significantly higher in the older compared to young group (p = 0.002). Conductance was related to both activity (p = 0.002) and age (p = 0.003). A prolonged time for blood flow to recover was found in the older compared to the young group (p = 0.038) independent of activity status.

Conclusions: The prolonged recovery time in the older subjects may suggest a reduced vascular reactivity associated with increased cardiovascular disease risk. Peak blood flow capacity is maintained in older subjects by physical activity. In summary, maximal flow capacity and prolonged recovery of blood flow are influenced by different mechanisms in young and older active and inactive subjects.

Figure 1

Normalized maximal blood flow for aging effects on left and activity effects on right (Means ± SD). Young is the sum of young active (YA) and young inactive (YI). Older is sum of older active (OA) and older inactive (OI). Active is sum of young active (YA) and older active (OA). Inactive is sum of young inactive (YI) and older inactive (OI). & Active and inactive groups are significantly different at p < 0.001.

Figure 2

Conductance of normalized maximal blood flow for aging effects on left and activity effects on right (Means ± SD). Young is the sum of young active (YA) and young inactive (YI). Older is sum of older active (OA) and older inactive (OI). Active is sum of young active (YA) and older active (OA). Inactive is sum of young inactive (YI) and older inactive (OI). * Young and older groups are significantly different at p = 0.003. & Active and inactive groups are significantly different at p = 0.002.

Figure 3

Half time to recovery of blood flow in seconds for aging effects on left and activity effects on right (Means ± SD). Young is the sum of young active (YA) and young inactive (YI). Older is sum of older active (OA) and older inactive (OI). Active is sum of young active (YA) and older active (OA). Inactive is sum of young inactive (YI) and older inactive (OI). * Young and older groups are significantly different at p = 0.038.