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The microvasculature is critical in the control of blood flow. Aging and reduced physical activity (PA) may both decrease microvascular function.The primary aim was to evaluate the influence of age on microvascular function in adults with similar PA levels. Secondary aims were to assess the reliability of muscle functional magnetic resonance imaging in older adults (OA) and the relationship between PA and microvascular function in OA.Microvascular blood-oxygen-level dependent (BOLD) responses were measured in young adults (YA, n = 12, mean ± SD age = 21 ± 1 yr old, PA = 239 ± 73 × 103 counts per day) and OA (n = 13, 64 ± 4 yr old, PA = 203 ± 48 × 103 counts per day). Functional magnetic resonance images (3T, echo planar BOLD) of the leg were acquired after brief (1 s) maximal voluntary isometric contractions. The test–retest reliability of BOLD responses and the Pearson correlation between peak BOLD and PA were assessed in a group of OA (OA-r) with a broad range of PA (66 ± 5 yr old, n = 9, PA range = 54 × 103 to 674 × 103 counts per day).Peak BOLD microvascular responses were reduced for OA compared with YA. OA peak BOLD was 27% lower in the soleus (3.3% ± 0.8% OA vs 4.5% ± 1.4% YA; P = 0.017) and 40% lower in the anterior compartment (1.6% ± 0.6% OA vs 2.7% ± 1.1% YA; P = 0.006). Coefficients of variation were 8.6% and 11.8% for peak BOLD in the soleus and anterior compartment, respectively, with an intraclass correlation of 0.950 for both muscle regions. The correlation between peak BOLD and PA was r ≥ 0.715, P ≤ 0.030.Aging was associated with reduced microvascular function in leg muscles, independent of PA. The findings also revealed good reliability for BOLD magnetic resonance imaging in OA for the soleus and anterior compartment muscles.