The mechanisms for the age-related increase in fatigability of limb muscles during moderate-to high-velocity dynamic contractions are unresolved. PURPOSE: Determine whether the increased fatigability in older adults during dynamic exercise is associated with blunted blood flow and greater reductions in tissue oxygenation of the working muscles. METHODS: Fatigability, blood flow, and tissue oxygenation of the knee extensor muscles were measured in 10 young women (22.9 ± 3.8 yrs), 10 young men (22.3 ± 3.1 yrs), 9 old women (75.5 ± 4.2 yrs), and 11 old men (75.6 ± 4.7 yrs). Participants performed 80 maximal velocity contractions (1 every 3 s) with a load equivalent to 20% of their maximal voluntary isometric contraction. Blood flow through the superficial femoral artery was quantified before and immediately following the exercise via Doppler ultrasonography. Tissue oxygenation (StO 2 ) and deoxygenated hemoglobin (deoxy[heme]) of the rectus femoris were measured during exercise via near-infrared spectroscopy (NIRS). RESULTS: Fatigability (reduction in power) was less in young (22 ± 13 %) compared with older adults (38 ± 20 %, p=0.007) with no sex differences (p=0.432). Absolute blood flow after exercise was ~31% greater in young (1,140 ± 360 mLꞵmin -1 ) compared with older adults (869 ± 360 mLꞵmin -1 , p=0.009) and ~22% greater in men (1,100 ± 339 mLꞵmin -1 ) compared with women (899 ± 360 mLꞵmin -1 , p=0.043). However, blood flow normalized to the thigh lean tissue mass did not differ between young (185 ± 52 mLꞵmin -1 ꞵkg -1 ) and older adults (161 ± 49 mLꞵmin -1 ꞵkg -1 , p=0.154) or between men (163 ± 40 mLꞵmin -1 ꞵkg -1 ) and women (184 ± 61 mLꞵmin -1 ꞵkg -1 , p=0.223). There were also no associations between fatigability and absolute (p=0.865) or normalized end exercise blood flow (p=0.869). NIRS data could only be obtained from 16 of 20 young (10 men) and 12 of 20 older adults (9 men) due primarily to the amounts of subcutaneous adipose tissue. There were no age or sex differences in StO 2 or deoxy[heme] at the end of exercise for the remaining 28 participants (All p>0.05). CONCLUSION: These data suggest that the ability to deliver blood and oxygenate the working muscle are preserved in older adults during fatiguing knee extension exercise and that other factors must be responsible for the age-related increase in fatigability during dynamic exercise.