Aged rats exhibit a decreased muscle microvascular O₂ partial pressure (PO_2mv) at rest and during contractions compared to young rats. Age-related reductions in nitric oxide (NO) bioavailability due, in part, to elevated reactive O₂ species constrain muscle blood flow (Q_m). Antioxidants may restore NO bioavailability, Q_m and ameliorate the reduced PO_2mv. The purpose of this investigation is to test the hypothesis that antioxidants would elevate Q_m and therefore PO_2mv in aged rats. PO_2mv and Q_m were measured in the spinotrapezius while muscle oxygen consumption (VO_2m) was estimated in 20 anesthetized male F344xBN rats at rest and during 1 Hz contractions before and after antioxidant intravenous infusion (76 mg/kg vitamin C and 52 mg/kg tempol). Muscle force production was measured in a subset of animals. Before infusion, contractions invoked a biphasic PO_2mv that fell from 30.6±0.9 mmHg to a nadir of 16.8±1.2 mmHg with an 'undershoot' of 2.8±0.7 mmHg below the subsequent steady-state (19.7±1.2 mmHg). The principal effect of antioxidants was to elevate baseline PO_2mv from 30.6±0.9 to 35.7±0.8 mmHg (P<0.05) and reduce or abolished the 'undershoot' (P<0.05). Antioxidants reduced Q_m and VO_2m during contractions (P<0.05)whilst decreasing force production 16.5% (P<0.05)and elevating the force production to VO_2m ratio (0.92±0.03 to 1.06±0.6, P<0.05). Thus, antioxidants increased PO_2mv by altering the balance between muscle O₂ delivery and VO_2m at rest and during contractions. It is likely that this effect arose from antioxidants reducing myocyte redox below the level optimal for contractile performance and directyly (decreased tension) or indirectly (altered balance of vasoactive mediators)influencing O₂ delivery and VO_2m.