Hemodynamic and oxygen uptake responses across gastrocnemius muscle of LZR and OZR in response to three minutes of 5 Hz muscle contraction. Data (mean±SE) are presented for femoral artery blood flow (Panel A), vascular resistance across the gastrocnemius muscle (Panel B), oxygen extraction (Panel C), oxygen uptake (VO2) by the muscle (Panel D), normalized O2 conductance across the muscle (Panel E) and developed tension by the gastrocnemius (Panel F). Values are presented under control conditions and following treatment of OZR with phentolamine (10 mg/kg), TEMPOL (50 mg/kg), SQ-29548 (10 mg/kg) or all three substances. * p<0.05 vs. LZR (n=5 animals); † p<0.05 vs. OZR (n=15 for control; n=5 for each treatment group; all oxygen extraction and VO2 data are from n=5 animals). The legend for all panels is presented in Panel B.