This study investigated differences in average V̇O2 of maximal effort interval running to maximal effort constant rate running at lactate threshold matched for time. The average V̇O2 and distance covered of 10 recreational male runners (V̇O2 max: 4158 ± 390 mL·min-1) were compared between a maximal effort constant-rate run at lactate threshold (CRLT), a maximal effort interval run (INT) consisting of 2 min at V̇O2 max speed with 2 minutes at 50% of V̇O2 repeated 5 times, and a run at the average speed sustained during the interval run (CR submax). Data are presented as mean and 95% confidence intervals. The average V̇O2 for INT, 3451 (3269-3633) mL·min-1, 83% V̇O2 max, was not significantly different to CRLT, 3464 (3285-3643) mL·min-1, 84% V̇O2 max, but both were significantly higher than CR sub-max, 3464 (3285-3643) mL·min -1, 76% V̇O2 max. The distance covered was significantly greater in CLRT, 4431 (4202-3731) metres, compared to INT and CR sub-max, 4070 (3831-4309) metres. The novel finding was that a 20-minute maximal effort constant rate run uses similar amounts of oxygen as a 20-minute maximal effort interval run despite the greater distance covered in the maximal effort constant-rate run.