The recovery duration and the work-to-recovery ratio are important aspects to consider when designing high-intensity aerobic interval exercise. This study examined the effects of recovery duration on total exercise time performed above 80, 90, and 95% of maximum oxygen consumption (VO2max) and maximum heart rate (HRmax) during a single bout of high-intensity interval exercise. We also evaluated the effects on VO2 and heart-rate kinetics, blood-lactate concentration, and rating of perceived exertion (RPE). Eleven moderately trained men (22.1 ± 1 year) completed, in three separate sessions, four 4-minute runs at 90% of maximal aerobic velocity (MAV), with 2, 3, or 4 minutes of active recovery. Recovery duration did not affect the percentage of VO2max attained or total exercise time above 80, 90, and 95% of VO2max. Exercise time above 80 and 90% of HRmax was longer with 2 and 3 minutes of recovery than with 4 minutes (p ≤ 0.05). Oxygen-uptake and heart-rate amplitude were lower, mean response time was slower, and blood lactate and RPE were higher with 2 minutes than with 4 minutes of recovery (p ≤ 0.05). In conclusion, aerobic metabolism attains its upper functional limits with 2, 3, or 4 minutes of recovery during four 4-minute high-intensity intervals; thus, all recovery durations could be used to enhance aerobic capacity in sports, fitness, and clinical settings. Short recovery (2 minutes), compared with longer recovery (4 minutes), however, evokes greater cardiovascular and metabolic stress and activates anaerobic glycolysis to a greater extent, and could therefore be used by athletes to induce a greater overall physiological challenge.