Rest 1 minute between exercises.
A popular regimen based on a 1996 study uses 20 seconds of ultra-intense exercise (at an intensity of about 170% of VO2max) followed by 10 seconds of rest, repeated continuously for 4 minutes (8 cycles). In the original study, athletes using this method trained 4 times per week, plus another day of steady-state training, and obtained gains similar to a group of athletes who did steady state (70% VO2max) training 5 times per week. The steady state group had a higher VO2max at the end (from 52 to 57 ml/kg/min), but the Tabata group had started lower and gained more overall (from 48 to 55 ml/kg/min). Also, only the Tabata group had gained anaerobic capacity benefits.