This six-move abs-specific workout is split into two mini-circuits of three moves each, or tri-sets. Each tri-set is essentially a mini-circuit containing three exercises. That means you’ll do moves 1a, 1b and 1c in order, sticking to the reps detailed and only resting after all the reps of the move 1c.
Do three circuits of the first tri-set, which works your upper abs and lower abs, then the fast-twitch muscles of both. Then move on to the second tri-set, in which the three moves work your upper abs, your side abs and then your entire core, repeating the same pattern to do three circuits of moves 2a, 2b and 2c. Tighten your abs before the first rep of each set, so they are fully engaged for the duration.