Summer is right around the corner, and if you're looking for a challenge—and a six-pack—Jeff Cavaliere, C.S.C.S., of Athlean-X has you covered with an ab workout that’s built for all fitness levels.

Abs can be the most obstinate body part to train, with long and arduous workout routines seemingly yielding little reward compared to other muscle groups. According to strength coach Jeff Cavaliere ...