Tip: The Sicilian Crunch

Abs respond better to heavy weights because of their muscle fiber makeup. Here's one way to nail those fast-twitch fibers.

The abs are composed of primarily type-II or fast-twitch (FT) muscle fibers. That means they're best suited for heavier weight and lower-rep sets rather than excessive numbers with bodyweight alone. The Sicilian crunch is a great exercise to hit them.

This exercise really taps into those FT fibers under load. During this movement, the lower body is secured as the upper body moves.