From bridge with feet elevated and legs straight, crunch, bringing knees to chest, straighten legs and repeat.
TRX Trunk Tricks
From standing position with arms forward, one arms goes high, the other lower to challenge the core further in anti-rotation.
From standing position with arms forward in front of the chest, one arms bends, other goes out to the side straight as the body lowers into a press up position, repeat on the other side.
From standing position with arms forward, reach arms overhead to change angle of the body to challenge the core.
From plank position, lift hips to draw knees in to chest.
From plank position, bend elbows to lower chest towards ground before pushing back up.