The moves: Performing a crunch in a push-up position.

REVERSE CRUNCH - Working on upper extremity strength and core stability, firefighter Jeffrey Butkowski performs reverse crunches as he bends and pulls in his knees while his feet are positioned on a stability ball. CNS Photo by Nadia Borowski Scott.

Works on: Upper extremity strength, shoulder and abdominal stabilization.

Set-up: Kneel on the ground in front of an exercise ball. Lay your chest onto the ball and roll over the top until the hands contact the ground. Walk out with the hands until the ball rolls down to the lower thighs.

Steps: Keep the abdominal muscles tight and the low back flat. Pull the ball up toward the arms by bending with the hips and knees (the ball rolls down the legs). Pause at the end for three seconds and then slowly straighten the legs to push the ball back.

Repetitions: Three sets of 10 repetitions. Count the leg motion out and back as one repetition.

Precautions: Do this exercise in an open area in case you lose your balance and fall off the ball. Do not hold your breath. Keep the head and neck in line with the rest of the back. Do not let the back sag toward the ground.