4 for your core

Squeezing in a fast workout usually means little or no time for your core. But with this challenging core workout regimen, you'll train your torso with every exercise, for a stronger six-pack and a sturdier spine.

The Exercises

Pullup with Leg Raise

Grab a pullup bar with an overhand grip, hands slightly more than shoulder-width apart. Cross your ankles and bend your knees until your feet are behind you. Pull your chest to the bar. Using your abs and hip flexors, pull your knees up and in toward your chest. Lower yourself. Do four to six reps.

Lateral Raise with Rotation

Stand holding a pair of dumbbells at your sides. With your arms slightly bent at the elbows, raise the weights up until your arms are parallel to the floor. Rotate your torso as far as possible to one side. Rotate back to the center, and lower your arms. Repeat to the opposite side. That's one rep. Do six.

Lunging Crunch

With your back to a high pulley cable, hold the rope handle at your chest so that the ends drape over your shoulders. Lunge forward. As your front foot hits the floor, do a standing crunch. Sink down until your back knee is just off the floor. Brace your abs as you stand up. Do 10 reps with each leg.

Chest Press with Crunch

With your feet on the floor and your back on a Swiss ball, hold a pair of dumbbells at your shoulders. Press the weights up. Once your arms are straight, lift your shoulder blades off the ball, pushing the weights higher. Pause, then lower your shoulder blades and the weights. Do 10 reps.

Complete these four exercises without rest. Once you've done all the movements, rest for 45 seconds; then repeat twice. Perform three times a week.