Here are five simple abdominal exercises that can be done in five short minutes. Spend 45 seconds on each exercise, take a 15-second break, and then move on to the next exercise. 5 in 5: Tighten Up Your Core With These 5 in 5 mins!

#1: Bicycle Crunch

Targeting more muscles than the traditional crunch, the bicycle crunch works the upper abs, lower abs, and the obliques. Lie on your back and place your hands behind your head. Lift your legs and bend them at 90 degrees. Then engage your abs, lift your head, and twist so your right elbow reaches toward your left knee while your right leg straightens. Hold for two seconds. Now extend your left leg and twist so your left elbow reaches toward your right knee. Hold for two seconds. Continue alternating sides for 45 seconds.