According to a San Diego State University study, the bicycle is one of the <a href="http://www.shape.com/fitness/workouts/abs-workout-fastest-way-lose-belly-fat" target="_hplink">most effective abs exercises</a> you can do, and this weighted version will have your rectus abdominus working overtime.
<strong>How to do it: </strong>Start lying on your back with both knees bent. Extend your arms overhead, bending your left arm behind your head and holding onto your right arm, just above your elbow, with your left hand. Bend your right knee and press your right foot on the inside of your extended left leg (left leg should be off the floor and low). Lift your right shoulder off the floor and turn it in towards your left leg, while you lift both legs up about 45 degrees. Lower back to start position, that's one rep. Perfrom 15 reps on each side.
<strong>Bonus tip:</strong> Exhale as you perform the movement, and think of drawing your belly button in deeper to your spine on the hardest part of the move.