This is the fourth post in our series of Fitness Saturday exercises—workouts appropriate to women in the second half of life. Personal trainer Brooke Marrone, president and founder of Brooke Marrone Fitness, in New York City, is our fitness guru.

Finally, an ab exercise where you get to lie on your back! The Bicycle Twist is known to be one of the very best ways to work your core. There is so much more to this one move than the basic crunch, which often gets a bad rap. For optimum results, perform this exercise in a circuit with the other three moves we have gone over this month.  

• Lie flat on the floor with your feet shoulder-width apart and your hands gently behind your head.

• Imprint your spine into the floor (pretend like you are trapping someone underneath your low back) and pull your knees into your chest.

• Slowly lift your head and shoulder blades off the floor (make sure not to lift from your neck), and as you exhale, rotate to the right, bringing the left elbow toward the right knee as you extend the other leg out straight.

• Repeat on the other side, creating a pedal motion with your legs. Make sure you continue to breathe evenly throughout the exercise and that you do not rest your head down in between kicks. Do three sets of ten.

Modifications:

If you have a bad back, you can follow the above instructions for this exercise minus the kick. Keep your knees in to your chest as you twist side to side until you feel comfortable working up to your kick. Also, the lower you kick, the harder the exercise. Make sure never to put your back at risk, and go only as low with your kick as you feel comfortable.

Beginners:

1. Lie flat on the floor with your knees bent and your feet shoulder-width apart, with your hands gently behind your head.
2. Slowly lift your head and shoulder blades off the floor, and as you exhale, rotate to the right as you crunch up and bring your left knee in to meet you right elbow, then return to your starting position. Make sure you continue to breathe evenly throughout the exercise as you alternate 20 times.

The main muscle targeted during bicycle crunches is the rectus abdominus, which is located in the front of your body and flexes the torso and spine. The secondary muscles worked are the obliques (side abdominals), which help you move from side to side and twist your torso.