Primary muscles worked: Internal and external obliques (sides and front of the abdomen)
Starting position: Lie on your back with your right knee bent and right foot flat on the floor. Cross your left leg over your right, with your left ankle resting just above your right knee. Place both hands behind your head, with elbows out to the side.
Action: As you exhale, left your head and both shoulders off the floor and twist so that your right armpit moves in a line toward your left knee. Contract the abdominals as fully as you comfortably can. Hold for one count at the top of the contraction and exhale the remaining air. Inhale as you return toward the starting position. Do not allow your abdominals to relax between repetitions. Continue the set until you have completed your repetitions. Then repeat on the opposite side.
Tips:
- Do not allow your elbow to cave in toward your knee.
- Keep your elbows back.
- Keep your head in line with your spine.
- For a more advanced exercise, cross your legs more fully, so that one knee rests on the other.
- For a less advanced exercise, allow one elbow to remain in contact with the floor.

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There's certainly no shortage in number of abdominal exercises taught by different trainers in different styles and many of those are excellent in engaging the abdominal muscles.
However the best way is to strengthen your abdominal muscles from the inside out. Training the stabilizing muscles gives you a strong foundation to work on the abdominal wall muscles (six packs) later.
According to the study(*) powered by ultrasound imaging to measure the activation of two major stabilizing abdominal muscles during abs exercises, the side bridge is the most effective exercise at facilitating contraction of transverse abdominals and internal obliques.
To perform this exercise: you start from lying on your side resting on one forearm and placing the opposite hand on your waist, engage all abdominal muscle with drawing in your stomach and lift your hips up from the floor to make a straight line from head to toes. Pause for a second and return to the starting position and repeat.
Intermediate practitioners can start from side plank position, supporting their body weight with one hand instead of the forearm and continue with dropping the hip to the floor, pause, lift and repeat.
Advance practitioners can start from positioning feet on a bench and supporting the body weight with one hand on the floor, lowering the hip to the floor, pause, lift and repeat.
As you progress in all the variation above you can move the free hand from the waist position to extended position.
(*) Teyhen DS. Rieger JL. Changes in deep abdominal muscle thickness during common trunk-strengthening exercises using ultrasound imaging. J Orthop Sport Phys Ther. Oct. 2008:38(10):596-605
Prior to prescribing any form of exercise, it would be best to know your current fitness level, age, and exercise history. However, below is an exercise to get beginners started but be sure to only complete if you feel comfortable. Also, please contact me so I am able to further assist you after receiving feedback from the list above:
- Extended plank – lay face down. Place your hands next to your chest. Lift your body up so you are balanced on your knees. This position might be challenging so start here. If you are able to hold this position then lift your body so you are balancing between the palms of your hands and the toes of your feet, a push-up position. Hold for :30 or up to :30 and rest. Complete 2-3 times.
There are many variations of abdominal exercises, but four of the most effective -- and complementary -- are the decline crunch, exercise ball crunch, the intercostals cable pull-down, and the leg-up off a bench.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.