Perhaps more so than any other body part, abdominal exercises are something everyone really has to find their own way with. Everything related to how many repetitions, sets, variety of exercises, and how often you train them is very much an individual thing. From my experience I feel that how hard you train your abs determines how often to train them.
I am always asked, perhaps more than any other body part, what is the best abs workout?
For women I recommend using a little bit of resistance, not particularly what one would consider a heavy weight, and aim for a burn that comes in the 15 repetition range. Favorite ab exercises for me are the knee raise all the way up into the chest and to really emphasize the crunching motion of bringing your lower abs into this movement as well. Follow that with weighted cable crunches in the same rep range which with a mind-muscle association that focuses on the upper abs. Finally I will end with twists either with a medicine ball or seated using a barbell working the oblique. These can be performed either as a three or four set circuit, or finish each set of an exercise before moving onto the next one. Personally I prefer these exercises in an ab circuit.
My recommendation for men is much the same as above however while women generally strive for a flatter firm abdominal region, men usually are looking for their abs to ‘pop’ out. This requires the abdominal muscles to grow more, become bigger, and that can only be done with greater resistance, which meaning heavier weight. Because the abs are a stabilizing group in all of the heavy compound exercises which are key to overall muscle development, it is important for men, in particular, to train their abs heavy. Not being able to lift your max in say, the squat or deadlift, because your core is not strong enough to stabilize with your spine and support the weight means your muscle gain will be limited.
Starting with the lower abdominal exercise of hanging knees raise, place a dumbbell between your knees or locked in between your feet, and use your abdominals to pull your knees up into your chest while concentrating on the crunching motion of the lower abs while minimizing the use of the hip flexors. Your knees should be together throughout the motion, exhale as your knees come up to the chest, and lower under control. With the cable crunch I bring the rope attachment down so that each end is below each of my ears, and slowly ab crunch down while exhaling. Coming back up under control I raise until my back is straight, not so high as to alleviate tension, and then crunch down once more. Remember not to sit back on your heels and leave some room between the heels and your backside. For both of these exercises I recommend going as heavy as possible while being able to perform 10-12 reps with strict form to failure. Use a 2-1-3 cadence – 2 seconds crunching, 1 second pause, and 3 seconds on the negative portion of the movement.
Follow those with seated medicine balls or barbell twists. I do not go heavy with these and strive for 25 reps. The reason to go light with the oblique muscles is that I simply do not want the appearance of a thick wide waist, I would prefer to be lean and tight at the sides and not bulky.
How often you train your abs will depend on how you feel. Some believe it is okay to train the abs every day with the argument that the abdominals are used so often every day in other movements that they require a heavy workload in order to stimulate growth. One caveat though is that if your muscles are sore it is due to the micro-trauma that we cause with weight training and is a sign that the muscle has yet to recover and grow, in this case you must wait. Personally, because I use heavier weights and difficult resistance even with my abs, I train abdominals only twice per week. If done properly (train hard and heavy) your abs will ache in pain for at least one day after performing these exercises in this circuit manner.
Remember that the effectiveness of various abdominal exercises will differ from person to person and depending on your objectives, how much effort you put forth and how your body responds. For a toned flat mid-section strive for 20 reps of these 3 exercises performed in a circuit and planks can be added as well to increase stability. For more pronounced abdominal muscles and deeper cuts it is required to perform low repetitions with heavy weight and hard work.
Finally, remember that not even the best abdominal workout for you can ever overcome a poor diet.