See January 22 blog post for abdominal plank exercise.
Here are variations for your transverse oblique muscles:
From the plank position, bring your right leg at a 90-degree angle out parallel to your side and back to the plank position. Repeat for four sets of ten repetitions. Do the same for the left leg.
From the plank position, lift your right leg at a 90-degree angle up so your ankle goes over your right gluteus maximus muscle. Repeat for four sets of ten repetitions. Do the same for the left leg. This also works your glueteus maximus muscles.
Disclaimer: None of the above information can be taken as a substitute for advice from a medical professional, such as a physician.
My third book, Pocket Guide to Fitness, is available on www.louizapatsis.com, http://www.authorhouse.com, www.bn.com and http://www.amazon.com. If you look up my name on those Web sites, you will find my other books The Boy in a Wheelchair and Life, Work and Play: Poems and Short Stories.