Hi
Welcome to the MedHelp forum!
There is a chance that you have compression of the spinal nerves in the lumbo-sacral spine region. This can happen due to overuse of the lower back as in work requiring too much of bending, lifting weight, fall on the back, overweight, canal stenosis, bone disease, spondylosis, poor posture etc. In your case the abdominal work out could have precipitated it. The treatment is to remove the compression. You have to discuss the best treatment option with a neurologist, which can range from medication to physiotherapy to traction, lumbar belt or even surgery.
Alternatively you can visit a chiropractor or a physical therapist and learn some exercises which you can do to relieve the compression.
Hope this helps. It is difficult to comment beyond this at this stage. Please let me know if there is any thing else and do keep me posted. Take care!
You may want to see a Chiropractor. It sounds like you might have a pinched nerve especially since your having lower back pain, numbness and tingling in your legs.
Take care. Remar