Exercise - Phase III: Lower Back And Abs

Just over a week ago I visited my physical therapist and asked for recommendations for lower back and abdominal exercises.  He said that many of the PT exercises I was already doing were helping with the lower back, which I agreed with.  He said I should concentrate on the abdominal muscles and, by doing so, I would further strengthen my lower back muscles.  With that, he left me with three exercises that would concentrate on the abs.  These three exercises have become Phase III of my exercise program.

1. The first is a Three Point Stance which exercises the abductors, obliques, trapezius, glutes, and triceps.  There are two variations of this exercise that exercise different muscle groups - mostly on the sides of the abdomen.  These two variations are by far the hardest for me so far.  The exercise is explained here (Page one of the PDF file).
   
2. The second is Straight Leg Raise Crossovers which exercises the abdominal muscles.  This is a pretty straight forward exercise though I have to work on keeping my lower back flat on the floor to reduce lower back stress.  (See page two of the PDF file.)
   
3. The last exercise is the All Four Swiss Ball Belly Lift which also exercises the abdominal muscles.  Not sure if I'm doing this one correctly as I don't feel much abdominal muscle engagement.  I'll have to play around with this one until it feels right. (See page three of the PDF file).

I'm doing these exercises twice a week (Tuesday and Thursday).  I've noticed some sore muscles that I didn't know I had so I think I'm doing something right.  Fortunately the aches are not in my lower back so I don't think I'm doing any damage.

As I added a new phase to my exercise regimen, I modified what I was already doing.  I reduced my PT exercises (I kind of think of these as Phase 0) from five days a week down to three (M - W - F).  I have also reduced my push ups to three days a week (M - W - F also).

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Speaking of aching and push ups, I have been feeling an aching and a weak feeling in my left arm that I think is a result of the push ups.  I was hoping it would go away when I reduced the push ups from four to three days.  It really hasn't so I'm taking a week off from doing push ups to see if it gets better.  After skipping just one day my arm feels much better.  I must be pushing this old body a little too much.