There is actually quite a bit of research on L-Arginine and sperm quality in men. As you can probably quess, there are generally always more studies in men than women, in all health issues. Just the plain truth unfortunately. Here is a link to L-Arginine improving ovarian response and egg quality in so called "poor responders". I used it during my last two IVF's (out of four), and it worked very well for me.
And yes, the health food store person is correct, body builders use all kinds of amino acids to build muscle. Amino acids are responsible for generating and maintaining cell production, and muscle cells. L-Arginine is an amino acid, which is more symply called a protein. Co-enzyme Q10 is needed in the repairing of cells and so the two work together.
All the best, baby dust............Hadley