The data on carnitine is equivical.  There is no clear consensus as 
to its effectiveness in exercise performance in humans.  It does 
appear safe in large doses.   In individuals with cardiac compromise 
or pulmonary diseases it is known to enhance exercise 
capacity, likely due to cardiac tissue's reliance on fats.   Better 
research really needs to be done with this supplement.
Beth Glace, M.S.
Sports Nutritionist
lb@nismat.org