I've never heard of a formula. I think it is more individual than that. I will say that I began working out (again) after not doing so for the first 3 months or so of Atkins. I felt a little funky the first time - a bit dizzy and disoriented - but only that once. I did not raise my carbs at all (I want to be able to access fat for endurance), but I drink a protein shake (ugh) or eat cheese (yum) after my workouts to provide my body with a quick source of protein for muscle repair. I suggest you try it, and see what your body tells you.

A good book for weight training on Low Carb is the TNT workout by Jeff Volek (co author of many LC books) and a guy who writes for Men's Health Mag (which seems to have a LC slant). The book recommends an LC diet with several variations (more protein and/or more carbs) depending on what your personal goals are - losing weight, gaining muscle, etc. The used copies at Amazon can be had for a couple of dollars.