To fully develop the ham's, the function of the ham's should be worked; curling the heel up to the butt. GM'ings, SLDL's, lunges, step-up's (great exercise), etc all affect the stablization and muscle factor of the ham's and are execellent movements. Think of the ham's akin to the biceps, which both can function as a 180 degree muscle action, from the bottom (stretched) to the contraction point (top). Not too many guy's with impressive arm do only stretching movements like DL's, hanging from a chinning bar only, etc to build those 19" gun's.
If you don't have a ham machine (either sitting, lying or standing) but you do have a workout partner than you might try something like this. Lay face down on a high bench and have him/her hold the ankles as you curl the ham's up. Don't stop at just the 90 degree point , but curl all the way down and try to touch your butt with the heels. If your not use to a full contraction than be warned about major cramping of the ham's. Go slowly, at first, with this manuel resistence exercise. Can also do one leg at a time, alternate each set. If working alone, than place the heels under a stable object like a BB, piece of equipment, etc. Some guy's will put a lose strap around the end of a bench and slide their heels under it and do them that way. Start from the kneeling position and let yourself down to the floor slowly. This is a somewhat advance exercise so you may have to curl yourself up to the starting position (kneeling) with the help of the hands, in a push-up style. After a few workouts the ham's should be strong enought to do the curling on their own. As you get stronger, hold a BB plate at your chest. Suggest that these ham curling motions be done after SLDL's, GM'ing, etc so the muscles are warmed up and ready. Good Luck.
