I think that what 0311 was saying about people bouncing up and down
doing calf raises is one of the major problems trainees have, no matter what rep range or style your using.
The important thing is not to concentrate on just getting reps but on raising the heel as high as possible. I think a lot of people never get a full
contraction. And whether your doing the extended negatives or not, which do work very well, you definitely need to pause at the point of maximum stretch, again, no matter what style of training you're using. The calves are like loaded springs that will bounce you up and down with
very little effort if you don't take a moment to eliminate momentum.
The posterior calves are made up of the gastrocnemius medial and lateral heads. Underneath these lies the soleus.
Generally, the gastroc medial is 51% slow twitch and 49% fast twitch. The lateral head is about 46% slow twitch and 54% twitch fibers. The soleus is about 90% slow twitch fibers, however.
That might give you an idea of what rep ranges to employ. Remeber that
the fast twitch 2A and 2B are larger and have the greatest potential for
growth. But slow twitch fibers will grow, too.
As far as the seated calf raises, they are really only good for the soleus and I recomment doing them for that since it's the only way to hit it thoroughly. The soleus goes all the way underneath the gastroc and so will make the entire calf seem larger. In fact it is the largest anyway. You'll want a 25 to 50 rep range with slow controlled reps. NO BOUNCING. Hit 'em with lower reps sometimes also to bring up that 10% of fast twitch fibers.
Damn, I could go on and on about calves. Mine are the bane of my existence, but they do grow, and so will yours.
Here is some good calf info:
http://www.abcbodybuilding.com/calvesanatomy.php
http://www.abcbodybuilding.com/calvesanatomypart2.php
http://www.abcbodybuilding.com/calvesanatomypart3.php
http://www.abcbodybuilding.com/calvesanatomypart4.php
*Edit* Now that I have learned more about muscle fiber recruitment and I know that you can't selectively isolate fiber types I no longer recommend these articles or all of my statements in this post.