it has a lot of different training techniques. weight lifting is certainly a part of it, along with core exercises, tubing exercises, throwing regimens, plyos, and a lot of other conditioning workouts as well.
lol my dad has bought just about every pitching book that exists but what i really like about tuff cuff is that it goes into a lot of detail telling you what to do for a pitching workout every day, year round. i've tweaked the workouts to suit me somewhat but it's a good basis.
i don't wanna start another epic RIstar vs. Letstalkpitching.com War but honestly man, you should check out what some of these books and coaches say. if you wanna do your own thing that's cool but i think that what has helped my pitching over the years is just opening myself lots of different opinions, taking some in and throwing others out.