Weight gain and workout

Its my senior year summer and next year im playing at a D1 college. In the begining of the year my fastball was about 84-87. I have not worked out since the fall because i had no time in season and havent been running and my fastball has been about 82-84. I have been doing alot of research on how to work out and gain velocity and everything talks about fast twitch muscle fibers. It says to do high weight lifts with low reps to gain power and explosiveness. Is this correct? I am also gonna start long tossing and running. Can anyone please give me some advice on how to workout and what type of running I should be doing. Thanks

I also forgot to add that i lost like 15 pounds. im not sure if gaining the weight back will lead to velocity gain.

Pavel in his book Power to the People advocates this. Also, Barry Ross 's book on sprinting advocates high weights and low rep to gain strength without gaining weight. The idea would be to lift 5 days a week and the do 1-3 sets of 2-3 reps at 90% of you 1 rep max. Each set is 5 minutes apart. Ross also suggest a short set of pylos after each set such as 10 box jumps to further increase explosiveness.

My 14 year old son has been doing this and in one month has increased his deadlift max to 300 lbs despite weighing 134 lbs. I think it has helped his running speed as at school they timed the kids 40 yard dash time and won running a 4.65 on grass and in tennis shoes.