13U Workout Program

What’s a good Workout Program for a 12 1/2 year old? Looking for year round(in/out season). His velocity is already above average, but would like to increase it with mainly, and most importantly, preventing injury.

Thanks in advance!

What is your workout routine?

I’m going to start going to the gym, so I’d like to get some feedback about effective workouts. Whats your routine?

Update: Routine as in, lift weights, run the treadmill, etc.