Core is such an integral part of fitness that is neglected by many and in turn is a huge weakness for many athletes of all sports. Everything comes from the core, after all the core is a huge link in the energy transfer for all compound multi joint movements. Without a strong core, the rest of the muscles in our body cannot move weight to their potential. Here is a few core workouts geared towards competitive athletes that are meant to help increase strength, power, and explosiveness. I recommend doing core 3 days per week, mix it up don't do the same workout consecutively, and challenge yourself. If the reps is to easy stay in that rep range and add weight.
Workout#1: 5 rounds
Reverse hyper: 10-12 reps
Strict Paralett Leg Raise:10-12 reps
Grappler/Landmine Rotations:10-12 reps (Full rotation)
Zercher good Morning:10-12 Reps
Workout #2:5 Rounds
GHD Extensions:10-12
Toes to Bar:10-12
Windmills:10-12 (each side)
Workout #3: 3 Rounds
10 Turkish get-up (5 each side go heavy)
1 min weighted plank (set sandbag over lower back)