With all of the fancy weight training exercises it is easy to forget the basic fundamental movements that all athletes need to be efficient at especially at the younger ages of 13 and younger. Don't try to lift weights before learning how to lift your own body weight correctly.
1) Push up/Dips
Too often have I seen young athletes perform push ups incorrectly by only bending their elbows a few inches and diving their heads to the ground to count it as a repetition. Mastering push ups and dips will develop a stronger and more explosive chest, shoulder, and triceps which will also translate to future barbell movements.
2) Pull up/Chin up
Regardless of age, mastering the pull up and chin up will lead to a well developed back and a healthy pair of shoulders. Many young athletes sit all day at a desk with rounded shoulders and the pull ups will help balance many of the postural problems that we have in this day.
3) Lunge/Squat Variation
Having a pair of strong legs is absolutely vital in all sports and mastering the lunges will fix strength imbalances with the lower body and also build mental toughness which is very important and highly underrated in today day.
4) Sprints/Hill Sprints
All sports require athletes to move quickly and be able to produce force at will. When sprints are performed correctly, it truly is a total body workout and everything from your legs, core, and shoulders will be trained and developed in a way that not many things can simulate.
Program Idea for Novice 13 and younger athlete
*Do Not Follow This Exact Program*
This is just an example and should be CUSTOMIZED by a trainer/coach who knows what the athletes strength and weaknesses are and also what attributes they require.
10 Minute Dynamic Warm up 3 - 100 Meter Sprints 3 Sets of 10 Meter Walking Lunges
30 Pull ups in as few sets as possible 30 Dips in as few sets as possible