Strength & Conditioning
If there is a bigger topic in sports, I don't know what it would be. There are entire organizations built around this, career fields dedicated to it, and a bazillion books and videos on the topic, but my primary concern is the research dedicated to strength & conditioning. As with any major topic, there are arguments on all sides as to which program is best, what exercises work best, who has the best ideas and even what time of day is best to workout.
There are no less than 20 variables to decide what type of program is right for the athlete. It all comes down to what the goals are and what the athlete's game-time requirements will be. This means a high school three-sport athlete should have at least 3 different workout plans during the year.
Here are some things to consider:
What equipment is available?
Ensure the resistance is diversified to attain maximum effectiveness.
Bodyweight training? Elastic resistance? Plyometric resistance?
Do you want muscular endurance, increased muscle mass, or increased strength?
How important is speed? Agility? Quickness? Strength? Power?
How many times per week will the athlete train? What days?
How many times per week will the athlete stress each muscle group?
In what order does the athlete stress the muscles?
How many sets? Reps? How quick are the reps? What's the rest period?
Will eccentric exercises work best?
How long will the workout last?
How do you determine the appropriate weight for your goals? When should you increase that weight?
How does the athlete pick the exercises to conduct - research by a professional or what the other guys in the locker room do?
Forced reps, negatives, tapering, continuous tension, unilateral training, supersets, circuits?
How should the athlete breath during eccentric motion versus concentric motion?
ALL OF THIS IS TO SAY - THERE IS NO SINGLE ANSWER FOR A GROUP OF PEOPLE.
See the videos below for information regarding "a way" to develop a program from one of the leaders in the field and a walk through of one of the best Strength & Conditioning programs in the country.
Eric Cressey from Cressey Sports Performance, a leader on the topic, on creating a strength and conditioning program.
Iowa Football Developmental Strength & Conditioning Program