Off-season and in-season training vary from sport to sport and through various levels. To avoid over-training young athletes, follow the simple 10 percent rule: Do not increase weight, training activity, mileage or pace by more than 10 percent a week. This prevents stressing the body beyond capacity by allowing it to rest, rebuild, and recover. In fact, increasing training intensity too quickly can actually lead to a decrease in aerobic capacity.
When designing an off-season training regimen, the ultimate goal is preventing injury and bringing athletes to peak performance levels. While different sports and ages require different approaches, the most important thing is to, remember the 10 percent rule. As a general guideline, it should take an athlete six to eight weeks of training to safely reach optimal performance for an upcoming season.
For all sports, focus on improving core stability and balance first. A sound core and optimal balance is crucial to controlling and stabilizing the limbs. An example of this would be growing a strong trunk to support the limbs of a tree.
Next, focus on improving overall cardiovascular fitness and endurance, focusing on long duration and low intensity workouts. Even if the sport is primarily anaerobic, an athlete with a strong cardiovascular status will advance faster when training for aerobic/high-explosion activities. In youth and high school athletics we are training the total athlete, not just athletes for an individual sport. Coaches should have a strong understanding of what is and is not needed for training healthy athletes.