Stage IV, which lasts from ages 11-15 in girls and 12-16 in boys, is a window of accelerated adaptation to aerobic, speed, agility and strength training, and for maximum improvement in skill development. This stage also serves as a the foundation of good training habits. The emphasis remains on learning the basics through training, and competition remains secondary. The key focus for this stage is on ‘Building the Physical Engine’: improving endurance, speed and core strength to achieve a level of fitness that allows the athlete to maintain high volume, high quality training; continuing to develop the technical skills of their sports, and if desired, preparing for single sport specialization.
Monitoring for the start of the growth spurt by checking height every month is crucial as almost all participants will move through their major growth spurt during this stage. A decrease in coordination should be anticipated during that period due to rapid growth and a change in body proportions, and coaches and parents should provide reassurance if skills athletes had previously learned need to be refined.
The response to strength training is maximized for girls 1-2 months after the end of their growth spurt. Injury prevention and bodyweight exercises should have already been taught, so that by the time they reach peak height velocity they are ready to begin free weight training. Proper performance of the exercises and core and stabilizer strength are crucial to allow the athlete to progress towards maximal strength training by the end of the phase. The endurance window is between 11 and 15 years old of age, and should be developed to enhance recovery during competition, improve regeneration, and build training capacity.
Perhaps most importantly, the second speed and explosiveness window for for girls is between 11 and 13 years and between 12 and 16 for boys. Performing proper speed training during this period is critical, because it will determine the athlete’s maximal potential for speed. Finally, flexibility training should be emphasized to manage the rapid growth of bones.
Throughout the stage athletes should undergo physical testing and functional assessments two times a year, and adults should provide variation in off court/field and on court/field activities to avoid overuse injuries.
From a psychological perspective, by this point in time the athlete should take personal responsibility for training, preparation, performance and recovery. They should be giving consistent effort during practice and performance. They should also have a training diary and be able to self-reflect after training and competition. Finally, the risks and negative performance effects of tobacco, drugs and alcohol, which have often been covered by parents and schoolteachers already, should be reinforced by coaches in the context of general health, eligibility to play, and optimizing sports performance.