The involvement of young athletes in strength training programs has attracted a significant degree of commentary in the world of sports science in recent years. With young athletes seemingly more physically able to perform at a higher athletic level at ever younger ages, there is often an assumption that strength training will make the talented young athlete even more effective. There are significant physiological and emotional factors that affect youth strength training that are not present in similar adult programs. Strength training for young people must be approached with caution.
Defining who is a young athlete is a variable proposition. The age of puberty, the phase in physical development when a person grows to physical and sexual maturity, has been determined to have fallen significantly over the past 100 years, particularly among females in North America. A modern female can begin to exhibit the physical changes associated with puberty as ages as young as eight years old, or as old as 13. The modern age for the onset of male puberty ranges from 10 years of age to 14 years.
The determination of puberty is fundamentally important to the consideration of what, if any, weight training a young athlete may safely undertake. Puberty is a genetically determined process for every individual; it is the period when the body grows faster than at any other time in a person's life, other than during infancy. Puberty may last between 18 months and four years or more. During puberty, as the bones grow, the stresses on both the bone structure and the connective tissue in the related joints can become significant. The long bones of the body, particularly the tibia and fibula (lower leg), femur (thigh), and the humerus (upper arm), have growth plates located at the epiphysis, a segment located near the end of each of these bones. The growth plate is fundamental to the healthy and orderly growth of the bone to maturity. Until adulthood, the growth plate remains softer than the other regions of the bone, and it is far more vulnerable to physical damage from a direct trauma, as well as that caused by repetitive stress or the application of excessive forces that may occur through weight training, excessive training mileage, or other forms of resistance.
During puberty, there are also significant imbalances in the body between bone and connective tissues growth rates in specific places. The well-known adolescent knee ailment, Osgood Schlatter disease (OSD), occurs when the growth of the tibia is at a different rate than that of the patella (kneecap) tendon to which the tibia is connected. OSD causes swelling and pain in the area below the patella because the repetitive extension of the tendon through running takes place with an imbalance between the tendon and the tibia, causing strain on the tendon. OSD will often make running or weight-bearing exercise difficult until the relative growth of the two structures is equal.
Strength training in adults is usually intended to develop the three separate but related aspects of strength: maximum strength, the greatest amount of force that can be produced in a single muscular contraction; elastic strength, which is the ability of the muscles to respond and contract quickly; and strength endurance, the ability to sustain a level of force through a number of repetitions. Overload training is the most common form of strength training in adults, where muscles are built up and sustained through a repeated cycle of overload and recovery.
For children who have not yet reached puberty, any form of weight training is dangerous to the child's long-term musculoskeletal health. There is little benefit to be derived from such programs until puberty has determined more definitively the adult shape and characteristics of the person. Focused stretching and flexibility exercises will benefit all active persons of any age; the introduction of resistance and weight training is of little benefit to a child.
Training to develop maximum strength is a dangerous process for a pubescent athlete. Overload resistance training, plyometrics jump programs, intense resistance running, or any repetitive weight-bearing training activity carries with it significant structural risks. Sports science research confirms that any strength training done by persons whose bodies have not reached maturity should be confined to the exercises that focus on endurance and elastic strength; strength training should not be maximal weight training for these persons. The components of a healthy and useful strength training program for a young athlete will include a number of components, all of which emphasize athlete safety and long-term physical development.
Any youth training program must entail active supervision; young people will test themselves when permitted, and risk injury by lifting an excessive amount of weight or otherwise attempting a resistance movement that is dangerous to them. There must be a focus on instruction and the development of technique; the young athlete must have detailed instruction regarding any weight-bearing motion, with the emphasis at all times on smooth movements that take the weight or object through a full range of motion in the applicable joints. The companion to smoothness of motion is control of motion, to permit the young athlete to proceed with safety and confidence. To best enhance the range of motion desired in these programs, stretching and flexibility exercises should be incorporated with the strength training.