The most important thing to know about youth resistance training is that it IS safe, and there ARE studies out there that prove this. There is actually a decreased rate of injury for young weight lifters, as long as there is proper supervision and support. Epiphyseal, or growth plate, injuries have been reported in the past but are due to poor form and lack of supervision. No cases of reported injury have been shown in any supervised youth resistance training study! In 1998, Micheli reported that preadolescents may be at a lower risk of injury than adolescents because the epiphyseal plates are more resistant to shearing type forces. "The safety and effectiveness of youth resistance training are now well documented, and the qualified acceptance of youth strength training by medical and fitness organizations is becoming universal" (Avery D. Faigenbaum, EdD, Clin Sports Med 2000). In the reported injury cases, more than 50% of overuse injuries could be prevented if fundamental fitness skill development were emphasized vs. sport specific skills (Amith et al, 1993). In one specific study of teenage female soccer players, the ones who participated in a pre-season training program had fewer instances of knee and ankle injuries.
Strength gains have been well documented in youth training and has been seen in ages as young as 6, while the majority of studies that have been done show a strength increase of 30-40%! Some of the bad rap for resistance training comes from the early studies done using low resistance and low volume with short time lines. The increases were hard to tell apart from natural growth and development. This brought the conclusion that training was not necessary and more so just an unnecessary risk.
In quantitative aspects, the gains seen in prepubescent children are similar to those seen in adolescents and untrained adults. The gains in strength and performance are most likely due to neurological changes rather than hypertrophy, seeing that the level of circulating androgens(sex hormones) is inadequate. Along with the neurological gains that included increased motor unit activation, coordination, recruitment and firing, are intrinsic adaptations that include excitation/contraction coupling, myofibrillar packaging density, and better muscle fiber composition. Bottom line, these athletes became stronger and faster.
Another benefit of youth training is increased bone mineral density. It is documented that childhood may be a good time for bone modeling and remodeling to respond to mechanical loading. This can be especially
beneficial for females who may later on in life face osteoporosis. A significant decrease in body fat percentage has also been seen in preadolescents. Psychological benefits from resistance training have also
been noted that can include self-concept, self-esteem, body cathexis, socialization skills and mental discipline.
As we age we begin to lose muscle function and even total muscle fibers. The percentage of type II muscle fibers can decreased fivefold by the time you are 80 years old! The muscle fiber cross sectional area(muscle mass) also decreases as much as five to six fold! On average, 27% of one's total amount of muscle fibers will be lost between the age of 30 and 70 years of age. At 20 years of age approximately 90% of muscle area is without fat. By the age of 80 that number has fallen to under 60%. These percentages may not seem significant, but they are when you realize that muscle fibers such as type II are the ones that stop you from falling. These fast twitch muscle fibers are able to fire with such speed and precision that they can catch you if you are about to fall, and seeing that walking entails programmed falls with each step these fibers seem more and more important. A decrease of 40-50% in myosin ATPase, and enzyme that releases that energy from ATP, is seen between 20 and 75 years of age. This loss results in the loss of both force and power.
A 50% increase has been shown in anaerobic performance after weight training in the elderly which was measured by the Wingate (sprint) test. After a 10 week periodized training session for men of age 63 there was a 16- 18% change from the baseline measurements in both strength and power. This increase was even greater than males that were performing the same training protocol in their 30's!