http://www.newsday.com/news/health/the-daily-apple-1.4760551/is-resistance-training-a-safe-option-for-children-1.5045315
Here’s something to keep in mind: The art of resistance training -- if
done correctly and with good form -- will not stunt growth.
For years the general fitness public has embraced the idea that
resistance training posed a risk to adolescents because it could lead to
stunted growth as a result of growth plate fractures.
While it is a reasonable concern, research says the problem is often
caused by human error. Most growth plate fractures have been seen in
those adolescents who train incorrectly, lift objects that are too
heavy, or fall into another object while training. This has been
recorded primarily in poorly supervised, heavy, over-the-head type
lifts.
Growth plates (their scientific name is epiphyseal plates) are located
at the ends of long bones, primarily in the arms and legs. While the
child is growing, the bones elongate from these plates. If the growth
plates are damaged, the bone’s blood and nutrient supply may be
disturbed, resulting in growth trauma.
An epiphyseal plate fracture has not been reported in any youth
resistance training study that adhered to established training
guidelines, according to the National Strength and Conditioning
Association.
A doctor should always be consulted before starting any exercise
regimen and that's especially true for children, but a properly designed
and supervised resistance training program can help promote exercise
habits in children and adolescents, improve motor skills, contribute to
enhanced sports performance and increase a young athlete’s resistance to
sports-related injuries. It can also lessen their risk of developing
heart problems, the NSCA notes.
Programs for adolescents should focus on the basics, making the
exercises easy to learn and leaving less room for error. Even though
there is no minimum age for resistance training, children can begin to
enjoy a regimen as early as ages 6 to 8, as long as they are mentally
and physically competent.
To start, try calisthenics -- jumping jacks, pushups, sit-ups, etc. --
which younger people tend to enjoy. Calisthenics, which are aerobic in
nature, enforce the use of a child's own body weight, without the use of
added foreign weight such as dumbbells. They are also a good way to
practice muscular coordination.
Stay away from plyometric exercises during the beginning phases of
resistance training. While jumping onto and off objects may seem like
the norm for some, others can easily lose their balance, slip and even
fall off the top of the plyometric boxes, causing injury.
Eventually, more advanced exercises can be added to a routine, but with
caution. External weights may be used, such as elastic bands, dumbbells
or plate-loaded machines but proper form should first be taught,
stressed and supervised, and the weight should be kept light. In the
beginning stages of the resistance program, the repetitions should range
from 10 to 15 per set, and one to three sets should be performed
encompassing a variety of upper- and lower-body exercises, specifically
focusing on movements that strengthen the abdominal and lower back
areas.
A general overall fitness rule regarding repetitions is: two to five
for strength/power (anaerobic), six to 12 for size (anaerobic/aerobic)
and more than 12 for endurance (aerobic). As a child advances through
the routine, it can be progressed by increasing the number of sets
and/or decreasing the number of repetitions.
Children should train less than adults do, typically two to three times
a week on nonconsecutive days, allowing 48 to 72 hours between
sessions. Each workout should be preceded by a five- to 10-minute
dynamic warm-up, such as hops and skips.
Done correctly, beginning a resistance program early in life cannot
only be beneficial for a child’s short- and long-term health but can
also pave the road to a hearty athletic career.