There is no real danger in kids performing machine based training under the proper supervision and appropriate guidelines. Many studies done the world over have concluded that strength based training programs done on this kind of fitness equipment is very safe for young children (again under appropriate guidelines). My issue is not whether or not kids CAN perform this kind of training, my question is WHY they need to.
Back tracking for a second, I have watched (as I’m sure we all have) a very young baby struggle to get to their feet. In terms of strength output, this equates to a near maximal load. No one seems to be concerned about it until that child becomes eight or so years old and wants to lift weights… Then people want to call the police on you because you had the ignorance to let a child perform strength training! The bottom line is that kids CAN handle strength training based loads… heck they do everyday – hopscotch, tag, bowling, ANY sport – all these things require varying degrees of strength.
Now the question of why. I just have never been convinced by any article, book or study championing child strength training that kids SHOULD use machine based fitness equipment. The reality is that sport AND life are based on the functionality of movement. Juan Carlos refers to it as the Four Pillars of human movement; Paul Check has a similar model which incorporates six stages.
My point being that whether you are dealing with a young athlete or just a young fitness participant, your goals as Youth Fitness Professionals should involve obtaining health and/or sporting proficiency on a useable level. Machines provide support (I have trained so many young athletes who simply cannot produce stability in all three planes), and the force application is both pre-set (which just begs for biomechanical dysfunction) as well as pre-guided (unfortunately sport and life are not).
My other concern with machines is that they inhibit two very important concerns when dealing with young athletes (actually when dealing with anyone):
1. It is very hard to train unilaterally when using machines (one side of the body at a time). Unilateral training, in my mind, is one of the most crucial components of developing young athletes.
Youth Fitness Professionals
2. You simply cannot train (either produce force through or learn to stabilize) the transverse plane. As referenced in many Kinesiology based books, over 85% of our core musculature is oriented horizontally or diagonally – we are designed for rotation, yet machines don’t allow for it.
My suggestion for working with young athletes (and this is based on several factors including age, emotional maturity, current physical proficiency) is as follows –