Up to twelve years, has not yet started hormonal changes, boys muscle contains little protein, minerals, fat and lots of water. Therefore, the muscles of the child quickly tire of, they are not yet ready to withstand any great physical exertion. In addition, there is a growing skeleton, and quite a large waste of energy can slow down this growth.In the intervertebral discs of the teenager also contains a lot of moisture, therefore, the physical vertical load on the spine can contribute to the emergence of intervertebral hernia.
Boys can strengthen muscles using bodyweight exercises without any weights, that is, without the use of weights and barbells. About the barbell and the weights and nothing to think about until age 16, and then you can engage with them only under the guidance of a coach.The boys 14-15 years old you can do exercises with dumbbells (weighing not more than 1-1,5 kg), lying just below the spine to protect from deformation.
To begin exercises with the pull-UPS on the horizontal bar, push-UPS and sit-UPS. In the 13-14 years is enough to be able to catch up 3-4 times. And if in 15 years the guy can make 20 pull-UPS – he's strong and ready to training with weights.
Also, increase muscle strength many stretching exercises that make the muscles supple. At the same time, tension, repeated many times to give the muscles endurance. Therefore, the most useful exercise for the boys, exercises with an expander.To train you must first for an hour a day. And do it in the middle of the day. A rest day should not be complete inaction of the muscles that maybe even a little sore after yesterday's workout, you need rest day to perform gentle exercises based on stretching. So the muscles can recover faster and prepare for the next workout.
During exercise, the load should be variable: worked the muscles of my hands, then worked the calf when he exercises the abdominals, you can then perform exercises for the hips or the upper body and so on.