Training and Exercise for Children and Teenagers - Part 1

Doug Lawrenson
Written By: Doug Lawrenson
December 22nd, 2007
Updated: June 13th, 2020
Categories: Articles Training
107.2K Reads
Part 1 in a 4 part series for children and teenagers. This article is a must read for teens who should understand their body before they start training!

Training and exercise for children and teenagers. This article is huge! So huge it has been split into a 4 part series. You can see the 4 parts below or click the continue link at the bottom of each part.

Part 1: Introduction & Body Composition and Development of Tissue

Children and young adults, who embark on a training regime, normally drop out within the first 3 months of training. Most are disillusioned with training as the results don’t come quick enough or as easy as they may be have been led to believe, which is normally because of the super hyped adverts in magazines and elevated promises from supplement companies. The main reason for failure is incorrect training, and in most cases overtraining. Weight training and bodybuilding for young people should be in a gradual and in a specific pattern. Many people ask, what age can I start weight training, and encouragement should be shown to these youngsters to participate in all types of sport and training with the object of obtaining and helping with full normal body development and learning skills.

Weight training can improve strength, increase muscle tone, lose bodyfat and gain muscle mass and importantly improve their bone density. But if done incorrectly then training with weights can also lead to injury of tendons, ligaments, muscle, and bone. Many people learn weight training from training at home, or by watching friends in a gym. But a lot of time, what these people are watching is incorrect lifting technique, which can lead to injuries. Some common training injuries that may occur include:

  • Sprains
  • Strains
  • Tendonitis
  • Fractures
  • Dislocation

Continually using the same, improper weight training technique can result in chronic injuries. Over time, you may find yourself with:

  • Rotator cuff damage
  • Muscle overload
  • Bone stress injuries
  • Nerve damage

Most of the above will hamper any goals from training that you may have, and may put you out of training for many months. So it is important to start off on the right foot with correct knowledge of how the human body works and with correct training technique. As mentioned above many youngsters learn weight training by watching friends or by getting their own weights and training at home. I always advise against training at home or with friends until some training experience is gained from a weight training specialist, coach, athletic trainer or certified fitness and exercise specialist who has been specifically trained in weight training techniques. Then if you want to train at home at least you will have knowledge of correct training technique. Even if you are not a complete novice it is always advisable to schedule time with a trainer to oversee your training technique to make sure that what you are doing is the right way.

With the growing interest in sport and competition for teens over the years the question about, is training physically or psychologically harmful, and is commonly asked.

To answer the question above we really need to examine the processes of growth and development, and examine how these processes affect the responses and adaptations to exercise and also motor ability and sports performance, including the consideration of special issues relating to training of young athletes.

The terms growth, development and maturation are all aspects of the changes that the teen body will go through. Growth refers to the increase in the size of the body or parts. Development refers to the differentiation of cells along specialised lines of function (e.g., organ systems) so reflecting the functional changes that occur with growth. Maturation refers to the process of becoming an adult and taking on the adult form and becoming fully functional and defined by the system or function being considered. For example, skeletal maturity refers to having a fully developed skeletal system and in which all the bones have completed normal growth and ossification (bone formation). The state of the adolescent’s maturity can be classified by:

  • Age in years.
  • Skeletal age.
  • Stage of sexual maturity.

Body composition and development of tissue.

The understanding of the physical capabilities of teenagers and potential impact that sports activities can have on young athletes, we need to consider the physical state of the teen’s body.

Height and weight.

Studies have been conducted with regard to the changes in height and weight that accompany growth. Just before puberty the rate of change in height increases markedly, followed by a less growth response until full height is reached at the age of about 16 in girls and 18 in males. As with height, the peak rate of growth in bodyweight occurs at approximately 12.5 years in girls and 14.5 years in males, slightly later than height.


Bones, joints, cartilage, and ligaments form the body’s structural support. Bones provide points of attachment for the muscles, protect delicate tissues, and act as reservoirs for calcium and phosphorus, and some are involved in blood cell formation. During foetal development, as well as during the initial 14-22 years of life, membranes and cartilage are transformed into bone though the process called ossification (bone formation). The average ages at which the different ones in our bodies begin formation vary widely, but bones typically begin to fuse in the preteens and are all fused by the early 20’s. On average girls achieve full bone maturity several years before boys. The structure of mature long bones is complex. Bone is a living tissue that requires essential nutrients, so it receives a rich blood supply. Bone consists of cells distributed through a matrix or lattice-type arrangement, and it is dense and hard because of deposits of lime salts, mainly calcium phosphate and calcium carbonate. For this reason, calcium is an essential nutrient, particularly during periods of bone growth and in the later years of life when bone tends to become brittle because of bone mineral losses associated with aging. Bones also store calcium. When our blood calcium level is high, excess calcium can be deposited in our bones for storage, and when calcium levels are too low, bone is broken down, to release calcium into the blood. When an injury occurs or when stress is placed on a bone, more calcium is deposited. Thus, throughout life our bones are constantly changing. Exercise is essential for proper bone growth. Although exercise has little or no influence on bone lengthening, it does increase bone width and bone density by depositing more minerals in the bones matrix, which increases the bones strength.

In males, the total muscle mass increases from 25% of total bodyweight at birth to about 50% or more in the adult.


From birth through adolescence, the body’s muscle mass steadily increases, along with the youngster’s weight. In males, the total muscle mass increases from 25% of total bodyweight at birth to about 50% or more in the adult. Much of the weight occurs when the muscle development rate peaks at puberty. This peak corresponds to a sudden, almost 10 fold increase in testosterone production. Girls don’t experience such a rapid acceleration of muscle growth at puberty, but their muscle mass does continue to increase, although much slower, to about 40% of their total body weight as adults. This difference is largely attributed to hormonal differences at puberty. Increases in muscle mass with age appear to result from hypertrophy (increase in size) of existing fibres, with little or no hyperplasia (increase in fiber number). This hypertrophy results from increases in myofilaments and myofibrils (filaments found inside muscle fibers). Increases in muscle length as young bones elongate result from increases in the number of sacromeres (A sacromere is composed of two kinds of myofilaments, and muscle is made of bundles of sacromeres) and from increases in length of existing sarcomeres. Muscle mass peaks in females at age 16-20 years and in males at 18-25 years. Unless it is increased further though exercise, diet, or both.

Muscle Map

Nervous System.

As growth of children increases they develop better balance, agility and coordination as their nervous system develops. Myelination (maturation of nerve cells that allow nerve impulses to travel faster) of the nerve fibres must be completed before fast reactions and skilled movements can occur because conduction of an impulse along a nerve fibre is considerably slower if myelination is absent or incomplete. The myelination occurs most rapidly during childhood and continues well beyond puberty. Although by practicing an activity or skill will improve performance to a certain level, the full development of an activity or skill depends on full maturation (and myelination) of the nervous system. The development of strength and muscle size is also influenced by myelination.

This article continues in part 2 >>

Posted on: Mon, 01/07/2013 - 18:40

Love this site, lots of great info. I just wish I'd read some of this when I was 16 and just starting to go to the gym! I'm 21 now with all sorts of back pains and joint mobility/ flexibility problems which I suspect are the result of not training in a balanced way!

Posted on: Thu, 09/06/2012 - 07:17

thanks a lot for the thing more i want to confirm is that my daughter is 10 yrs old n she is going with me in aerobic classes n the trainer is realy an expert . do u think these classes will be beneficial for her or reply soon n give the reason also. thanku

Ryan Parkinson
Posted on: Mon, 04/05/2010 - 01:47

I just wanted to say extremely great website, it has provided a tonne of information that can really guide me step by step in preparing myself for weight training... really appreciate it!!

Keep up the good work;)