There are a lot of factors that have influence on an athlete's performance and as a coach you must be aware of these. A 7-year old handball player is unable to learn the same as a 14-years old as their stage of development is not the same.

All starts their life lying on the back or on the belly in a cradle and are now beginning to develop physically, perceptual, motor co-ordination, socially and intellectual, and that is a process which take the time needed

The physical development
The physical development start at age zero and continues when the athlete is about 18 years old. The first 2-3 years the children grow very fast. Then the growth is levelled to a more constant level around 6 years old and then when the child is about 11 year old (girls) and 12 years old (boys) they start growing fast again.

The level can be seen in this drawing:

In the periods with great growth in height it is important that the players are not forced to hard physical training, as their bones and muscles are stretched violently. You will often hear the players talk about sore joints. Therefore you will only get results with physical training if you wait until end of the growing period. The co-ordination is best influenced in the period where there only is a little growth. At the same time of the growing in height the body also grow wider. The muscles get longer and become thicker. The period for growing wider happens in the period 6-11 years and 14-17 years. Because the body gets higher in the age of 11-14 years, the muscles cannot cope and this causes the co-ordination to be reduced.

The perceptual development
This is the ability to grasp and act. The player sees/grasp what happens - evaluate it - takes a decision about what to do - and act based on the previous details

When a certain situation arise on the court, the player will go through all those phases and - dependent on age and experience - a reaction will follow:

Example for an attacking player:
- The player grasp the situation (sees, hear, feels). It could be a running in from a teammate with the ball
- The situation evaluates. Recognition that an attack is performed.
- An evaluation is performed (perception). What shall I do in this situation? Must I run into a good position to receive the ball? Shall I set a screening? Will my teammate be caught in the defense and must I therefore be ready to help? If I get the ball then what shall I do?
- The decision is taken. I will run in to be able to receive the ball and try a shot after making an initial feint against my defender
- The decision is performed (motor). A fast start forward while being ready to receive the ball and perform the decision.

But no matter how good the perceptual ability is, it cannot be used if the motor is not working correctly. The player knows what to do, but the body cannot perform it.

The motor co-ordination development
The motor abilities develop while the player grows older. In the beginning the player only has the gross motor to work with, and learning the more fine aspects is impossible and can be harmful as well, as unnecessary muscle tensions are created, if a player is forced to do something, which does mot match their motor abilities.

The ability to perform fine motor movements arrives when the player is about 10-11 years old and only then a more advanced training can be started.

Before the puberty - gross motor co-ordination period
This is the period I call "the Bambi-period". The control of the movement of the body is not so great and the co-ordination is reduced. The gross motor co-ordination is the only available and the player can only perform gross, combined movements.

Learning the exercises must take the above mentioned into consideration. If a player for instance is to learn a throw in accordance with the following model:
1. Throw with the arm alone (no body movement)
2. Throw with a distinct movement of the upper body (shoulder forward while throwing)
3. Throw with the whole body (shoulder forward - hip forward)
4. Throw with the opposite leg in front without movement of the body
5. Throw with the opposite leg in front and full body movement

the final result will be that the movements are learned, but they will be hesitant and awkward and not performed as a natural movement. Every movement must be remembered and often one of them is forgotten.

Therefore all training in this period must be planned in accordance with the ability to move at hand, and the players must be comfortable with the basis movements in handball - all learned while playing with the ball.

After the puberty - fine motor co-ordination period
This period is the start, where the player is able to perform fine and differentiated movements. Techniques, which demand coordinated movements, can be refined. If we take the previous example, the final result will be a more natural, unstrained sequence, where the player does not use a lot of thinking about how to do it

There is a great difference between boys and girls when we talk about motor ability. The motor of the boys ends when they are about 18-20 years old while the girls reach their maximal motor abilities during their puberty.

The social development
Children under 6 years must be regarded as self-centered and they will start taking interest in their surroundings when they start at school, that is interest in others except their close friends. Therefore they are most socially comfortable when they work in smaller groups and the playing activities are kept in various forms of mini-play. In this period (6-10 years old) it is important that the trainer knows his/her role. The children identify themselves with the persons, they are in contact with, and the trainer might become an ideal they want to copy and don't differ whether the trainer is a good example or not.

When they become about 10 years old they will want some more firm forms of fellowship, which can develop into more organized group fellowships. Then exercises, which satisfy the wish of doing something with others, can be started.

When the players reach the age of about 15-16 years they have their own identity, which clearly can be seen in the connections between their friends and the choice of sport. Before that time they choose a sport because their friends are there. If the friends stop, they also stop. Later on it is not so important, and they can easily continue with their sport even if the friends have chosen another sport or stopped.

The intellectual development
Try to convince a 10-year-old player the value of energetic training to be the best player in the club in about 10 years time. This will normally be too abstract for a 10 years old. When the players are 7-12 years old they look at the situation here and now and only later on the more abstract kind of thinking is possible. The ability to master the abstract way of thinking is clearly seen when the youngest are playing a match. They have learned to move in and make a shooting threat and then shoot or pass the ball. The threat is made with great enthusiasm. Then a short pause while thinking and then the shot or the pass. The possibility that a teammate could be coming full at speed to receive the pass right after the threat is future.

Only in the age of 11-12 years and up it can be expected, that the players understand the meaning of some preliminary work in a game situation and the possibilities these preliminary work might cause. It is also now the more tactical elements in training can be put into good use

- - - - -

All the mentioned stages of age must be regarded on the whole. Of course  some players develop earlier and players who develops later. But because a 12-year-old player physical looks like a 16-year-old, you must not forget, that it is still a 13-year-old player you are working with, who most likely has a 12 years old way of thinking and abilities.