Speed in soccer (and rugby) takes on different forms. It is possible to see players run in a straight line (linear speed) or any combination of linear and curved movements. This means that the player can run in a straight line and then forward and to the left or forward and to the right or run left, right and forward or any combination of directions.
Most often we see a broken run characterized by stops and starts as well as changes in direction. As a result we see acceleration, deceleration, quick stops, starts and changes in direction. All of these forms of running are seen in competition.
In soccer speed training they occur independently and in various combinations of one or more. No one playing position can be characterized by only one type of run. This is one reason why tests such as the 40 yard dash and typical tests for agility are poor indicators of playing ability.
The ability to change direction while running is probably the most important characteristic of a high-level soccer or rugby player during execution of his game skills. Stopping, starting, changing direction while running with constant changes in direction are probably the most important characteristics of a high-level player.
The quicker the players can make changes in direction the more successful he will be. By making quick changes in direction the player is capable of eluding (or staying with) his opponent. The ability to accelerate then allows him to get more distance from his opponent or to stay with his opponent before he may once again have to make a quick change in direction.
The better athletes possess high levels of skill in order to execute the technique involved in making these movements. He must also have good running technique, know how to stop and start, execute an effective cutting action, have the ability to accelerate and use the skills automatically when the situation calls for it. This should be the most important goal in soccer speed training.
In addition to the skills, the player must be able to display high levels of concentric and eccentric strength and explosive power during execution of the skills. The skill and the physical abilities must be tightly joined together in order to demonstrate the best all-around running on the field. Development of only the physical abilities, separate from running or cutting technique will not produce a great player. This is a critical point that is often overlooked.
It is in this area that I see many soccer and rugby programs fall down in relation to developing the best player on the field. They do an effective job in developing the physical abilities such as strength and explosiveness, but they are developed independently as separate factors. They are not coupled with technique.
It is somehow assumed that development of strength or explosive power will automatically transfer to execution of the player’s running, cutting or skill execution. In reality, this does not happen.
It is a proven scientific fact that development of strength or explosive power or other physical abilities independently or separate from technique will not transfer to skill execution (performance on the field). The only time this can happen is with the young or novice athletes as for example, most high school players
This is why we see so little improvement in gameplay on the higher levels. The athletes become stronger and more explosive, but not better in playing. This is where specialized strength exercises come into play. They develop strength and technique simultaneously. However, because of the way most strength and conditioning programs are set up, technique is typically ignored.
Improved technique and the physical qualities specific to the technique is the key to improved performance on the field, especially on the higher levels. If they are not addressed, players will only be able to play on the same level or on a lower level of performance.
For more information see Build a Better Athlete.him It has detailed explanations on how each of these skills can be learned and improved. Also see Explosive Running for descriptions of the specialized strength exercises.