Exercises are often described as being functional. By this, the authors imply that the exercise is specific to a particular sport. The only criteria used for the exercise to be functional is that it involve the same muscles as are involved in execution of the sports skill.
This is far from what should be considered functional. When an exercise is truly functional, it is sports-specific and must fulfill very specific criteria. The exercise will then have an immediate and often dramatic effect on skill performance. Exercises that merely involve the same muscles that are used in the sport do not have such an effect.
In general, the more the exercise duplicates what occurs in execution of the sports skill, the greater will be the effect on performance. Merely involving the same muscles does not have the same effect. For example, doing an overhead press strengthens the deltoid muscle, which is used in many sports. In running, however, only the anterior deltoid is used to drive the arm forward. Thus, doing an exercise with the arms going overhead would not be specific to improving arm action in running since it doesn’t strengthen the muscles in the same way as they are used in execution of the sports skill. But, it would be considered functional according to trainers who promote this practice.
Of the criteria for specificity, one of the most important is that the exercise duplicate the same motor pathway as seen in the sports skill. When the exercise duplicates the same movement pattern as used in the sports skill, you develop strength in the same way that it is exhibited in the skill. In essence, the closer the strength or explosive exercise is to the actual sports skill, the greater will be the transfer to your sport, and you will see greater improvement in your performance.
However, doing exercises that involve the same muscles is still of value — especially in the general preparatory period. They become even more valuable the more they simulate what takes place in the skill execution.
For more details and examples of sport specific exercises, see Explosive Running, Womens Soccer: Using Science to Improve Speed, Explosive Golf, Explosive Basketball Training, Explosive Tennis and Build a Better Athlete