The principal of Specificity is a foundational aspect of every effective training program. Specificity of training refers to training in a specific way to produce a targeting change or end result. You can target specific muscle groups, energy systems, movement velocities, movement patterns or specific muscle action types. For example, if you want to strengthen your leg muscles, you select exercises like the Back Squat because of its emphasis on lower body development. This is referred to as “muscle group specificity”.
Another method of applying specificity is to target specific movement patterns. Movement pattern specificity is usually used in working with athletes or individuals who wish to develop strength that translates to a specific activity or sport.. For example, if you are a volleyball player, take into account the fact that volleyball involves repeated jumping movements, therefore incorporating movements like power cleans, power snatches and squats mimic the jumping movements in volleyball. The more similar the resistance training exercise is to the movement pattern, the greater the likelihood of transition to the targeted activity.
Source: NSCA’s Essentials of Personal Training