Specific
The principle of specificity refers to the effect that ex ercise training is specific to the muscles involved in that activity. the fiber types recruited. the principal energy system involved (aerobic versus anaerobi the velocity contraction, and the type of muscle contraction (ec. centric, concentric, or isometric) Indeed, one would not expect the arms to become trained during a 10-week running exercise program. However, this also means that if an individual participates in a low intensity, distance unning program that utilizes the slow-twitch muscle ttle or no training effect occurring in fibers, there fast-twitch ers in the same muscle specificity also refers to the types of adaptations occurring in muscle as a result of training. If a muscle is engaged in endurance types of exercise. the pri mary adaptations are increases in capillary and mi tochondria number, which increase the capacity of the muscle to produce energy aerobically. If a muscle is engaged in heavy resistance training, the primary adaptation is an increase in the quantity of the con tractile proteins, as the mitochondrial and capillary densities may actually decrease (59)