A critical aspect of physical fitness is the extra growth of muscle tissue. Hypertrophy training, commonly known as "bulking," relies on the body's ability to rebuild torn muscle tissue stronger than it was before being torn. Every time a given muscle is exercised beyond its accustomed use, the extra force of the muscle contractions cause small tears to appear in the muscle fibers. The body then uses protein to create extra muscle tissue. The training regimen must be consistent to condition the muscular system to trigger extra growth.
Two main components exist in a hypertrophy training regimen: diet and exercise. The exercise regimen tears down muscle tissue in order to reconstruct it, and a high-protein diet provides the nutrients necessary to replenish lost muscle tissue. Effective muscle growth training should incorporate each muscle group each day in turn to avoid over-training. Consecutive days working a single muscle group deprive the muscles of their recovery time; muscles typically require 48-72 hours to recuperate from heavy exertion. Hypertrophy training incorporates resistance workouts such as lifting weights.
Weightlifting can be done with free weights or with the help of exercise machines. Beginners to weight training should focus on machines because they provide a preset track that forces the muscle to move through its full range of motion. The use of free weights encourages the development of balance and core muscles in the abdomen, but injury can result from accidentally moving a muscle beyond its range of motion. Free weights should be used only under the supervision of a certified trainer and only at light weights. The level of weight used during exercise also plays a part in hypertrophy.
Maximum muscle growth occurs by developing fast-twitch and slow-twitch muscle fibers equally. Fast-twitch fibers provide higher amounts of force but tire out more quickly. Slow-twitch muscle fibers exert less force but have longer endurance times. Isometric exercises, in which force is exerted against an unmoving resistance, develop slow-twitch muscle fibers. Isotonic exercises, in which muscles contract at a steady rate, develop fast-twitch muscle fibers.
Hypertrophy training should be supplemented with foods such as lean meat, cottage cheese, milk and nuts. These foods contain high concentrations of protein. Carbohydrates should form a significant part of the diet as well, because they provide the energy necessary to fuel workouts and muscle regrowth. Eating meals before and after a workout produces the best results, but the workout should occur no earlier than one hour after a meal to allow the food time to digest.