Different goals require different training regimens. Powerlifters are interested in lifting the heaviest weight possible in proper form. Therefore muscle strength is determined by a one rep maximum (1RM). The key to determining strength, however, is not how big a muscle is (although big muscles are very strong) but how efficiently the muscle can be activated by the nervous system. Estimates are that the average person can recruit only about 50% of the fibers or a muscle to fire at once. Training can increase that to around 70%. Powerlifters, who train just for this purpose, can go as high as 90%. The greatest strength gains are made in training in the 3-6 rep range with heavy weight for 3-5 sets, with plenty of rest between sets. Bodybuilding is similar to powerlifting, but the goal is different. Bodybuilders also gain strength, but the main emphasis for them is to gain muscular size. And to achieve this, a different type of training regimen is used. The main adaptation responsible for muscle growth is hypertrophy, which is an increase in the diameter of the muscle fiber. This is accomplished by adding more muscle fibers ó packing in more actin and myosin filaments ó inside the muscle cell. Maximal increases in muscle size come from training in the 6-12 rep range with moderate weight. It is important to take each set to failure, and if you can do 12 reps without going to failure, the weight must be increased by at least 10%. Bodybuilders fare better when they do a higher volume of work than powerlifters. Bodybuilders may do 4-6 sets per exercise and more exercises per muscle group. Rest is also reduced to 1-2 minutes between sets and the eccentric, or lowering, portion of the exercise is emphasized to provide the micro-trauma in the muscle responsible for causing the greatest growth. Bodybuilders often find that incorporating both styles of training into their own program. One way is to start with some heavy sets or low reps to failure, followed by some moderate sets or high reps to failure. Another is called “periodization,” which involves some light training for several weeks, followed by a period of bodybuilding-style training, followed by a period of powerlifting-style training. Other sports like foot, basketball, sprinting, boxing, etc., require more than just strength and size. They require power, which is a combination of strength and speed. Training for speed involves trying to lift the weight as quickly as possible. Plyometrics is a way of overloading the muscle prior to an explosive contraction with speed-strength as the goal. This increases the contraction speed and strength because the muscle is stretched before the contraction, causing a more powerful contraction than if the muscle were contracted from its normal resting length. The best form of training for endurance activity is the activity itself. The intensity is very low and the volume very high. Because the type of fibers (type I) responsible for endurance activity have very little capacity for hypertrophy, therefore endurance training does not result in a great increase in muscle size.

Concentric muscle actions occur when a muscle is shortening. This happens when force generated inside the muscle is greater than the resistance to it shortening. During a concentric muscle action, action potentials arrive at the muscle cell, causing a neurotransmitter to be released into the cell where it causes a release of calcium. The release of calcium sets off a series of events leading to the actin-myosin cross-bridges. ATP is consumed as the sarcomere shortens. When a muscle fiber contracts, each of the individual sarcomeres contract and ATP is consumed. Concentric muscle actions are the only true muscle contractions. Isometric muscle actions refer to a situation when the force generated by the muscle is exactly equal to balance the resistance. It refers to any time the muscle is working by is not changing length. Eccentric muscle action refers to when the muscle is generating force but less than the resistance on the muscle. An example is the lowering phase of a biceps curl. The muscle is still generating force, but instead of it contracting (getting shorter) it is lengthening. Isokinetic muscle actions the same velocity. During isometric and eccentric actions, the same things happens as does during the concentric phase, except the muscle is not able to overcome the resistance of the force against it. In the isometric the sarcomeres remain the same and in the eccentric the sarcomeres actually lengthen. This causes damage to the actin-myosin cross-bridges and also to the entire sarcomere. Following intense training, “Z-band streaming” occurs as myofilaments stream from the sarcomere. Under extreme conditions, the sarcomere ruptures and the cellular contents leak out. Scientists believe that most muscle damage in training occurs during eccentric muscle actions when external forces rip apart the myofibers. This is also the main cause of soreness a day or two after training, called delayed onset soreness (DOMS). This tissue damage that occurs after training is a stimulus for inflammation, which signals the immune system activate to clean up the damaged cells. During this process damaged cells are repaired and the tissue is returned to its original state. However, the body doesnít like the inflammation and repair process, so it overcompensates during the repair process so the next time the muscle can handle the weight and not get damaged. For this process to occur, two things more important than any others, must occur. The first is that there must be a threshold of intensity exceeded to stimulate growth. The second is the principle of progressive resistance. This means that as muscle grows to adapt to the stress put upon it, the stress must also increase or the muscle will not continue to be damaged and overcompensate during the repair process, thus accounting for growth. For maximal gains in strength, you want to train with heavy weight at low reps. For maximal gains in size, you want to train with a weight that can be handled for 6-10 reps. Anytime you do more than 12 reps, youíre training the endurance aspect of the muscle and will do little for improvement in muscle size or strength. Most muscle growth occurs through hypertrophy, which means that the muscle cells grow. More myofibrils are created as more actin and myosin is added. Hyperplasia is the actual growth of new muscle cells. This usually occurs when there is a great deal of damage done to surrounding muscle cells. For this to happen the training stimulus must be of high intensity with heavy resistance and low repetitions. It has been shown in studies that muscle cells which are damaged leak some substance that acts as a signal for satellite cells to grow.