Weight training is a form of exercise for developing the strength and size of skeletal muscles. It is a common type of strength training which uses the force of gravity (in the form of weighted bars, dumbells or weight stacks) to oppose the force generated by muscle through concentric or eccentric contraction. Weight training is also referred to as a type of resistance training (in the broad sense meaning any resistance to muscular contraction), which is often confused with elastic resistance training, which uses tension generated by stretched or bent materials to resist the force of contraction.

Properly performed, weight training can provide significant functional benefits and improvement in overall health and well-being including increased bone, muscle, tendon and ligament strength, improved joint function, reduced potential for injury, improved cardiac function and elevated good cholesterol. In one common training method, the technique involves lifting progressively increasing amounts of weight, and uses a variety of exercises and types of to target specific muscle groups. Weight training is primarily an anaerobic activity, although some proponents have adapted it to provide the benefits of aerobic exercise.

Weight training differs from bodybuilding, weightlifting, and powerlifting, which are sports rather than forms of exercise. Weight training, however, is often part of their training regimen.

Hippocrates explained the principle behind weight training when he wrote "that which is used develops, and that which is not used wastes away." Progressive resistance training dates back at least to Ancient Greece, when legend has it that wrestler Milo of Croton trained by carrying a newborn calf on his back every day until it was fully grown. Another Greek, the physician Galen, described strength training exercises using the halteres (an early form of dumbbell) in the 2nd century.

Another early device was the Indian club, which came from ancient Persia where it was called the "meels." It subsequently became popular during the 19th century, and has recently made a comeback in the form of the clubbell.

The dumbbell was joined by the barbell in the latter half of the 19th century. Early barbells had hollow globes that could be filled with sand or lead shot, but by the end of the century these were replaced by the plate-loading barbell commonly used today.

Strength training using isometric exercises was popularised by Charles Atlas from the 1930s onwards. The 1960s saw the gradual introduction of exercise machines into the still-rare strength training gyms of the time. Weight training became increasingly popular in the 1980s, following the release of the bodybuilding movie Pumping Iron and the subsequent popularity of Arnold Schwarzenegger. Since the late 1990s increasing numbers of women have taken up weight training, influenced by programs like Body for Life: currently nearly one in five U.S. women engages in weight training on a regular basis.

Weight training can be one of the safest forms of exercise, especially when the movements are slow, controlled, and carefully defined. However, as with any form of exercise, improper execution can result in injury. When the exercise becomes difficult towards the end of a set, there is a temptation to "cheat", i.e. to use poor form to recruit other muscle groups to assist the effort. This may shift the effort to weaker muscles that cannot handle the weight. For example, the ''squat'' and the deadlift are used to exercise the largest muscles in the body—the leg and buttock muscles—so they require substantial weight. Beginners are tempted to round their back while performing these exercises. This causes the weaker lower back muscles to support much of the weight, which can result in serious lower back injuries. To avoid such problems, weight training exercises must be performed correctly. Hence the saying: "train, don't strain".


An exercise should be halted if marked or sudden pain is felt, to prevent further injury. However, not all discomfort indicates injury. Weight training exercises are brief but very intense, and many people are unaccustomed to this level of effort. The expression "no pain, no gain" refers to the discomfort expected from such vigorous effort. It does NOT suggest ignoring the more severe pain that comes from injury.

Discomfort can arise from other factors. Individuals who perform large numbers of repetitions, sets and exercises for each muscle group may experience lactic acid build-up in their muscles. This is experienced as a burning sensation in the muscle, but it is perfectly harmless. These individuals may also experience a swelling sensation in their muscles from increased blood flow (the "pump"), which is also harmless.

Beginners are advised to build up slowly to a weight training programme. Untrained individuals may have some muscles that are comparatively stronger than others. An injury can result if, in a particular exercise, the primary muscle is stronger than its stabilising muscles. Building up slowly allows muscles time to develop appropriate strengths relative to each other. This can also help to minimise delayed onset muscle soreness. A sudden start to an intense programme can cause significant muscular soreness. Unexercised muscles contain cross-linkages that are torn during intense exercise.


Weight trainers commonly spend 5 to 20 minutes warming up their muscles with aerobic exercise before starting a workout. They also stretch muscles after they have been exercised. The exercises are performed at a steady pace, taking at least two to four seconds to lift and lower the weight, to avoid jerks that can damage muscles and joints.

Exercises where a barbell is held above the body, such as the squat or the bench press, are normally performed inside a squat cage, which can catch the bar, or in the presence of one or more spotters, who can safely re-rack the barbell at the end of the set if the weight trainer is unable to do so.

Anyone beginning an intensive physical training programme is typically advised to consult a physician, because of possible undetected heart or other conditions for which such activity is contraindicated.

There have been mixed reviews regarding the use of weightlifting belts and other devices, such as lifting straps. Critics claim that they allow the lifter to use more weight than they should. In addition, the stabiliser muscles in the lower back and gripping muscles in the forearms receive less benefit from the exercises.

An isolation exercise is one where the movement is restricted to one joint and one muscle group. For example, the leg extension is an isolation exercise for the quadriceps. The other muscle groups are only minimally involved—they just help the individual maintain a stable posture—and movement occurs only around the knee joint.

Compound exercises work several muscle groups at once, and include movement around two or more joints. For example, in the leg press movement occurs around the hip, knee and ankle joints. This exercise is primarily used to develop the quadriceps, but it also involves the hamstrings, glutes and calves.

Compound exercises are generally similar to the ways that people naturally push, pull and lift objects, whereas isolation exercises often feel a little unnatural.


Each type of exercise has its uses. Compound exercises build the basic strength that is needed to perform everyday pushing, pulling and lifting activities. Isolation exercises are useful for "rounding out" a routine, by directly exercising muscle groups that cannot be fully exercised in the compound exercises.

The type of exercise performed also depends on the individual's goals. Those who seek to increase their performance in sports would focus mostly on compound exercises, with isolation exercises being used to strengthen just those muscles that are holding the athlete back. Similarly, a powerlifter would focus on the specific compound exercises that are performed at powerlifting competitions. However, those who seek to improve the look of their body without necessarily maximising their strength gains (including bodybuilders) would put more of an emphasis on isolation exercises.

Free weights are dumbbells and barbells. Unlike exercise machines, they do not constrain users to specific, fixed movements, and therefore require more effort from the individual's stabiliser muscles. It is often argued that free weight exercises are superior for precisely this reason. As exercise machines can go some way toward preventing poor form, they are somewhat safer than free weights for novice trainees. Moreover, since users need not concentrate so much on maintaining good form, they can focus more on the effort they are putting into the exercise. However, most athletes, bodybuilders and serious fitness enthusiasts prefer to use compound free weight exercises to gain functional strength.


Some free weight exercises can be performed while sitting or lying on a Swiss ball. This makes it more difficult to maintain good form, which helps to exercise the deep torso muscles that are important for maintaining a good posture.

There are a number of exercise machines that are commonly found in neighbourhood gyms. The Smith machine is a barbell that is constrained to move only vertically upwards and downwards. The cable machine consists of two weight stacks separated by 2.5 metres, with cables running through adjustable pulleys (that can be fixed at any height) to various types of handles. There are also exercise-specific weight machines such as the leg press. A multigym includes a variety of exercise-specific mechanisms in one apparatus.

One limitation of many free weight exercises and exercise machines is that the muscle is working maximally against gravity during only a small portion of the lift. Some exercise-specific machines feature an oval cam (first introduced by Nautilus) which varies the resistance so that the resistance, and the muscle force required, remains constant throughout the full range of motion of the exercise.

Weight trainers commonly divide the body's individual muscles into ten major muscle groups. These do not include the hip, neck and forearm muscles, which are rarely trained in isolation. The most common exercises for these muscle groups are listed below. (Videos of these and other exercises are available at exrx.net and from the University of Wisconsin.)
The sequence shown below is one possible way to order the exercises. The large muscles of the lower body are normally trained before the smaller muscles of the upper body, because these first exercises require more mental and physical energy. The core muscles of the torso are trained before the shoulder and arm muscles that assist them. Exercises often alternate between "pushing" and "pulling" movements to allow their specific supporting muscles time to recover. The stabilising muscles in the waist should be trained last.

Super slow: Super slow repetitions are performed with lighter weights. The lifting and lowering phases of each repetition take 10 seconds or more.

Timed rests: By strictly controlling the rest periods between reps and sets a trainer can reduce their level of blood oxygenation, which helps to increase the stress on the muscles.

Wrist straps: Wrist straps (lifting straps) are sometimes used to assist in gripping very heavy weights. They are particularly useful for the deadlift. Some lifters, however, avoid using wrist straps in order to develop their grip strength. Wrist straps can allow a lifter initially to use more weight than they might be able to handle safely for an entire set. They can also place potentially harmful stress on the bones of the wrist. Instead, wrist curls and reverse wrist curls can be done to improve grip strength.