Strength training

Strength training is the use of resistance to muscular contraction to build the strength, anaerobic endurance and size of skeletal muscles. There are many different methods of strength training, the most common being the use of gravity or elastic/hydraulic forces to oppose muscle contraction. See the resistance training article for information about elastic/hydraulic training, but note that the terms "strength training" and "resistance training" are often used interchangeably.

When properly performed, strength training can provide significant functional benefits and improvement in overall health and well-being including increased bone, muscle, tendon and ligament strength and toughness, improved joint function, reduced potential for injury, improved cardiac function and elevated good cholesterol. Training commonly uses the technique of progressively increasing the force output of the muscle through incremental increases of weight, elastic tension or other resistance, and uses a variety of exercises and types of equipment to target specific muscle groups. Strength training is primarily an anaerobic activity, although some proponents have adapted it to provide the benefits of aerobic exercise through circuit training.

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

History
Until the 20th century, the history of strength training was essentially a history of weight training. With the advent of modern technology, materials and knowledge, the methods that can be used for strength training have multiplied significantly.

Hippocrates explained the principle behind strength training when he wrote "that which is used develops, and that which is not used wastes away", referring to muscular hypertrophy and atrophy. 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. Ancient Persians used the meels, which became popular during the 19th century as the Indian club, 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 with isometric exercise 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. Strength 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 strength training, influenced by programs like Body for Life; currently nearly one in five U.S. women engages in weight training on a regular basis.

Basic principles
The basic principles of strength training involve a manipulation of the number of repetitions (reps), sets, tempo, exercises and force to cause desired changes in strength, endurance, size or shape by overloading of a group of muscles. The specific combinations of reps, sets, exercises, resistance and force depend on the purpose of the individual performing the exercise: sets with fewer reps can be performed using more force, but have a reduced impact on endurance.

Strength training also requires the use of 'good form', performing the movements with the appropriate muscle group(s), and not transferring the weight to different body parts in order to move greater weight/resistance (called 'cheating'). Failure to use good form during a training set can result in injury or an inability to meet training goals - since the desired muscle group is not challenged sufficiently, the threshold of overload is never reached and the muscle does not gain in strength.

The benefits of strength training include increased muscle, tendon and ligament strength, bone density, flexibility, tone, metabolic rate and postural support.

Weight training
Weight and resistance training are popular methods of strength training which use gravity (through weight stacks, plates or dumbells) or elastic/hydraulic resistance respectively to oppose muscle contraction. Each method provides a different challenge to the muscle relating to the position where the resistance to muscle contraction peaks. Weight training provides the majority of the resistance at the initiating joint angle when the movement begins, when the muscle must overcome the inertia of the weight's mass (however, if repetitions are performed extremely slowly, inertia is never overcome and resistance remains constant). In contrast, elastic resistance provides the greatest opposition to contraction at the end of the movement when the material experiences the greatest tension while hydraulic resistance varies depending on the speed of the submerged limb, with greater resistance at higher speeds. In addition to the equipment used, joint angles can alter the force output of the muscles due to leverage and the relative overlap of actin and myosin contractile proteins.

Resistance training
Resistance training is a form of strength training in which each effort is performed against a specific opposing force generated by resistance (i.e. resistance to being pushed, squeezed, stretched or bent). Exercises are isotonic if a body part is moving against the force. Exercises are isometric if a body part is holding still against the force. Resistance exercise is used to develop the strength and size of skeletal muscles. Properly performed, resistance training can provide significant functional benefits and improvement in overall health and well-being.

The goal of resistance training, according to the American Sports Medicine Institute (ASMI), is to "gradually and progressively overload the musculoskeletal system so it gets stronger." Research shows that regular resistance training will strengthen and tone muscles and increase bone mass.

Isometric training
Isometric exercise or 'isometrics' are a type of strength training in which the joint angle and muscle length do not change during contraction. Isometric exercises are opposed by a force equal to the force output of the muscle and there is no net movement. This mainly strengthens the muscle at the specific joint angle at which the isometric exercise occurs, with some increases in strength at joint angles up to 20° in either direction depending on the joint trained. In comparison, isotonic exercises strengthen the muscle throughout the entire range of motion of the exercise used.

Terminology
Strength training has a variety of specialized terms used to describe parameters of strength training:


 * Exercise - different exercises involve moving joints in specific patterns to challenge muscles in different ways
 * Form - each exercise has a specific form, a topography of movement designed to maximize safety and muscle strength gains
 * Rep - short for repetition, a rep is a single cycle of lifting and lowering a weight in a controlled manner, moving through the form of the exercise
 * Set - a set consists of several repetitions performed one after another with no break between them with the number of reps per set and sets per exercise depending on the goal of the individual. The number of repetitions one can perform at a certain weight is called the Rep Maximum(RM). For example, if one could perform 10 reps at 75 lbs, then their RM for that weight would be 10RM.
 * Tempo - the speed with which an exercise is performed; the tempo of a movement has implications for the weight that can be moved and the effects on the muscle

According to popular theory:
 * Sets of one to five repetitions primarily develop strength, with less impact on muscle size and none on endurance.
 * Sets of six to twelve repetitions develop a balance of strength, muscle size and endurance.
 * Sets of thirteen to twenty repetitions develop endurance, with some increases to muscle size and limited impact on strength.


 * Sets of more than twenty repetitions are considered to be focused on aerobic exercise. They do still use the anaerobic system, but usually at a rate through which it can consistently remove the lactic acid generated from it.

Individuals typically perform one to six sets per exercise, and one to three exercises per muscle group, with short breaks between each set - the specific combinations of reps, exercises, sets and break duration depends on the goals of the individual program. The duration of these breaks determines which energy system the body utilizes. Performing a series of exercises with little or no rest between them, referred to as "circuit training", will draw energy mostly from the aerobic energy system. Brief bursts of exercise, separated by breaks, are fueled by anaerobic systems, which use either phosphagens or glycolysis.

For developing endurance, gradual increases in volume and gradual decreases in intensity is the most effective program.

It has been shown that for beginners multiple-set training offers minimal benefits over single set training with respect to either strength gain or muscle mass increase, but for the experienced athlete multiple-set systems are required for optimal progress. However, one study shows that for leg muscles three sets are more effective than one set.

Beginning weight-trainers are in the process of training the neurological aspects of strength, the ability of the brain to generate a rate of neuronal action potentials that will produce a muscular contraction that is close to the maximum of the muscle's potential.

Weights for each exercise should be chosen so that the desired number of repetitions can just be achieved.

Progressive overload
In one common method, weight training uses the principle of progressive overload, in which the muscles are overloaded by attempting to lift at least as much weight as they are capable of. They respond by growing larger and stronger. This procedure is repeated with progressively heavier weights as the practitioner gains strength and endurance.

However, performing exercises at the absolute limit of one's strength (known as one rep max lifts) is considered too risky for all but the most experienced practitioners. Moreover, most individuals wish to develop a combination of strength, endurance and muscle size. One repetition sets are not well suited to these aims. Practitioners therefore lift lighter (sub-maximal) weights, with more repetitions, to fatigue the muscle and all fibres within that muscle as required by the progressive overload principle.

Commonly, each exercise is continued to the point of momentary muscular failure. Contrary to widespread belief, this is not the point at which the individual thinks they cannot complete any more repetitions, but rather the first repetition that fails due to inadequate muscular strength. Training to failure is a controversial topic with some advocating training to failure on all sets while others believe that this will lead to overtraining, and suggest training to failure only on the last set of an exercise. Some practitioners recommend finishing a set of repetitions just before the point of failure; e.g. if you can do a maximum of 12 reps with a given weight, only perform 11. Adrenaline and other hormones may promote additional intensity by stimulating the body to lift additional weight (as well as the neuro-muscular stimulations that happen when in “fight-or-flight” mode, as the body activates more muscle fibres), so getting "psyched up" before a workout can increase the maximum weight lifted.

Weight training can be a very effective form of strength training because exercises can be chosen, and weights precisely adjusted, to safely exhaust each individual muscle group after the specific numbers of sets and repetitions that have been found to be the most effective for the individual. Other strength training exercises lack the flexibility and precision that weights offer.

Recovery
There are many theories as to why weight training creates muscle growth. All muscle contractions are traumatic, this is mediated by the protein dystrophin. The function of weight training is to stimulate hypertrophy. Repeated training increases production of dystrophin and increases the rate of lactic acid metabolism. Weight training programs should therefore allow the muscles time to repair and grow, otherwise overtraining can occur. Therefore the individual should exercise caution in increasing the level of exertion. Muscle growth is normally completed within 36 to 96 hours, depending upon the intensity of the workout. Novices may work out every other day, often scheduling workouts on Mondays, Wednesdays and Fridays. As weight trainers grow fitter and stronger, it takes more intense workouts to fully challenge their muscles. More advanced practitioners may exercise specific muscle groups only every three or four days - since they are capable of producing maximum force output from the muscle, their workouts have the potential to damage the muscle to a much greater extent and require longer periods to repair and replete to a greater strength. Recovery must also take longer because high level forces produced by proficient weight trainers cause far more damage to the ligaments, tendons and bones involved; because many of these tissues are not heavily vascularized, it takes longer for them to repair than blood-rich muscles. Depending on the workout regimen, the limiting factor may not be muscular damage or energy levels, but may instead be the ability of the body to repair the supporting tissues around joints and bones.

One solution to scheduling workouts around these needs is to split one's routine between several workouts, by exercising certain muscle groups on one day and the remainder on another. By targeting different muscle groups, workouts can be scheduled more frequently than would otherwise be possible.

Intensity, volume, and frequency
Three important principles of strength training are intensity, volume and frequency. Intensity refers to the amount of force required to achieve the activity, and in this case, refers to the mass of the weights being lifted (lifting 20 kg requires more force or intensity than lifting 10 kg regardless of how many reps/sets are done). Volume refers to the number of muscles worked, exercises, sets and reps during a single session. Frequency refers to how many training sessions are performed per week.

These principles are important because they are all mutually conflicting, as the muscle only has so much strength and endurance, and takes time to recover due to microtrauma. Increasing one by any significant amount necessitates the decrease of the other two, eg. increasing weight means a reduction of reps, and will require more recovery time and therefore fewer workouts per week. Trying to push too much intensity, volume and frequency will result in overtraining, and eventually lead to injury and other health issues such as chronic soreness and general lethargy, illness or even acute trauma such as avulsion fractures. A high-medium-low formula can be used to avoid overtraining, with either intensity, volume, or frequency being high, one of the others being medium, and the other being low. One example of this training strategy can be found in the following chart:

A common training strategy is to set the volume and frequency the same each week (eg. training 3 times per week, with 2 sets of 12 reps each workout), and steadily increase the intensity (weight) on a weekly basis. However, to maximize progress to specific goals, individual programs may require different manipulations, such as decreasing the weight, and increase volume or frequency.

Making program alterations on a daily basis (daily undulating periodization) seems to be more efficient in eliciting strength gains than doing so every 4 weeks (linear periodization), but for beginners there are no differences between different periodization models.

Periodization
Periodization is the adjusting of sets, reps and weight to control volume and intensity. When done correctly, volume should slowly decrease throughout a training cycle while intensity should slowly increase. With strength training, a lifter should begin a training cycle with a higher rep range than he will finish with. For example, a lifter might begin a training program performing sets with 8 reps. Throughout the course of his/her training program, the lifter will slowly increase the weight while slowly decreasing the reps. This is enough time for the neuromuscular system to adapt and become more efficient.

For this example, the lifter has a 1 rep max of 225 lb:

This is an example of periodization where the volume decreases while the intensity and weight increases.

Benefits
The benefits of weight training include greater muscular strength, improved muscle tone and appearance, increased endurance, enhanced bone density, and improved cardiovascular fitness.

Many people take up weight training to improve their physical attractiveness. Most men can develop substantial muscles; most women lack the testosterone to do this, but they can develop a firm, "toned" (see below) physique, and they can increase their strength by the same proportion as that achieved by men (but usually from a significantly lower starting point). Ultimately an individual's genetics dictate the response to weight training stimuli to some extent.

The body's basal metabolic rate increases with increases in muscle mass, which promotes long-term fat loss and helps dieters avoid yo-yo dieting. Moreover, intense workouts elevate the metabolism for several hours following the workout, which also promotes fat loss.

Weight training also provides functional benefits. Stronger muscles improve posture, provide better support for joints, and reduce the risk of injury from everyday activities. Older people who take up weight training can prevent some of the loss of muscle tissue that normally accompanies aging&mdash;and even regain some functional strength&mdash;and by doing so become less frail. They may be able to avoid some types of physical disability. Weight-bearing exercise also helps to prevent osteoporosis. The benefits of weight training for older people have been confirmed by studies of people who began engaging in it even in their 80s and 90s.

Stronger muscles improve performance in a variety of sports. Sport-specific training routines are used by many competitors. These often specify that the speed of muscle contraction during weight training should be the same as that of the particular sport.

Though weight training can stimulate the cardiovascular system, many exercise physiologists, based on their observation of maximal oxygen uptake, argue that aerobics training is a better cardiovascular stimulus. Central catheter monitoring during resistance training reveals increased cardiac output, suggesting that strength training shows potential for cardiovascular exercise. However, a 2007 meta-analysis found that, though aerobic training is an effective therapy for heart failure patients, combined aerobic and strength training is ineffective.

One side-effect of any intense exercise is increased levels of dopamine, serotonin and norepinephrine, which can help to improve mood and counter feelings of depression.

Is strength training the same as bodybuilding?
Bodybuilding is a sport in which the goal is to increase muscle size and definition. This increases the endurance of muscles, as well as strength, though not as much as if it were the primary goal. Bodybuilders compete in bodybuilding competitions, and use specific principles and methods of strength training to maximize muscular size and develop extremely low levels of body fat. In contrast, most strength trainers train to improve their strength and endurance while not giving special attention to reducing body fat below normal. Strength trainers tend to focus on compound exercises to build basic strength, whereas bodybuilders often use isolation exercises to visually separate their muscles, and to improve muscular symmetry. Pre-contest training for bodybuilders is different again, in that they attempt to retain as much muscular tissue as possible while undergoing severe dieting. However, the bodybuilding community has been the source of many of popular strength training's principles, techniques, vocabulary, and customs.

Bodybuilding, strongman competitions and other sports are illustrations of how the basic principles and methods of strength training can be applied to achieve very different goals.

Is nutrition relevant for strength trainers?
Most people think of dieting in terms of weight loss, but strength trainers can also adjust their diet to improve the results from their workouts. Adequate protein is required for building skeletal muscle. Various sources advise weight trainers to consume a high protein diet with anywhere from 1.4 to 3.3 g of protein per per kg of body weight per day (0.6 to 1.5 g per pound). Protein that is not needed for cell growth and repair nor consumed for energy is converted by the liver into fat, which is then stored in the body. Some people believe that a high protein diet entails risk of kidney damage, but studies have shown that kidney problems only occur in people with previous kidney disease. An adequate supply of carbohydrates is also needed as a source of energy and for the body to restore glycogen levels in muscles.

A light balanced meal consumed prior to the workout (usually one to two hours beforehand) ensures that adequate energy and amino acids are available to perform the intense bout of exercise. Water is consumed throughout the course of the workout to prevent poor performance due to dehydration. A protein shake is often consumed immediately following the workout, because both protein uptake and protein usage are increased at this time. Glucose (or another simple sugar) is often consumed as well since this quickly replenishes any glycogen lost during the exercise period. To maximise muscle protein anabolism, recovery drink should contain glucose (dextrose), protein (usually whey) hydrosylate containing mainly dipeptides and tripeptides, and leucine. Some weight trainers also take ergogenic aids such as creatine or steroids to aid muscle growth. However, the effectiveness of some products is disputed and others are potentially harmful.

Will women gain mass comparable to men?
Due to the androgenic hormonal differences between men and women, women are unable to develop large muscles regardless of the training program used. Normally the most that can be achieved is a look similar to that of a fitness model. Muscle is denser than fat, so someone who builds muscle while keeping the same body weight will occupy less volume; if two women weigh the same but have different lean body mass percentages, the one with more muscle will appear thinner.

The results obtained by female bodybuilders are extremely atypical: they are self-selected for their genetic ability to build muscle, perform enormous amounts of exercise, their musculature is exaggerated by very low body fat and like many male bodybuilders their results may be enhanced by anabolic steroids. Unless a woman dedicates her life to bodybuilding, she will not achieve the same results as a professional female bodybuilder. In addition, though bodybuilding uses the same principles as strength training, it is with a goal of gaining muscle bulk. Strength trainers with different goals and programs will not gain the same mass as a female professional bodybuilder.

Are light, high-repetition exercises effective for 'toning' muscles?
Some weight trainers perform light, high-repetition exercises in an attempt to "tone" their muscles without increasing their size. This comes from misunderstanding the meaning of the word "tone." What most people refer to as a toned physique is one that combines reasonable muscular size with moderate levels of body fat. The use of the word "tone" in this sense is inaccurate: a more appropriate term would be "definition".

Muscle tone is a physiologic term that refers to the constant, low-frequency contractions that occur in all muscles all the time, even at "rest", which prepare them for future activity. This continuous slight tension in torso muscles contributes to maintaining good posture. High-repetition exercises should increase muscle size, but will not improve the latter type of muscle "tone". Even performed as aerobic exercises they will have limited benefit, since aerobic exercise is most effective when it engages the whole body.

To define muscles requires a combination of weight training to increase muscle size and low levels of body fat.

Is strength training safe for children?
This depends on what type of strength training is utilized. Orthopaedic specialists used to recommend that children avoid weight training because the growth plates on their bones might be at risk. The very rare reports of growth plate fractures in children who trained with weights occurred as a result of inadequate supervision, improper form or excess weight, and there have been no reports of injuries to growth plates in youth training programs that followed established guidelines. The position of the National Strength and Conditioning Association is that strength training is safe for children if properly designed and supervised.

Younger children are at greater risk of injury than adults should they drop a weight on themselves or perform an exercise incorrectly; further, they may lack understanding of, or ignore the safety precautions around weight training equipment. As a result, supervision of minors is considered vital to ensuring the safety of any youth engaging in strength training.

Can strength training help with weight loss?
An exercise like sit-ups or abdominal crunches uses a much smaller volume of muscle than whole-body aerobic exercise and is therefore less efficient at burning calories than an exercise like jogging. Instead, high weight/low rep exercises can be used to maintain or increase the body's muscle mass while dieting. This helps to prevent the metabolic slowdown that otherwise often limits the effect of dieting and causes post-diet weight gain.

This too depends on the type of strength training utilized. Because weight training generally is used for bulking, this type of exercise more than likely will increase weight because of the muscle gain. However, when resistance or circuit training is used, because it is not geared towards bulking, women tend to lose weight more quickly.

Because most strength training builds lean muscle, it is natural for a person to gain weight, initially, since muscle is heavier than fat. However, as lean muscle is built, as a result, the weight will begin to regulate and decrease. Lean muscle helps raise the metabolism which helps keep weight down.

Safety
Strength training can be a safe form of exercising, however each category has it advantages as well as disadvantages. 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&mdash;the leg and buttock muscles&mdash;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, which, contrary to popular belief, is not the cause of the harmless burning sensation in the muscles. 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 program. 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 program 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 program 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'. Using a belt is more controversial as it does not prepare people for real situations, as they do not normally wear lifting belts when performing real-life tasks. This can lead to inadequate inter-abdominal pressure and torso/lower back stabilization ability. Some criticize that the gripping muscles in the forearms receive less benefit from the deadlift when using straps. This is not a concern to people who do other exercises for forearm development, or who are not concerned with forearm development. Strap-like implements are commonly used in real-life deadlifting situations, and in many cases weights are levered against the body or sandwiched between the arms, so that not as much gripping strength is used anyway. One less abrasive alternative to deadlifting with straps would be to lift wearing wrist weights, as they would add to the weight without further stressing the grip.

Isotonic, isometric and plyometric exercises
These terms combine the prefix "iso" (meaning "same") with "tonic" (strength) and "metric" (distance). In "isotonic" exercises the force applied to the muscle does not change, and in "isometric" exercises the length of the muscle does not change.

Weight training is primarily an isotonic form of exercise, because the muscles are used to push or pull weighted objects. Any object can be used for weight training, but dumbbells, barbells and other specialised equipment are normally used because they can be adjusted to specific weights, and are easily gripped. However, some exercises are not strictly isotonic because the force on the muscle varies as the joint moves through its range of motion, even though the force of the exercise remains constant.

Some forms of weight training use isometric contractions to further stress the muscles after or during a period of isotonic exercise. In this case the muscles flex and hold a stationary position, and no movement of a load takes place.

Another form of training that often uses weights has a different goal. Plyometric exercises exploit the stretch-shortening cycle of muscles to enhance the myotatic (stretch) reflex. This involves rapid alternation of lengthening and shortening of muscle fibers against a resistance. The resistance involved is often a weighted object such as a medicine ball, but can also be the body itself as in jumping exercises. Plyometrics is used to develop explosive speed, and focuses on power instead of maximal strength, and may be used to improve the effectiveness of a boxer's punch, for example, or to increase the vertical jumping ability of a basketball player.

Isolation exercises versus compound exercises
An isolation exercise is one where the movement is restricted to one joint. For example, the leg extension is an isolation exercise for the quadriceps. The other muscle groups are only minimally involved&mdash;they just help the individual maintain a stable posture&mdash;and movement occurs only around the knee joint. Other examples are the straight-legged deadlift (hip extension) and the dumbbell/barbell curl (elbow flexion).

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 maximizing their strength gains (including bodybuilders) would put more of an emphasis on isolation exercises.

Equipment
There are a number of exercise machines and other equipment that are commonly found in strength training facilities.


 * Smith machines have a barbell constrained to move only in the vertical single Plane
 * Cable machines 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
 * A variation of a cable machine is a wide-grip bar attached to a weight stack and a seat, used specifically for pulldown exercises that train the latissimus dorsi muscle

There are also exercise-specific weight machines such as the leg press. A multigym includes a variety of exercise-specific mechanisms in one apparatus.

Free weights include dumbbells, barbells and other objects. Unlike some exercise machines, they do not constrain users to specific, fixed movements, and require more stabilization skills. It is often argued that free weight exercises are superior for precisely this reason. As exercise machines can prevent 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. Many serious athletes, bodybuilders and fitness enthusiasts prefer to train with free weights and compound exercises.

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.

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.

Types of strength training
There are different ways to increase strength, each with its own goals, equipment, methods and/or results.
 * Isometric exercise
 * Plyometrics
 * Pilates
 * Martial arts

Apart from the obvious weights and resistance bands, there are a number of other items of exercise equipment that can be used while or to compliment strength training:


 * Swiss balls or Wobble boards
 * Levering weights like Indian clubs
 * Punching bag

Aerobic exercise versus anaerobic exercise
Strength training exercise is primarily anaerobic. Even while training at a lower intensity (training loads of ~20-RM), anaerobic glycolysis is still the major source of power, although aerobic metabolism makes a small contribution. Weight training is commonly perceived as anaerobic exercise, because one of the more common goals is to increase strength by lifting heavy weights. Other goals such as rehabilitation, weight loss, body shaping, and bodybuilding often use lower weights, adding aerobic character to the exercise.

Except in the extremes, a muscle will fire fibres of both the aerobic or anaerobic types on any given exercise, in varying ratio depending on the load on the intensity of the contraction. This is known as the energy system continuum. At higher loads, the muscle will recruit all muscle fibres possible, both anaerobic ("fast-twitch") and aerobic ("slow-twitch"), in order to generate the most force. However, at maximum load, the anaerobic processes contract so forcefully that the aerobic fibers are completely shut out, and all work is done by the anaerobic processes. Because the anaerobic muscle fibre uses its fuel faster than the blood and intracellular restorative cycles can resupply it, the maximum number of repetitions is limited. In the aerobic regime, the blood and intracellular processes can maintain a supply of fuel and oxygen, and continual repetition of the motion will not cause the muscle to fail.

Circuit weight training is a form of exercise that uses a number of weight training exercise sets separated by short intervals. The cardiovascular effort to recover from each set serves a function similar to an aerobic exercise, but this is not the same as saying that a weight training set is itself an aerobic process.

Exercises for specific muscle groups


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.

Advanced techniques
A number of techniques have been developed to make weight training exercises more intense, and thereby potentially increase the rate of progress:

Set structure

 * Drop sets: Drop sets do not end at the point of momentary muscular failure, but continue with progressively lighter weights.


 * Pyramid sets: In a pyramid the weight is first increased, and then decreased over a series of sets. A full pyramid typically includes five sets of approximately 12, 10, 8, 10 and 12 reps. The first two sets are performed with light to medium weights to warm up the muscles. The middle set is the work set, and uses the heaviest weight possible. The last two sets are drop sets, and further fatigue the muscle with progressively lighter weights. This technique provides a combination of volume and intensity, and is therefore popular with bodybuilders. However, the full pyramid may be too much for a beginner to handle, so it is only recommended for experienced trainers.


 * Burnouts: Burnouts combine pyramids and drop sets, working up to higher weights with low reps and then back down to lower weights and high reps.


 * Diminishing set: The diminishing set method is where a weight is chosen that can be lifted for 20 reps in one set, and then 70 repetitions are performed in as few sets as possible.


 * Rest-pause (heavy singles): Rest-pause heavy singles are performed at or near 1RM, with ten to twenty seconds of rest between each lift. The lift is repeated six to eight times.  It is generally recommended to use this method infrequently.

Combined sets

 * Supersets: Supersets combine two or more exercises with similar motions to maximize the amount of work of an individual muscle or group of muscles. The exercises are performed with no rest period between the exercises. An example would be doing bench press, which predominantly works the pectoralis and triceps muscles, and then moving to an exercise that works just the triceps such as the triceps extension or the pushdown.


 * Push-pull supersets: Push-pull supersets are similar to regular supersets, but exercises are chosen which work opposing muscle groups. This is especially popular when applied to arm exercises, for example by combining biceps curls with the triceps pushdown. Other examples include the shoulder press and lat pulldown combination, and the bench press and wide grip row combination.


 * Pre-exhaustion: Pre-exhaustion combines an isolation exercise with a compound exercise for the same muscle group. The isolation exercise first exhausts the muscle group, and then the compound exercise uses the muscle group's supporting muscles to push it further than would otherwise be possible. For example, the triceps muscles normally help the pectorals perform their function. But in the "bench press" the weaker triceps often fails first, which limits the impact on the pectorals. By preceding the bench press with the pec fly, the pectorals can be pre-exhausted so that both muscles fail at the same time, and both benefit equally from the exercise.


 * Breakdowns: Breakdowns were developed by Fred Hatfield and Mike Quinn to work the different types of muscle fibers for maximum stimulation.  Three different exercises that work the same muscle group are selected, and used for a superset.  The first exercise uses a heavy weight (~85% of 1 rep max) for around five reps, the second a medium weight (~70% of 1 rep max) for around twelve reps, and finally the third exercise is performed with a light weight (~50% of 1 rep max) for twenty to thirty reps, or even lighter (~40% of 1 rep max) for forty or more reps.  (Going to failure is discouraged.) The entire superset is performed three times.

Beyond failure

 * Forced reps: Forced reps occur after momentary muscular failure. An assistant provides just enough help to get the weight trainer past the sticking point of the exercise, and allow further repetitions to be completed. Weight trainers often do this when they are spotting their exercise partner. With some exercises forced reps can be done without a training partner. For example, with one-arm biceps curls the other arm can be used to assist the arm that is being trained.


 * Cheat reps: Cheating is a deliberate compromise of form to maximize reps. Cheating has the advantage that it can be done without a training partner, but compromises safety.


 * Rest-pause (post-failure): After a normal set of 6-8 reps (to failure), the weight is re-racked and the trainer takes 10-15 deep breaths, and then performs one more repetition.  This process can be repeated for two further repetitions. The twenty-rep squat is another, similar approach, in that it follows a 12-15 rep set of squats with individual rest-pause reps, up to a total of 20 reps.


 * Negative reps: Negatives are performed with much heavier weights. Assistants lift the weight, and then the weight trainer attempts to resist its downward progress through an eccentric contraction. Alternatively, an individual can use an exercise machine for negatives by lifting the weight with both arms or legs, and then lowering it with only one. Or they can simply lower weights more slowly than they lift them: for example, by taking two seconds to lift each weight and four seconds to lower it.


 * Partial reps: Partial reps, as the name implies, involves movement through only part of the normal path of an exercise. Partial reps can be performed with heavier weights. Usually, only the easiest part of the repetition is attempted.


 * Burns: Burns involve mixing partial reps into a set of full range reps in order to increase intensity. The partials can be performed at any part of the exercise movement, depending on what works best for the particular exercise.  Also, the partials can either be added after the end of a set or in some alternating fashion with the full range reps.  For example, after performing a set of biceps curls to failure, an individual would cheat the bar back to the most contracted position, and then perform several partial reps.

Other techniques

 * Progressive movement training: Progressive movement training attempts to gradually increase the range of motion throughout a training cycle. The lifter will start with a much heavier weight than they could handle in the full range of motion, only moving through the last 3-5” of the movement.  Throughout the training cycle, the lifter will gradually increase the range of motion until the joint moves through the full range of the exercise.  This is a style that was made popular by Paul Anderson.


 * 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 avoid using wrist straps in order to develop their grip strength, just as some go further by using thick bars. Wrist straps can allow a lifter initially to use more weight than they might be able to handle safely for an entire set, as unlike simply holding a weight, if it is dropped then the lifter must descend with it or be pulled down. Straps place stress on the bones of the wrist which can be potentially harmful if excessive.