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The history of strength training started with the ancient Greeks. Hippocrates eloquently 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 to at least the 6th century BC, when legend has it that wrestler Milo of Croton trained by carrying a newborn calf on his back every day until the calf was fully grown. Another Greek, the physician Galen, described strength training exercises using the halteres (an early form of dumbbell) in the 2nd century AD.
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 we use 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.
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.
Types of strength 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 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 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.
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.
|Load (% of 1RM)
|Reps per set
|Sets per exercise
|Rest between sets (mins)
|Duration (seconds per set)
|Speed per rep (% of max)
|Training sessions per week
|Table reproduced from Siff, 2003|
Weights for each exercise should be chosen so that the desired number of repetitions can just be achieved.
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.
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 variables 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 variables 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:
Intensity (% of 1RM)
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 is the modulating of volume and intensity over time, to both stimulate gains and allow recovery. Commonly, volume is decreased during a training cycle while intensity is increased. In this template, a lifter would 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:
||Peak Intensity(Last Set)
||% of 1 Rep Max(Last Set)|
||95 lb x 8reps
||100 lb x 8reps
||110 lb x 8reps
||115 lb x 8reps
||120 lb x 8reps
||105 lb x 8reps
||110 lb x 7reps
||115 lb x 7reps
||125 lb x 7reps
||130 lb x 7reps
||110 lb x 7reps
||120 lb x 7reps
||125 lb x 6reps
||135 lb x 6reps
||140 lb x 6reps
||125 lb x 6reps
||130 lb x 6reps
||140 lb x 6reps
||145 lb x 5reps
||155 lb x 5reps
||130 lb x 5reps
||140 lb x 5reps
||150 lb x 5reps
||155 lb x 5reps
||165 lb x 4reps
||140 lb x 4reps
||150 lb x 4reps
||160 lb x 4reps
||165 lb x 4reps
||175 lb x 4reps
This is an example of periodization where the volume decreases while the intensity and weight increases.
There are a number of exercise machines
and other equipment that are commonly found in strength training facilities.
- Some 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.
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 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.