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, increased bone density, a temporary increase in metabolism, 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.

Weight training

Weight and resistance training are popular methods of strength training that use gravity (through weight stacks, plates or dumbbells) 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", is 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.[4] In comparison, isotonic exercises strengthen the muscle throughout the entire range of motion of the exercise used.

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.

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 ten reps at 75 lbs, then their RM for that weight would be 10RM. 1RM is therefore the maximum weight that someone can lift in a given exercise - i.e. a weight that they can only lift once without a break.

• 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.

Realization of training goals

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.

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

Strength training is the key to maintaining good flexibility. It takes your body parts through a full range of motion and if you use the right technique, you will be able to develop strength throughout an entire range of movement. The ability of the body to resist the stresses that can result from an injury can be increased by obtaining a greater amount of strength. That is true in the athletic world and it has its advantages in performing everyday activities, such as lifting or carrying objects. Strength contributes to the overall efficiency of the human body. Starting a strength training program, means you have started a new lifestyle because strength is reversible. It will decline if you do not continue to obtain a strength stimulus throughout your entire life.

Types of exercises

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 or the body with a weight vest that allows movement such as the Hyper Vest. 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—they just help the individual maintain a stable posture—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.