| Strength is recognized as the ability to exert force, typically measured in the amount of weight a person can lift or manipulate. There are five broad categories of strength, each with its own special training requirements: absolute, limit, speed, anaerobic, and aerobic.  There are many factors that influence strength.
- Structural/Anatomical - muscle fiber arrangement, musculoskeletal leverage, ratio of fast vs. slow-twitch fibers, tissue leverage, scar tissue and adhesions (motion-limiting factors), elasticity, intramuscular/intermuscular friction, etc.
- Physiological/Biochemical - stretch reflex, Golgi tendon organ sensitivity, hormonal function, energy transfer systems efficiency, extent of hyperplasia, myofibrillar development, motor unit recruitment, cardiovascular and cardiorespiratory factors, etc.
- Psychoneural/Learned Responses - arousal level, pain tolerance, level of concentration, social learning, skill level, spiritual factors, etc.
- External/Environmental - equipment, weather, altitude, gravity, opposing/assisting forces, etc. 
Muscular strength is a general component of fitness. Strength training can boost metabolism, help decrease body fat, decrease risk for osteoporosis, bolster self-esteem, preserve physical independence, and of course, increase strength.
Training for StrengthEdit
Training maximal strength requires between four to six reps with about two minutes rest between sets. Training for hypertrophy, as opposed to maximal strength, requires between eight to twelve reps with about sixty seconds between sets. Metabolic conditioning should be between twelve to fifteen (plus) reps with less than sixty second rest periods. 
It has been shown that maintaining strength levels requires fairly little time investment compared with maintaining aerobic or muscular endurance capacity. This is not to say that maintaining strength levels doesn't require persistence or effort. Skeletal muscles will substantially decrease in size and strength (atrophy) with complete inactivity, such as following a serious injury. Some studies have shown that it takes less effort to regain lost strength than it takes to gain it. Intensity, rather than exercise duration or frequency is the key stimulus for increasing or maintaining strength.
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Absolute strength, also known as maximal strength, is defined as the amount of musculoskeletal force you can generate for one all-out effort, irrespective of time or bodyweight.  It is typically measured in terms of performance of a maximal, single repetition lift (one rep max [1RM]).
Limit strength is considered to be absolute strength enhanced by ergogenic substances of any type (including supplements or drugs), hypnosis, electrotherapy, or other techniques. Where absolute strength is reached solely through training, such aids increase the potential for strength above the normal capacity. 
Speed-Strength is defined as work divided by time, where work is defined as force x distance. Therefore, speed strength is defined as force x distance, divided by time (power). Speed-Strength is characterized by three distinct components: starting strength, explosive strength, and reactive strength.
Anaerobic strength is musculoskeletal force that does not require oxygen; energy for anaerobic strength comes primarily from the glycolytic pathway. It involves the development of severe oxygen debt, as the emphasis is on repetitive muscular capacity without entering into the aerobic phase of energetics. Examples of this are found in wrestling, boxing, and high-repetition training (greater than 20 reps). The two types of anaerobic strength are speed-endurance and strength-endurance. 
Aerobic strength is the force produced footfall-per footfall in the face of high oxygen debt, such as that which occurs during long distance training or events.