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Muscles contraction is the source of power for all movement in the body.

Muscle strength depends on

  • Age. As we get older our muscle strength decrease. However, studies show that people of all ages can increase their muscle size and strength through a safe and effective strength training program. The rate of muscle and strength and muscle gain is greater during our younger years. After reaching normal physical maturity, the rate muscular improvement decreases.
  • Gender.  Gender does not affect the quality of our muscle but does influence the quantity. Although men’s and women’s muscle tissue are characteristically the same, men generally have more muscle tissue than women do because muscle size is increased by testosterone, the male sex hormone. 
  • Size. The larger the muscles, the stronger the person; therefore most men are stronger than most women.
  • Limb and muscle length. Another strength factor that is naturally determined is limb length. Persons with short limbs tend to be able to lift more weight because of advantageous leverage factors. Some people have long muscles, and some people have short muscles. Those with relatively long muscles have greater potential for developing size and strength than persons with relatively short muscles.
  • Point of tendon attachment. Muscle strength is also influenced by the point of tendon attachment to the bones. For example, if two people have the same arm and muscle length, the one whose bicep tendon attaches to the forearm farthest from the elbow joint a biomechanical advantage and he is able to lift more weight in biceps exercises such as the biceps curl.
  • Training. Muscles that have been properly trained will be stronger and quicker than untrained muscles.
  • Coordination. Coordination of all muscles and joints in direction of movement with the right sequence and timing.
  • Timing. Correct timing of muscle contraction and expansion in relation to the timing of the movement of the joints.

Muscle types

The human body contains over 400 muscles that are divided into two classes:
  • Smooth. Smooth muscles perform the involuntary functions of the body, such as circulation and digestion. 
  • Striated. Striated muscles may be voluntarily contracted, such as muscle groups in the arms and legs. When a striated muscle is stretched, it will contact more forcibly than it would had it not been stretched. However, the stretching must immediately precede the contraction. 
Martial artists are most concerned with striated muscles since these are the ones that allow them to perform the martial arts. In addition, they are the ones that may be most affected by training.

Striated muscles

Striated muscles are composed of two types of fibers:
  • Slow twitch (Type I). Slow twitch fibers are used in activities that must be sustained over a long period, such as distance running, cycling, and swimming. The cells within these muscles excel at clearing waste and using oxygen as fuel and, within the muscles, there’s a high-density of capillaries, which helps bring blood to the muscles. These fibers have a high capacity for aerobic energy production and can remain active for a long period while producing relatively small amounts of lactic acid. This is important because lactic acid build-up in the muscle tissue causes the muscle to fatigue and eventually stop working. The ability to maintain low levels of lactic acid means an increased capacity for work. People who have a high percentage of slow twitch fibers excel at endurance activities.
  • Fast twitch (Type II). Fast twitch fibers generate far more power and strength, but they fatigue much faster and require more time for recovery. There are two types of fast-twitch fibers: 
  • Type IIa. This type yields more endurance but produces slightly less strength.
  • Type IIb. This type creates the most strength but yields less endurance. 
Fast twitch fibers are used in activities that require explosive power for a short period, such as sprinting, broad jumping, and sparring, which involves periods of low activity punctuated with bursts of high activity. These fibers have a great capacity for anaerobic energy production, which allows them to produce intense power and speed of contraction; however, this also causes them to accumulate large amounts of lactic acid and fatigue quickly. People who have a high percentage of fast twitch fibers excel at activities that require explosive power. 
Therefore, to develop sparring abilities, it would seem best to increase the percentage of fast twitch muscle fibers in your body. Unfortunately, this is not possible. The ratio of fast and slow twitch muscle fibers is determined early in life and cannot be markedly changed. Studies have shown that distance runners have high percentages of slow twitch fibers and sprinters have high percentages of fast twitch fibers but that the activity in which they participate is not responsible for these percentages. Instead, it is believed that some people participate in endurance sports because they naturally excel in this area. In the same respect, people who are naturally fast, tend to participate in sports that require speed and power.
Although you cannot change the ratio of muscle fibers, you can improve what you have through training. Slow and fast twitch muscle fibers are generally intermingled, with a higher percentage of fast twitch fibers. Through training, you may improve the metabolic efficiency of either type of muscle fiber.


Muscles generate power by contraction. Contraction is determined by the types of muscle fibers used and the firing rate of the neurons within the fibers. The voluntary contraction of a muscle begins with the smallest units of slow twitch muscles. These motor units (muscle fiber groups) have the lowest response threshold, create the least amount of tension, and are the most resistant to fatigue. As muscle tension increases, more motor units are recruited from the larger fast twitch fibers. As tension continues to rise, fewer motor units need to be activated because the large fast twitch units contain more plentiful and more powerful muscle fibers. However, because these large fibers are the ones that generate peak tension in the muscle, they fatigue quickly and require more recovery time.

For example, whether you walk one mile or sprint one mile, you use the same basic muscle groups over the same distance. However, walking requires less tension in the muscles and therefore relies on the low threshold-low tension motor units so fatigue is slow to develop; whereas, sprinting requires maximum muscle tension on every stride. When muscle fibers must produce maximum tension repeatedly over long periods of time, they fatigue sooner.

Contraction speed is determined by the rate at which the skeletomotor neurons stimulate the muscle fibers. The more frequently the neurons fire, the more tension that is produced by the muscle. At peak tension, the neurons fire so rapidly that the muscle fiber is unable to relax from one stimulation to the next, resulting in the generation of maximum force.

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