Strength

Muscles have seven characteristics related to physical ability. Each characteristic is associated with a different aspect of physical ability. Taekwondo demands certain requirements of muscles depending in the circumstances. Sometimes you need maximum strength to release from a grip. Sometimes you need quickness for strikes. Sometimes you need speed to run away. Of these seven characteristics, the first five are the most important to develop for martial artists.   

• Speed. How fast the muscle fibers contract. The most important muscle trait for a martial artist. For example, if Zorro (small man with small, fast sword) fought Conan (huge man with large, bulky sword) who would win? Zorro would probably cut Conan fifty times before he could swing his broad sword.
• Strength. How many muscle fibers contract at once. For the greatest strength, many muscles must contract together or in sequence.
• Stretch. How far muscles stretch (flexibility). To kick high and quickly while preventing injuries, you must have flexibility that allows a wide range of motion.
• Stamina. Your endurance or VO2 uptake capacity. Most fights finish in a few seconds. So why do you need Stamina? Good endurance allows you to repeat techniques many times in training with proper form. You must repeat a technique thousands of times before it becomes instinctive. For that type of training, you need endurance.
• Smarts. Muscle memory or learned neural pathways. Muscles have memory. Once you train a technique thousands of times, it become automatic and you do not have to think about the action. 
• Shape. Amount of fat around muscle. Some people call this muscle tone or definition. If you have a lot of body fat your muscles, will not show and you will be round and soft looking. If you remove that fat, your muscles will look cut and firm. It is the same muscle, but the amount of fat around it makes the shape change. Fat slows you down by adding extra weight you have to move, but it also provides padding against impacts and insulation against body heat loss.
• Size. Amount of muscle mass. The most powerful weight lifters are not as big as most body builders yet they have more strength.

Shape and size are not of great importance to martial artists, but they do seek to increase one or more of the other five characteristics.

Strength

When we think of great strength , we think of the ability to pick up heavy weights. But there is more to strength than just this. Strength can be loosely defined as the ability to apply musculoskeletal force. For a more precise definition, we must first consider the various types of strength expression available to athletes:

• Limit Strength. The amount of musculoskeletal force you can generate for one all-out effort. Limit strength is your athletic "foundation." Limit strength can only be demonstrated or tested in the weight room during the performance of a maximal lift. While only power lifters need to maximize and demonstrate this type of strength, martial artists need to develop high levels of limit strength in every muscle group.
• Absolute Strength. Absolute strength is the same as limit strength with one important distinction. Limit strength is achieved while "under the influence" of some work producing aid (supplements, hypnosis, therapeutic techniques, etc.), while absolute strength is achieved through training alone.
• Relative Strength. Whereas absolute strength refers to strength irrespective of bodyweight, relative strength is a term used to denote an athlete's strength per unit of bodyweight. Thus if two athletes of different bodyweights can squat 300 pounds, they have equal absolute strength for that lift, but the lighter athlete has greater relative strength.

All sports that have weight classes are dependent on relative strength, as do sports where the athlete must overcome his or her bodyweight to accomplish a motor task, such as Taekwondo, long jump, sprinting, etc. Some sports that have aesthetic requirements, such as figure skating, gymnastics, etc. rely upon the development of strength without a commensurate gain in bodyweight.

Strength may be developed through two very different means: (1) by applying stress to the muscle cells themselves or (2) by targeting the nervous system. The first method uses bodybuilding methods (6-12 reps) to increase strength by increasing muscle size. The second method still uses weightlifting but with a higher intensity (1-4 reps) to increase strength as a result of the body's improved ability to use more of its existing motor unit pool.

Athletes who need absolute strength, such as shot putters, football linemen, etc., use both methods extensively. First, bodybuilding methods are used, followed by nervous system training. The result is an increase in bodyweight and absolute strength. However, as the athlete becomes larger, relative strength decreases. For martial artists and other athletes who depend upon relative strength, bodybuilding methods should be used sparingly, unless a higher weight class is desired. Most strength training is characterized by high intensity, low repetition sets, which improve strength through neural adaptations rather than increases in muscle size.

Stretch-Shorting Cycle (SSC)

Human movement, such as throwing, jumping, and even walking, is characterized by an eccentric phase immediately followed by a concentric phase, called the stretch-shortening cycle (SSC). During the eccentric phase, the tendons develop and stores potential kinetic energy, similar to a stretched elastic band. Then, during the concentric phase, this potential kinetic energy is returned, resulting in greater force output than if the movement had begun concentrically. During many movements, such as jumping rope, the muscle maintains static contraction, with movement being provided by the storing and release of elastic energy through the tendons. Since static muscular activity uses up less energy than concentric activity, SSC is an extremely energy-efficient way of moving. The efficiency of the SSC is easy to test:

• Perform a vertical jump in a normal manner, where you first crouch, and then jump upwards as explosively as possible.
• Next, crouch, but pause for five seconds, and then jump upward.
• Measure each attempt.
• You will see that the jump where the crouch (or eccentric phase) was IMMEDIATELY followed by the jump was more successful. The key to preserving as much potential kinetic energy as possible is to switch from eccentric to concentric as rapidly as possible.

SSC may be seen in Taekwondo by watching how fighters camber, or cock their kicks before they are executed. Punches all start from the guard, or chambered position.

Strength training methods should reflect the SSC nature of athletic skills. The best forms of resistance training to use are constant resistance, or "free weights," and variable resistance machines that attempt to "match" the resistance values to the strength curve of the muscle being trained. Free weights are preferred because machines tend to rob the synergists and stabilizers of adaptive stress.

Rate of Force Development (RFD)

Many martial artists work hard to improve their absolute (or maximum) strength, but this is not the type of strength they need. In the martial arts, the amount of time to develop maximum muscular force is limited to only a fraction of a second. While high levels of absolute strength are for the development of speed strength, too much lifting of heavy weights at slow speeds, without making the conversion to speed strength later in the training cycle, results in slow athletes.

The ability to apply muscular force rapidly is called rate of force development, or RFD. Training with heavy weights significantly improves absolute strength, but RFD remains largely unchanged. Only when speed strength methods, such as plyometrics or ballistic training, are used is the RFD significantly improved. However, absolute strength declines during this period, and,  if absolute strength is allowed to degrade too much, RFD will suffer. For this reason, many coaches alternate between maximum strength and speed strength phases during the competitive period.

While constant resistance is the most conventional form of weight training used by athletes, it has one distinct disadvantage: deceleration. For example, in the bench press, you lower the bar to your chest, and then ram it to arms length. You may think this is an explosive movement, but as your arms reach extension, the antagonists, lats, biceps, rhomboids, and medial traps, begin to contract in an effort to decelerate the bar before it leaves your hands. This disadvantage may be overcome by strengthening the antagonists and stabilizers and using ballistic training.

Strengthening the Antagonists and Stabilizers

Muscles work in pairs, for every muscle in the body, there is another muscle that is capable of opposing its force. This pairing permits movement, however, if one part of a pair becomes stronger than the other, force output suffers. For example, if you only train the quadriceps muscle since it extends the leg during kicking, the hamstrings, which are the antagonists in kicking movements, weaken in proportion to the quads, and power output declines. The weaker the antagonists are, the sooner they will contract and oppose the prime movers, resulting in a slower movement. Stronger antagonists are less sensitive to this protective response.

Insufficient stabilizer strength also limits power output. Stabilizers are muscles which anchor or immobilize one part of the body, allowing another part, such as a leg,  to exert force. The most important stabilizers are  the abdominals and trunk extensors. If the motor cortex detects that it cannot stabilize the force provided by the prime movers, it will not allow the prime mover to contract with full force. In other words, the force output of the prime movers is limited by the strength of the stabilizer muscles.

Ballistic Training

Ballistic training involves plyometrics, modified Olympic lifting, jumping, throwing, and striking movements (such as punching a heavy bag or kicking a shield). The obvious advantage of ballistic training is that it lacks a deceleration phase, making it much more coordination-specific for most athletes. Ballistic training is initiated after significant preparatory training with lighter resistances to strengthen tendons and ligaments. Without such preparation, ballistic training would result in too much risk.

Sources

Staley, C. (1997). Strength Development Fundamentals for Martial Artists.