Reaction Times

Large vs Small Muscle Movement and Reaction Times

In the next belt curriculum you will study the muscular system in detail. One of the areas you will study involves fast-twitch and slow-twitch muscles. People who are exposed to long duration exercises (long-distance running, swimming, etc.) will generally have a larger percentage of slow-twitch muscles (perhaps as much as 80% of the muscles in the body might be slow-twitch muscles). A person who practices fast response times (drummer, martial artist) or experiences sudden bursts of movements (weight lifters) usually have more fast-twitch muscle (up to 80% of their muscles might be fast twitch muscle).

When you are in direct contact with an opponent you will rely more on fast-twist muscles. Your reaction time in response to a movement by your opponent should be as short as possible. This reaction time is the function of several factors that should be addressed independently.

The first factor is observation. If you observe something it takes, on average, about 250 milliseconds for the information to travel from your eyes to the brain, for the brain to make sense of what has been observed, and for you to initiate appropriate muscle movements. Regardless of which muscles you need to move this level of processing time is needed to determine movement is necessary and to then decide what specific of movement is warranted. It takes a full quarter of a second to do this computation.

Interestingly the response time to an audible event rather than a visual event results in somewhat shorter response times (on the order of 200 milliseconds). So your reaction time will be longer if you respond to a visual event than if you respond to an audible event. Your response time to touch will be roughly the same as response time to an audible event. These numbers can vary somewhat depending your age and overall physical condition. Response times for young adults might be as rapid as 190 milliseconds in response to visual stimuli and 160 milliseconds for audible stimuli.

This all means that you can respond faster to audible and tactile sensory events than visual events. The differences are not dramatically large, but they can be significant in a conflict, especially if you can continually react faster than your opponent.

But even if these response times were all the same there can still be significant differences in movement times. Let’s explore an example. Assume you have stepped slightly to the ear side when your opponent has thrown a Migi Oi Tsuki. You place your right hand on the inside of the opponent’s right wrist and your left hand over top of the opponent’s right elbow. Now you wait for any movement on the part of your opponent. Let’s say it consistently takes 200 milliseconds for you to detect this movement (using whichever method is best for the situation) and to initiate a response.

When you detect the movement you might decide to pull down abruptly with your left hand, pressing it firmly into the opponent’s elbow joint. This requires movement of your upper arm, forearm and perhaps some wrist movement as well.

You could also decide to simply rotate your left wrist inward slightly causing a structural manipulation of the opponent. This might well be faster because the bones that must move are shorter and will therefore move more rapidly. So your overall response time may be faster than if you moved the larger muscles in your arm.

Taking this a step further, you might elect to only pull your left ring finger inward. The bones involved are quite short and are generally manipulated by fast twitch muscles. This movement will be small, but fast. It can still be used to restrict the retraction of the opponents arm or to initiate some form of arm manipulation.

When working with a partner consider what is the minimal movement necessary to accomplish a task. Moving a single finger or toe is much faster than moving an entire arm or leg. It simply takes longer to move a larger lever. Often a finger movement is every bit as effective at controlling or manipulating an opponent when compared with moving an arm. If you intend to use a powerful strike, then you may want to move the entire arm (or leg). But here too you will often find that a smaller movement is faster and equally effective. How you move is much dependent on what you wish to accomplish.

You will benefit from exploring small and faster movements that limit the involvement of larger limbs, muscles, and bones. It takes some time to appreciate which skills benefit most from large or small skeletal movements. You are likely quite familiar with the benefits of large skeletal movements. Now it is time to begin considering how truly fast and effective small skeletal movements can be when applied at the right time and in an optimal manner.

Work with your Uke to see how you can use minimal movement to manipulate, control, or strike a potential opponent. Notice how much faster your response time is if you rely on the sense of touch rather than the visual senses to detect when to move. Also notice how a very slight hip, shoulder, leg, arm, finger, or foot movement can quickly disorient or control your Uke.


Another extremely critical element in the ability to develop faster response times is to remain as relaxed as possible. This can be difficult, especially if you are suffering from an adrenaline rush that occurs the moment a conflict begins. But if you cannot relax then your reaction times will be much slower. Let’s explore why.

Almost by definition if you are not relaxed then you are holding a significant number of muscles in tension. You are expending energy to keep these muscles taught. This means one side of a limb is taught, while the other side is not.

Since most skeletal muscles work as simple levers you will find that one set of muscles pulls the lever in one direction, while another set pulls the muscle in the opposite direction. Let’s look at the biceps and triceps for clarification. The biceps pull your forearm inward toward the shoulder (retraction). Your triceps move the forearm away from your shoulder (extension). This accounts, in part, for the simple hinge motion of the elbow joint.

These muscles work in a coordinated fashion. As a simplification, one set of muscles relaxes and then the other undergoes flexure. This helps ensure the two muscles do not compete with one another during periods of typical movement.

If you are already holding a muscle in tension, and the opposing muscle must move a bone in a different direction then you must first relax the muscle that is in tension. This takes some time. This adds to your reaction time. If both muscles were relaxed then you would only need to flex the required muscle. In reality this can be a much more complex issue than what we are presenting here, but you should be able to do this simple experiment to see the effects yourself.

Have your Uke hold two hand training bags vertically so they are roughly 12 inches (30 cm) apart in front of you. Place the open palm of one of your hands onto one of the two bags. Now try two different variations of movement that cause you to slam the back of your open hand into the opposite bag.

  1. Tense the muscles of your forearm and hand so they press forward lightly yet firmly into the first bag. Now, as quickly as possible, drive the back of your open hand into the opposite bag. Note how long this seemed to take (it may be difficult to measure, but you will get a sense for the time required).
  2. Place your hand against the first bag, but this time keep all of the muscles of the hand and forearm as relaxed as possible. Now drive the back of your open hand into the opposite bag. Note how long this seemed to take.

You will likely notice a subtle yet distinct difference in these two times. In most cases you will find the relaxed hand motions are significantly faster.

Your reaction times will benefit from avoiding unnecessary tension in your body. Try to notice whenever your body is unnecessarily tense and then immediately seek to relieve this tension. When you perform an action try avoid using more power and tension than necessary. If you use more force than required then you will leave your muscles in tension longer than necessary. All of this contributes to slower reaction times.

You may also notice over time that if you hold muscles in tension that your brain tends to pay less attention to the subtle inputs derived from the sense of touch. People who have very focused muscle tension often do not even notice that you are touching their arm or other tensed areas of their body. It is hard to react quickly to a sensory input if you are ignoring it.

In order to benefit most from the sensory inputs above you will want to keep your muscles relaxed so they can respond quickly to the ultimate actions determined by the brain. In the midst of a conflict it is beneficial to remain calm so you will both notice the various stimuli derived from your senses and react in the shortest possible time when necessary.

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