The Lengths of the Various Response Phases
Scientific study has enabled us to understand the length of the stages of the motor control process under varying conditions. For example, the clarity and intensity of a stimulus affect identification time (the greater the clarity and intensity of the stimulus, the shorter the reaction time). The time required to choose a response is influenced by the number of alternatives from which the responder can select and how "natural" the stimulus and response are to each other (e.g., it might take longer for a person to begin writing a nonsense syllable after hearing a gunshot than to begin running). Response direction time is greater wher a the reaction called for is more complex or longer in duration
It appears that when a stimulus presents itself the mind has a "window" of approximately on twentieth of a second in which to absorb all stimuli That is, if a stimulus to which a person will respond presents itself, there will be a period of approximately 50 milliseconds (mseca) during which the person can notice other stimuli and consider them in the response). After that period the mind begins to process the information received for a period of approximately one-fifth of a second. During that processing period, reaction to a new stimulus cannot take place. Reaction time to a stimulus can be lengthened when someone is either physically or mentally occupied doing something else, so concentration is critical when reaction time is a factor in performance. Anticipation can shorten this reaction time because you can plan for a response and then execute it more efficiently. This is particularly true when the periods preceding a called for reaction are short. In such situations, these periods can be used as a technique "cue," and the response time can almost be eliminated. Under cued conditions, reaction times can drop to as low as 120 msecs.
The implications of reaction time for weightlifters are numerous, but perhaps the most important relates to what the lifter is told to focus on at various stages in the lift. It is not uncommon for a coach to describe what actually happens during a lift and then to expect the lifter to think about that sequence while performing it. A common example is what occurs when some coaches teach the jerk. These coaches instruct the lifter to drive the bar to the top of the head in the jerk and then to split. The most obvious problem with such an instruction is that while the bar does reach or approach such a height during the execution of the jerk, the skilled lifter begins to move into the receiving position while the bar is between the level of the shoulders and the chin. If the lifter waits until the bar reaches the top of his or her head before splitting, the bar will be falling before the lifter can get into position. A more subtle problem arises out of the limitations placed on the lifter by reaction time. Although the typical lifter 18 actually moving into the split when the bar is at throat level, if he or she waits until the bar is felt to reach that level, actual movement into the split will be delayed by two-tenths of a second, and the timing of the lifter's movement will thereby be inappropriate. The lifter needs to think of splitting earlier in the movement, so that his or her body has time to react and execute the movement into the split at the correct moment. Failure to account for reaction time is a major and common coaching mistake.
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