I should further elaborate on this quarter second rule for the sake of discussion since our time was so limited at camp.
'Reaction time'is in direct relation to the clarity of mind at the time a stimulus is presented. The quarter second rule applies to the cognitive process of perception, analyzation, planning, and motor initiation.
Stress level plays an important role in your ability to react to a threat within a beneficial timing. The quarter second rule can easily turn to one second reaction time or even greater period of time if there is distress.
Directly related to heart rate,there is overwhelming evidence that performance is influenced by the type and amount of stress that the performer is facing.
There is an immediate deterioration of physical and physiological ability when the heart rate increases above approx. 175 BPM (Levitt 1972). At this point, perceptual ability,cognitive processing, motor skill performance and of course reaction time are all in jeopardy. The fastest and hardest hitters will not survive an encounter if they cannot control their heart rate while under attack.
I believe that training to minimize the catastrophic affects of stress is far more important than training fast and powerful techniques (not to minimize the importance of these teachings). Unfortunately, this is much overlooked in our modern dojo style instruction. We should train to maintain our mental focus when a threat occurs,to maintain clarity of mind, and to keep our heart rate at optimum performance levels during the encounter. These are all processes of biofeedback. Look to your kata for instructions on how to do this.
If we are to discuss the reality of defense i.e, hit fast, hit hard, we have to get back in touch with the heart and mind of the warrior. These things, I think, were better understood by the men who lived and died by the quick movement of the sword, but it is not beyond us to uncover the legacy they have left behind.