One of our newer members is a professional musician. His kendo is visibly improving from week to week, but like almost everyone who starts as an adult he tends to use more physical power than he needs to.
Trying to find an easy analogy, I thought about my experience as an incompetent bedroom guitarist and realised that the inability to relax was the major reason for my lack of progress. When you watch great musicians they seem able to chill completely and just come in on the beat with lightest of touches. Amateurs like me on the other hand can be seen staring intently at the fret-board with their tongues poking out as they manfully prod at the strings.
In kendo relaxation is equally if not more important. You have to relax in order to keep an effective kamae and to be able to move easily. Shoulders, elbows, wrists and your grip on the shinai must be loose and must remain so throughout the striking process. People are often confused by the instruction to apply pressure, or tension and relax. What is generally meant is that your legs, hips and abdomen should be braced, but that your chest, shoulders and arms should not be tense.
To get this feeling you should push your shoulders back as if you are trying to make your chest feel wider. Then you should check that there is space between your upper arms and the sides of your body. Elbows should be bent. There is no reason why your left arm should not rest on your dou. Your right arm should certainly not be straight, as some people believe that it should, as it would pull your right shoulder forward and spoil your kamae.
Your left wrist needs to be turned slightly outwards to support the shinai, but this does not mean that it should be tense. Your right wrist should be in a completely natural position. Your grip should be relaxed. You need to grip only with the little and ring fingers of each hand, with the other fingers following without making intentional contact with the tsuka of the shinai.. The points of contact for the gripping fingers are the finger tips and the opposing point of the palm. You should not apply pressure with the inside surface of the fingers. Finally your tenouchi on striking the target should amount to no more than a squeeze without changing your grip.
Of course with kendo and music and I imagine any other activity that requires physical dexterity, the more you practise the more relaxed you become. Maybe there is a chance that if I keep playing my scales I may become another Carlos Santana or Eric Clapton. At the current rate of progress it should only take another 120 years.