Kendo sparring training provides an invaluable insight into metsuke, maai and deai, ki no musubi; and totally improves Aikido because it reveals insights into many attributes of combat that require speed and attrition to understand.
Some people have called Aikido the swordsman’s jujitsu as a result.
If you do decide to try kendo, be sure to begin slowly and softly and to escalate the intensity safely as you build up tolerances progressively. Otherwise, people won’t come back. The black and blue bruises are not as bad as they look and soon go away. Make sure to keep your elbows tucked in.
NEVER use tsuki in the beginning as it poses a very serious risk of grave injury and even death. (The shinai can shatter and penetrate the faceguard of the men with grave consequences) Use only proper shomenuchi and yokomenuchi cuts with men, kote and do frontal cuts as targets. (no wild sideswipes-they can be dangerous and leave you wide open to brutal counters)
Leave tsuki out of this training until you’ve been practicing for at least two years and have developed sensitivity, skill and clear understanding at high speed. Also, leave out leg strike for as long and if you intend to at some stage add them to the repertoire, get some suneatte, or knee and shin guard as used in Naginata.
This is not true armor combat where you look to penetrate the chinks. Rather, the armor in this case, in conjunction with the skillful Japanese design of the split bamboo shinai, is designed to minimize impact and the harm that would result if equivalent speed and power were used with a solid weapon and no armor. Bogu and shinai are training tools. Care for them well and yourself and all training partners. As with all armored training it can give you a false sense of security if approached with a wrong attitude. Conversely, it can also provide an appreciation of the dangers of such combat if it were real.
An experienced instructor is recommended, so you can get the basics in order first. If you’ve been practicing properly taught Aiki Ken and Jo, your Kendo will be strong. Sometimes too strong for practice. You will need to learn to tone it accordingly.
It is a good practice to use a heavy suburito to warm up solo, and to tire the shoulders first. Also, to build up a correct action. When you are physically tired your ki will flow better. Breathe. Suburito practice alone will correct and improve posture and stability and augment Aikido taijutsu exponentially. The Suburito is self explanatory, for practicing suburi.
Kendo training can also have high cardio value and is lots of fun. It can become addictive. Do not neglect your basic Aikido, Aiki Ken and Jo training as a result. Forget about “winning and losing” and train to learn and to improve, self correcting as you go. Then take it to the mat and do “jujutsu like a swordsman,” practicing Aikido basics.
It is also helpful to read the Book of Five Rings or Go Rin No Sho by Miyamoto Musashi when engaging in this practice. At first, it will seem cryptic, but particularly with swordwork of any kind it, will soon begin to reveal and unlock its “secrets” and you will gain remarkable insights.
When returning to Aiki Ken, be sure to slow down again, practice in a controlled manner, and of course not make human contact, as bokken and jo can be deadly and injurious weapons as shown by the aforementioned Mr. Musashi in his experiences in duels.