I was curious how important people consider grip strength to be as a part of Japanese swordsmanship? My sensei is personally big into it and I know you need a good grip to do tameshigiri so your sword doesn't come out of your hand. Any thoughts?

Grip strength comes with time and practice. I don't think you need to worry too much about building it outside of regular class. I've seen some folks who've been practicing for more than 30 years who almost looked like Popeye because their forearms were so large from swinging steel for so long. Grip strength lies in the finger extensor muscles, which are in the forearms.

Now all that said, don't think I mean that it is important to hold the sword tightly. It's a lot more complicated than that. These muscles build up not because you are using your fingers to grip tightly, but rather because you are using your fingers to manipulate the blade during a swing. As with many of the details of JSAs, it's difficult to explain in writing.

My sensei always said it was like holding a bird: tight enough it does not get away, loose enough not to crush it. The grip is relaxed until the part of the cut when contact would be made with your target, real or imagined. The grip relaxes again after you have passed through your target.

At least that is the way I practice it. And, yes, my forearms show it.

I definitely agree that the correct grip is most important. So with proper form the proper hand tension just happens naturally?

Long Sensei,
Joshua-san is a student of mine here at Nevada Budo. I believe his curiosity about grip strength is not only about holding the sword. Personally, I train my grip strength quite often. I have found that my technique has improved because of this training. The way I see it, the better my physical fitness, the better my technique (in many aspects of budo) will be able to become.
Respectfully,
Ron Taniguchi Jr.