There has always been a debate in kendo about how far back your hands should go in the back-swing preceding a men strike. Some sensei will tell you that the shinai should stop at a 45 degree angle with the left hand held just above the mengane, others will advise you to bring the left hand back in line with the back of your men. Less frequently in waza geiko and jigeiko, but certainly in suburi there is a school of thought that says the hands should go to the back of your neck and that your shinai should hit your buttocks before you bring it forward.
You will also probably have had varied instruction on the ideal shape of the cut and path that the shinai should travel. Different schools of thought include pushing the point forward throughout the backswing and cut, keeping your left hand at the same distance from all parts of the body as you raise the shinai, bringing the point back so that the shinai is horizontal when above your head and the list goes on.
To quote the Japanese Proverb, “There are many paths to the top of the mountain”. Most kendo teachers would agree that theirs is not the only way to hit men, but it is a way of making their students use their shoulders, elbows and wrists when doing so. The key point is to teach students to relax their arms and push up with the left hand, using all three joints as they do so. The right hand then follows using minimal force until it’s time to make tenouchi.
It is not essential to make big cuts in kendo, but until you can do so correctly, it is unlikely that you will be successful making small strikes. If you ask a raw beginner to make a small attack to kote, where the point of the shinai moves only a few centimetres, he or she will probably do so by using the left hand as a pivot and make the strike with the power of their right hand. If when they do this you talk about using the power of the left hand, it would be very difficult to put into effect.
On the other hand, by asking them to bring their hands up to above or behind their heads, you teach them to cut correctly. Once they can do this then the next challenge is to reduce the size of the cut, replacing the momentum of a big swing with sharp tenouchi.