I classified the positions of the sinai point in the descriptions and pictures in the published Kendo guidance books, and it developed that there are 4 types of the *Shomen-suburi.
1. Swing back the sinai with the point at the buttocks.
2. Swing back the sinai with the point pointing at the floor.
3. Swing back with the sinai parallel to the floor.
4. Swing back the sinai with the point pointing the ceiling diagonally.
 I directed my attention to the movements of the sinai point in the every Shomen-suburi stage and compared the difference of these 4 types of the Shomen-suburi. The following is the way how I experimented.
 5 kendo experienced subjects who hold from the 3rd grade to 4th grade cooperated with this experiment. In this experiment, the subjects swung the sinai once in the way of 4 types of the Shomen-suburi each. The subjects were required to be conscious of the position of the sinai point when they swung back. hi-speed video camera (Nac, HSV-500C3 shutter speed) was used to measure the swing speed from one direction 7m. I used MOVIAS to analyze the picture of the Shomen-suburi.
 The results are as follows. I could recognize that the speed of the sinai point became slow at the 8th stage when they swung back the sinai with the point downward, and also I found that the speed of the sinai point became the fastest at the 8th stage when they swung back with the sinai parallel to the floor. Consequently kendo teachers should guide the players to do the Shomen-suburi with the point parallel to the floor, instead of explaining how far they should swim back the sinai.
*I define the Shomen-suburi as the followings in this experiment.
  1. Swing back and forth
  2. Stop the sinai at the height of the head in the space.