Fig. 1 (a) Front image of swing motion of the human body (b) Side image of swing motion of the human body

Fig. 2 (a) Torque produced during optimized swing motion. Numerical subscripts 1, 2, and 3 represent the body trunk, arm, and wrist, respectively. (b) Torque produced during actual swing motion. The torque values are used as the initial conditions. The solid line, dotted line with long segments, and dotted line with short segments correspond to the body parts mentioned in Fig. 2a.

Then, three-dimensional data of the swing motion are extracted from these images; on the basis of these data, the torque values around the body trunk, arms, and wrists are calculated (Fig. 2b). Subsequently, by using the actual swing motion data as the initial conditions, the optimizing simulation is carried out using a torque model to obtain the optimal data of swing motion (Fig. 2a).
Finally, by clarifying the difference between the optimal and actual swing motion, the features of the present swing motion of the subject can be evaluated. On the basis of these observations, the subject is advised accordingly to improve his/her swing technique training.

Figs. 1 and 2 show the actual results obtained by applying this system to the subject selected from among the senior players.
As shown in the results, even for a senior player, the actual swing motion (Fig. 2b) differs from the more effective optimal motion (Fig. 2a) with regard to achieving the same swing speed.
This suggests that even a senior player provides a significant room for improvement in his/her swing motion.
Since training for achieving a better swing motion can be determined if this difference is carefully examined, the optimizing calculation becomes very useful. In fact, because of undergoing training guidance according to this system, the senior golfer learned the best swing to increase his carry. Although the system provides room for improvement, it can be considered that the effectiveness of our training support system has been sufficiently clarified at the present prototype stage ( --> see Reference (2)).

For the future, we expect to develop this system into a guiding system for leading golf players to improve their present swing into an ideal one. Further, we aim to provide the subjects with made-to-order training techniques that are suited to the body type, muscle power, and flexibility of each individual subject. Further, such system should enable skill improvements in not only swing motion in golf but also in other sports as well. Instead of merely intending to avoid wasting training and effectively improving skills, it is necessary to introduce provisions that avoid the possibility of subjects sustaining injuries during training even if the avoidance mechanism is a detour. In turn, such provisions allow the system to support medical rehabilitation.

Physically analyzed results of the optimal swing motion (Fig. 2a):
It was revealed that the third inertial force (other than the centrifugal force and Coriolis force)—“the saving force”— plays an important role during effective swing motion ( --> see Reference (3)).
The so-called term “left wall” is considered to be used in two different senses. Among these, it was shown that the “left wall” when used for expressing the wall to stop an unnecessary movement at the moment of impact results from swing motion, and not because of an intentional movement ( -->see Reference (3)).
The results demonstrated the mechanism of an effective swing motion as follows: (1) Gradually increase the initial speed of body rotation at the start of swing motion and decrease the acceleration of the speed instead of decelerating and (2) add the torque around the neck during a strike at the moment immediately before impact (see the optimum swing motion shown in Fig. 2a and Reference (3)).