A Quantitative Model To Evaluate Wrist-Rotation In Golf (P2)
In order to effectively analyze performance of a golfer, a precise understanding of the complicated movements involved in the golf swing is required. We use a typical model of the golf swing which splits a complete swing into several major parts. The model helps in determining signiﬁcant factors of improper actions. In the following, we present our model of the swing along with common mistakes that lead to a bad swing.
Golf Swing Model
A full swing is a complex motion of the body aimed at accelerating the club at great speed. The motion starts at an initial position, referred to as the address position, followed by the swing. A golf swing can be divided into smaller segments. Our sport training system is based on a golf swing model which considers a full swing composed of four major segments: takeaway,backswing,downswing,andfollow-through. Take away starts as the ﬁrst movement after the address position and ends when the club is approximately parallel to the target line and at waist level.The backswing follows the takeaway and continues until the golf club is lifted to its highest point behind the player. Following this is the downswing in which the club is brought back down to hit the ball. After impact with the ball,thefollow-through motion brings the club to its stopping point in front of the player. These segments are demonstrated in Fig. 1.
The choice of the aforementioned model simpliﬁes evaluation of the movement by breaking a complex motion into less complicated actions. It further enables more precise analysis of the actions by reporting the quality of each individual part of the swing. Furthermore, the data obtained by our system veriﬁes that each segment can be speciﬁed by particular patterns in the signal. We will provide the evidence later in this paper.
For a golf player to develop a sound swing, it is required to know principles that are essential to building a prefect swing. Applying these fundamental guidelines helps individual golfers improve their proﬁciency by learning how to establish positions as well as how to adjust those parts of the swing that is not fundamentally correct. The goal in achieving a perfect swing is to hit the ball squarely and straight. This would also give the golfer maximum distance. Consequently, it is importan to investigate actions that prevent development of a perfectswing. According to the literature, there are two kinds of common mistakes new players make resulting in a poor shot : wrist rotation and out-of-plane movements. In this study, we focus on evaluating golf swing interms of the angle of wrist rotation. However, we make our experiments highly controlled to prevent introducing effects of other mistakes, e.g. out-of-plane movements, in our results. Wrist rotation occurs when the player rotates the wrists clockwise or counterclockwise resulting in the golf club to become “open” or “closed,” respectively. This can happen during any segment of the swing.The result is that at impact, the golf ball will go either to the right or the left of the target line. Hitting the ball with an open clubface will cause the ball to ﬂy to the right of the target line (slice), while hitting the ball with a closed clubface will cause the ball to ﬂy to the left of the target line (hook). Both of these outcomes are highly undesirable when playing a game and result from the rotation of the wrist.
The second common swing mistake is out-of-plane movement. The golf swing plane is deﬁned by the plane which contains the line created by the golf club at address and the target line. This is demonstrated in Fig. 2. A swing is considered an in-plane swing if the swing, including takeaway, backswing, downswing, and follow-through, remains on a plane at the address position.Out-of-plane movements can happen during any segment of the swing.They can be due to several important movements and postures including over-bending the elbows,raising the arms too high, not raising the arms enough, and bending the wrists among others. Each of these actions has a different effect on the outcome of the swing. In general, outof-plane movements cause the ball to leave the target line, but more importantly, they reduce strength of the swing resulting in a weak impact and shorter driving distance.