MOVEMENT ANALYSIS

Movement Analysis

Movement Analysis

Introduction

Football is the most popular sport in the world (Lees and Nolan, 1998). Biomechanics is often applied to football to define the characteristics of skills, to gain an understanding of their mechanical effectiveness and to identify factors essential for optimal performance (Lees and Nolan, 1998). The instep kick has been subject to the majority of biomechanical analysis and research (Barfield et al., 2002; Dorge et al., 2002; Lees and Nolan, 2002; Nunome et al., 2002; Shan and Westerhoff, 2005). Subjects are typically instructed to kick a stationary ball at a target from a distance of 8 to 12 m, corresponding to the penalty kick. The instep kick is often used when taking a penalty kick, as a combination of increased ball speed and shot accuracy can be maintained (Lees and Nolan, 1998).

Relatively limited scientific research has been undertaken on the technical aspects of football penalty kicks (Morya et al., 2003), despite their importance in competition. When taking penalties players may adopt the 'open loop' strategy by selecting one corner of the goal to shoot at, ignoring any actions the goalkeeper may take (Kuhn, 1988). Considering the kicking accuracy of modern professional football players, and the time required for a goal-keeper to reach the corners of the goal (Morris and Burwitz, 1989), it is surprising that 25% to 33% of penalty kicks in official competitions are missed (Kuhn, 1988). Therefore, there is a need to examine the factors underpinning penalty kick success.

Kicking accuracy is an important component of football performance, and can be defined as the ability to kick the ball at a specified area (Finnoff et al., 2002). Finnoff et al. (2002) suggested a valid and reliable method of measuring accuracy is to measure the distance of the ball from a specific target. This method provides information on the degree of accuracy as opposed to simply the ability to hit or miss the target.

Kinematic Variables in Penalty Kicks

When taking penalty kicks football players often approach the ball at an angle (Kellis et al., 2004). In general play, the approach angle is often dependent on the preference of the individual and the kick situation (Lees and Nolan, 1998). An angled approach is commonly used as it orientates the body to gain greater hip and knee flexion range of motion, and enables the kicking leg to be tilted in the frontal plane so that the foot can be placed further under the ball, thus enabling better ball contact (Lees and Nolan, 1998). Isokawa and Lees (1988) investigated the effects of approach angle on kick kinematics in trainer football players. Six male subjects took a one step run up to kick a stationary ball using approach angles of 0[degrees], 15[degrees], 30[degrees], 45[degrees], 60[degrees] and 90[degrees]. They found an approach angle of 30[degrees] to 45[degrees] to be optimal, with maximum velocity of the shank achieved with an approach angle of 30[degrees] and the maximum ball speed achieved with an approach of ...