Introduction In badminton, the most commonly used stroke is the overhead smash. Often, it is the execution of this stroke that determines the advantage of one player over another. Although badminton is one of the most popular racket sports in the world, there is still a lack of scientific research on this sport in comparison with other racket sports such as tennis. There are relatively few scientific investigations of how a badminton smash is executed. A study of the mechanics involved in the overhead smash would provide crucial informa- tion for the enhancement of player performance and thus would be of great interest to sports scientists and badminton coaches. There are a few descriptive studies on the overhead badminton smash. Earlier biomechanical analyses of the badminton smash are largely qualitative in nature. © 2005 isea Sports Engineering (2005) 8, 171–178 171 Correspondence address: Wangdo Kim, PhD. Biomechanics Laboratory Legacy Research Center 1225 NE 2nd Ave. Portland, OR 97232 USA Tel: 503-413-5438 Fax: 503-413-5216 E-mail: mwdkim@gmail.com Using dual Euler angles for the analysis of arm movement during the badminton smash Koon Kiat Teu*, Wangdo Kim † , John Tan ‡ , and Franz Konstantin Fuss § *Division of Engineering Mechanics, School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore † Biomechanics Laboratory, Legacy Research Center, Portland, Oregon, USA ‡ Physical Education and Sports Science, National Institute of Education, Singapore § Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore Abstract Camera techniques are typically used in the study of human movement. However, as the number of joints and markers involved in a study increases, data extraction and calculation become increasingly tedious and complicated. To overcome this challenge, we propose a method of study that simplifies data extraction and calculation by using an electrogoniometer and dual Euler angles. The contribution of the rotation of each arm segment to produce a racket head’s speed was identified in the context of a badminton smash. The contribution of each segment rotation was computed using dual velocity analysis. A set of orthogonal Cartesian frames was established for computing the anatomical rotational velocities for each of the three segments of the upper arm. Electrogoniometers were attached to the subjects during the execution of the smash to obtain measurements of joint angles throughout the motion. To test the algorithm, the calcu- lated velocity of the racket head was compared to the measured velocity. The calculated velocity was derived from an algorithm, while the measured velocity was obtained from a video image. The results are similar, indicating that the dual velocity method is suitable for determining segmental velocities in such kinematic situations. Keywords: arm segment rotation, dual Euler angle, dual velocity, goniometer, kinematics, racket head speed