Motion analysis of front crawl swimming applying CAST technique by means of automatic tracking

Abstract

Kinematic analysis of swimming is of interest to improve swimming performances. Although the video recordings of underwater swimmers are commonly used, the available methodologies are rarely precise enough to adequately estimate the three dimensional (3D) joint kinematics. This is mainly due to difficulties in obtaining the required kinematic parameters (anatomical landmarks, joint centres and reference frames) in the swimming environment. In this paper we propose a procedure to investigate the right upper limb's 3D kinematics during front crawl swimming in terms of all elbow and shoulder degrees of freedom (three rotations of the shoulder, two of the elbow). The method is based upon the calibrated anatomical systems technique (CAST), a technique widely used in clinics, which allows estimation of anatomical landmarks of interest even when they are not directly visible. An automatic tracking technique was adopted. The intra-operator repeatability of the manual tracking was also assessed. The root mean squared difference of three anatomical landmarks, processed five times, is always lower than 8 mm. The mean of the root mean squared difference between trajectories obtained with the different methodologies was found to be lower than 20 mm. Results showed that complete 3D kinematics of at least twice as many frames than without CAST can be reconstructed faster and more precisely.

Application of Video-Based Methods for Competitive Swimming Analysis: A Systematic Review

“…Digitization involves the reconstruction of a swimmers body movement by tracking the displacement of markers placed at specific anatomical locations. Up to 31 landmarks have been included in the reviewed literature, 36 although the number of specific locations of the markers will depend on the aims of the study. It is important to note that the swimmer cannot typically hear or see the videographer whilst performing trials so it is vital that instructions regarding the protocol are clearly communicated to the swimmer in advance to improve the efficiency and accuracy of data collection.…”

“…Another automated tracking system recently described is based on the Calibrated Anatomical System Technique (CAST). 36 The CAST system, frequently seen in clinical settings, estimates anatomical landmarks based on joint degrees of freedom and can be used to estimate the position of hidden landmarks. 92 Initial results indicate that this approach may be suitable for swimming applications, 36,71 although the procedures are still time-consuming and complex, with 31 anatomical landmarks required during swimmer preparation for one arm and a portion of the trunk to be digitized, which perhaps offsets the time gained elsewhere.…”

Optimising filtering parameters for a 3D motion analysis system

“…Moreover, experimental set-ups for underwater 3D reconstruction using video cameras (e.g. Ceccon et al, 2013;Silvatti et al, 2013) were found to be less precise compared to values obtained above water (Ehara et al, 1995). Therefore, underwater environments represent a context where optimising precision is of particular concern.…”

“…Deschodt, 1996). However, as pointed out by Ceccon et al (2013), the majority of kinematic studies do not provide a full description of joint kinematics in terms of Euler angles. This might be related to the poor visibility of bony landmarks during the stroke and the complex calculations that are needed to convert kinematic data to Euler angles.…”

“…To determine segment orientations, additional technical markers on the skin of the subject may be used, a method called the Calibrated Anatomical System Technique (CAST) (Cappozzo et al, 2005). Recently, Ceccon et al (2013) were the first to employ this technique in swimming research. They concluded that the use of additional technical markers led to an increase in the percentage of video frames in which segment positions and orientations could be determined.…”