The biomechanics of the sprint start in a cerebral palsied athlete

Abstract

Since athletes with disabilities have progressively entered the world of competitive sport, growing pressure and expectation has been placed on their standard of performance. The aim of this study was, therefore, to perform an in-depth kinematic and kinetic analysis of the sprint start, from block start to the third step out of the blocks, in an elite T36 cerebral palsy sprinter. One sprinter, fitted with 69 spherical retro-reflective markers, performed six maximal sprint starts. An automatic opto-electronic motion analysis system comprising of fifteen cameras (250 Hz), with synchronised force plates (Kistler, 1000 Hz), collected three-dimensional (3-D) marker trajectories of the four-segment model and corresponding ground reaction forces (Nexus, Vicon). This provided the necessary data for further inverse dynamics analyses (Visual3D). The results showed that predominant contributors to performance were step lengths over the first three steps, knee extensor moments, vertical centre of mass velocity at block exit, and extension of the trunk in the first three steps. Most notably, a more flexed trunk at block exit (28°), continued flexion until step three (38°), and a lower vertical velocity at block exit (0.31 m·s−1), while exhibiting a large knee peak extensor moment (212 N and 141 N for consecutive touchdowns), is suggested to produce a superior performance (values taken from the best performed trial). Additionally body mass, average horizontal external power, resultant centre of mass velocity and step length were significantly reduced in the T36 sprinter when compared to existing literature on able-bodied sprinters. The limited power production during the sprint start in this specific T36 athlete was likely due to the reduced body mass and velocity exhibited, which may be manifestations of cerebral palsy itself that cannot be overcome.