Effects of a Body-Weight Supporting Kite on Sprint Running Kinematics in Well-Trained Sprinters.
Data of elite sprinters indicate that faster athletes realize shorter ground contact times compared to slower individuals. Further, the importance of the so called [spacing acute]front side mechanics[spacing acute] for elite sprint performance is frequently emphasized by researchers and coaches. Recently it was demonstrated that using a body-weight supporting kite during full effort sprints in highly trained sprinters leads to a reduction in ground contact time. The aim of this study was to investigate possible negative effects of this body-weight supporting device on sprint running kinematics, which was not clarified in previous studies. Eleven well trained Austrian sprinters performed flying 20m-sprints under two conditions: (1) free sprint (FS); and (2) body-weight supported sprint (BWS). Sprint cycle characteristics were recorded during the high-speed phase by a 16 camera 3D-system (Vicon), an optical acquisition system (Optojump-next), and a high-speed camera. Paired sample t-tests and Cohen's d effect-size were used to determine differences between sprinting conditions. Compared to FS, BWS caused a decrease in ground contact time by 5.6% and an increase in air time by 5.5% (both p<0.001), whereas stride length and rate remained unchanged. Furthermore, a reduced hip joint extension at and after take-off, an increased maximal hip joint flexion (i.e. high knee position), and a smaller horizontal distance of the touchdown to the centre of gravity could be observed (all p<0.01). These results indicate no negative effects on [spacing acute]front side mechanics[spacing acute] during BWS and that sprinting with a body-weight supporting kite appears to be a highly specific method to reduce ground contact time in well trained sprinters.
Copyright (C) 2015 by the National Strength & Conditioning Association.
Autor / Fonte:Sascha Kratky, Michael Buchecker, Jürgen Pfusterschmied, Csaba Szekely, Erich Müller Journal of Strength and Conditioning Research 2015 August 11