Change of Direction (COD) requires high-speed stopping and starting, acceleration, faking, cutting and reaccelerating, and also contains both a physical and perceptual-cognitive component. Physical components include ground reaction force (GRF), proper form and technique, and sport-specific movements. Key cognitive components include visual scanning, reaction time and decision making based on an opponent’s action. Change of direction speed is considered a preplanned action, whereas agility includes both the physical aspects of directional change and the cognitive and decision making realm (reaction to a stimulus) needed to respond to an opponent’s action. The study described below involves only the physical components of COD.
Mechanical variables during change of directions (for example, braking and propulsive forces, impulses, and ground contact times (GCT), have been identified as determinants of faster change of direction speed (CODS) performance. The purpose of this study was to investigate the mechanical determinants of 180° CODS performance with mechanical characteristic comparisons between faster and slower performers; while exploring the role of the penultimate foot contact (PEN) during the change of direction. Forty multidirectional male athletes performed 6 modified 505 (mod505) trials (3 left and right), and ground reaction forces were collected across the PEN and final foot contact (FINAL) during the change of direction. Pearson’s correlation coefficients and coefficients of determination were used to explore the relationship between mechanical variables and mod505 completion time. Independent T-tests and Cohen’s d effect sizes (ES) were conducted between faster (n = 10) and slower (n = 10) mod505 performers to explore differences in mechanical variables. Faster CODS performance was associated (p≤ 0.05) with shorter GCTs (r = 0.701–0.757), greater horizontal propulsive forces (HPF) (r = −0.572 to −0.611), greater horizontal braking forces (HBF) in the PEN (r = −0.337), lower HBF ratios (r = −0.429), and lower FINAL vertical impact forces (VIF) (r = 0.449–0.559). Faster athletes demonstrated significantly (p ≤ 0.05, ES = 1.08–2.54) shorter FINAL GCTs, produced lower VIF, lower HBF ratios, and greater HPF in comparison to slower athletes. These findings suggest that different mechanical properties are required to produce faster CODS performance, with differences in mechanical properties observed between fast and slower performers. Furthermore, applying a greater proportion of braking force during the PEN relative to the FINAL may be advantageous for turning performance.
Coaching Application: Change of direction speed is largely determined by the amount of force (GRF-ground reaction force) one can apply to the ground with the plant foot and the speed (GCT-ground contact time) with which horizontally- and vertically-directed force is applied to to shorten the braking effect of the plant foot and the step prior to the plant (penultimate foot contact). Correct form and technique is also important in the proper execution of various fakes and cuts used in tam sports, and, in applying greater force application with the penultimate foot-ground contact.
Keep in mind that typical COD drills do not transfer well to specific team sports. It requires ingenuity on the part of coaches and players to develop drills that mimic game situations and the movements commonly encountered during competition. This approach is superior and offers the best opportunity for transfer to playing speed in a sport.
Dos’Santos, Thomas; Thomas, Christopher; Jones, Paul A.; Comfort, Paul. 2017. Mechanical Determinants of Faster Change of Direction Speed Performance in Male Athletes. Journal of Strength & Conditioning Research. March, Vol. 31, Issue 3, 696-705.