ABSTRACT
Moderate angle cutting maneuvers (between 45º and 90º) are common and essential performance skills for success in multidirectional sports. Research addresses the injury risks of cutting but few studies have attempted to quantify the performance of the cut itself. PURPOSE: To identify any anthropometric, kinematic, and/or kinetic markers of a high-performance cut so they may be taught and lead to more effective training. METHODS: Ten college-aged male athletes (mass 73.97 ± 8.77kg, height 1.81 ± 0.07m) and ten non-athletes (mass 87.37 ± 13.93kg, height 1.85 ± 0.04m) completed five moderate angle cutting trials with a speed constraint of 4.03 m/s - 4.44 m/s through a 3 m in to and 3 m out of a 60° change in direction set-up. Kinetic and kinematic measurements were recorded through ground reaction forces and lower limb angles. RESULTS: A Bonferroni correction revealed that athletes spent significantly less time in the propulsion phase (52.0% ± 0.02%, p < 0.02) compared to non-athletes (55.4% ± 0.03%, p < 0.02). The propulsion phase was determined as the percentage of the contact phase the knee was extending (e.g. Green, et al, 2012). The athletes produced significantly greater instantaneous values of X GRF, Y GRF, and Z GRF during the propulsion phase (p < .05). CONCLUSION: Greater GRFs coupled with shorter propulsion phases by the athletes accounted for the lack of differences in the propulsion impulse between the two groups. Changing direction in a shorter time improves an athlete's ability to evade an opponent, by decreasing the time an opponent has to react to a new direction.
ABSTRACT
PURPOSE: The purpose of this study was to develop and validate a data-supported prediction equation (Lankford equation) for walking metabolic cost ([Formula: see text]), and to compare this equation to the ACSM, Pandolf, Minetti, and LCDA equations. The current study also investigated how kinematics of incline walking relates to mechanical efficiency and metabolic cost. METHOD: Subjects consisted of 145 recreationally fit individuals. Walking speeds were between 1 AND 3 mph with grades ranging from - 18 to 40%. The Lankford equation was then compared to four other reference equations using adjusted R-squared (R2) and Root Mean Square Error (RMSE) as primary metrics to determine correlation with measured CW. Kinematics data collected from reflective markers placed on bony landmarks were compared to CW, incline, and metabolic efficiency to determine the interrelationship between these variables. RESULTS: The Lankford equation for estimating [Formula: see text] was validated with an adjusted R2 = 0.89 and a RMSE of 5.92 Kj min-1, shown to have the highest accuracy among all equations tested. A 0.21 efficiency plateau was observed above 15% incline, and hip, knee, HAT, thigh, and shank angles at foot touch down were found to be highly correlated with [Formula: see text] (r > 0.980). CONCLUSION: The Lankford equation is a validated and highly accurate prediction equation for steady-state walking across a wide range of inclines and speeds and is applicable to the general public. Altered leg swing observed above 15% incline was found to account for the mechanical efficiency plateau and the rectilinear increase in [Formula: see text] with increasing incline.
