Round reaction forces and knee joint moments during basketball jab step cutting maneuver Wing-Kai Lam * , Rui Ding and Jason Cheung Li Ning (China) Sports Goods Co., Ltd, Sports Science Research Center, No. 8 Xing Guang 5th Street, Opto-Mechatronics Industrial Park, Zhongguancun Science & Technology Area, Tongzhou District, Beijing P.R. China 101111, Beijing, 101111 China Introduction Basketball game involves multi-directional cutting maneuvers (CMs) in response to the opponents. Lab based cutting maneuver tests involving lateral shuffling and 45  cutting, have reported high ground reaction forces (GRFs) (2.97 BW, Dayakidis and Boudolos, 2006) and external knee moments (2 Nm/kg, Beiser et al. 2001) which was considered as risk factor for anterior cruciate ligament (ACL) injuries (Boden et al. 2000). A frequently used jab step CMs in a basketball game is the fake, plant and cut movements. This is particularly used by offensive players with or without the ball in hand during a tight one-on-one situation. The offensive player usually gives a quick fake to the dominant side, which involves leg planting and shoul- der movement followed by speed cutting to the opposite direction of which the defender is directed. There is a lack of biomechanics information in the current literature about this highly relevant CM. There is unknown about the magnitudes of GRFs and knee moments during this jab step CM and the potential influences from different basketball footwears. Purpose of the study This study was to evaluate the peak GRFs and knee moments during a game-like jab step CM and examine its potential to differentiate footwear performance in a lab based test. Methods Eleven male college basketball players (age: 23.6  0.9 years, height: 177.4  5.6 cm, mass: 74.1  6.3 kg) par- ticipated in this study. Sixteen reflective markers were placed over the lower extremities accord- ing to Vicon’s ‘Plug in Gait’ model to measure kinematic information. To mimic the game situation, subject was asked to hold the ball between his knees in the ready position (Figure 1), and performed a right- front jab step with his right (dominant) foot planted on the force platform together with ball and shoulder movements to the same direction. Upon sensing of subject step (Gate 2), a random light signal (Smart Speed Timing system) will then pop up at the same (Gate 3) or opposite side (Gate 4) and the subject cut and dribbled to the signal direction with his maximum speed. The elapsed time between the sensing and the signal gates was used to measure agility performance. A wooden top AMTI force platform was used to measure the GRFs of the dominant leg of the subject. Three shoe conditions with different cushioning materials embedded in both heel and forefoot regions were randomized. The heel impact scores, Peak g: soft (10.23), medium (11.1) or hard (12.86) were measured using an impact tester (ImpactPlus 3.0, Exeter research). Five successful trials were collected for each shoe and side. Period from initial contact to push off was extracted to calculate peak GRFs and knee moments. Positive knee moments defined as internal flexion, varus and internal rotation moments. All variables were analyzed using three-way repeated measures ANOVA (alpha ¼ 0.05). Results The ICC values of cutting performance for each shoe and side ranged from 0.71 to 0.94 indicated good repeatability of the test trials. Subjects cutting to the opposite side resulted in greater peak sagittal moment, coronal moment and horizontal GRF than cutting to the same side (ps 5 0.05). Moreover, greater peak sagittal moment and horizontal GRF were found during push off phase than the planting phase (ps 5 0.05). In addition, shoe B had lower peak vertical GRF value compared to Shoe C (p 5 0.05). No significant effect was determined for transverse moment. *Corresponding author. Email: wkgilbert@hotmail.com S94 Abstracts ISSN 1942–4280 print/ISSN 1942–4299 online ß 2011 Taylor & Francis DOI: 10.1080/19424280.2011.575835 http://www.informaworld.com