5 research outputs found
Reducing anterior cruciate ligament injury risk factors by training perception: How vital is maintaining the perception-action coupling?
This study investigated the effect of maintaining perception-action coupling during a 4-week perceptual training program aiming to reduce biomechanical risk factors associated with ACL injury. Kinetic (valgus and internal rotation knee moments) and neuromuscular (total knee muscle activation and directed co-contraction ratios) variables were calculated during evasive sidestepping of 3D-projected opponents in 1-on-1, 2-on-2 and 3-on-3 game-based situations pre and post-intervention training. An additional transfer scenario was assessed post-intervention. Twenty-six amateur Australian Rules footballers were allocated to control (C), uncoupled (U) or coupled (PA) groups. Participants completed biweekly perceptual training containing 48 trials requiring a verbal (uncoupled) or running sidestep (coupled) response while counting the number of attentional cues displayed. Training groups showed no reductions in peak valgus and internal rotation moments, however, a small decrease in peak valgus moments was observed in the transfer condition. Coupled training displayed significant group differences in medial-lateral co-contraction ratios from controls. No changes in muscle activation patterns pre-post ARF were observed, however C and UC groups redirected co-contraction ratios laterally in the transfer condition. Results suggest that attentional cueing perceptual training with a coupled response may have a beneficial impact on kinetic ACL injury risk factors and maintain muscle activation levels associated with decreased ACL injury risk
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Expanded rock blast modeling capabilities of DMC{_}BLAST, including buffer blasting
A discrete element computer program named DMC{_}BLAST (Distinct Motion Code) has been under development since 1987 for modeling rock blasting. This program employs explicit time integration and uses spherical or cylindrical elements that are represented as circles in 2-D. DMC{_}BLAST calculations compare favorably with data from actual bench blasts. The blast modeling capabilities of DMC{_}BLAST have been expanded to include independently dipping geologic layers, top surface, bottom surface and pit floor. The pit can also now be defined using coordinates based on the toe of the bench. A method for modeling decked explosives has been developed which allows accurate treatment of the inert materials (stemming) in the explosive column and approximate treatment of different explosives in the same blasthole. A DMC{_}BLAST user can specify decking through a specific geologic layer with either inert material or a different explosive. Another new feature of DMC{_}BLAST is specification of an uplift angle which is the angle between the normal to the blasthole and a vector defining the direction of explosive loading on particles adjacent to the blasthole. A buffer (choke) blast capability has been added for situations where previously blasted material is adjacent to the free face of the bench preventing any significant lateral motion during the blast