LANDING STRATEGY VARIATIONS: EFFECTS OF SKILL LEVEL, TASK DEMANDS AND MOVEMENT TYPE
AbstractINTRODUCTION: The loading of various body structures during landing has been implicated as a source of injury in many sport activities, with injury prevention the focus of most contemporary sport related landing research. Subjects have typically been tested under isolated experimental conditions while performing the movement task of landing and remaining in a stable position (1). Though this movement modality may provide for a large degree of experimental control, such studies of discrete, endpoint landings may not account for all biomechanical aspects of landings performed in conjunction with other movements; a situation which is present in cases where high rates of injury have been reported (2). The purpose of the present study was therefore to evaluate selected aspects of lower extremity function during discrete, endpoint landings and during landings preparatory to a subsequent movement activity, represented by a drop jump. METHODS: Eight female subjects (four skilled athletes, four recreationally active individuals) performed five discrete landings followed by five drop jumps from four initial drop heights (16, 32, 48 and 64cm). Ground reaction force (GRF) and sagittal plane kinematic data were collected for each trial, producing 11 GRF, 18 kinematic and 5 lower extremity stiffness variables for each trial. Of these 34 total variables, 20 represented impact phase parameters, and 14 represented post impact phase parameters. A three-way repeated measures ANOVA was conducted for each variable using the mean of the five trials performed by each subject at respective height and movement conditions. RESULTS AND CONCLUSIONS: A large number of significant main effects in absence of interaction effects illustrates the richness of the three-way ANOVA design with respect to the data set being evaluated. These results highlighted functional differences between discrete and preparatory landings. Both skilled and recreational subjects allowed greater impact forces in the case of the discrete landing. Impact force modulation was attributed largely to differing roles of knee joint function relative to each category of landing. Significant group differences indicated that skilled subjects maintained knee joint angular kinematics optimal for jump performance across the range of heights, where the recreational subjects employed knee joint kinematics indicating a dominant influence of landing demands as opposed to optimizing the landing for vertical jump performance. REFERENCES: 1. Dufek, J.S. and Bates, B.T. Biomechanical factors associated with injury during landing in jump sports. Sports Medicine , 12 (5), 326-337, 1991. 2. Hopper, D.M, Hopper, J.L., and Elliott, B.C. Do selected kinanthropometric and performance variables predict injuries in female netball players? Journal of Sports Sciences, 13, 213-222, 1995.
Authors can retain copyright, while granting the International Society of Biomechanics in Sports (ISBS) the right of first publication.