The Effect Of Height And Post-Landing Movement Task On Landing Performance

The purpose of this research was to evaluate selected biomechanical aspects of drop jumps and stable landings performed from increasing heights. The related literature indicates that landings performed in an experimental setting have been to a large degree isolated landing tasks, with subjects landing and remaining in a stable position. It was the intent of this research to address the interactive demands of the complete jumping/landing task. Seven subjects performed three stable landings (L) and three drop jumps (DJ) from each of four initial drop heights (15, 30, 45 and 60cm). All landings were performed with both feet contacting a force platform (500 Hz). Right knee sagittal plane angular displacement was recorded at 500 Hz via an electrogoniometer. Vertical GRF variables used to evaluate landing included maximum impact force (Fmax) normalized to subject body mass, and the time at which the amount of vertical impulse (Timp-land) necessary to account for the downward momentum of the body was achieved. To derive Timp-land, the total body vertical momentum at contact was estimated using contact velocity (calculated from initial drop height) and subject mass. Integration of the GRF curve was perforrned to establish the time relative to contact at which impulse sufficient to reduce landing momentum to zero was achieved. Timpland was therefore indicative of the time period over which the landing phase could be considered complete. In addition, maximum flexion angle at the knee (Kmax) was used in the analysis. Group mean values summarized across heights were as follows for the Land D movement tasks, respectively: Fmax: 52.0 and 41.8N /kg; Timp-land 0.118 and 0.126 sec; Kmax: 71.3 and 80.1 deg. Pearson product correrations were performed for each subject, relating initial drop height (Ht) to each of the three independent variables describing landing. Six of seven subjects (86%) exhibited strong positive correlations (r > .7071; explained variance> 50%) between Ht and Kmax and Ht and Timp-land . indicating an impact force increase and concomitant increase in time over which greater landing momentums were accounted for, observable for landing with and without the peformance of a subsequent jump. The Ht, Kmax relationship was strong and positive for the L conditions (71 % with r > .7071), but only one of seven subjects exhibited a significant Ht, Kmax relationship for the DJ performances. These results suggest that increased knee flexion is a common component of a strategy to absorb landing momentum over longer periods as height increases for stable landings. This does not, however, appear to allow for complete accommodation of Fmax across the full range of heights. The absence of a strong relationship between Ht and Kmax with DJ performance is suggestive of a change in kinematic strategy with the addition of the post-landing movement task

LANDING STRATEGY VARIATIONS: EFFECTS OF SKILL LEVEL, TASK DEMANDS AND MOVEMENT TYPE

INTRODUCTION: 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

Midwest vision for sustainable fuel production

This article charts the progress of CenUSA Bioenergy, a USDA-NIFA-AFRI coordinated agricultural project focused on the North Central region of the US. CenUSA’s vision is to develop a regional system for producing fuels and other products from perennial grass crops grown on marginally productive land or land that is otherwise unsuitable for annual cropping. This article focuses on contributions CenUSA has made to nine primary systems needed to make this vision a reality: feedstock improvement; feedstock production on marginal land; feedstock logistics; modeling system performance; feedstock conversion into biofuels and other products; marketing; health and safety; education, and outreach. The final section, Future Perspectives, sets forth a roadmap of additional research, technology development and education required to realize commercialization

Knee movement patterns of injured and uninjured adolescent basketball players when landing from a jump: A case-control study

BACKGROUND: A common knee injury mechanism sustained during basketball is landing badly from a jump. Landing is a complex task and requires good coordination, dynamic muscle control and flexibility. For adolescents whose coordination and motor control has not fully matured, landing badly from a jump can present a significant risk for injury. There is currently limited biomechanical information regarding the lower limb kinetics of adolescents when jumping, specifically regarding jump kinematics comparing injured with uninjured adolescents. This study reports on an investigation of biomechanical differences in landing patterns of uninjured and injured adolescent basketball players. METHODS: A matched case-control study design was employed. Twenty-two basketball players aged 14–16 years participated in the study: eleven previously knee-injured and eleven uninjured players matched with cases for age, gender, weight, height and years of play, and playing for the same club. Six high-speed, three-dimensional Vicon 370 cameras (120 Hz), Vicon biomechanical software and SAS Version 8 software were employed to analyse landing patterns when subjects performed a "jump shot". Linear correlations determined functional relationships between the biomechanical performance of lower limb joints, and paired t-tests determined differences between the normalised peak biomechanical parameters. RESULTS: The average peak vertical ground reaction forces between the cases and controls were similar. The average peak ground reaction forces between the cases and controls were moderately correlated (r = -0.47). The control (uninjured) players had significantly greater hip and knee flexion angles and significantly greater eccentric activity on landing than the uninjured cases (p < 0.01). CONCLUSION: The findings of the study indicate that players with a history of knee injuries had biomechanically compromised landing techniques when compared with uninjured players matched for gender, age and club. Descriptions (norms) of expected levels of knee control, proprioceptive acuity and eccentric strength relative to landing from a jump, at different ages and physical developmental stages, would assist clinicians and coaches to identify players with inappropriate knee performance comparable to their age or developmental stage

ABIN1 dysfunction as a genetic basis for lupus nephritis

The genetic factors underlying the pathogenesis of lupus nephritis associated with systemic lupus erythematosus are largely unknown, although animal studies indicate that nuclear factor (NF)-?B is involved. We reported previously that aknockin mouse expressinganin active form of ABIN1 (ABIN1[D485N]) develops lupus-like autoimmune disease and demonstrates enhanced activation of NF-?B and mitogen-activated protein kinases in immune cells after toll-like receptor stimulation. In the current study, we show that ABIN1[D485N] mice develop progressive GN similar to class III and IV lupus nephritis in humans. To investigate the clinical relevance of ABIN1 dysfunction, we genotyped five single-nucleotide polymorphisms in the gene encoding ABIN1, TNIP1, in samples from European-American, African American, Asian, Gullah, and Hispanic participants in the Large Lupus Association Study 2. Comparing cases of systemic lupus erythematosus with nephritis and cases ofsystemic lupus erythematosus without nephritis revealed strong associations with lupus nephritis at rs7708392 in European Americans and rs4958881 in African Americans. Comparing cases of systemic lupus erythematosus with nephritis and healthy controls revealed a stronger association at rs7708392 in European Americans but not at rs4958881 in African Americans. Our data suggest that variants in the TNIP1 gene are associated with the risk for lupus nephritis and could be mechanistically involved in disease development via aberrant regulation of NF-?B and mitogen-activated protein kinase activity. Copyright © 2013 by the American Society of Nephrology

Moving from a continuum to a community: reconceptualising the provision of support

The notion of the continuum is applied to special education in diverse contexts across many nations. This paper explores its conceptual underpinnings, drawing upon a systematic search of the literature to review recurring ideas associated with the notion and to explicate both its uses and short-comings. Through a thematic analysis of the literature the research team derived twenty-nine continua, situated within six broad groupings (space, students, staffing, support, strategies and systems). This provides a clear structure for reconsidering the issues which the notion of the continuum is supposed to describe and enables a reconceptualisation of how the delivery of services is represented. We present the initial underpinnings for a community of provision, in which settings and services work together to provide learning and support for all children and young people in their locality

Genetic association analyses implicate aberrant regulation of innate and adaptive immunity genes in the pathogenesis of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a genetically complex autoimmune disease characterized by loss of immune tolerance to nuclear and cell surface antigens. Previous genome-wide association studies (GWAS) had modest sample sizes, reducing their scope and reliability. Our study comprised 7,219 cases and 15,991 controls of European ancestry, constituting a new GWAS, a meta-analysis with a published GWAS and a replication study. We have mapped 43 susceptibility loci, including ten new associations. Assisted by dense genome coverage, imputation provided evidence for missense variants underpinning associations in eight genes. Other likely causal genes were established by examining associated alleles for cis-acting eQTL effects in a range of ex vivo immune cells. We found an over-representation (n = 16) of transcription factors among SLE susceptibility genes. This finding supports the view that aberrantly regulated gene expression networks in multiple cell types in both the innate and adaptive immune response contribute to the risk of developing SLE