THE EFFECT OF VISUAL GAZE LOCATION ON BLOCK-START BIOMECHANICS IN ATHLETICS

This study investigated the effects of varying visual gaze location (VGL), by means of externally-focused instruction, during the block-start “set” phase with the intention of optimizing block-start biomechanics for faster starts in an athlete-specific manner. Nine collegiate sprinters performed a series of block-starts while directing their VGL to their personal baselines, and at 0.5m, 1m, 2m and 3m from the start line. Twelve infrared opto-reflective cameras and one force plate were utilized to assess trunk, hip, knee and centre of mass kinematics, and blocks push-phase kinetics. An eyetracker was used to determine participants’ VGL. Some postural changes observed were a significant decrease in pelvic height in the “set” position, and more upright trunk postures at toe-off from the blocks, when participants gazed further at 2m and 3m. Gazing at 1m was effective in eliciting changes to pelvic horizontal velocity. These results suggest that manipulating VGL could help certain athletes to optimize their block-start biomechanics for faster starts. Coaches can consider redirecting VGL in addition to usual instructional methods to improve the block-start performances of athletes

GAZE AND STEP CONTROLS OF AN ELITE ATHLETE DURING APPROACHING DIFFERENT HURDLE HEIGHTS

This study investigated the gaze and step controls of one elite male hurdler when approaching hurdles at different heights. Across a 16 m runway, the participant performed three normal sprinting trials, and three hurdle running trials to clear a low, medium and high hurdle respectively. Gaze behaviour was captured using a mobile eye tracker that was mounted on the participant’s head and was filtered using a low-pass filter. In normal sprinting, the step length increased gradually from the first to eighth step. In the hurdle running trials, step length did not increase in the last step and fixations remained on the hurdle. The duration of fixations on the hurdle was lengthened by 21% and 44% in the middle and high hurdle trials, respectively, compared with the low hurdle trials. This pilot study provides foundational information on the interaction between gaze and hurdle running to clear hurdles of different heights that could potentially be optimized to improve performance in hurdling

IS THE VELOCITY PERTURBATION METHOD SUITABLE FOR THE CALCULATION OF THE USEFUL MECHANICAL POWER OUTPUT OF SPRINT KAYAKERS IN OUTDOOR CONDITIONS?

This study assessed whether the Useful Mechanical Power Output (PMO) estimated using the Velocity Perturbation Method (VPM) would be a valid biomechanical measure of performance enhancement in sprint kayaking that would not be affected by changes in environmental conditions. Twelve national-age K1 sprint kayakers performed twelve trials each of 60m maximal effort sprints within two separate sessions, six of which were conducted while towing a hydrodynamic object of known resistance. The opposing wind condition in each trial was recorded and classified as either mild or strong. The sprint velocities at towing-free and towing conditions under similar wind velocities and the resistance of the hydrodynamic object were matched to estimate the PMO. Non-significant differences in PMO between mild and strong wind conditions were observed. However, the typical error of PMO in both wind conditions were larger than 26% of the mean values, which hindered the ability of the PMO to detect the smallest worthwhile enhancement that would be valuable for high-performance kayak sprinting

The transfer of dry-land strength & power into thrust in competitive swimming

The aim was to compare the transfer of dry-land strength and power (S&P) of the shoulder into thrust in front-crawl between swimmers of different competitive levels. Four elite and six sub-elite swimmers were selected to perform a dry-land or an in-water test in random order. The dry-land S&P measurements comprised mean torque, peak torque and mean power of the shoulder rotators of the dominant and non-dominant upper-limbs that were assessed on an isokinetic dynamometer at 90°/s and 180°/s. In-water mean thrust, peak thrust and peak power were collected using an in-house customised system composed of differential pressure sensors and an underwater camera during a 25 m freestyle swim at three different paces (400 m pace, 200 m pace, all-out). There were non-significant and trivial variations in dry-land S&P between elite and sub-elite swimmers. The variations were non-significant but mostly large in the case of thrust. Correlation coefficients of elite swimmers were significantly larger than sub-elite counterparts. In conclusion, elite swimmers seem to be more efficient than sub-elite swimmers at transferring dry-land S&P into thrust.This work was supported by the Singapore Sports Science & Technology Research Grantinfo:eu-repo/semantics/publishedVersio

Correlation between Y-balance test scores with knee moments during single-leg landing : implications on anterior cruciate ligament injury risk

The single-leg jump landing accounts for many non-contact ACL injuries in netball. Several factors place females at higher risk than males when performing this movement. Poor neuromuscular control and technique in particular exacerbate the external moments applied to the knee. A combination of high peak knee valgus moments (PKVM), flexion moments (FM) and internal rotation moments (IRM) can easily rupture the ACL. The Y-Balance Test (YBT), a quick and simple-to-administer screening tool, can be used to predict general lower extremity injuries through assessment of dynamic balance. This study explored the correlation between different knee moments during the forward single-leg jump landing (FSJL) and reach scores in the different YBT directions. It was hypothesized that further reach scores would correspond to lower knee moments. Twenty-one injury-free female national team netballers were recruited to perform randomly sequenced FSJL from maximal distance and YBT for the lower extremity. Three-dimensional motion analyses coupled with a force platform captured data modelled using the UWA lower limb model and marker set in order to identify knee joint moments during the weight-acceptance phase. Significant positive correlation was found between FM and posteromedial reach (r = 0.576, p = 0.006), and composite scores (r = 0.499, p = 0.021); while negative correlation was found between IRM and anterior reach (r = -0.452, p = 0.04). The findings suggest that reach scores are representative of knee joint moments during FSJL. This supports the hypothesis that the YBT could be an indicative screening tool for predicting non-contact ACL injury risk. Keywords: non-contact acl injury, single-leg jump landing, knee joint moment, y-balance testBachelor of Science (Sport Science and Management

The Association Between Functional Movement Screen Scores and Knee Valgus Moments During Unplanned Sidestep Cutting in Netball

# Background Regular employment of three-dimensional (3D) motion analyses to assess and monitor knee valgus moments; a contributor to non-contact anterior cruciate ligament (ACL) injury; during unplanned sidestep cutting (USC) is costly and time-consuming. An alternative quick-to-administer assessment tool to infer an athlete's risk for this injury could allow prompt and targeted interventions to mitigate this risk. # Purpose This study investigated whether peak knee valgus moments (KVM) during weight-acceptance phase of an unplanned sidestep cut were correlated with composite and component scores of the Functional Movement Screen (FMS™). # Study Design Cross-sectional, Correlation # Methods Thirteen female national-level netballers performed six movements of the FMS™ protocol and three trials of USC. A 3D motion analysis system captured lower limb kinetics and kinematics of each participant's non-dominant leg during USC. Averages of peak KVM across USC trials were calculated and examined for correlations with composite and component scores of the FMS™. # Results No correlations were found between FMS™ composite or any of its component scores with peak KVM during USC. # Conclusions The current FMS™ did not show any correlations with peak KVM during USC on the non-dominant leg. This suggests that the FMS™ has limited utility in screening for non-contact ACL injury risks during USC. # Level of Evidence

IMPROVING ACCURACY, RELIABILITY AND AGREEMENT OF SWIM COACHES’ HAND-TIMING: EXPLORING A STANDARDIZED METHOD FOR HAND-TIMING

The purpose of this study was to determine the current accuracy and reliability of, and agreement amongst, coaches’ hand-timing (HT) for a 15 m swim, and to assess if a standardized method of performing the HT can improve these. Three national coaches simultaneously timed two swimmers, each performing seven 15 m swims, for a total of fourteen trials. HT from each coach was compared to 2D video-derived timings, as the reference standard, for assessment of accuracy and reliability, while HT between coaches were compared to assess their agreement with one another. These were compared pre- and post-intervention where a method for performing the HT was introduced. Following this intervention, there appears to be a trend for improved accuracy and reliability within coaches, and improved agreement between coaches’ HT, all of which would present the swimmers with more meaningful timings to assess training progress

Adhesion, proliferation, and gene expression profile of human umbilical vein endothelial cells cultured on bilayered polyelectrolyte coatings composed of glycosaminoglycans

This study characterized human umbilical vein endothelial cell HUVEC adhesion, proliferation, and gene expression on bilayered polyelectrolyte coatings composed of an outermost layer of glycosaminoglycans hyaluronan, heparin, or chondroitin sulfate, with an underlying layer of poly-l-lysine or chitosan. The proportion of cells that adhered to the various polyelectrolyte coatings after 1 and 2 h incubations was quantified by the WST-8 assay. Interchanging poly-l-lysine with chitosan resulted in significant differences in cellular adhesion to the outermost glycosaminoglycan layer after 1 h, but these differences became insignificant after 2 h. The proliferation of HUVEC on the various bilayered polyelectrolyte coatings over 10 days was characterized using the WST-8 assay. Regardless of whether the underlying layer was poly-l-lysine or chitosan, HUVEC proliferation on the hyaluronan outermost layer was significantly less than on heparin or chondroitin sulfate. Additionally, it was observed that there was more proliferation with poly-l-lysine as the underlying layer, compared to chitosan. Subsequently, real-time polymerase chain reaction was used to analyze the expression of seven genes related to adhesion, migration, and endothelial function (VWF, VEGFR, VEGFA, endoglin, integrin-α5, ICAM1, and ICAM2 by HUVEC cultured on the various bilayered polyelectrolyte coatings for 3 days. With poly-l-lysine as the underlying layer, biologically significant differences greater than twofold in the expression of VWF, VEGFR, VEGFA, endoglin, and ICAM1 were observed among the three glycosaminoglycans. With chitosan as the underlying layer, all three glycosaminoglycans displayed biologically significant differences in the expression of VWF and VEGFR compared to the chitosan control. CT-HA displayed the highest level of expression of VWF, whereas expression levels of VEGFR were almost similar among the three glycosaminoglycans.Published versio

Malaysia and Singapore

10.1177/0021989405060473Journal of Commonwealth Literature404139-15