Kinematics of the Final Approach and Take-Off Phases in World-Class Men and Women Pole Vaulters

The pole vault is a highly technical event where the athletes must successfully convert horizontal velocity during the run-up to vertical velocity at take-off. The aim of this study was to compare the kinematics of men's and women's world-class pole vaulting. Video data were collected of the best clearances by 14 men and 11 women at the 2018 IAAF World Indoor Championships using three high-speed cameras (200 Hz). Running velocity, step lengths, step times, and pole angles were measured during the run-up; during take-off, distance from the plant box, angle and velocity of take-off, and relative positions of the foot and hands were measured. Men achieved greater clearance heights with faster run-ups, faster take-off velocities and higher hand grip positions (all p < 0.001), with each of the last three steps longer for men when expressed as absolute values (all p < 0.001), but not when expressed relative to stature. There were no differences in run-up pole angles, step times, take-off angle, take-off contact time or time from pole plant to take-off. Women differed in their approach and take-off for characteristics affected by stature and strength, such as fewer run-up steps, shorter take-off distances, and lower grip heights. These lower grips result from a shorter, lighter pole, and this disadvantage was greater than slower run-up velocities. Coaches should therefore note that sex-based differences occur in the pole vault that result from anthropometric differences, but which do not negate the adoption of similar technical models of vaulting

Trends in Outcomes for Neonates Born Very Preterm and Very Low Birth Weight in 11 High-Income Countries

Objective To evaluate outcome trends of neonates born very preterm in 11 high-income countries participating in the International Network for Evaluating Outcomes of neonates. Study design In a retrospective cohort study, we included 154 233 neonates admitted to 529 neonatal units between January 1, 2007, and December 31, 2015, at 24(0/7) to 31(6/7) weeks of gestational age and birth weight <1500 g. Composite outcomes were in-hospital mortality or any of severe neurologic injury, treated retinopathy of prematurity, and bronchopulmonary dysplasia (BPD); and same composite outcome excluding BPD. Secondary outcomes were mortality and individual morbidities. For each country, annual outcome trends and adjusted relative risks comparing epoch 2 (2012-2015) to epoch 1 (2007-2011) were analyzed. Results For composite outcome including BPD, the trend decreased in Canada and Israel but increased in Australia and New Zealand, Japan, Spain, Sweden, and the United Kingdom. For composite outcome excluding BPD, the trend decreased in all countries except Spain, Sweden, Tuscany, and the United Kingdom. The risk of composite outcome was lower in epoch 2 than epoch 1 in Canada (adjusted relative risks 0.78; 95% CI 0.74-0.82) only. The risk of composite outcome excluding BPD was significantly lower in epoch 2 compared with epoch 1 in Australia and New Zealand, Canada, Finland, Japan, and Switzerland. Mortality rates reduced in most countries in epoch 2. BPD rates increased significantly in all countries except Canada, Israel, Finland, and Tuscany. Conclusions In most countries, mortality decreased whereas BPD increased for neonates born very preterm

Comparing very low birth weight versus very low gestation cohort methods for outcome analysis of high risk preterm infants

© 2017 The Author(s). Background: Compared to very low gestational age (<32 weeks, VLGA) cohorts, very low birth weight (<1500 g; VLBW) cohorts are more prone to selection bias toward small-for-gestational age (SGA) infants, which may impact upon the validity of data for benchmarking purposes. Method: Data from all VLGA or VLBW infants admitted in the 3 Networks between 2008 and 2011 were used. Two-thirds of each network cohort was randomly selected to develop prediction models for mortality and composite adverse outcome (CAO: mortality or cerebral injuries, chronic lung disease, severe retinopathy or necrotizing enterocolitis) and the remaining for internal validation. Areas under the ROC curves (AUC) of the models were compared. Results: VLBW cohort (24,335 infants) had twice more SGA infants (20.4% vs. 9.3%) than the VLGA cohort (29,180 infants) and had a higher rate of CAO (36.5% vs. 32.6%). The two models had equal prediction power for mortality and CAO (AUC 0.83), and similarly for all other cross-cohort validations (AUC 0.81-0.85). Neither model performed well for the extremes of birth weight for gestation (<1500 g and ≥32 weeks, AUC 0.50-0.65; ≥1500 g and <32 weeks, AUC 0.60-0.62). Conclusion: There was no difference in prediction power for adverse outcome between cohorting VLGA or VLBW despite substantial bias in SGA population. Either cohorting practises are suitable for international benchmarking

Anthropometric and kinematic influences on release speed in men's fast-medium bowling

The main aim of this study was to identify significant relationships between selected anthropometric and kinematic variables and ball release speed. Nine collegiate fast-medium bowlers (mean ± s: age 21.0 ± 0.9 years, body mass 77.2 ± 8.1 kg, height 1.83 ± 0.1 m) were filmed and reconstructed three-dimensionally. Ball release speeds were measured by a previously validated SpeedchekTM Personal Sports Radar (Tribar Industries, Canada). Relationships between selected anthropometric variables and ball release speed and between kinematic variables and ball release speed were investigated using Pearson’s product-moment correlation coefficients (r). A significant relationship was found between the horizontal velocity during the pre-delivery stride (r = 0.728, P < 0.05) and ball release speed (31.5 ± 1.9 m´ s- 1). We believe that the high correlation was due to the bowlers using techniques that allowed them to contribute more of the horizontal velocity created during the run-up to ball release speed. We also found that the angular velocity (40.6 ± 3.4 rad ´ s- 1) of the right humerus had a low correlation (r = 0.358, P > 0.05) with ball release speed. Although the action of the wrist was not analysed because of an inadequate frame rate, we found high correlations between ball release speed and shoulder-wrist length (661 ± 31 mm; r = 0.626, P < 0.05) and ball release speed and total arm length (860 ± 36 mm; r = 0.583, P < 0.05). We conclude that the variance in release speed within this group may be accounted for by the difference in radial length between the axis of rotation at the glenohumeral joint and the release point

Kinematics of the Final Approach and Take-Off Phases in World-Class Men and Women Pole Vaulters

The pole vault is a highly technical event where the athletes must successfully convert horizontal velocity during the run-up to vertical velocity at take-off. The aim of this study was to compare the kinematics of men&apos;s and women&apos;s world-class pole vaulting. Video data were collected of the best clearances by 14 men and 11 women at the 2018 IAAF World Indoor Championships using three high-speed cameras (200 Hz). Running velocity, step lengths, step times, and pole angles were measured during the run-up; during take-off, distance from the plant box, angle and velocity of take-off, and relative positions of the foot and hands were measured. Men achieved greater clearance heights with faster run-ups, faster take-off velocities and higher hand grip positions (all p &lt; 0.001), with each of the last three steps longer for men when expressed as absolute values (all p &lt; 0.001), but not when expressed relative to stature. There were no differences in run-up pole angles, step times, take-off angle, take-off contact time or time from pole plant to take-off. Women differed in their approach and take-off for characteristics affected by stature and strength, such as fewer run-up steps, shorter take-off distances, and lower grip heights. These lower grips result from a shorter, lighter pole, and this disadvantage was greater than slower run-up velocities. Coaches should therefore note that sex-based differences occur in the pole vault that result from anthropometric differences, but which do not negate the adoption of similar technical models of vaulting. Copyright © 2022 Hanley, Gravestock, Hopkinson, Paradisis, Merlino and Bissas

Sprint mechanical and kinematic characteristics of national female track and field champions and lower-level competitors

The current study examines the sprint mechanical and kinematic characteristics between national female track and field champions (NC) and lower-level female competitors (LL). Sixteen female athletes (8 National Champions, 8 Lower-level competitors) participated in this investigation. The testing procedures consisted of two maximal 30-m sprints. The velocity-time data, captured by three high-speed cameras, was used to calculate the variables of the horizontal F-v profile (theoretical maximal values of force [F0], velocity [V0], power [Pmax], the proportion of the theoretical maximal effectiveness of force application in the antero-posterior direction [RFmax], the rate of decrease in the ratio of horizontal force [DRF]) and essential kinematics characteristics. The NC female athletes showed higher values for Pmax (t = 3.26, p = 0.006), V0 (t = 6.27, p = 0.000) and RFmax (t = 2.58, p = 0.022) compared to LL female competitors. No statistical differences were observed for F0 (t = 1.027, p = 0.32) and DRF (t = 0.917, p = 0.375). Mean running velocity, step frequency and contact time were higher in all but one (0-5 m) 5-m distance intervals of the 30-m sprint. No differences were found in the mean step length, relative step length and flight time in the intervals (0-5, 5-10, 10-15, 15-20, 20-25, and 25-30 m). The faster female athletes in our study demonstrated the capacity to reach superior running velocities, develop larger horizontal forces at higher velocities, apply more effectively the force on the ground in the acceleration phase, show higher values of step frequencies and spent less time in contact with the ground than slower athletes. © 2021, Editura Universitatii din Pitesti. All rights reserved