ECSS Paris 2023: OP-BM21
INTRODUCTION: Monitoring of the 400m front-crawl test is of crucial interest to provide valuable feedback on performance and technique, driving construction of training plan and race strategy. Thus, some studies looked at pacing during this event but were limited to split times with narrow performance level [1], reduced sample size [2], and without technical considerations [3]. Then, there is a need for analyzing pacing and kinematics associated with performance at various levels, especially because speed management regarding individual stroke mechanics remains unclear. This study aimed at modeling kinematical features during 400m tests to profile functional patterns of pacing and technical regulations according to specific performance groups and the overall population. METHODS: 123 trained to elite swimmers performed a 400m all-out in front-crawl with an Inertial Measurement Unit (Xsens DOT, The Netherlands) on the sacrum. Participants were divided into 4 balanced groups from lowest (G1) to best (G4) final time. Speed, stroke rate (SR), stroke length (SL) and jerk cost (JC) were computed by lap and fitted using hierarchical generalized additive models [4] to describe both the relationships between kinematics and performance and evaluate profiles of regulation across the laps. Fisher tests and visualizations of the functional responses were used for interpretations. Significance was set at p<0.05. RESULTS: Significant relationships with performance displayed an inverse-sigmoïd shape for SL, with inflection points at 1.12 and 1.62 m/stroke, and a rising shape for JC with a deviation for G1. Kinematical profiles displayed significant regulations as reverse J-shape pacing with deviation for G1 that steeper this pattern, reverse J-shape and positive profile for respectively SR and SL functional response with both common opposite deviations for G1 and G4 that correspondingly mitigate and steeper the global regulation, U-shape for JC with deviation for G2 that mitigate the common profile, by opposition of G3 and G4 that steeped it with a higher extent for G4. CONCLUSION: Useful technical benchmarks regarding the common and group-specific kinematical regulation across 400m on a large database were provided. Key points of global performance are a SL and a JC respectively higher to 1.25 m/stroke and 15 g²/s²x10-3, even if low intra-cyclic acceleration fluctuations is fundamental for improvement beyond G3. Preserving energy for finish, by the ability to lower the fast start and accentuate the end spurt is a determinant of progress. Such effective pacing involves typical kinematical regulations targeting to maintain stroke smoothness as much as possible, while displaying both opposite and major variations in SR and SL modulations. This framework allows to tailor and drive the development of race strategy by understanding and diagnosing the underlying technical requirements of successful pacing skills. 1. Lipinska et al., 2020, 2. Correia et al., 2023, 3. Morais et al., 2019, 4. Pedersen et al., 2019
Read CV Antoine BouvetECSS Paris 2023: OP-BM21
INTRODUCTION: This study aims to investigate the stress and strain characteristics of the tibia in female badminton players during lateral and backward jump smashes under general and specific fatigue conditions, using the AnyBody multi-body dynamics simulation software and finite element analysis, to assess the impact of fatigue type on the risk of tibial injury. METHODS: The boundary conditions and loads on the tibia were obtained through inverse dynamics simulation using the AnyBody software. CT imaging was performed on the badminton players tibiae, followed by 3D reconstruction and reverse modeling to create solid models. Finite element models were established through material assignment and mesh division, and stress and strain data of the tibia during backhand area lateral and backward jump smashes under different fatigue states were acquired using the Abaqus finite element analysis software. RESULTS: The anterior medial and posterior aspects of the mid-lower third of the tibial shaft were identified as stress concentration areas. Under no fatigue, the peak stresses at these sites during backward jump smashes were 27.3 MPa and 40.96 MPa, respectively, with a peak strain of 1509 με. For lateral jump smashes, the peak stresses were both 12.99 MPa with a peak strain of 1062 με. Under general fatigue, the peak stresses for backward jump smashes were 54.56 MPa and 85.74 MPa (199.9% and 209.3% of no fatigue), with a peak strain of 3246 με (215.1% of no fatigue), and for lateral jump smashes, they were 40.8 MPa and 61.19 MPa (314.1% and 471.1% of no fatigue), with a peak strain of 2328 με (219.2% of no fatigue). Under specific fatigue, the peak stresses for backward jump smashes were 61.13 MPa and 87.31 MPa (224.0% and 213.2% of no fatigue), with a peak strain of 3639 με (241.1% of no fatigue), and for lateral jump smashes, they were 45.28 MPa and 67.91 MPa (348.6% and 522.8% of no fatigue), with a peak strain of 2588 με (243.7% of no fatigue). Moreover, under different fatigue states, the stress and strain on the anterior medial and posterior aspects of the tibia during backward jump smashes were consistently higher than those during lateral jump smashes. CONCLUSION: In the non-fatigued state, female badminton players are less likely to injure their tibiae during lateral jump smashes as bone absorption and remodeling reach equilibrium. However, backward jump smashes present a certain risk of tibial injury. Under general and specific fatigue, lateral and backward jump smashes can lead to higher degrees of microfractures, posing a risk of stress fractures in the tibia, with the risk being higher under specific fatigue than general fatigue.
Read CV Binyong YeECSS Paris 2023: OP-BM21
INTRODUCTION: Cricket fast bowlers utilise various techniques to help propel the ball faster, including some techniques which carry injury risk. Biomechanical studies have demonstrated technique related factors which can influence performance and injury risk. This study aims to evaluate technique differences between elite and sub elite fast bowlers, to understand the factors contributing to performance and injury risk. METHODS: 15 male Indian elite and 15 sub elite fast bowlers underwent 3D biomechanical analysis of their bowling action in an indoor biomechanics lab. Front foot Peak Vertical Ground Reaction Force (pVGRF), Lateral Trunk Flexion (LTF), Knee Flexion at Front Foot Contact (KF at FFC), Maximum Knee Flexion (MKF) during front foot contact phase, Stride Length (SL), Ball Release Height (BRH) and ball speed were calculated. After tests for normality, the t-test (parametric method for normally distributed variables) & Mann Whitney U test (non-parametric method for variables not following normal distribution) were used to study differences among the groups. RESULTS: Elite bowlers when compared to sub elite bowlers, had significantly higher mean pVGRF (p=0.03), SL (p<0.001), MKF (p=0.02), LTF (p=0.008), BRH (p=0.02) and ball speed (p=0.019). Mean KF at FFC showed no difference between the two groups (p=0.85). CONCLUSION: Elite bowlers bowled with longer stride length and higher ball release height which could contribute to the greater bowling speeds. Elite bowlers demonstrated higher lateral trunk flexion and higher ground reaction forces which carries higher risk of lumbar spine injury. However, elite bowlers also had higher knee flexion during front foot contact phase, which could mitigate injury risk to some extent. These findings are important for injury prevention, however need to be considered along with other factors such as bowling workload, strength & conditioning status and spinal maturity.
Read CV Sai Aditya RamanECSS Paris 2023: OP-BM21