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Scientific Programme

Biomechanics & Motor control

CP-BM04 - Applied Biomechanics

Date: 04.07.2024, Time: 18:30 - 19:30, Lecture room: Boisdale 2

Description

Chair TBA

Chair

TBA
TBA
TBA

ECSS Paris 2023: CP-BM04

Speaker A Issei Ogasawara

Speaker A

Issei Ogasawara
Osaka University, Department of Sport and Health Sciences
Japan
"The deterministic condition for the ground reaction force acting point on the combined knee valgus and tibial internal rotation moments in early phase of cutting maneuvers"

INTRODUCTION: Anterior cruciate ligament (ACL) injury frequently occurs during the early deceleration phase of landing or cutting with the rapid increase of ground reaction force (GRF). The combined knee valgus and tibial internal rotation (VL+IR) moments was shown to stress ACL and regarded as a mechanism of non-contact ACL injury. To utilize this knowledge for non-contact ACL injury prevention in sports, it is required to elucidate how the GRF acting point (center of pressure: CoP) at the stance foot produces combined knee VL+IR moment in risky maneuvers, such as cuttings. However, the effects of GRF acting point at foot on the development of the combined knee VL+IR moment in cutting are still unknown. METHODS: In this study, we first introduced the deterministic mechanical condition that the CoP position relative to the tibial rotation axis differentiates the GRF vector directional probability for the combined knee VL+IR moment development. Then, we tested a stochastic aspect of our theory in that when the CoP is posterior to the tibial rotation axis, the GRF vector is more likely to produce the combined knee VL+IR moment than when the CoP is anterior to the tibial rotation axis in lab-controlled in-vivo experiment. Fourteen females performed 60° cutting under forefoot/rearfoot strike conditions (10 trials each). The positions of lower limb markers and GRF data were measured, and the knee moment due to the GRF vector was calculated. The trials were divided into anterior- and posterior-CoP groups depending on the CoP position relative to the tibial rotation axis at each 10 ms interval from 0 to 100 ms after foot strike, and the occurrence rate of the combined knee VL+IR moment was compared between trial groups. RESULTS: As a result of theoretical consideration, the deterministic condition suggested that when the CoP is posterior to the tibial rotation axis (e.g., GRF acted at the heel side), the spatial probability of the combined knee VL+IR moment was maximized. In addition, we theoretically expected that the posterior-CoP group showed significantly higher occurrence rates of combined knee VL+IR moment (maximum of 82.8%) at every time point than those of the anterior-CoP trials. CONCLUSION: This study first identified deterministic condition for GRF acting point that could generate risky knee biomechanics. This theoretical finding universally explains the injury mechanism of non-contact ACL injury in several sorts of sports. The results experimentally supported the validity of the deterministic mechanical condition. They may suggest the foot strikes inducing the posterior CoP should be avoided to reduce the risk of combined VL+IR knee stress.

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ECSS Paris 2023: CP-BM04

Speaker B Hui-Wen Hsiao

Speaker B

Hui-Wen Hsiao
National Taiwan Normal University, Physical Education and Sport Sciences
Taiwan
"Contributions of Lower Limb Symmetry and Stiffness in ACL Reconstruction Athletes During Single-Leg Drop Jumps"

INTRODUCTION: Athletes are found to have altered landing mechanics in the reconstructed leg after anterior cruciate ligament reconstruction (ACLR) and returning to sports, potentially increasing injury risk due to lower limb asymmetry. Stiffness plays a crucial role during jump-landing performances and injuries. This study investigated whether ACLR affects vertical and joint stiffness, and lower extremity joint contributions during single-leg drop jumps (SLDJ), compared to healthy controls. Additionally, limb asymmetries in ACLR athletes were analyzed by comparing reconstructed and non-reconstructed sides. The results will elucidate the effects of ACLR on stiffness, limb symmetry, and injury risk during sports-related movements. METHODS: This study included 10 ACLR athletes and 11 healthy athletes and performed three SLDJ per leg from a 30 cm platform. Lower extremity kinematic and kinetic data were collected using a 10-camera Vicon motion capture system synchronized with one Kistler force plate. The first ground contact and jump phase of each SLDJ were analyzed. Joint angles, moments, and stiffness were calculated using Visual 3D. The dominant leg was identified as the preferred kick leg. Independent t-tests compared SLDJ performance and symmetry indices between ACLR and healthy groups. Paired t-tests compared biomechanical variables between reconstructed and non-reconstructed legs within the ACLR group. RESULTS: The limb symmetry index of hip joint stiffness was significantly lower in the ACLR group compared to the healthy group (88 vs 112). The ACLR group also showed significant asymmetry in knee range of motion, peak knee moment, and peak knee power during landing. No differences were found between legs in the ACLR group for vertical stiffness or joint stiffness. However, the reconstructed leg had a significantly lower knee flexion range of motion and knee extension moment than the non-reconstructed leg. Besides, the reconstructed leg had lower peak knee extension power during landing and propulsion. Regarding performance, the reconstructed leg in the ACLR group showed significantly lower jump height and reactive strength index compared to the non-reconstructed leg and the healthy group. CONCLUSION: Despite returning to play post-rehabilitation, ACLR athletes showed no side-to-side differences in stiffness index, suggesting stiffness may not reliably indicate ACL reconstruction function. However, knee joint contribution was asymmetric, although ACLR joint stiffness and limb symmetry resembled healthy controls during landing. Reduced knee power generation likely impaired landing and propulsion, influencing SLDJ movement and jump performance. In ACLR athletes, knee angle and moment differences between both legs indicate potentially higher injury risk and burden on the reconstructed side. Our results demonstrate persistent knee joint asymmetries in ACLR athletes after rehabilitation, highlighting the need to monitor knee biomechanics to mitigate injury risk when returning to sports.

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ECSS Paris 2023: CP-BM04

Speaker C SO ITAYA

Speaker C

SO ITAYA
Doshisha univercity, Faculty of Health and Sports Science
Japan
"Relationship between Shoulder Joint Function and Counter Movement Jump Height utilizing Arm Swing Motion"

INTRODUCTION: The arm-swing motion has a significant impact on the jumping height. Previous study reported Performing the arm-swing motion obtain floor reaction force and generate jumping power (1). Shoulder joint functions, such as muscle strength and flexibility, influence the arm-swing movement, however, this has not been examined yet. The purpose of this study was to clarify the relationship between shoulder joint function and jumping height. The hypothesis was that greater muscle strength and flexibility of the shoulder joints correlates with jumping height utilizing arm-swing motion. METHODS: Participants were 30 healthy young men (20.9 ± 1.3 years, 173.4 ± 5.1 cm, 64.2 ± 9.9 kg). Using the Multi Jump Tester II (Qsfix, Inc., Japan), counter movement jump (CMJ) heights were measured under two conditions: with arm-swing and without arm-swing .Voluntary isometric maximal contractions (MVC) of the shoulder joint were measured in four directions; flexion, extension, abduction, and horizontal adduction using a hand-held dynamometer (Moby, Sakai Medical Co., Ltd., Japan). Shoulder joint range of motion (ROM) were taken in four directions; flexion, extension, abduction, and horizontal abduction using a goniometer. Muscle shear moduli were measured using the ultrasound shear wave elastography (Aixplorer, SuperSonic Imagine, France). The measurements were taken at the pectoralis major, pectoralis minor, trapezius, and latissimus dorsi muscle. Pearson correlation coefficient or Spearmans rank correlation coefficient were used to determine the association between the CMJ heights and these shoulder joint functions (MVCs, ROMs, and muscle shear moduli). RESULTS: The CMJ heights with arm-swing were correlated with all MVCs (flexion; r = 0.625, p < 0.01, extension; r = 0. 466, p < 0.01, abduction; r = 0.479, p < 0.01, horizontal adduction; r = 0.444, p < 0.05). On the other hand, the CMJ height without arm-swing was correlated with flexion MVC only ( r = 0.445, p < 0.05). No significant correlations were found between the CMJ height with/without arm-swing and the other measurements. CONCLUSION: Our results suggest that shoulder MVCs are correlated with CMJ height utilizing arm-swing. However, jumping ability is influenced not only by the upper limbs, but also by the lower limbs and trunk. Therefore, it is necessary to examine the jumping ability involving both the lower limbs and the trunk. References: 1)Mackay H,Br J Sports Med.2003 Contact: cgtg0044@mail4.doshisha.ac.jp

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ECSS Paris 2023: CP-BM04