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Wing-Kai Lam, Winson Chiu-Chun Lee, Wei Min Lee, Christina Zong-Hao Ma and Pui Wah Kong

Previous studies have shown that shoe bending stiffness was related to changes in joint kinematics and kinetics as well as athletic performance. 1 Increasing forefoot bending stiffness of a shoe, which can be achieved by inserting a forefoot plate or increasing the midsole hardness, has the

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Marianne J. R. Gittoes, David G. Kerwin and Mark A. Brewin

The impact loads experienced in landing may be influenced by the joint kinematic strategy used. This study aimed to enhance the understanding of the sensitivity of impact loading to the timing of joint kinematic strategies in simulated forefoot landings. Coordinate and force data of drop landings were used to initiate, drive, and evaluate a wobbling mass model. Ankle, knee, and hip joint angle profile timings were modified in the simulated motions. Changes to the timing of the ankle and knee joint angle profiles were associated with substantial changes in the peak vertical ground reaction force (GFzmax) of up to 3.9 body-weights (BW) and 1.5 BW, respectively, whereas loading was less sensitive to temporal changes in the hip joint strategy. Accentuated impact loads incurred by a modified knee flexion action may be explained by the need to maintain an ordered and controlled load attenuation strategy. Individual strategies and external and joint reaction forces should be considered for developing insight into loading in impact landings.

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Cale Jacobs and Carl Mattacola

Context:

Decelerating movements such as landing from a jump have been proposed to be a common mechanism of injury to the anterior cruciate ligament (ACL).

Objective:

To compare eccentric hip-abductor strength and kinematics of landing between men and women when performing a hopping task.

Setting:

Research laboratory.

Patients:

18 healthy subjects (10 women, 8 men).

Main Outcome Measures:

Eccentric peak torque of the hip abductors and peak knee-joint angles during a 350-millisecond interval after impact.

Results:

No significant sex differences were present, but there was a significant inverse relationship between women's eccentric peak torque and peak knee-valgus angle (r = –.61, P = .03).

Conclusions:

Women with larger eccentric peak torque demonstrated lower peak knee-valgus angles. By not reaching as large of a valgus angle, there is potentially less stress on the ACL. Increasing eccentric hip-abductor strength might improve knee-joint kinematics during landing from a jump.

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Joshua T. Weinhandl, Jeremy D. Smith and Eric L. Dugan

The purpose of the study was to investigate the effects of fatigue on lower extremity joint kinematics, and kinetics during repetitive drop jumps. Twelve recreationally active males (n = 6) and females (n = 6) (nine used for analysis) performed repetitive drop jumps until they could no longer reach 80% of their initial drop jump height. Kinematic and kinetic variables were assessed during the impact phase (100 ms) of all jumps. Fatigued landings were performed with increased knee extension, and ankle plantar flexion at initial contact, as well as increased ankle range of motion during the impact phase. Fatigue also resulted in increased peak ankle power absorption and increased energy absorption at the ankle. This was accompanied by an approximately equal reduction in energy absorption at the knee. While the knee extensors were the muscle group primarily responsible for absorbing the impact, individuals compensated for increased knee extension when fatigued by an increased use of the ankle plantar flexors to help absorb the forces during impact. Thus, as fatigue set in and individuals landed with more extended lower extremities, they adopted a landing strategy that shifted a greater burden to the ankle for absorbing the kinetic energy of the impact.

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Yi-Ju Tsai, Chieh-Chie Chia, Pei-Yun Lee, Li-Chuan Lin and Yi-Liang Kuo

trunk-flexion angle and improved core stability after training. Biomechanical links between trunk, hip, and knee joint kinematics have been reported previously. 37 The result of smaller hip and knee-flexion angles after training may be a concern of potential risk for knee injuries. Decreased knee

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Vera Moniz-Pereira, Silvia Cabral, Filomena Carnide and António P. Veloso

The purpose of this research was to study the sensitivity of lower limb joint kinematics and kinetics, calculated during different functional tasks (walking, stair descent and stair ascent) in a sample of older adults, to different pose estimation algorithms and models’ joint constraints. Three models were developed and optimized differently: in one model, each segment had 6 degrees of freedom (segment optimization, SO), while in the other two, global optimization (GO) was used, with different joint constraints: (1) GO, allowing all joint rotations; (2) GOR, allowing three rotations at the hip, one at the knee (flexion/extension) and two at the ankle (dorsi/plantar flexion and eversion/inversion). The results showed that joint angles are more sensitive to the model’s constraints than joint moments and, the more restrictive the model, the higher the differences between models, especially for the frontal and transverse planes (max. RMS difference during gait: 11.7 degrees (64%) vs 0.12 N·m/kg (35.4%). In addition, except for knee abduction/adduction angle, differences between SO and GO models were relatively low. Since GO avoids the nonanatomical dislocations sometimes observed in SO, choosing this model seems to be reasonable for future studies with a similar sample and study design.

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Hans H.C.M. Savelberg, Ingrid G.L. Van de Port and Paul J.B. Willems

By manipulating trunk angle in ergometer cycling, we studied the effect of body configuration on muscle recruitment and joint kinematics. Changing trunk angle affects the length of muscles that span the hip joint. It is hypothesized that this affects the recruitment of the muscles directly involved, and as a consequence of affected joint torque distributions, also influences the recruitment of more distal muscles and the kinematics of distal joints. It was found that changing the trunk from an upright position to approximately 20 deg forward or backward affected muscle activation patterns and kinematics in the entire lower limb. The knee joint was the only joint not affected by manipulation of the lengths of hip joint muscles. Changes in trunk angle affected ankle and hip joint kinematics and the orientation of the thigh. A similar pattern has been demonstrated for muscle activity: Both the muscles that span the hip joint and those acting on the ankle joint were affected with respect to timing and amplitude of EMG. Moreover, it was found that the association between muscle activity and muscle length was adapted to manipulation of trunk angle. In all three conditions, most of the muscles that were considered displayed some eccentric activity. The ratio of eccentric to concentric activity changed with trunk angle. The present study showed that trunk angle influences muscle recruitment and (inter)muscular dynamics in the entire limb. As this will have consequences for the efficiency of cycling, body configuration should be a factor in bicycle design.

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Yvette L. Kerkum, Merel-Anne Brehm, Annemieke I. Buizer, Josien C. van den Noort, Jules G. Becher and Jaap Harlaar

A rigid ventral shelf ankle foot orthosis (AFO) may improve gait in children with spastic cerebral palsy (SCP) whose gait is characterized by excessive knee flexion in stance. However, these AFOs can also impede ankle range of motion (ROM) and thereby inhibit push-off power. A more spring-like AFO can enhance push-off and may potentially reduce walking energy cost. The recent development of an adjustable spring-hinged AFO now allows adjustment of AFO stiffness, enabling tuning toward optimal gait performance. This study aims to quantify the mechanical properties of this spring-hinged AFO for each of its springs and settings. Using an AFO stiffness tester, two AFO hinges and their accompanying springs were measured. The springs showed a stiffness range of 0.01−1.82 N·m·deg−1. The moment-threshold increased with increasing stiffness (1.13–12.1 N·m), while ROM decreased (4.91–16.5°). Energy was returned by all springs (11.5–116.3 J). These results suggest that the two stiffest available springs should improve joint kinematics and enhance push-off in children with SCP walking with excessive knee flexion.

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Steven K. Boyd and Janet L. Ronsky

Abnormal joinl coniact mechanics in the knee joint due to loss of anterior cruciate ligament (ACL) are often speculated to play an important role in the development of osteoarthritis. In this study, a technique was developed so that contact of the patellofemoral (PF) joint could be estimated in situ using a mathematical contact model. The model inputs were PF joint kinematics measured in situ and the PF joint surface topology. Due to the small size of the joint, techniques for measuring joinl kinematics and surface topology with sufficient precision were paramount so that reasonable estimates of joint contact could be obtained. The sensitivity of the model to measurement errors was examined. Differences in joint contact between ACL-intacl and ACL-deficient conditions were analyzed. Statistically significant differences in contact areas were detected between the intact and ACL-deficient knee joint, and different coniact areas and locations as a function of joint angle and quadriceps muscular stimulation.

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Jae P. Yom, Kathy J. Simpson, Scott W. Arnett and Cathleen N. Brown

One potential ACL injury situation is due to contact with another person or object during the flight phase, thereby causing the person to land improperly. Conversely, athletes often have flight-phase collisions but do land safely. Therefore, to better understand ACL injury causation and methods by which people typically land safely, the purpose of this study was to determine the effects of an in-flight perturbation on the lower extremity biomechanics displayed by females during typical drop landings. Seventeen collegiate female recreational athletes performed baseline landings, followed by either unexpected laterally-directed perturbation or sham (nonperturbation) drop landings. We compared baseline and perturbation trials using paired-samples t tests (P < .05) and 95% confidence intervals for lower-extremity joint kinematics and kinetics and GRF. The results demonstrated that perturbation landings compared with baseline landings exhibited more extended joint positions of the lower extremity at initial contact; and, during landing, greater magnitudes for knee abduction and hip adduction displacements; peak magnitudes of vertical and medial GRF; and maximum moments of ankle extensors, knee extensors, and adductor and hip adductors. We conclude that a lateral in-flight perturbation leads to abnormal GRF and angular motions and joint moments of the lower extremity.