Understanding the effects of a sudden directional shift in somatosensory feedback and increasing task complexity on postural adaptation in individuals with and without chronic ankle instability.

Background: Individuals with chronic ankle instability (CAI) present somatosensory dysfunction following an initial ankle sprain. However, little is known about how individuals with CAI adapt to a sudden sensory perturbation of instability with increasing task and environmental constraints to maintain postural stability.

Methods: Forty-four individuals with and without unilateral CAI performed the Adaptation Test to a sudden somatosensory inversion and plantarflexion perturbations (environment) in double-, injured-, and uninjured- limbs.

Sensory Reweighting System Differences on Vestibular Feedback With Increased Task Constraints in Individuals With and Without Chronic Ankle Instability.

Context: Chronic ankle instability (CAI) is associated with a less flexible and adaptable sensorimotor system. Thus, individuals with CAI may present an inadequate sensory reweighting system, inhibiting their ability to place more emphasis (upweight) on reliable sensory feedback to control posture. However, how individuals with CAI reweight sensory feedback to maintain postural control in bilateral and unilateral stances has not been established.

The Impact of Differential Knee Laxity on Brain Activation During Passive Knee Joint Loading.

Although higher anterior knee laxity is an established risk factor of ACL injury, underlying mechanisms are uncertain. While decreased proprioception and altered movement patterns in individuals with anterior knee laxity have been identified, the potential impact of higher laxity on brain activity is not well understood. Thus, the purpose of this study is to identify the impact of different magnitudes of knee laxity on brain function during anterior knee joint loading.

Practice-Not Task Difficulty-Mediated the Focus of Attention Effect on a Speed-Accuracy Tradeoff Task.

External focus (attention to the movement effect) has been found effective in motor performance and learning. However, while some investigators have suggested that the effect of attentional focus varies with task difficulty, others reported external focus benefits regardless of difficulty. We hypothesized that attentional focus effects would vary with practice, due to changes in the individual's processing efficiency.

Ankle Dorsiflexion Affects Hip and Knee Biomechanics During Landing.

Background: Restricted ankle dorsiflexion range of motion (DFROM) has been linked to lower extremity biomechanics that place an athlete at higher risk for injury. Whether reduced DFROM during dynamic movements is due to restrictions in joint motion or underutilization of available ankle DFROM motion is unclear.

Hypothesis: We hypothesized that both lesser total ankle DFROM and underutilization of available motion would lead to high-risk biomechanics (ie, greater knee abduction, reduced knee flexion).

Relationship of Anterior Cruciate Ligament Volume and T2* Relaxation Time to Anterior Knee Laxity.

Background: High anterior knee laxity (AKL) has been prospectively identified as a risk factor for anterior cruciate ligament (ACL) injuries. Given that ACL morphometry and structural composition have the potential to influence ligamentous strength, understanding how these factors are associated with greater AKL is warranted.

Hypothesis: Smaller ACL volumes combined with longer T2* relaxation times would collectively predict greater AKL.

The Effects of Gluteal Strength and Activation on the Relationship Between Femoral Alignment and Functional Valgus Collapse During a Single-Leg Landing.

Context: A bias toward femoral internal rotation is a potential precursor to functional valgus collapse. The gluteal muscles may play a critical role in mitigating these effects.

Objective: Determine the extent to which gluteal strength and activation mediate associations between femoral alignment measures and functional valgus collapse.

A Magnetic Resonance Imaging-Compatible Device to Perform In Vivo Anterior Knee Joint Loading.

Context: Greater anterior knee laxity (AKL) is associated with impaired sensory input and decreased functional knee stability. As functional magnetic resonance imaging (MRI) is the gold standard for understanding brain function, methods to load the anterior cruciate ligament in the MRI environment could further our understanding of the ligament's sensory role in knee joint stability.

Objective: To design and validate an MRI-compatible anterior knee joint loading device.

Quadriceps muscle volume positively contributes to ACL volume.

Females have smaller anterior cruciate ligaments (ACLs) than males and smaller ACLs have been associated with a greater risk of ACL injury. Overall body dimensions do not adequately explain these sex differences. This study examined the extent to which quadriceps muscle volume (VOL ) positively predicts ACL volume (VOL ) once sex and other body dimensions were accounted for.

Sex-Specific Associations between Cartilage Structure and Metabolism at Rest and Acutely Following Walking and Drop-Landing.

Objective: Cartilage health is thought to be dependent on the relationship between mechanics, structure, and metabolism, rather than these individual components in isolation. Due to sex differences in cartilage health, there is need to determine if the relationships between these cartilage components separately for males and females. Therefore, we sought to determine the sex-specific associations between cartilage structure and metabolism at rest and their acute response following walking and drop-landing in healthy individuals.

Temporal kinematic differences throughout single and double-leg forward landings.

Screening methods for anterior cruciate ligament (ACL) injuries often involve double-leg landings, though the majority of ACL injuries occur during single-leg landings. Differences in kinematic temporal characteristics between single-leg and double-leg landings are poorly understood. The purpose of this study was to examine discrete and temporal kinematics associated with functional valgus collapse during single-leg and double-leg landings (LAND and LAND).

The Influence of Hip Structure on Functional Valgus Collapse During a Single-Leg Forward Landing in Females.

Clinical femoral anteversion (Craig test) and hip range of motion (ROM) have been associated with valgus collapse, but their clinical usefulness in predicting biomechanics is unknown. Our purpose was to determine the individual and combined predictive power of femoral anteversion and passive hip ROM on 3-dimensional valgus collapse (hip internal rotation and adduction, knee rotation, and abduction) during a single-leg forward landing in females. Femoral anteversion and passive hip ROM were measured on 20 females (24.

ACL Size and Notch Width Between ACLR and Healthy Individuals: A Pilot Study.

Background: Given the relatively high risk of contralateral anterior cruciate ligament (ACL) injury in patients with ACL reconstruction (ACLR), there is a need to understand intrinsic risk factors that may contribute to contralateral injury.

Hypothesis: The ACLR group would have smaller ACL volume and a narrower femoral notch width than healthy individuals after accounting for relevant anthropometrics.

Study Design: Cross-sectional study.

Sex Comparisons of In Vivo Anterior Cruciate Ligament Morphometry.

Context: Females have consistently higher anterior cruciate ligament (ACL) injury rates than males. The reasons for this disparity are not fully understood. Whereas ACL morphometric characteristics are associated with injury risk and females have a smaller absolute ACL size, comprehensive sex comparisons that adequately account for sex differences in body mass index (BMI) have been limited.

Potential Mediators of Load-Related Changes in Movement Complexity in Young, Healthy Adults.

Context: Movement screening has become increasingly popular among tactical professionals. This popularity has motivated the design of interventions that cater to improving outcomes on the screens themselves, which are often scored in reference to an objective norm. In contrast to the assumptions underlying this approach, dynamical systems theory suggests that movements arise as a function of continuously evolving constraints and that optimal movement strategies may not exist.

Potential Mediators of Load-Related Decreases in Movement Quality in Young, Healthy Adults.

Context: Predicting and promoting physical performance are important goals within the tactical professional community. Movement screens are frequently used in this capacity but are poor predictors of performance outcomes. It has recently been shown that prediction improved when movement quality was evaluated under load, but the mechanisms underlying this improvement remain unclear.

Passive Hip Range-of-Motion Values Across Sex and Sport.

Context:   Greater passive hip range of motion (ROM) has been associated with greater dynamic knee valgus and thus the potential for increased risk of anterior cruciate ligament injuries. Normative data for passive hip ROM by sex are lacking.

Objective:   To establish and compare passive hip ROM values by sex and sport and to quantify side-to-side differences in internal-rotation ROM (ROM), external-rotation ROM (ROM), and total ROM (ROM).

The Influence of Attentional Focus on Balance Control over Seven Days of Training.

This study examined the training effect of attentional focus (external focus, internal focus, or no focus instructions) on a dynamic balance task. Participants completed baseline balance testing, seven consecutive days of dynamic balance board training, and retention testing 24 hours after the last session. The novel finding of this study was the presence of a training effect on balance control when adopting an external focus relative to an internal focus or no focus instructions.

Cardiac and gait rhythms in healthy younger and older adults during treadmill walking tasks.

Background: Aging and pathology result in changes in the dynamics of several physiological subsystems. Often, these changes are concurrent, altering the dynamics between subsystems. Cardiac and gait rhythms are one example in which patterns change during physical activity.

Sport-specific biomechanical responses to an ACL injury prevention programme: A randomised controlled trial.

Anterior cruciate ligament (ACL) injury prevention programmes have not been as successful at reducing injury rates in women's basketball as in soccer. This randomised controlled trial (ClinicalTrials.gov #NCT02530333) compared biomechanical adaptations in basketball and soccer players during jump-landing activities after an ACL injury prevention programme.

Acute Serum Cartilage Biomarker Response after Walking and Drop Landing.

Introduction: An in-depth understanding of the healthy cartilage response to activities of daily living is needed to better understand the complex relationship between cartilage health and loading. The purpose was to assess the role of loading on the acute serum cartilage oligomeric matrix protein (COMP) response in recreationally active individuals.

Methods: Forty individuals without previous lower extremity injury participated in this repeated-measures study in which each participant completed all conditions during independent data collection sessions separated by at least 1 wk.