Influence of Anticipation on Movement Patterns in Subjects with ACL Deficiency Classified as Noncopers

Study Design: Two-factor, mixed experimental design. Objectives: To compare movement patterns of subjects who are anterior cruciate ligament (ACL) deficient and classified as noncopers to controls during early stance of anticipated and unanticipated straight and cutting tasks. Background: Altered neuromuscular control of subjects that are ACL deficient and noncoper theoretically influences movement patterns during unanticipated tasks. Methods and Measures: The study included 16 subjects who are ACL deficient, classified as noncopers, and 20 healthy controls. Data were collected using an Optotrak Motion Analysis System and force plate integrated with Motion Monitor Software to generate knee joint angles, moments, and power. Each testing session included anticipated tasks, straight walking task (ST), and 45° side-step cutting tasks (SSC), followed by a set of unexpected straight walking (STU) and unexpected sidestep cutting (SSCU) tasks in a random order. For all tasks speed was maintained at 2 m/s. Peak knee angle, moment, and power variables during early stance were compared using 2- way mixed-effects ANOVA models. Results: For both the straight and sidestep tasks, the noncoper group did not show a dependence on whether the task was anticipated or unanticipated (group-by-condition interaction) for the knee angle (straight, P = .067; side-step cutting, P = .103), moment (straight, P = .079; side-step cutting, P = .996), and powers (straight, P = .181; side-step cutting, P = .183) during the loading response phase. However, during both straight and side-step cutting tasks, the subjects in the noncoper group used significantly lower knee flexion angles (straight, P = .002; side-step cutting, P = .019), knee moments (straight, P = .005; sidestep cutting, P,.001), and knee powers (straight, P = .013; side-step cutting, P,.001). Conclusions: This study suggests subjects that are ACL deficient and classified as noncopers use a common abnormal movement pattern of lower knee extensor loading even during unanticipated tasks

Knee and Hip Angle and Moment Adaptations During Cutting Tasks in Subjects With Anterior Cruciate Ligament Deficiency Classified as Noncopers

Study Design: Two-factor mixed-design study, with factors including group (control and noncoper) and task (sidestep, crossover, and straight). Objectives: To compare the knee and hip joint angles and moments of control subjects and subjects with an anterior cruciate ligament (ACL) deficient knee classified as noncopers, during a sidestep, crossover, and straight-ahead task. Background: Subjects with ACL deficiency primarily note difficulty with cutting tasks as opposed to straight-ahead tasks. Yet, previous studies have primarily focused on straight-ahead tasks. Methods and Measures: Fifteen subjects with ACL deficiency classified as noncopers, based on the number of giving-way episodes (1) and global question of knee function (60%), were included in this study. These subjects (10 male, 5 female; age range, 18-47 years). Position data collected at 60 Hz were combined with anthropometric and ground reaction force data collected at 420 Hz to estimate 3- dimensional knee and hip joint angles and moments. All subjects performed 3 tasks including a step and 45 degree sidestep cut, step and 45 degree crossover cut, and step and proceed straight. Two-way mixed model ANOVAs were used to compare peak angle and moment variables between 10% and 30% stance. Results: The ACL-deficient noncoper group had 1.8 degree to 5.7 degree less knee flexion angle compared to the control group across tasks (P.043). The ACL-deficient noncoper group used 22% to 27% lower knee extensor moment during weight acceptance compared to the control group (P.001). The sagittal plane hip extensor moments were 34% to 39% highter in the ACL-deficient noncoper group compared to the control group (P.025). Hip frontal (P.037) and transverse plane (P.04) moments also distinguished the ACL-deficient noncoper from the control group. Conclusions: This study suggests that individuals who do not cope well after ACL injury rely on a hip control strategy during cutting tasks

Comparison of Frontal Plane Trunk Kinematics and Hip and Knee Moments during Anticipated and Unanticipated Walking and Side Step Cutting Tasks

Background: Frontal plane trunk and lower extremity adjustments during unanticipated tasks are hypothesized to influence hip and knee neuromuscular control, and therefore, contribute to anterior cruciate ligament (ACL) injury risk. The aims of this study were to examine frontal plane trunk/hip kinematics and hip and knee moments (measures of neuromuscular control) during unanticipated straight and side step cut tasks. Methods: Kinematic and kinetic variables were collected while subjects performed two anticipated tasks, including walking straight (ST) and side step cutting (SS), and two unanticipated tasks (STU and SSU). Foot placement, thorax–pelvis–hip kinematic variables and hip and knee moments were calculated over the first 30% of stance. Findings: Hip abduction angles and knee moments were significantly affected by task and anticipation. Hip abduction angles decreased, by 4.0–7.68, when comparing the SSU task to the ST, STU and SS tasks. The hip abduction angles were associated with foot placement and lateral trunk orientation. Interpretation: Hip abduction angles and foot placement, not lateral trunk flexion influence trunk orientation. Anticipation influences hip and knee neuromuscular control and therefore may guide the development of ACL prevention strategies

Analysis of EMG patterns of control subjects and subjects with ACL deficiency during an unanticipated walking cut task

Purpose: The purpose of this study was to describe the muscle activation patterns of the vastus lateralis (VL), medial hamstrings (MH) and lateral hamstrings (LH) associated with subjects that were anterior cruciate ligament (ACL) deficient and controls. Methods: A total of 54 subjects participated in this study including 25 ACL deficient subjects subdivided into copers (n = 9) and non-copers (n = 16) using clinical criteria. Muscle activation patterns were recorded at 1000 Hz during an unanticipated side step cut task. The root mean square processed data (time constant 11 ms) were ensemble averaged from 20% of stance before heel strike to toe off. Using the first five harmonics of the Fourier Coefficients as features, muscle activation patterns were divided using a cluster analysis algorithm. Results: A majority (76-93%) of control subjects used three muscle activation patterns for each muscle. The coper group preferentially used a particular VL and MH activation pattern \u3e2 times more frequently than controls. The non-coper group also preferentially used a MH activation pattern \u3e2 times more frequently than controls and utilized a unique MH and LH activation pattern, distinct from the copers and controls. Conclusions: Specific muscle activation patterns distinguish subsets of subjects that are healthy and injured, suggesting possible patterns of muscle activation that contribute to coping status. © 2006 Elsevier B.V. All rights reserved