From Control to Chaos: Visual-Cognitive Progression During Recovery from ACL Reconstruction.

BACKGROUND: Anterior cruciate ligament tear is a serious knee injury with implications for central nervous system (CNS) plasticity. To perform simple knee movements, people with a history of ACL reconstruction (ACL-R) engage cross-modal brain regions and when challenged with cognitive-motor dual-tasks, physical performance deteriorates. Therefore, people with ACL-R may increase visual-cognitive neural processes for motor control. CLINICAL QUESTION: What components of CNS plasticity should the rehabilitation practitioner target with interventions, and how can practitioners augment rehabilitation exercises to target injury associated plasticity? KEY RESULTS: This clinical commentary (1) describes the neurophysiological foundation for visual-cognitive compensation after ACL-R, (2) provides a theoretical rationale for implementing visual-cognitive challenges throughout the return to sport (RTS) continuum, and (3) presents a framework for implementing visual-cognitive challenges from the acute phases of rehabilitation. The 'Visual-Cognitive Control Chaos Continuum (VC-CCC) framework consists of five training difficulties that progress visual-cognitive challenges from high control to high chaos, to better represent the demands of sport. CLINICAL APPLICATION: The VC-CCC framework augments traditional rehabilitation so that each exercise can progress to increase difficulty and promote sensorimotor and visual-cognitive adaptation after ACL-R.

Development and Reliability of a Visual-Cognitive Reactive Triple Hop Test.

CONTEXT: Current lower-extremity return to sport testing primarily considers the physical status of an athlete; however, sport participation requires continuous cognitive dual-task engagement. Therefore, the purpose was to develop and evaluate the reliability of a visual-cognitive reactive (VCR) triple hop test that simulates the typical sport demand of combined online visual-cognitive processing and neuromuscular control to improve return to sport testing after lower-extremity injury. DESIGN: Test-retest reliability. METHODS: Twenty-one healthy college students (11 females, 23.5 [3.7] y, 1.73 [0.12] m, 73.0 [16.8] kg, Tegner Activity Scale 5.5 [1.1] points) participated. Participants performed a single-leg triple hop with and without a VCR dual task. The VCR task incorporated the FitLight system to challenge peripheral response inhibition and central working memory. Maximum hop distance, reaction time, cognitive errors, and physical errors were measured. Two identical testing visits were separated by 12 to 17 days (14 [1] d). RESULTS: Traditional triple hop (intraclass correlation coefficients: ICC(3,1) = .96 [.91-.99]; standard error of the measurement = 16.99 cm) and the VCR triple hop (intraclass correlation coefficients(3,1) = .92 [.82-.97]; standard error of the measurement = 24.10 cm) both demonstrated excellent reliability for the maximum hop distance, and moderate reliability for the VCR triple hop reaction time (intraclass correlation coefficients(3,1) = .62 [.09-.84]; standard error of the measurement = 0.09 s). On average, the VCR triple hop resulted in a hop distance deficit of 8.17% (36.4 [5.1] cm; P < .05, d = 0.55) relative to the traditional triple hop. CONCLUSIONS: Hop distance on the VCR triple hop had excellent test-retest reliability and induced a significant physical performance deficit when compared with the traditional triple hop assessment. The VCR triple hop reaction time also demonstrated moderate reliability.

Combining Neurocognitive and Functional Tests to Improve Return-to-Sport Decisions Following ACL Reconstruction.

SYNOPSIS: Neuroplasticity after anterior cruciate ligament (ACL) injury alters how the nervous system generates movement and maintains dynamic joint stability. The postinjury neuroplasticity can cause neural compensations that increase reliance on neurocognition. Return-to-sport testing quantifies physical function but fails to detect important neural compensations. To assess for neural compensations in a clinical setting, we recommend evaluating athletes' neurocognitive reliance by augmenting return-to-sport testing with combined neurocognitive and motor dual-task challenges. In this Viewpoint, we (1) share the latest evidence related to ACL injury neuroplasticity and (2) share simple principles and new assessments with preliminary data to improve return-to-sport decisions following ACL reconstruction. J Orthop Sports Phys Ther 2023;53(8):1-5. Epub: 16 May 2023. doi:10.2519/jospt.2023.11489.

Cognitive Load Influences Drop Jump Landing Mechanics During Cognitive-Motor-Simulated Shooting.

INTRODUCTION: Military duties require immense cognitive-motor multitasks that may predispose soldiers to musculoskeletal injury. Most cognitive challenges performed in the research laboratory are not tactical athlete specific, limiting generalizability and transferability to in-field scenarios. The purpose of this study was to determine the impact of a cognitive-motor multitask (forward drop jump landing while simultaneously performing simulated shooting) on knee kinetics and kinematics. METHODS: Twenty-four healthy collegiate Reserve Officer's Training Corps members (18 males and 6 females, 20.42 ± 1.28 years, 174.54 ± 10.69 cm, 78.11 ± 14.96 kg) volunteered, and knee kinetics and kinematics were assessed between baseline and cognitive-loaded conditions. Repeated measures ANOVAs were conducted for each dependent variable with the within-subject factor of condition (baseline vs. cognitive load). RESULTS: Univariate ANOVAs indicated that knee flexion angle at initial contact (IC) (decreased 6.07°; d = 3.14), knee flexion displacement (increased 6.78°; d = 1.30), knee abduction angle at IC (increased 2.3°; d = 1.46), peak knee abduction angle (increased 3.04°; d = 0.77), and peak vertical ground reaction force (increased 0.81 N/kg; d = 2.13) were significant between conditions (P < .001). Therefore, cognitive load resulted in decreased knee flexion and increased knee abduction angle at IC and greater peak vertical ground reaction force, all factors commonly associated with knee injury risk. Peak knee flexion angle and knee abduction displacement were not significant between conditions (P > .05). CONCLUSIONS: Cognitive challenge induced knee landing biomechanics commonly associated with injury risk. Injury risk screening or return-to-training or duty assessments in military personnel might consider both baseline and cognitive conditions.

Development and reliability of a visual-cognitive medial side hop for return to sport testing.

OBJECTIVES: To develop and evaluate the reliability of a new visual-cognitive medial side hop (VCMH) test that challenges physical and cognitive performance to potentially improve return to sport testing. DESIGN: Test-retest experimental design. SETTING: Laboratory. PARTICIPANTS: Twenty-two healthy college students participated (11 females; 23.5 ± 3.64 years; 172.9 ± 11.58 cm; 74.1 ± 17.25 kg; Tegner Score 5.6 ± 1.1). MAIN OUTCOME MEASURES: Subjects performed a medial side hop for distance with and without a visual-cognitive task (VCMH). Maximum hop distance and cognitive errors were measured. RESULTS: There was strong reliability for the traditional medial side hop (ICC3,1 = 0.88[0.72, 0.95]; SEM = 7.16 cm) and VCMH distances (ICC3,1 = 0.86[0.66, 0.94]; SEM = 6.82 cm). Maximum hop distance was significantly lower during the VCMH (86.9 ± 18.2 cm) compared to the traditional medial side hop (96.3 ± 20.7 cm; p < 0.05; d = 0.74), with a performance deficit of 9.69%. CONCLUSION: The VCMH has high test-retest reliability and resulted in a significant dual-task cost with a reduction in physical performance when compared to the traditional medial side hop.

Visual cognition associated with knee proprioception, time to stability, and sensory integration neural activity after ACL reconstruction.

Visual cognitive ability has previously been associated with anterior cruciate ligament injury and injury risk biomechanics in healthy athletes. Neuroimaging reports have identified increased neural activity in regions corresponding to visual-spatial processing, sensory integration, and visual cognition in individuals after anterior cruciate ligament reconstruction (ACLR), indicating potential neural compensatory strategies for motor control. However, it remains unclear whether there is a relationship between visual cognition, neural activity, and metrics of neuromuscular ability after ACLR. The purpose of this study was to (1) evaluate the relationship between visual cognitive function and measurements of neuromuscular control (proprioception and time to stability [TTS]), isokinetic strength, and subjective function, and (2) examine the neural correlates of visual cognition between ACLR (n = 16; time since surgery 41.4 ± 33.0 months) and demographically similar controls (n = 15). Visual cognition was assessed by the ImPACT visual motor and visual memory subscales. Outcome variables of proprioception to target knee angle 20°, landing TTS, strength, and subjective function were compared between groups, and visual cognition was correlated within groups to determine the relationship between visual cognition and outcome variables controlled for time from surgery (ACLR group). The control group had better IKDC scores and strength. Visual memory and visual motor ability were negatively associated with proprioception error (r = -0.63) and TTS (r = -0.61), respectively, in the ACLR group but not controls. Visual cognition was associated with increased neural activity in the precuneus and posterior cingulate cortex in the ACLR group but not control participants. These data suggest the neural strategy in which ACLR participants maintain proprioception and stability varies, and may depend on visual cognition and sensory integration neural activity.

Cognitive Load Impairs Time to Initiate and Complete Shooting Tasks in ROTC Members.

INTRODUCTION: Multitasking typically requires an individual to simultaneously process cognitive information while performing a motor task. Cognitive motor interference (CMi) is encountered when cognitive challenges negatively impact motor task performance. Military personnel encounter cognitively taxing situations, especially during combat or other tactical performance scenarios, which may lead to injury or motor performance deficits (i.e., shooting inaccuracy, delayed stimulus-response time, and slowed movement speed). The purpose of the current study was to develop four cognitive motor shooting paradigms to determine the effects of cognitive load on shooting performance in healthy Reserve Officers' Training Corps (ROTC) cadets. METHODS: Thirty-two healthy collegiate ROTC members (24 male and 8 female; 20.47 ± 1.24 years, 174.95 ± 10.58 cm, and 77.99 ± 13.90 kg) were recruited to complete four simulated shooting tasks with additional "motor" challenge (180° turn, gait, weighted, and unweighted landing) and with and without a "cognitive" decision-making challenge requiring response selection and inhibition to both auditory and visual stimuli, totaling eight multi-task cognitive motor shooting conditions. The current study was approved by the university's Institutional Review Board. Task initiation (seconds), task completion (seconds), and number of misses were calculated to determine marksmanship efficiency and accuracy. For each task, a multivariate repeated-measures analysis of variance (ANOVA) was conducted for the combined dependent variables. If the overall multivariate repeated-measures ANOVA was significant, follow-up univariate ANOVAs were conducted for each dependent variable. Alpha was set at α = 0.05 for all analyses. RESULTS: Task initiation increased for the cognitive condition for the 180° turn (4.29 ± 1.22 seconds baseline, 5.09 ± 1.39 seconds cognitive; P < .05), gait (2.76 ± .60 seconds baseline, 3.93 ± .62 seconds cognitive; P < .05), unweighted (1.27 ± .57 seconds baseline, 3.39 ± .63 seconds cognitive; P < .05), and weighted landing (1.46 ± .72 seconds baseline, 3.35 ± .60 seconds cognitive; P < .05). Task completion time increased for the cognitive condition for the 180° turn (3.48 ± 1.53 seconds baseline, 4.85 ± 1.24 seconds cognitive; P < .05), gait (7.84 ± 2.07 seconds baseline, 9.23 ± 1.76 seconds cognitive; P < .05), unweighted (5.98 ± 1.55 seconds baseline, 7.45 ± 1.51 seconds cognitive; P < .05), and weighted landing (6.09 ± 1.42 seconds baseline, 7.25 ± 1.79 seconds cognitive; P < .05). There were no statistically significant differences in the number of misses for any of the tasks between conditions (P > .05). CONCLUSIONS: The addition of a cognitive load increased both task initiation and task completion times during cognitive motor simulated shooting. Adding cognitive loads to tactical performance tasks can result in CMi and negatively impact tactical performance. Thus, consideration for additional cognitive challenges into training may be warranted to reduce the potential CMi effect on tactical performance.

Integrating neurocognitive challenges into injury prevention training: A clinical commentary.

Despite the efforts of many traditional lower extremity injury prevention programs (IPP), the incidence of anterior cruciate ligament injuries in young athletes continues to rise. Current best practices for IPPs include training lower extremity neuromuscular control and movement quality during cutting, jumping, and pivoting. Emerging evidence indicates neurocognition may contribute to injury incidence and injury risk biomechanics. Therefore, IPP outcomes may improve if clinicians also consider neurocognitive contributions to neuromuscular control and athletic performance. A substantial barrier to neurocognitive challenge integration during injury prevention training in the group setting is the lack of structured neuromuscular and neurocognitive progressions. Therefore, our aim is to provide clinicians with a defined framework and recommendations from clinical experience for how to implement neurocognitive challenges within group IPPs that requires minimal extra time and resources. This clinical commentary proposes a three-phase model adopted from motor learning literature to simultaneously progress neuromuscular and neurocognitive challenges through a structured IPP.

Quadriceps Strength Influences Patient Function More Than Single Leg Forward Hop During Late-Stage ACL Rehabilitation.

BACKGROUND: A comprehensive battery of tests are used to inform return to play decisions following anterior cruciate ligament (ACL) reconstruction. Performance measures contribute to patient function, but it is not clear if achieving symmetrical performance on strength and hop tests is sufficient or if a patient also needs to meet minimum unilateral thresholds. HYPOTHESIS/PURPOSE: To determine the association of quadriceps strength and single-leg forward hop performance with patient-reported function, as measured by the IKDC Subjective Knee Form (IKDC), during late-stage ACL rehabilitation. A secondary purpose was to determine which clinical tests were the most difficult for participants to pass. STUDY DESIGN: Descriptive Laboratory Study. METHODS: Forty-eight individuals with a history of ACL-R (32 female, 16 male; mean±SD age=18.0±2.7 y; height=172.4±7.6 cm; mass=69.6±11.4 kg; time since surgery=7.7±1.8 months; IKDC=86.8±10.6) completed the IKDC survey, quadriceps isometric strength, and single-leg forward hop performance. The relationship between IKDC scores and performance measures (LSI and involved limb) was determined using stepwise linear regression. Frequency counts were used to determine whether participants met clinical thresholds (IKDC ≥ 90%, quadriceps and single-leg forward hop LSI ≥ 90%, quadriceps peak torque ≥ 3.0 Nm/kg, and single-leg forward hop ≥ 80% height for females and ≥ 90% height for males). RESULTS: Quadriceps LSI and involved limb peak torque explained 39% of the variance in IKDC scores while measures of single-leg forward hop performance did not add to the predictive model. Nearly 90% of participants could not meet established clinical thresholds on all five tests and quadriceps strength (LSI and peak torque) was the most common unmet criteria (71% of participants). CONCLUSIONS: During late-stage ACL rehabilitation deficits in quadriceps strength contribute more to patient function and are greater in magnitude compared to hop test performance. LEVEL OF EVIDENCE: Cross-Sectional Study, Level 3.

Knee Kinetics in Baseball Hitting and Return to Play after ACL Reconstruction.

The purpose of this study was to describe the knee kinetics of baseball hitting, develop a tool to predict knee kinetics from easily obtainable measures, and to compare knee kinetics to other exercises along the rehabilitation continuum to determine a timeline for when hitting may resume after ACL reconstruction. Nineteen high school baseball athletes (16.3±0.8 yrs, 180.6±5.7 cm, 78.4±10.8 kg) participated. Participants took ten swings off a tee. Kinetic data were recorded using an electromagnetic tracking system. Data from swings with the top three exit velocities were averaged for analysis. Linear regressions were used to determine if predictors of height, mass, age and exit velocity could predict the following torques: bilateral knee net, extension, internal and external rotation, valgus and varus torque; and anterior force. Backwards regression models revealed independent variables could significantly predict front knee net, internal and external rotation, extension, and varus torque, and anterior force; and back knee net and valgus torque. Based on the kinetics of baseball hitting compared to those of rehabilitation exercises, if the involved knee is the front, we suggest tee hitting may be initiated at 13 weeks after ACL reconstruction. If the involved knee is the back, we suggest tee hitting may initiated at 17 weeks after ACL reconstruction.