The purpose of this study was to identify how the brain simultaneously perceives proprioceptive input during joint loading in anterior cruciate ligament reconstruction (ACLR) patients, when compared to healthy controls. Seventeen ACLR patients (ACLR) and seventeen controls (CONT) were tested for the somatosensory cortical activation using electroencephalography (EEG) while measuring knee laxity using a knee arthrometer. The relationship between cortical activation and joint laxity within group was also examined. The ACLR patients had increased cortical activation (36.4% ± 11.5%) in the somatosensory cortex during early loading (ERD1) to the injured limb compared to the CONT's matched limb (25.3% ± 13.2%, P = 0.013) as well as compared to the noninjured limb (25.1% ± 14.2%, P = 0.001). Higher somatosensory cortical activity during midloading (ERD2) to the ACLR knee positively correlated with knee laxity (mm) during early loading (LAX1, r = 0.530), midloading (LAX2, r = 0.506), total anterior loading (LAXA, r = 0.543), and total antero‐posterior loading (LAXT, r = 0.501), while the noninjured limb revealed negative correlations between ERD1 and LAXA (r = −0.534) as well as between ERD2 and LAX2 (r = −0.565). ACLR patients demonstrate greater brain activation during joint loading in the injured knees when compared to healthy controls’ matched knees as well as contralateral healthy knees, while the CONT group shows similar brain activation patterns during joint loading between limbs. These different neural activation strategies may indicate neuromechanical decoupling following an ACL reconstruction and evidence of altered sensorimotor perception and control of the knee (neuroplasticity), which may be critical to address after surgery for optimal neuromuscular control and patients’ outcomes.

Context Fear of reinjury after an anterior cruciate ligament (ACL) reconstruction (ACLR) may be associated with persistent deficits in knee function and subsequent injury. However, the effects of negative emotion on neuromuscular-control strategies after an ACL injury have remained unclear. Objective To identify how negative emotional stimuli affect neural processing in the brain and muscle coordination in patients after anterior cruciate ligament reconstruction compared with healthy control participants. Design Case-control study. Setting Neuromechanics laboratory. Patients or Other Participants Twenty patients after unilateral anterior cruciate ligament reconstruction and 20 healthy recruits. Main Outcome Measure(s) Electrocortical θ (4–8 Hz) activity (event-related synchronization, % increased power relative to a nonactive baseline) at selected electrodes placed at the frontal (F3, Fz, F4) and parietal (P3, Pz, P4) cortices using electroencephalography, neurophysiological cardiac changes (beats/min), and subjective fear perceptions were measured, along with joint stiffness (Nm/°/kg) with and without an acoustic stimulus in response to 3 types of emotionally evocative images (neutral, fearful, and knee-injury pictures). Results Both groups had greater frontoparietal θ power with fearful pictures (Fz: 35.9% ± 29.4%; Pz: 81.4% ± 66.8%) than neutral pictures (Fz: 24.8% ± 29.7%, P = .002; Pz: 64.2 ± 54.7%, P = .024). The control group had greater heart-rate deceleration with fearful (−4.6 ± 1.4 beats/min) than neutral (−3.6 ± 1.3 beats/min, P < .001) pictures, whereas the ACLR group exhibited decreased heart rates with both the fearful (−4.6 ± 1.3 beats/min) and injury-related (−4.4 ± 1.5 beats/min) pictures compared with neutral pictures (−3.4 ± 1.4 beats/min, P < .001). Furthermore, during the acoustic startle condition, fearful pictures increased joint stiffness (Nm/°/kg) in the ACLR group at the midrange (0°–20°: 0.027 ± 0.02) and long range (0°–40°: 0.050 ± 0.02) compared with the neutral pictures (0°–20°: 0.017 ± 0.01, P = .024; 0°–40°: 0.043 ± 0.02, P = .014). Conclusions Negative visual stimuli simultaneously altered neural processing in the frontoparietal cortices and joint-stiffness regulation strategies in response to a sudden perturbation. The adverse effects of fear on neuromuscular control may indicate that psychological interventions should be incorporated in neuromuscular-control exercise programs after ACL injury.

Functional knee instability, which is defined as repetitive episodes of the knee "giving way" during physical activity, has received great attention to identify mechanisms due to serious pathological complications. Growing evidence suggests that insufficient neural adaptation in the central nervous system (CNS) may result in permanent functional deficits in patients with anterior cruciate ligament (ACL) injuries. The purpose of this review was to address neurophysiological mechanisms underlying functional joint instability following an anterior cruciate ligament rupture. METHODS: Previous studies conducted from PubMed with particular emphasis on mechanisms underlying joint instability and neuromuscular control deficits after an anterior cruciate ligament were reviewed. RESULTS: Inappropriate neuromuscular control, inconsistent correlations between joint laxity and functional outcomes, and altered neural activation in the brain during proprioceptive tasks may underscore the idea that persistent functional joint instability is an indication not only of the peripheral deafferentation input, but also neuromechanical decoupling between the injured ACL and CNS due to neuroplasticity. CONCLUSIONS: Persistent functional instability can develop following knee joint injury due to altered neural processing in the CNS. Therefore, it must be considered for improving patient outcomes, minimizing functional disability, and returning to one's chosen physical activity in ACL patients.

Purpose Poor balance in anterior cruciate ligament reconstruction (ACLR) patients indicates neuromuscular control (NMC) deficits, which may be associated with altered cortical activation in the brain. This study examines cortical activation patterns in ACLR patients compared with healthy controls during a single‐leg balance task with and without visual feedback. Methods Thirteen ACLR patients (ACLR, 23.38 ± 3.38 years) and thirteen healthy controls (CONT, 23.54 ± 3.48 years) performed a single‐leg balance task with both visual feedback (VF) and non‐visual feedback (NVF) with continuous electroencephalograph (EEG) monitoring. Knee function was also evaluated through a subjective assessment survey. Results Frontal theta power was significantly higher with VF compared to NVF. Significant group‐by‐condition interaction effect for parietal alpha‐2 revealed that the CONT group had increased activation with VF, whereas the ACLR group had increased activation with NVF. A negative correlation emerged between KOS‐ADL in the ACLR group with parietal alpha‐2 during NVF and occipital alpha‐2 during VF. Conclusion ACLR patients had comparable single‐leg balance to healthy controls, yet different cortical activation patterns emerged on EEG. ACLR patients with better knee function showed greater cortical activation in the somatosensory and visual cortices. Further research should consider these cortical changes in restoration of balance after ACLR.

This study aimed to compare immediate changes in the thickness of the rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL), vastus medialis (VM), and vastus medialis oblique (VMO) muscles after open kinetic chain exercise (OKCE) and closed kinetic chain exercise (CKCE) and identify the effect of both exercise types on each quadricep muscle for early rehabilitation to prevent knee joint injury. Twenty-six healthy participants (13 males and 13 females) were randomly divided into the OKCE (n = 13) and CKCE (n = 13) groups. The thickness of their quadriceps muscles was measured using a portable ultrasonic imaging device before and after exercise in the sequence RF, VI, VL, VM, and VMO. A two-way repeated measures analysis of variance was used to compare the thickness of each component of the quadriceps muscles between the two groups. The thickness of the RF, VL, VM, and VMO muscles increased after OKCE, and the thickness of the VI muscle showed the greatest increase with a medium–large effect size (F = 8.52, p = 0.01, and d = 0.53). The thickness of the VI, VL, VM, and VMO muscles increased after CKCE, and the VMO muscle had the largest effect size (F = 11.71, p = 0.00, and d = 1.02). These results indicate that the thickness of the quadriceps muscles can be selectively improved depending on the type of exercise.

Postural control, which is a fundamental functional skill, reflects integration and coordination of sensory information. Damaged anterior cruciate ligament (ACL) may alter neural activation patterns in the brain, despite patients’ surgical reconstruction (ACLR). However, it is unknown whether ACLR patients with normal postural control have persistent neural adaptation in the brain. Therefore, we explored theta (4–8 Hz) and alpha-2 (10–12 Hz) oscillation bands at the prefrontal, premotor/supplementary motor, primary motor, somatosensory, and primary visual cortices, in which electrocortical activation is highly associated with goal-directed decision-making, preparation of movement, motor output, sensory input, and visual processing, respectively, during first 3 s of a single-leg stance at two different task complexities (stable/unstable) between ACLR patients and healthy controls. We observed that ACLR patients showed similar postural control ability to healthy controls, but dissimilar neural activation patterns in the brain. To conclude, we demonstrated that ACLR patients may rely on more neural sources on movement preparation in conjunction with sensory feedback during the early single-leg stance period relative to healthy controls to maintain postural control. This may be a compensatory protective mechanism to accommodate for the altered sensory inputs from the reconstructed knee and task complexity. Our study elucidates the strategically different brain activity utilized by ACLR patients to sustain postural control.

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INTRODUCTION:Research suggests that physical activity (PA) levels decline with age, with older adults having a tendency to not meet PA recommendations (i.e., 150 weekly minutes of moderate-vigorous aerobic PA and 2+ days of muscle-strengthening). Perceived confidence can positively influence PA levels, with higher levels of confidence resulting in greater amounts of PA. High intensity functional training (HIFT) classes can aid in meeting PA recommendations by helping participants meet basic psychological needs, providing community, and scaling workouts to accommodate varying skill levels, thus supporting perceived confidence. PURPOSE: The purpose of this study was to examine the relationship between age and perceived confidence amongst individuals aged 18-76 attending HIFT classes. METHODS: Eighty-four participants (56% female, 91.7% white, 92.8% some college education or higher; M age = 39.0 ± 18.0 years, age range = 18-76) with varying levels of HIFT experience (range = 0 -120 months; mean weekly attendance = 3 days/week) completed an online survey answering questions regarding how confident they were when completing various aspects of activities/sports. Correlations were computed between age and confidence for the various aspects of activities/sports. RESULTS: Significant negative correlations existed between age and confidence in one's ability to complete physical exercises or compete in a sport requiring effort [r(80)= -.