Editorial: Integrative Physiology of Common Chronic Musculoskeletal Disorders

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Cross-education does not accelerate the rehabilitation of neuromuscular functions after ACL reconstruction: a randomized controlled clinical trial

Purpose: Cross-education reduces quadriceps weakness 8 weeks after anterior cruciate ligament (ACL) surgery, but the long-term effects are unknown. We investigated whether cross-education, as an adjuvant to the standard rehabilitation, would accelerate recovery of quadriceps strength and neuromuscular function up to 26 weeks post-surgery. Methods: Group allocation was randomized. The experimental (n = 22) and control (n = 21) group received standard rehabilitation. In addition, the experimental group strength trained the quadriceps of the non-injured leg in weeks 1–12 post-surgery (i.e., cross-education). Primary and secondary outcomes were measured in both legs 29 ± 23 days prior to surgery and at 5, 12, and 26 weeks post-surgery. Results: The primary outcome showed time and cross-education effects. Maximal quadriceps strength in the reconstructed leg decreased 35% and 12% at, respectively, 5 and 12 weeks post-surgery and improved 11% at 26 weeks post-surgery, where strength of the non-injured leg showed a gradual increase post-surgery up to 14% (all p ≤ 0.015). Limb symmetry deteriorated 9–10% more for the experimental than control group at 5 and 12 weeks post-surgery (both p ≤ 0.030). One of 34 secondary outcomes revealed a cross-education effect: Voluntary quadriceps activation of the reconstructed leg was 6% reduced for the experimental vs. control group at 12 weeks post-surgery (p = 0.023). Both legs improved force control (22–34%) and dynamic balance (6–7%) at 26 weeks post-surgery (all p ≤ 0.043). Knee joint proprioception and static balance remained unchanged. Conclusion: Standard rehabilitation improved maximal quadriceps strength, force control, and dynamic balance in both legs relative to pre-surgery but adding cross-education did not accelerate recovery following ACL reconstruction

NEURAL CORRELATES OF LOWER EXTREMITY INTERLIMB COORDINATION DURING A NOVEL MULTI-JOINT BILATERAL LEG PRESS

Alexis B. Slutsky-Ganesh1, Manish Anand1, Jed A. Diekfuss1, Dustin R. Grooms2, Gregory D. Myer1. 1Emory University, Atlanta, GA. 2Ohio University, Athens, OH. BACKGROUND: Athletes with high injury risk landing mechanics rely on greater recruitment of cognition-based brain regions for knee motor control. However, prior research utilizing functional magnetic resonance imaging (fMRI) and 3D motion analysis to isolate neural activity of knee motor control has been limited to unilateral movements, and thus could not evaluated lower extremity motor coordination. The purpose of this study was to investigate the relationship between bilateral knee motor control kinematics and brain activity using a novel, multi-joint fMRI leg press paradigm. METHODS: Seventeen adolescent female athletes (15.0 ± 1.4 years) completed a bilateral leg press during fMRI with concurrent 3D motion capture to quantify interlimb coordination via the correlation between peak-to-peak knee flexion cycle time between legs. Participants completed 4-30sec blocks of bilateral, ankle, knee, and hip flexion and extension movements against resistance, interspersed with 30-sec rest blocks while undergoing brain fMRI. During the movement blocks, participants moved to the beat of a metronome (1.2 Hz) while fully instrumented for biomechanical assessment using a single camera, MRI-compatible 3D motion analysis system. Standard preprocessing and statistical analyses for task-based neuroimaging were completed in FSL, with lower extremity coordination as a covariate of interest. A cluster wise multi-comparison correction was applied at z\u3e3.1 and p \u3c.05. RESULTS: Less lower extremity coordination during the bilateral leg press resulted in greater activation in the posterior cingulate gyrus and precuneus (voxels=478, zmax=5.56, p\u3c.001), bilateral clusters in the lateral occipital cortices (right: voxels=157, zmax =5.29, p\u3c.021; left: voxels=141, zmax =6.84, p=.033), and the right hippocampus (voxels=138, zmax =4.13, p=.036). CONCLUSIONS: Less lower extremity coordination during a leg press maneuver resulted in greater activation of attention- and memory-related brain regions. Such increased activity may indicate elevated cognitive appraisal of motor control, limiting or interfering with optimal processes for coordination. Future research aiming to improve bimanual motor coordination should consider interventional approaches capable of promoting neural efficiency of cognitive and memory regions during physical activity (e.g., dual-task neuromuscular training)