Brain activation and single-limb balance following anterior cruciate ligament reconstruction

To compare brain activity between individuals with anterior cruciate ligament reconstruction (ACLR) and controls during balance. To determine the influence of neuromodulatory interventions (external focus of attention [EF] and transcutaneous electrical nerve stimulation [TENS]) on cortical activity and balance performance. Individuals with ACLR (n = 20) and controls (n = 20) performed a single-limb balance task under four conditions: internal focus (IF), object-based-EF, target-based-EF, and TENS. Electroencephalographic signals were decomposed, localized, and clustered to generate power spectral density in theta and alpha-2 frequency bands. Participants with ACLR had higher motor-planning (d = 0.5), lower sensory (d = 0.6), and lower motor activity (d = 0.4–0.8), while exhibiting faster sway velocity (d = 0.4) than controls across all conditions. Target-based-EF decreased motor-planning (d = 0.1–0.4) and increased visual (d = 0.2), bilateral sensory (d = 0.3–0.4), and bilateral motor (d = 0.4–0.5) activity in both groups compared to all other conditions. Neither EF conditions nor TENS changed balance performance. Individuals with ACLR exhibit lower sensory and motor processing, higher motor planning demands, and greater motor inhibition compared to controls, suggesting visual-dependence and less automatic balance control. Target-based-EF resulted in favorable reductions in motor-planning and increases in somatosensory and motor activity, transient effects in line with impairments after ACLR. Sensorimotor neuroplasticity underlies balance deficits in individuals with ACLR. Neuromodulatory interventions such as focus of attention may induce favorable neuroplasticity along with performance benefits.