Enhanced Brain Connectivity Following Six Weeks of Upper Extremity Offset Loading in Neurotypical Adults—A Preliminary Study

Symmetrical resistance training induces corticospinal and cortical network plasticity; however, the neural consequences of asymmetrical resistance training (offset loading or OL) remain unclear. In this preliminary study, fourteen healthy adults completed eighteen supervised upper-extremity training sessions over a 6-week intervention period. Participants were allocated to either an offset loading (OL) intervention group (n = 8) or a conventional symmetrical resistance training active control group (AC; n = 6). Electroencephalography (EEG) recordings were acquired during motor task performance at baseline, 3 weeks, and 6 weeks. Directed functional connectivity among predefined cortical regions was quantified, and longitudinal changes were assessed using Friedman tests with false-discovery-rate correction for multiple comparisons. Significant changes in the OL group were observed involving two cortical pathways after correction for multiple testing. Connectivity from the right parietal cortex to the right sensorimotor cortex increased over time (Friedman χ2 = 8.00, q = 0.037), with post hoc analyses showing a significant increase between the midpoint and post-training assessments (q = 0.047; effect size r = 0.894). No significant longitudinal changes in cortical connectivity were identified in the AC group. Six weeks of OL training was associated with selective strengthening of directed connectivity within prefrontal-to-sensorimotor and parietal-to-sensorimotor cortical pathways. In contrast, conventional symmetrical resistance training was not associated with detectable changes in connectivity. These findings suggest that asymmetrical loading may induce task-specific reorganization of cortical networks involved in sensorimotor processing and motor control.