coactivate

Coactivate is a verb meaning to activate two or more elements at the same time. It is formed from the prefix co- and the verb activate, and is used in fields such as physiology, neuroscience, and psychology to describe simultaneous recruitment or engagement of systems, muscles, neurons, or cognitive processes.

In motor control and biomechanics, coactivation most often refers to the concurrent contraction of antagonist muscles around a joint. This coactivation increases joint stiffness and stability, aiding precision and protection but raising metabolic cost and potentially hindering rapid movement. It varies with task demands, development, and learning, and is commonly quantified with electromyography by comparing the overlapping activation of muscle pairs. Abnormal patterns of coactivation can appear after neurological injury, contributing to stiffness and movement inefficiency.

In neuroscience, coactivation can describe simultaneous activity of different brain regions during a task, detected with functional imaging or electrophysiology. Such coactivation patterns reflect distributed network recruitment and can change with practice or strategy. It is distinct from functional connectivity, which characterizes correlated activity across regions over time rather than task-evoked synchronization.

Examples include coactivation of wrist flexors and extensors during stabilization tasks, or recruitment of multiple motor areas during complex motor learning. In genetics and pharmacology, coactivation can also mean simultaneous activation of genes, promoters, or signaling pathways in response to stimuli, though the term is less standard in those contexts.