In an approach to generating preflex stimulation, one or more computer processors monitor one or more sensing devices for data associated with a user activity. Based, at least in part, on the data associated with the user activity, the one or more computer processors predict a user reaction associated with the user activity. The one or more computer processors transmit a preflex stimulus to at least one muscle of the user, wherein the at least one muscle is associated with the user reaction. The one or more computer processors determine a reaction time of the at least one muscle to the preflex stimulus.