Language understanding is a socially coordinated activity, but the mechanisms of social coordination in language are poorly understood. Evidence from embodied cognition has shown that movement-induced fatigue of actions slows comprehension of language that refers to those actions. Research on the mirror neuron system suggests that action systems of the brain are also involved in social understanding of actions performed by another, empathy, and possibly language. Here, we show that simultaneous performance and observation of kinematically similar actions produced a fatigue-like effect in sentence judgment times relative to dissimilar control actions. The results suggest that the same action systems used in language processing are influenced by social actions.