The definition of action adopted in this study stipulates that actions are intentional bodily movements, understood as exertions. The last chapter indicated that, due to the intrinsic antinomy of action, action explanation can be accounted for by neither a normative nor an expressive model of explanation, due to their insufficient reference to the material and modal constraints on action. This chapter will explore how an existential analysis can account for at least one material constraint on action: the conditions that physical movement imposes on action. The next chapter will consider the modal constraint.