Work recovery research has focused mainly on how after-work break activities help employees replenish their resources and reduce fatigue. Given that employees spend a considerable amount of time at work, understanding how they can replenish their resources during the workday is critical. Drawing on ego depletion (Muraven & Baumeister, 2000) and self-determination theory (Deci & Ryan, 1985), we employed multi-source experience sampling methods to test the effects of a critical boundary condition, employee lunch break autonomy, on the relation between lunch break activities and end-of-workday fatigue. Although specific energy-relevant activities had a main effect on end-of-workday fatigue, each of these was moderated by the degree of autonomous choice associated with the break. Specifically, for activities that supported the psychological needs of relatedness and competence (i.e., social and work activities, respectively), as lunch break autonomy increased, effects switched from increasing fatigue to reducing fatigue. To the extent that lunch break activities involved relaxation, however, lunch break autonomy was only important when levels of relaxation were low. We conclude that lunch break autonomy plays a complex and pivotal role in conferring the potential energetic benefits of lunch break activities. Contributions to theory and practice are discussed. [ABSTRACT FROM AUTHOR]