While people's willingness to work hard can be reduced in teams (i.e., effort losses in teams as compared with individual work), it is less recognized that teamwork can also stimulate additional efforts (i.e., effort gains). Building on and extending existing theory, we (a) suggest an integration of these two research streams, and (b) provide evidence for team-related effort gains in action teams. In a first study, we tested our predictions by reanalyzing a field data set of 302,576 swimming performances in individual and relay races (Neugart & Richiardi, 2013). Consistent with our hypotheses, we observed a linear increase in effort across the relay. The first relay swimmers showed effort losses in the relay as compared with the individual competition whereas the remaining relay swimmers showed effort gains. However, this was only evident (a) when team members could realistically expect meaningful team outcomes in return for their performance, and (b) when the valence of these outcomes was equivalent to individual competitions. If such favorable conditions were not given, we found effort losses in team as compared with individual competitions at all relay positions. Results of a second study (N = 228) showed that the linear increase in effort across the relay was indeed attributable to the team members' serial position and not to their relative strength. Together, the studies demonstrate the motivating potential of teamwork even in the high performance contexts of action teams, such as competitive sports relays, where athletes are already highly motivated in their individual competitions. (PsycINFO Database Record