The investigators seek to examine the effect of incentives for routine exercise on the development of persistent exercise habits. Specifically, the purpose of this study is to determine whether healthy habits can be formed more effectively when people are rewarded for repeated engagement in a given healthy behavior at a specific, routinized time each day rather than at any time. Through a partnership with a Fortune-500 company, the investigators plan to run a large-scale, randomized field controlled trial with approximately 3,000-4,000 participants aimed at increasing exercise rates (as measured by gym visits). During an incentivized four week intervention period, the investigators will encourage participants to select a two-hour window during the day when they feel they are most willing and able to exercise. Depending on condition, participants will [a] receive no further instruction or incentives (control condition), [b] receive a $3 or $7 bonus for each day they exercise during the incentive period (flexible incentive condition), or [c] receive a $3 or $7 bonus for each day they exercise if and only if they exercise within their specified "workout window" (routine incentive condition). Additionally, participants in a fourth condition, the social routine incentive condition, will face the same incentives as those in the routine incentive condition, but will be required to coordinate the workout window they select with a partner in their office. The investigators predict that the less flexible incentives will lead to greater habit formation than flexible incentives, producing larger and longer-lasting increases in exercise post-intervention. The investigators further predict that coordinating with a workout partner will produce even stronger habit formation. The investigators will collect and analyze data from participants' worksite gyms, which track gym entries and exits, as well as pedometer data when available.