It relies on the same principle I posted about yesterday in regards to saving money: budgeting by day, week or month can make a big difference in how you view something:
Two studies demonstrated that leading individuals to mentally reframe the time required for an exercise program (e.g., 2 hr per week) in terms of the equivalent daily amount (e.g., 17 min per day) reduced the perceived time commitment and increased people’s willingness to try the program. Study 2 also identified a cognitive mechanism that mediated the effect of temporal framing on exercise intentions. Consistent with findings in other domains (Gourville, 1998), reframing exercise duration in daily units led participants to retrieve comparison activities that were relatively short and manageable, which in turn increased their willingness to try the target exercise.
Source: “Only Minutes a Day: Reframing Exercise Duration Affects Exercise Intentions and Behavior” from Basic and Applied Social Psychology, Volume 33, Issue 2, 2011, Pages 118 – 127