A 20-week starting choice led to more good exercise weeks than 8 weeks
Who it’s about: Adults
- Helped
People first shown a 20-week contract had more good exercise weeks than those shown 8 weeks: about 4, against 3.
Large randomised trial of 8,809 adults who set up an online exercise contract · vs people first shown an 8-week contract · they rated themselves · ⚠ not yet checked by other scientists; summary claims more than the results show; numbers unreliable
The study
Who took part
8,809 adults who started an exercise contract on the website stickK.com. There you promise to exercise and can put money at stake. They were about 33 on average and about 4 in 10 were men. About 7 in 10 used the site from the US.
What they did
Each person was shown a contract length of 8, 12 or 20 weeks as the starting choice. They could change it with one click. Everyone picked how often to exercise, and could choose to lose money for each failed week. People mostly reported their own weekly success.
What happened
The results cover 3,397 people. Those first shown 20 weeks had about 4 good exercise weeks, against 3 for those shown 8 weeks. The 12-week choice made no clear difference. The paper's summary doesn't match its own numbers, and other scientists have not checked it.
Source
Nudges in Exercise Commitment Contracts: A Randomized Trial (2015)
Tools in this study
Rule · how much4
Commit for a longer stretchChoose a longer commitment period, e.g. a 20-week rather than an 8-week contract.
