Getting people to stick to a workout routine is a worthy goal — but it’s also a nebulous one. Despite great interest from policymakers to promote exercise as a way to boost public health, there is still relatively little reliable data regarding what makes people stick to their routines.

A new megastudy aims to address that lack of data through the use of a massive number of participants to rigorously test and compare the efficacy of multiple incentives for keeping people committed to their workouts. The study tested 54 different behavioral interventions on a large number of participants in order to determine and compare the efficacy of each.

Keep gyming

“We found that rewarding participants with a bonus of [US$0.09] for returning to the gym after a missed workout produced an estimated 0.40 more weekly gym visits per participant (a 27% increase in exercise) compared with the placebo control,” the study reports, on the most efficient incentive recorded during the trials. “Second, offering participants larger incentives, [US$1.75] produced an estimated 0.37 more weekly gym visits per participant (a 25% increase in exercise) compared with the placebo control.”

The team worked with over 61,000 gym members, all of whom were subscribed to an American fitness chain. Over a four-week period, the various encouragement programs the authors experimented with boosted gym attendance between 9% and 27%.

Due to the scale of the study, 30 scientists from 15 different US universities participated. They worked in small, independent teams, and designed a total of 54 different intervention strategies to try and boost the participants’ rates of gym attendance. Each of these was meant to last a total of four weeks and ranged from digital experiences, text reminders, weekly emails, to rewards.

Just under half of these interventions (45%) had a significant effect on increasing the weekly gym visit numbers of participants. The single most effective intervention involved offering participants a cash reward for returning to the gym after missing a workout.

That being said, however, it was surprisingly hard to change the long-term habits of the participants; only 8% of the interventions trialed in the study led to participants maintaining a measurable change in their behavior after the four-week intervention period.

Beyond helping policymakers and other figures of authority better motivate people to stick to a workout routine, the work also helps showcase the potential of megastudies in furthering our understanding of particular topics. The authors themselves note that examining multiple interventions side-by-side gave them much better context than working with each strategy individually. Even those that did not lead to a noticeable increase in user gym attendance can yield valuable data when placed in the wider setting of the study, they explain.

“The megastudy paradigm ensures that all results, including null results, are published and that insights can still be gleaned from comparing treatments across studies, as illustrated both by this megastudy and a follow-up megastudy testing the best strategies for nudging vaccination,” they write.

Such a research framework also helps address one of the main limitations of behavioral science: the need to test interventions both in the field (in real-life settings), to account for the multitude of factors shaping each of our lives, and in a controlled research setting. When examining individual methods in distinct groups, the authors explain, it becomes difficult to compare results directly with other trials; due to this, it’s not possible to test whether the differences in results come down to the interventions themselves, or to the differences among the participants.

Beyond the immediate results, the team hopes their work will help improve the accuracy of behavioral research in the future, and give us new tools to reliably study human behavior.

The paper “Megastudies improve the impact of applied behavioural science” has been published in the journal Nature.