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Exercise & Fitness

Activity trackers: Can they really help you get fit?

October 23, 2017

About the Author

photo of Robert H. Shmerling, MD

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio
View all posts by Robert H. Shmerling, MD


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Chris Choi
October 30, 2017


This is something that our team is currently working on. We strongly believe that fitness data alone cannot change people’s behavior. We tried to figure out how we would be able to increase the engagement level of our users.

In our app called SPRYFIT, we combined “money incentive” and “loss aversion” to motivate people. Currently, there are a bunch of games such as 10K steps per day for three weeks challenge.

At SPRYFIT, users pay an entry fee to join the challenge and exercise not to lose their money. ( Loss Aversion) If the users meet their daily goal for a certain period, they receive their entry fee back plus extra cash coming from those who don’t meet the goal. Based on the past 6 months data, this increased the users’ success rate a lot. In addition, most of our users are joining the challenge continuously.

We track our users’ data from their wearables devices and fitness apps.

Liz Feinauer
October 28, 2017

The idea behind fitness trackers is great. However, if they are going to be beneficial, the individual must have some self-motivation also. One thing that these fitness trackers need to work on in order to really help individuals to get fit is their accuracy of calories burned. In a recent study conducted by Standford, fitness activity trackers were far off from being accurate on measuring energy expenditure. The most accurate device was off by 27% on measuring energy expenditure. The least accurate device was off by 93%. Many individuals may be relying on these trackers to help them determine the amount of calories burned in order to determine how many calories they can consume for the rest of the day. If the devices are not accurate, it is just another way in which they may keep people from getting fit and may make them even less motivated to use them if incentives are not involved.

Dusheck, J. (2017). Fitness trackers accurately measure heart rate but not calories burned. Retrieved from

Anne Thompson
October 27, 2017

In a way, these results are not surprising–studies in psychology have shown that external rewards can actually decrease motivation for an activity that might otherwise be liked. (see Nisbett’s study with kindergarten kids and drawing.)

The trick is to increase intrinsic motivation, not extrinsic. Old fashioned behaviorism is not particularly effective and can be counterproductive.

I see no reason why trackers could not be combined with a program to increase intrinsic motivation for exercise. I think they work that way for me (a step counter that I can read easily and a fitbit zip.) I hope researchers will forget giving extrinsic rewards, and design research with some hope of succeeding long term!

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