Does an app actually get you moving? Yes, a bit

Writing this from a company that builds exactly this kind of challenge app is not without irony. But if we are going to ask you to trust what we publish, the least we can do is also show you the studies that leave us looking merely average. And this meta-analysis leaves us precisely there: we work, just less than we would like to put on a poster.

The result, unretouched

The review pools 18 randomised trials on standalone digital behaviour change interventions: the app and you, with no coach behind it, no follow-up calls, nobody messaging on Monday to ask how the weekend went.

The verdict: they improve physical activity, with an effect size of 0.324, and they improve body measures, at 0.269. On the scale normally used, 0.2 counts as a small effect and 0.5 as a medium one. So we are talking about something real and something modest at the same time. It is not nothing; it is not a transformation either.

And the certainty is low, which is worse

Here comes the part we would rather not tell you. The authors downgraded the certainty of the evidence to "low" for physical activity because of publication bias and risk of bias in the studies. Publication bias means, roughly, that trials where the app did nothing are less likely to have been published. Nobody writes an enthusiastic paper about the intervention that went nowhere.

Low certainty means the number above could shift quite a bit as new studies arrive. It is not a false finding: it is a provisional one. And that is worth saying out loud in a sector that lives on promising results.

Who benefits most

One interesting finding: the improvement in physical activity was larger in people with a health condition than in healthy people. Which makes sense when you think about it. If you already run three times a week, an app has little room to improve you. If you have been sedentary for years and have a medical reason to move, that room is enormous.

It fits with something we have argued here before, explaining why routine beats motivation: the tool does not create the willingness, it organises the willingness you already have. And with the idea that real change comes from small habits, not from a January surge.

Why we are telling you anyway

Because a challenge gathers those ingredients almost by definition: a target in kilometres, a log of what you add, and a bar that moves. The Infinite Challenge has no expiry date either, which is precisely where most people fall off. If you come up short this week, next week you carry on from where you were.

But we are not going to tell you the app will change your life, because the meta-analysis does not say that. It says it helps a bit, and that it helps more when somebody else is involved. So use it for what it is: an honest counter reminding you of what you already did, not a magic motivator. Getting out of the door is still on you.

Standalone digital behaviour change interventions significantly improved physical activity, on low-certainty evidence.

Lee and Park, npj Digital Medicine, 2025

The least sellable conclusion

An app is a small, cheap lever. Compared with doing nothing, it wins. Compared with a group of people waiting for you at eight on Tuesday, it probably loses. The good news is that you do not have to choose: the counter works just as well when you go out with company, and then you get both.