Many people in the UK now use apps, smartwatches or wearable devices to track their physical activity. Fitness trackers promise to help users become fitter, happier and healthier versions of themselves. For many people, they can be useful: a nudge to move more, a way to notice patterns, or a reminder that activity does not have to happen in a gym.
But self-tracking devices do more than record behaviour. Through prompts, defaults, streaks, badges and automated feedback, they also shape it. There is good evidence that tracking can help some people become more active. But there are also growing reports of anxiety, shame and disordered eating among people who track closely.
This raises questions about how common these harms are and why they happen, which is what I have spent the past decade researching. Here are five reasons tracking can become harmful.
1. The fixation on steps
The 10,000-step target comes from a marketing slogan for a 1960s Japanese pedometer, and has no firm scientific basis as a universal target. Researchers continue to debate the ideal number, with some pointing to around 7,000 as a more realistic and beneficial target for many adults. Yet 10,000 steps remains widely treated as a badge of good health.
The trouble is that a single target cannot fit everyone. It can also distort what people think activity is worth. A tracker may misread wrist movement, or fail to capture cycling, swimming or strength training properly because these do not look like stepping.
This means trackers often privilege what they can easily count. Steps are visible, while strength work, mobility, Pilates, rehabilitation and recovery can appear less important, even though they may be exactly what someone needs. This can give users a skewed sense of what counts as worthwhile movement.
2. Movement loses its joy
The hardest part of becoming active is making it a habit that lasts. Chasing a target can work against that if it turns movement into a chore rather than something enjoyable. The point becomes closing a ring instead of noticing what your body can do.
Research suggests that repeatedly failing to meet goals can lead people to abandon both the device and the habits they were trying to build. Enjoyment helps habits stick, while external metrics can erode the internal motivation to move.
So the next time you head out, try leaving the numbers alone. Take a friend, put on a podcast, or call your mum. When you feel satisfied, go home. The activity still counts, and over time it may help you reach your goals without making the numbers the only measure of success.
3. The more-is-more approach
Many devices still make “more” feel like the default measure of success. The prompts are persistent, the summaries often feel like gentle reproaches, and the clearest currency is usually steps.
What this often misses is ability, skill and context. Do you know how much exercise you need? What kind of movement might cause injury? Can you interpret your own VO2 max data? These competencies are often taken for granted, but many people have never had the chance to build them.
Our research shows that people are most vulnerable to harm when they are left to manage with assumptions already made for them. They may hand their judgement over to the device and accept whatever it tells them. Yet the device may not know enough about whether you are recovering from illness, short on sleep, injured, newly active or pregnant to interpret today’s data safely.
4. The default user does not exist
Much of the design and marketing of these devices is aimed at a standard, average consumer. But research repeatedly shows that this person does not exist. We differ in our bodies, histories, goals and circumstances, so asking everyone to squeeze into the same mould is poor design.
The problem is the body imagined by the device: often able-bodied, non-pregnant, already confident with exercise and free to prioritise activity every day. Some defaults also follow narrow social norms, often built around male bodies, and amplify questionable ideas about health and beauty.
Think of BMI, which can penalise muscular bodies and treat perfectly healthy women’s bodies as problems to be solved. Similar assumptions can be baked into self-trackers when they nudge users towards weight loss by default or reinforce dated ideals about size and ability. At their worst, they can push some people towards over-exercising or under-eating, with real damage to body and mind.
5. It blames you when things go wrong
Sedentary living is a society-wide problem. Yet trackers often frame inactivity as a matter of individual willpower. That can draw attention away from the conditions that shape how much people move: safe streets, time, money, caring responsibilities, disability, local facilities and access to green space.
Many people report feeling pressure from the device. When life gets in the way of their targets, they may feel shame, failure, or give up altogether.
Research shows that people use these devices for a wide range of reasons and goals. That means support and personalisation are essential to making tracking safer. Devices should account for individual goals, experience and context rather than loading all responsibility onto the user, a familiar and unfair pattern across health and social care.
Some would call these harms unintended side effects. But they are also the predictable result of design choices that reward more, simplify health into scores and treat missed targets as personal failure.
For users, the first shift is to treat tracking as information rather than instruction. A watch can tell you what it has measured. It cannot tell you what your body needs today.
The bigger responsibility sits with developers. Trackers could place less emphasis on fixed step targets, make strength and non-step activity more visible, build in rest and recovery without guilt, and offer safer defaults for people with different bodies, abilities, health histories and goals.
None of this means abandoning the technology – it means refusing to let a made-up number decide whether movement has counted.
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