What activity data you actually need from participants

An activity challenge produces a small but sensitive set of data. A scorecard that looks harmless can turn into a record of who exercises how much, who takes sick leave, and who is travelling for work. This article describes how to keep it to a minimum.

Three questions before collecting anything

1. Is this figure needed to calculate the score? If not, do not collect it.
2. Does it need to be attached to a person’s name? Many figures are only needed at team level.
3. How long will it be kept? A 12-week challenge does not need three years of personal data.

Data worth keeping

Four fields are enough to operate the scorecard:

Two important points:

• Activity minutes may be treated as health data when they reveal information about a person’s health; check with your DPO. Both the Information Commissioner’s Office and the European Commission place health data in the category that needs a stronger legal basis than ordinary data.
• A participant code is better than a name. Keep the code-to-name mapping in a separate table that only the coordinator can open. When the challenge ends, the published scorecard uses codes, and the mapping is deleted.

Data not worth keeping

• GPS coordinates.
• Heart rate and finer measurements (heart rate variability, sleep).
• Screenshots of an app.
• Weight, body mass index.
• Hour-by-hour training schedules.

None of these are needed to count points. If somebody proposes adding one, the only question worth asking is: “How would the scorecard be calculated differently without this field?”

How to collect data from a smartwatch

Three routes, in descending order of safety:

1. Participants read the figure and report it themselves. No data connection at all; the site only receives the number they type in. This is the safest route and suits an internal challenge.
2. Export a file and send it. Participants export a standard format and send it to the organisers, who read only the duration and activity-type columns and discard everything else.
3. Connect directly to an API. Only do this with a data processing agreement in place and with participant consent per data type. It needs someone genuinely responsible for the technical side.

With options 1 and 2, no continuous health record is built up on the site’s side — only isolated numbers.

A minimum disclosure statement

Send this before the challenge starts:

• We store: participant code, date, number of minutes, activity type.
• We do not store: location, heart rate, sleep, weight, screenshots.
• The code-to-name mapping is held only by the coordinator and destroyed after the final results are published.
• All personal data is deleted 90 days after the end date.
• Participants can withdraw and ask for deletion at any time; withdrawing does not affect scores their teammates have already earned.

A note on the public scorecard

If the scorecard shows real names, someone off sick for a week watches their name drop in front of the whole company. That creates unnecessary pressure around the decision to rest when ill. The fix: publish by code, and publish team scores only, never an individual ranking.

Sources

• ICO, Guidance on special category data — health data falls in the category needing an additional legal basis.
• European Commission, What is considered personal data — the definition of personal data.
• Apple, sharing health data — how the app controls the data that is shared.

This article is operational guidance, not legal advice. Specific rules differ depending on where you operate.