> For the complete documentation index, see [llms.txt](https://docs.tryterra.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tryterra.co/faq/help-topics/data-api-sdk/data-model-fields-and-units/activity-elapsed-vs-active-seconds.md).

# Why doesn't activity end time equal start plus active seconds?

**The two durations measure different things, so a mismatch is expected.**

* The `start_time` to `end_time` span is the total **elapsed** duration of the workout, including any pauses or inactivity.
* `activity_seconds` (under `active_durations_data`) is the **active** moving/exercising time only.

So an activity recorded over many hours can have a much shorter active duration. Both match what the provider's own app shows.

The `low_intensity_seconds`, `moderate_intensity_seconds` and `vigorous_intensity_seconds` fields break down portions of `activity_seconds`, roughly relating as `activity = low + moderate + vigorous + rest`. Providers report these independently, so they are not guaranteed to sum exactly, and some providers do not support all buckets.

Field definitions are in the [activity data model](https://docs.tryterra.co/reference/health-and-fitness-api/data-models).