> ## Documentation Index
> Fetch the complete documentation index at: https://docs.uplift.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Acceleration / Deceleration

> A high-intensity change of speed.

> [!WARNING]
>
> The Game Data API is in preview. Endpoints, fields and limits may change before release, and it is not yet available to call.

## Technical Details

* **Variable Type:** Event
* **Event Types:** `acceleration`, `deceleration`
* **Subtypes:** None
* **Layer:** `position` (player positions only)
* **Returned By:** [List Game Events](https://docs.uplift.ai/api-reference/game-data/events/list.md)
* **Filter:** `event_type=acceleration,deceleration`

## Description

A high-intensity change of speed: `acceleration` when speeding up, `deceleration` when slowing down. For a deceleration, `peak_mps2` is negative.

Every event has the same envelope fields, including time, frames, player, team, pitch coordinates, `phase`, `team_possession_id`, `player_possession_id` and `confidence`. See [List Game Events](https://docs.uplift.ai/api-reference/game-data/events/list.md). The fields below are specific to this type and are returned in `attributes`.

## Attributes

| Field | Units | Description |
| - | - | - |
| `peak_mps2` | m/s² | Peak rate of change of speed. Negative for a deceleration. |
| `peak_total_mps2` | m/s² | Peak size of the acceleration in any direction. Always positive. |
| `entry_speed_kmh` | km/h | Speed at the start of the effort. |
| `exit_speed_kmh` | km/h | Speed at the end of the effort. |
| `duration_s` | s | Length of the effort. |
| `intensity_tier` | — | Intensity band, for example `moderate`. |

## Example

Only the type-specific fields and a few envelope fields are shown.

```json theme={null}
{
  "event_type": "deceleration",
  "attributes": {
    "peak_mps2": -5.6,
    "entry_speed_kmh": 27.1,
    "exit_speed_kmh": 9.4,
    "duration_s": 0.6,
    "intensity_tier": "moderate"
  }
}
```

## Related

* [Change of Direction](https://docs.uplift.ai/api-reference/game-data/event-catalogue/events/change-of-direction)
* [Get Physical Summary](https://docs.uplift.ai/api-reference/game-data/physical/get.md)


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