> ## 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.

# Cocking Phase Shoulder Abduction

> Abduction of the dominant shoulder at the end of the cocking phase of the serve.

## Technical Details

* **Variable Type:** Discrete Metric
* **Data Type:** Float
* **Units:** degrees (°)
* **Column Name:** `cocking_phase_shoulder_horizontal_abduction` (despite the column name, this metric is shoulder abduction, not horizontal abduction; the column name will be corrected in a future release)
* **Measurement:** Abduction angle of the dominant shoulder (relative to the trunk) at the [Max Shoulder ER](https://docs.uplift.ai/biomechanics/activities/tennis/events/max-shoulder-er) event
* **Optimal Direction:** Middle — moderate values are optimal

## Description

Cocking phase shoulder abduction measures how far the dominant upper arm is raised away from the side of the trunk at the [Max Shoulder ER](https://docs.uplift.ai/biomechanics/activities/tennis/events/max-shoulder-er) event. It reflects the arm slot of the cocking position ahead of acceleration.

## Normative Ranges

Percentile distributions by competition level from the 2026 Q2 dataset; the optimal range spans the 25th–75th percentiles. High School and College samples are not yet available. See [Tennis Overhand Serve: Normative Ranges](https://docs.uplift.ai/biomechanics/activities/tennis/tennis-overhand-serve-norms) for the full tables.

| Population | Optimal Range (25th–75th) | 10th | 25th | 50th | 75th | 90th |
| - | - | :-: | :-: | :-: | :-: | :-: |
| Youth | 75 – 98 ° | 68 | 75 | 87 | 98 | 102 |
| Professional | 93 – 104 ° | 88 | 93 | 98 | 104 | 109 |
| Broad (All Levels) | 86 – 101 ° | 72 | 86 | 95 | 101 | 107 |

## Use Cases

* Cocking phase mechanics
* Shoulder loading assessment
* Injury risk screening


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