> ## 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.

# Trunk to Arm Speed Up

> Ratio (multiplication factor) of speed increase from trunk to arm.

## Technical Details

* **Variable Type:** Discrete Metric
* **Data Type:** Float
* **Units:** ratio
* **Column Name:** `trunk_to_arm_velocity_speedup`
* **Aggregation:** mean
* **Precision:** 2
* **Calculation:** Peak arm angular velocity / Peak trunk angular velocity
* **Optimal Range:** 1.7+
* **Typical Range:** 1.64 – 1.99
* **Optimal Direction:** Higher is better

## Description

Trunk to arm speed up measures the multiplication factor of velocity increase from the trunk to the arm, indicating the efficiency of power transfer through the kinetic chain.

## Normative Ranges

Percentile distributions by competition level from the 2026 Q1 dataset; the optimal range spans the 75th–90th percentiles.

| Population         | Optimal Range (75th–90th) | 10th | 25th | 50th | 75th | 90th |
| ------------------ | ------------------------- | :--: | :--: | :--: | :--: | :--: |
| Youth              | 1.89 – 2.10               | 1.41 | 1.57 | 1.72 | 1.89 | 2.10 |
| High School        | 1.92 – 2.12               | 1.50 | 1.64 | 1.82 | 1.92 | 2.12 |
| College            | 2.02 – 2.23               | 1.57 | 1.71 | 1.86 | 2.02 | 2.23 |
| Professional       | 2.13 – 2.60               | 1.64 | 1.75 | 1.97 | 2.13 | 2.60 |
| Broad (All Levels) | 1.99 – 2.21               | 1.48 | 1.64 | 1.82 | 1.99 | 2.21 |

## Use Cases

* Power transfer analysis
* Kinetic chain efficiency