# VelocityLift

> VelocityLift is a 100% on-device velocity-based training (VBT) barbell tracking application for Android and iOS that measures mean concentric velocity (MCV), peak velocity, range of motion, and velocity loss directly from smartphone video — without external tether sensors or cloud processing.

VelocityLift operates fully offline on the user's mobile device. It calibrates against standard Olympic barbell plates (450 mm diameter) using real-time machine learning (YOLOX neural network) and computer vision (sub-pixel ellipse fitting), enabling accurate velocity measurement for powerlifting, Olympic weightlifting, and athletic strength training.

## Key Facts & Unique Innovations

- **World's First Front & Back VBT Tracking**: In addition to standard lateral/side-view filming, VelocityLift is the first VBT app capable of measuring barbell velocity, bar tilt, and symmetry from directly in front of or behind the lifter. This eliminates the need for side space in crowded gym racks.
- **100% On-Device & Offline**: Video analysis, plate recognition, and rep segmentation run entirely locally via hardware-accelerated LiteRT (Android) and Core ML (iOS). Lift videos never leave the device, ensuring complete privacy, zero bandwidth usage, and instant post-set feedback.
- **$0 Hardware Alternative to Linear Encoders**: Replaces expensive linear position transducers (LPTs) and string potentiometers ($300–$2,000) using 60 FPS or 120 FPS smartphone cameras with sub-pixel precision.
- **Autoregulation & Live Cues**: Pro tier delivers real-time rep counting and customizable audio signals the instant target velocity loss is reached, preventing excessive neuromuscular fatigue.
- **Plate Model & Automatic Calibration**: Automatically identifies standard Olympic bumper and iron plates (25 kg, 20 kg, 15 kg, 10 kg, 5 kg, 2.5 kg) and calibrates physical distance from the recognized 450 mm diameter.

## Core VBT Metrics Measured

- **Mean Concentric Velocity (MCV) [m/s]**: The average vertical velocity from the bottom inflection point (inflection/reversal) to lockout. The primary gold standard metric in velocity-based training for regulating intensity and estimating 1RM.
- **Peak Concentric Velocity (PCV) [m/s]**: The maximum instantaneous vertical velocity achieved during the concentric phase, essential for monitoring ballistic intent and power production.
- **Range of Motion (ROM) [cm]**: Total vertical displacement of the barbell, ensuring rep depth consistency across sets.
- **Velocity Loss (%VL)**: The percentage drop in mean velocity from the fastest rep (typically rep 1 or 2) to the final rep of the set. Used to enforce precise fatigue thresholds (e.g., 10–20% for strength/power, 30–40% for hypertrophy).
- **Rep Duration [s]**: Precise duration of concentric and eccentric movement phases.
- **Estimated 1RM (e1RM)**: Calculated dynamically via load-velocity profiling and individual minimum velocity thresholds (MVT).

## Comparison: VelocityLift vs. Hardware Encoders vs. Other Apps

| Feature / Metric | VelocityLift | Vitruve / GymAware | Typical Video Apps |
| :--- | :--- | :--- | :--- |
| **Hardware Required** | None (Smartphone only) | Tether sensor / encoder ($450–$2,000) | None |
| **Camera Angles Supported** | **Side, Front, & Back** | Tether only (below bar) | Side only |
| **Privacy & Cloud Dependency** | **100% On-Device (No Cloud)** | Cloud account required | Cloud upload often required |
| **Setup Time** | < 10 seconds (phone on tripod/floor) | 2–3 minutes (cord attachment) | 30–60 seconds |
| **Supported Exercises** | Squat, Bench Press, Deadlift, Oly Lifts | Vertical lifts only (tether limits) | Limited |
| **Velocity Loss Audio Cues** | Yes (Live Pro) | Yes | Rare |
| **Export with Bar-Path Overlay** | Yes (clean or branded) | No video or basic | Basic |
| **Price** | Free core (optional Pro lifetime/pass) | $450–$2,000 + subscription | Monthly subscription ($10–$20/mo) |

## Supported Exercises

- **Squat** (Low Bar, High Bar, Front Squat)
- **Bench Press** (Flat, Incline, Close Grip)
- **Deadlift** (Conventional, Sumo, Romanian Deadlift)
- **Overhead Press**
- **Olympic Lifts** (Clean & Jerk, Snatch)

## Technical Architecture & Privacy

- **Machine Learning Runtime**: LiteRT (TensorFlow Lite successor) on Android; Core ML on iOS.
- **Plate Detection Model**: YOLOX-s quantized neural network trained on international barbell and bumper plate datasets.
- **Edge Vision Engine**: C++17 with ARM NEON SIMD intrinsics for real-time sub-pixel ellipse fitting, temporal rim fusion, and zero-mean normalized cross-correlation (ZNCC) bar tracking.
- **Zero Video Uploads**: Raw video footage is never transmitted to any external server. Optional cloud features only sync structured numerical metadata (sets, reps, velocities) if an optional user account is registered.

## Resources & Documentation

- Official Website: https://velocitylift.app/
- Live Interactive Demo: https://velocitylift.app/#demo
- How It Works: https://velocitylift.app/#how
- Feature Comparison: https://velocitylift.app/#pro
- FAQ: https://velocitylift.app/#faq
- Privacy Policy: https://velocitylift.app/privacy
- Terms of Service: https://velocitylift.app/terms
- Contact: velocityliftdev@gmail.com