🏃 Strava Cheater - Activity Modifier

Modify your Garmin activity files to simulate different performance levels. Change activity speed, adjust timestamps, and re-import into Garmin Connect or Strava.

Disclaimer: This tool is for testing, training simulation, and educational purposes only. Do not use to artificially boost your public activity records on Strava or Garmin Connect.

📋 Features

• ✅ GPX File Support - Adjust timestamps to simulate faster/slower activities
• ✅ TCX File Support - Full support including cadence adjustments
• ✅ Speed Multiplier - Precise control over activity speed changes
• ✅ Detailed Output - View before/after duration and speed changes
• ✅ Error Handling - Graceful handling of missing or invalid files
• ✅ Easy Integration - Re-import modified files into Garmin Connect or your device

🚀 Quick Start

Installation

# Clone the repository
git clone https://github.com/snmslavk/strava-cheater.git
cd strava-cheater

# No dependencies required! The script uses only Python standard library.
# Tested with Python 3.7+

Basic Usage

# Increase speed by 10% (activity completes 10% faster)
python modify_activity.py activity.gpx --speed 1.1

# Decrease speed by 20% (activity takes 20% longer)
python modify_activity.py activity.tcx --speed 0.8

# Save to custom output file
python modify_activity.py activity.gpx --speed 1.15 --output my_modified_activity.gpx

📖 How It Works

GPX Files

1. Parses all trackpoints from the GPX file
2. Calculates the original activity duration
3. Computes new duration based on speed multiplier: new_duration = original_duration / speed_multiplier
4. Adjusts all trackpoint timestamps proportionally
5. Saves the modified file

TCX Files

1. Parses all trackpoints from the TCX file
2. Adjusts timestamps (same as GPX)
3. Bonus: Proportionally adjusts cadence values to simulate faster/slower movement
4. Saves the modified file with all metrics updated

Example Output

🔄 Processing GPX file...
📍 Speed multiplier: 1.1x

✅ GPX file modified successfully!
📁 Original file: my_run.gpx
📁 Modified file: my_run_modified.gpx

⏱️  Duration changes:
   Original: 00:30:45
   Modified: 00:27:54
   Time saved: 00:02:51

🏃 Speed multiplier: 1.10x
📊 Effective speed change: +10.0%

🎉 Done! You can now import 'my_run_modified.gpx' into Garmin Connect or your device.

🎯 Speed Multiplier Reference

Multiplier	Effect	Use Case
0.8	20% slower	Simulate easier pace
0.9	10% slower	Simulate recovery run
1.0	No change	Keep original
1.1	10% faster	Simulate faster pace
1.2	20% faster	Simulate hard effort
1.5	50% faster	Simulate sprint

📥 Getting Your Activity Files

From Garmin Device

1. Connect your Garmin device to your computer
2. Navigate to: Garmin/Activities/
3. Copy the .fit file to your computer
4. Convert .fit to .gpx or .tcx using:
   • Garmin BaseCamp
   • FitCSVTool
   • Online FIT converter

From Garmin Connect

1. Go to Garmin Connect
2. Find your activity
3. Click the download icon (⬇️)
4. Select "GPX" or "TCX" format
5. Save the file

From Strava

1. Go to your activity on Strava
2. Click "Export this activity"
3. Choose "GPX" format
4. Save the file

💻 Advanced Usage

Batch Processing

Process multiple files:

for file in *.gpx; do
  python modify_activity.py "$file" --speed 1.1
done

Chain Multiple Modifications

# First increase speed by 10%
python modify_activity.py activity.gpx --speed 1.1 --output activity_v1.gpx

# Then increase by another 5%
python modify_activity.py activity_v1.gpx --speed 1.05 --output activity_v2.gpx

TCX-Specific: Adjust Only Cadence

Since TCX files store cadence, modifications will adjust it proportionally:

• Speed 1.2x: Cadence increases by 20%
• Speed 0.9x: Cadence decreases by 10%

📤 Re-importing Modified Activities

To Garmin Connect

1. Go to Garmin Connect
2. Click "Import Activity" button
3. Select your modified .gpx or .tcx file
4. The activity will appear in your feed with updated metrics

To Your Garmin Device

1. Convert .gpx/.tcx back to .fit using BaseCamp or converter tool
2. Connect device to computer
3. Copy file to Garmin/Activities/
4. Sync with Garmin Connect

To Strava

1. Go to Strava
2. Click the "+" button → "Upload Activity"
3. Select your modified .gpx file
4. Choose activity type and details
5. Upload

⚙️ Technical Details

Supported Formats

• GPX: GPS Exchange Format (XML-based)
• TCX: Garmin Training Center XML format

Timestamp Adjustment Algorithm

The script applies proportional time adjustments:

for each trackpoint:
    proportion = (trackpoint_time - start_time) / total_duration
    new_time = current_time - (time_adjustment * proportion)

This ensures smooth, realistic time distribution throughout the activity.

What Gets Modified

✅ Modified:

• Trackpoint timestamps
• Activity duration
• Derived metrics (speed, average pace, etc. - calculated by Garmin/Strava)
• Cadence values (TCX only)

❌ Not Modified:

• GPS coordinates
• Elevation data
• Heart rate data
• Temperature
• Other sensors

🐛 Troubleshooting

"No trackpoints found in GPX file!"

• Your GPX file may be corrupted or empty
• Try exporting the activity again from Garmin Connect or Strava

"Trackpoints don't have time information!"

• The GPX/TCX file is missing timestamps
• This typically means it's an unsupported format variant
• Try converting with official Garmin tools

Import fails in Garmin Connect

• The file structure might have been corrupted
• Verify the file can be opened with a text editor (should see XML)
• Try exporting from the device again and re-modifying

Speed multiplier seems incorrect

• Remember: multiplier is inverted for time
  • 1.1x speed multiplier = activity takes 1/1.1 = ~91% of original time
  • Duration decreases, but speed multiplier increases

📚 Examples

Example 1: Make a training run look like a race

# Original: 10 km in 60 minutes (10:00/km pace)
python modify_activity.py training_run.gpx --speed 1.25

# Result: 10 km in 48 minutes (4:48/km pace)

Example 2: Simulate a recovery run

# Original: 5 km in 30 minutes (6:00/km pace)
python modify_activity.py hard_run.gpx --speed 0.85

# Result: 5 km in 35 minutes (7:03/km pace)

Example 3: Convert and compare performances

# Create multiple scenarios
python modify_activity.py my_run.gpx --speed 0.9 --output scenario_slower.gpx
python modify_activity.py my_run.gpx --speed 1.0 --output scenario_original.gpx
python modify_activity.py my_run.gpx --speed 1.1 --output scenario_faster.gpx

# Compare all three by importing to Garmin Connect

⚠️ Important Notes

1. Ethical Use Only - Use for testing, training simulation, and analysis
2. Don't Cheat Public Records - Artificially boosting public activities is against Strava/Garmin terms
3. Backup Original - Keep your original activity file as backup
4. Device Sync - Re-imported activities might get flagged as "manual" entries
5. Privacy - Only modify your own activities

🛠️ Development

Requirements

• Python 3.7+
• No external dependencies

Project Structure

strava-cheater/
├── modify_activity.py      # Main script
├── README.md               # This file
└── .gitignore              # Git ignore file

Contributing

Feel free to fork, modify, and improve this project!

📄 License

MIT License - Feel free to use for personal and educational purposes.

🤝 Disclaimer

This tool is provided as-is for educational and personal use. Users are responsible for:

• Using it ethically and responsibly
• Not violating Strava/Garmin Terms of Service
• Obtaining necessary permissions for activity data
• Backing up original files before modification

The authors accept no responsibility for misuse or damages caused by this tool.

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Happy training! 🏃‍♂️🚴‍♀️🏊‍♂️