Zwift TT Power Planner

🎯 How the Planner Works

This planner uses advanced physics modeling (CdA, rolling resistance, gradient) and physiological models (FTP, W' balance) to optimize power distribution across a time trial course. Instead of riding at constant power, the algorithm adjusts your effort based on gradient to minimize total time while staying within your physiological limits.

⚡ What is W' (W Prime)?

W' (pronounced "W prime") represents your anaerobic work capacity—the finite amount of energy above FTP that you can expend before exhaustion. Think of it as a battery:

• Depletion: When riding above FTP, you drain W' at a rate proportional to the power excess (e.g., 300W when FTP=250W drains W' faster than 260W)
• Recovery: When riding below FTP, W' recovers, but recovery rate depends on how far below FTP you are and your training level
• Empty Tank: If W' reaches zero, you're forced to reduce power dramatically (you've "blown up")

The planner optimizes power distribution to keep W' balance positive throughout the effort, allowing strategic surges on climbs while recovering on descents/flats.

🎚️ Key Parameters & Defaults

🔬 Why Accurate Parameters Matter

Garbage in = garbage out. Inaccurate inputs lead to unrealistic plans:

• FTP too high: Plan may deplete W' too quickly, forcing you to back off mid-effort
• FTP too low: Plan will be overly conservative, leaving time on the table
• W' too high: Plan may prescribe unsustainable surges, leading to blow-ups
• W' too low: Plan will be overly cautious, missing opportunities to push on climbs
• Weight/Height wrong: Physics calculations (speed, time) will be incorrect, especially on climbs

Use recent test data (Zwift ramp test, 20min FTP test) and realistic body measurements. The planner can lookup Zwift profiles automatically.

🚀 How to Use the Planner

1. Enter Rider Profile: Input Zwift ID and click "Lookup" to auto-populate name, weight, height, FTP (or enter manually)
2. Select Route: Choose a Zwift route from the dropdown and set number of laps
3. Adjust Power Settings: Click the ⚡ Power menu to set Reference Power, W', and Training Level
4. Generate Plan: Click "Generate Plan" to create the initial pacing strategy
5. Fine-Tune Gradient Power: Click 📊 Gradient to adjust power multipliers for different gradient ranges (e.g., push harder on steep climbs)
6. Auto Optimize (Optional): Click "Auto Optimise" to let the algorithm search for the fastest pacing strategy while maintaining positive W' balance
7. Review Charts: Check the power/speed/elevation chart and W'bal graph. Yellow warnings indicate potential W' depletion issues
8. Open Overlay: Click 📺 Race Overlay to open the dashboard view for following during your ride (shows current interval, upcoming intervals, distance offset, power bias controls)

💡 Pro Tips

• Start conservative: Use Auto Optimise to find the limit, then back off Reference Power by 2-5W for race day safety margin
• Watch W'bal graph: Green = comfortable, yellow = borderline, red = danger zone. Aim to finish with 1-3 kJ remaining
• Course-specific tuning: Use gradient tuning (📊) to push harder on climbs if you're a strong climber, or ease off if you prefer flat power
• Distance offset: On the overlay, use the distance slider to account for variations (e.g., if Zwift shows 2.3 km but plan shows 2.5 km, adjust offset)
• Race day execution: Follow the overlay interval targets, but use power bias (+/-) buttons to adjust on the fly if you're feeling strong/weak