How does W' recover during a race?

W' recharges only when pedaling below Critical Power (sub-CP). According to Skiba's model, the recovery rate is exponential, recharging fastest when coasting or spinning in Zone 1-2.

Updated: August 2026 • Verified v1.2

Cycling FTP & W' Balance Dynamic Battery Calculator

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tau_W = 546 * exp(-0.01 * (CP - P)) + 316; W'_bal(t) = W'_0 - (W'_0 - W'_bal) * exp(-1 / tau_W)

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Understanding Your Results

Displays dynamic W' battery percentage, minimum session battery level, total work above Critical Power (kJ), and real-time Time-to-Exhaustion (TTE).

Practical Guidance & Next Steps

When power drops below Critical Power, W' recharges exponentially governed by the recovery time constant tau_W; staying at low sub-CP intensity accelerates replenishment.

What is this?

A cycling physiology simulator that models anaerobic battery capacity (W'bal) depletion and recovery across variable power workout intervals.

How does it work?

1. Enter your Critical Power (CP / FTP) and W' capacity in kJ. 2. Select a preset workout (Microbursts, Over-Unders, Breakaway) or add custom power intervals. 3. View dynamic battery levels, minimum battery reached, and time to exhaustion at target attack wattage.

Why use it?

Reveals the hidden physiological battery that dictates whether a cyclist can survive hard surges, repeat attacks, and contest sprint finishes.

Technical Scope & Calculation Limitations

Assumes acute non-fatigued state; extreme prolonged endurance rides introduce progressive glycogen depletion and downward drift in W'.

Frequently Asked Questions

W' represents the finite amount of anaerobic work capacity (measured in kJ) available above Critical Power before acute muscle exhaustion forces power to drop.

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