What is W'bal?
W'bal (W Prime Balance) tracks in real time how much of your anaerobic work capacity (W') remains during a ride. W' is the fixed amount of work you can perform above your Critical Power (CP) before exhaustion — typically 15,000 to 25,000 joules for trained cyclists.
During efforts above CP, W'bal depletes at a rate equal to the power above CP. During recovery below CP, W'bal reconstitutes exponentially — faster at lower intensities and slower as you approach CP. When W'bal reaches zero, you can no longer sustain any effort above CP.
W'bal is invaluable for race pacing and interval design. It tells you exactly how many hard efforts you have left and how much recovery you need between them. Coaches use it to design interval sessions that target specific levels of anaerobic depletion, and riders use it in races to decide when to attack and when to sit in.