The W’ Balance functions allow you to plan your efforts to ensure you maximise your maximum available work above Critical Power.
What W’ is
Think of your ability to exercise above your Critical Power, your maximum power for 1 hour, as a battery. Go above your CP, you expend some of your battery. Go below your CP you recharge your battery. This is the concept of W’. W’ or W Prime, is also known as Anaerobic Work Capacity AWC.
How quickly you depleat or recharge your battery depends how far from your Critical Power you are. A rider with a CP of 200 Watts who is riding at 400 Watts will depleat their battery far quicker than riding at 300 Watts.
Similarly when they come to recharge their battery, riding at 100 Watts will recharge their battery, however resting at 0 Watts will do so much quicker.
W’ is the work of Dr. Philip Skiba, Prof. Andy Jones, Dr. Anni Vanhatalo, and Weerapong Chidnok.
The W’ Bal chart
The below image shows the warm up, race and cool down of a 10 mile time trial.
The warm up has no intensity above Critical Power. The W’ Balance is at full capacity.
As the time trial begins and I am working above Critical Power the available W’ or the W’ Balance is reduced. Interestingly in this Time Trial, I was severely fatigued by a 100 mile race a day or two before. At a few miles in, I start to hover around my Critical Power. This holds my W’ Bal steady, I am recharging and expending my battery at an equal rate.
From the turn I begin to work above Critical Power. Working above CP reduces the available W’ balance. Then in the final mile, I increase my effort further, this accelerates the expenditure of my battery.
After the race, I coast, stop and at most I soft pedal. This allows the W’ Balance to return quickly to full capacity.
Setting up your Athlete Profile
To activate the W’ features you must add a couple of details to your Athlete Profile.
Critical Power – The athletes maximum sustainable power for 1 hour.
W’ Joules – The available Joules above CP. This is the size of battery that can be expended. You are likely to discover what the W’ is for an athlete by looking at the W’ Bal expenditure of previous best efforts.