There are some hypotheses about what causes W' to recharge and what happens when we expend all our W'. Once you've expended all of your W', it's game over, you blow up and you're done for the time being. All the energy that would go into recharging your battery is going to power your performance. So it follows that if you burn your battery up, and then continue to perform just below your CP/FTP, your battery will recharge VERY slowly. Unfortunately, the recharge is slower than you think, especially the harder you work UNDER your CP/FTP. Once you let off the gas and drop below your CP/FTP, your battery begins to recharge. He has suggested that each effort above CP/FTP causes your battery to drain a little bit. Skiba has likened W' to a battery in the past. Everything above that line would represent W'.Īs a clearer description, Dr. Everything below that black line would be considered aerobic work that can go on for a LONG time. Although this represents an effort during a workout, it perfectly illustrates W'. If you look at the chart above, you'll see a black line drawn through the power curve. For the purpose of this podcast, we'll consider CP and FTP to be the same since they are numerically quite similar.Įssentially, W' is a measure of energy, specifically a measure of Anaerobic Work Capacity, or how much anaerobic effort an athlete can put out before fatiguing to exhaustion. It is similar to functional threshold power, but there are a few differences on the physiological level.

Critical Power, or CP for short, is essentially the power a muscle can provide without fatiguing significantly. He describes W' as the amount of work (in joules) that an athlete can perform ABOVE their Critical Power.

Goldencheetah cp chart interval