What is W prime and how can it make me a stronger cyclist

In this image, W prime is represented in the lower left-hand corner, as a percentage of whole. When a cyclist has an intense interval, W prime is depleted. During recovery from the interval, W prime makes a return at a somewhat consistent and well – known rate.


What is W prime?

W prime stands for a physical amount of anaerobic energy every individual has available to them above Critical Power. It is measured in joules and individuals have between 2000 and  28,000 Joules available above Critical Power. 

As you may remember from the previous blog post, Critical Power is the highest average power that an individual can maintain before their energy systems switch over to less efficient methods. When an individual generates power above Critical Power, they may do so over a very limited period of time. When an individual is pedaling below Critical Power, most of the energy comes from aerobic systems, which is the most efficient system in the body. 

Taking both time and intensity into consideration, W prime is the amount of work you can do above your critical power.

For example, look at the pic above.  This person is during an interval at 255% of Critical Power. And interval at 255% will drain your W prime very fast, and will need to be a short interval.   Whereas and interval at 120% will still drain your W prime because it is above CP, but will take much longer to delete it significantly. 

Everyone has a limited amount of W prime, and everyone regenerates their W prime in roughly the same time periods.  There are differences in both genetics and fitness, but now we have the ability to see how we are using our anaerobic capacity in right in front of us during our workout. We can see it being depleted as we are working hard during our interval, and also see its regrowth after the interval, during the recovery period.

The intervals within workouts at CCD are planned taking into account both W prime depletion rates, and recovery rates.

What we are doing in Cycling Performance Class right now.  All of our intervals over the next five weeks will begin with the same 15 minute protocol, which is designed to intentionally reduce a cyclist’s W prime. Once a cyclist is in a fatigued state, we are performing intervals that are longer, but are below Critical Power. The result is a more effective workout, because of the loss in W prime from the first 15 minutes. In most cases, W prime will return to something between 80 and 100%.   I have built intervals in the middle of the workout to once again, tax the anaerobic system and bring W prime back down to a level at or below 50%. Then the second threshold interval begins. This interval is again under Critical Power but still of adequate intensity, and it makes for a highly effective workout.


In this image, the green line indicates the cyclist’s W prime. You can see that with the first three intervals, W prime is reduced, while the longer interval shows that the green line begins to rise again as this person is recovering from the previous anaerobic intervals. As the second set of intervals begin, W prime once again declines, almost getting down to zero, before it rebounds. Working out at or with a reduced W prime, may improve performance because of cellular adaptations that occur during recovery.

We will be increasing the intensity of the intervals in order to witness progression. However, we are not going to attempt to dip too far down into our W prime in the second half of our intervals each day. The reason for this is because the focus for this two-month series is going to be on stamina and threshold intensity.  Threshold intensity is just slightly below Critical Power, thus making it aerobic, but it will be of sufficient intensity and close to Critical Power that it still presents quite the challenge.

Let’s go over the fundamentals:

·W prime is every cyclist’s measured anaerobic work capacity.

·Anaerobic work capacity is measured in joules, which is energy. Most cyclists have between 2000 J and 28,000 J available to them. It can be improved with fitness.

·To acquire W prime, a cyclist needs to perform Critical Power testing (stayed tuned for a more detailed blog on this later for those who have not done it). We peroform Critical Power Testing at Cycling Center Dallas and Online Bike Coach every eight weeks, and it consists of a three minute, eight minute, and 13 minute mean maximal power test each. These are done over two days or more.

·This series of classes, we are intentionally drawing upon W prime early, and then performing long intervals just under Critical Power in order to help improve stamina and rejuvenate that value.

W prime is the most modern way to observe the training dose of any set of intervals. This is exclusive to users of PerfPro studio, and Coach Wharton and Cycling Center Dallas, as well as Online Bike Coach. W prime is just as important as Critical Power. In many ways Critical Power will sometimes not improve, while W prime will improve.  That is especially important if you ride with groups, compete in cycling races, or even if you are going for Strava records over short distances. If your W prime improves,  your ability to handle surges, hills at pace, attacks and  repeated sprints will have also improved.

This is all an effect of specific interval type training, good Coaching, and experience. If you have any questions, or would like to learn more about how to use Critical Power and W prime when cycling outside, contact us for an appointment.

If you have not yet attended a Cycling Performance Class,
check the Class Schedule and sign up today to experience it for yourself! 

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