W' value in CP History

[Russell Brown]

Hi,

I'm a new Golden Cheetah user. First up I want to say thanks for the great software and it being open source. I hope one day I can contribute to it.

My question probably comes from the fact that I don't really understand W'. I'm looking at a chart under "trends" called "CP History". And the W' line is worrying me. Back in April it was at over 15kj, now it is down at 12.5kj. In fact on my CP chart W' is 12.7kj. 

How does Golden Cheetah estimate/calculate my W'?

How do I train it, as I assume higher is better? Back in April I was doing loads of very short, sharp, hard intervals, now I'm doing lots of long, steady, intervals around CP. And racing 1 or 2 TTs a week.

Is it right then that I could (if available) use W'bal for pacing? For example, if W'bal is not steadily declining over the course of a 20minute TT, then I am not going hard enough, right?

I guess in summary, my questions are:

1. W' bigger is better?

2. Why has my CP/FTP/20 minute power gone up but my W' gone down?

3. Is a good effort one that takes  w'bal close to 0?

Many thanks in advance, I do have a back log of reading on W' and CP to get through, but as a distributed systems software engineer, I have a backlog of reading for work to do that is far bigger.

Cheers

Russell

[Mark Liversedge]

On Tuesday, 30 June 2015 10:28:25 UTC+1, Russell Brown wrote:

My question probably comes from the fact that I don't really understand W'.

In the Critical Power Model you have Critical Power that represents the maximal power you can sustain before fatigue sets in. It has been shown to be pretty good for durations of 2-20 mins and breaks down at longer durations since factors that affect fatigue are not taken into account.

In well-trained athletes Critical Power has been shown to be 8-10% higher than key physiological markers like MLSS. It is really important to factor in the contribution from W' when thinking about power durations.

W' represents the amount of work you can do above CP. It was often called your anaerobic work capacity in the past. Many folks consider it to be closely related to fast twitch fibres. The more fast twitch you have, the greater your W'. Where CP is more closely related to your slow-twitch fibres. This is quite an oversimiplifcation but of you read the science section on the goldencheetah.org website you will get more technical info.

I'm looking at a chart under "trends" called "CP History". And the W' line is worrying me. Back in April it was at over 15kj, now it is down at 12.5kj. In fact on my CP chart W' is 12.7kj. 

Depending upon the training you do it is quite common to see W' and CP go up and down. We usually train to improve them, but not all people respond in the same way, and sometimes you end up improving one thing whilsts losing another.

One phenomena that is well documented is fibre "conversion" -- if you focus on endurance and threshold work you will see the ratio of fast to slow twitch change. More slowtwitch are good for endurance and so you may see your CP improve, but at the cost of fast twitch. So W' may reduce.

In terms of training approach you may find an 80:20 split of endurance to higher intensity is a better split (if you aren't doing much high intensity right now). I have seen a lot of threshold training addicts with weak sprints due to their training not physiology and they just focus on TTs and accept they won't win a bunch sprint.

 

How does Golden Cheetah estimate/calculate my W'?

Using a power duration model, check the CP chart video on the website.

 

How do I train it, as I assume higher is better? Back in April I was doing loads of very short, sharp, hard intervals, now I'm doing lots of long, steady, intervals around CP. And racing 1 or 2 TTs a week.

If thats your goal then maybe you don't need a higher W' ? If you are racing TTs then its not neccessary. I would still recommend some high intensity work you avoid falling into a training plateau. Its amazing what a few hard short killer workouts can do (but they hurt!).

 

Is it right then that I could (if available) use W'bal for pacing? For example, if W'bal is not steadily declining over the course of a 20minute TT, then I am not going hard enough, right?

Watch the video on intervals, in the second half there is an assessment of a Hilly TT from last year's Giro.

 

I guess in summary, my questions are:

1. W' bigger is better?

If you need to sprint yes.

 

2. Why has my CP/FTP/20 minute power gone up but my W' gone down?

Fibre conversion and a bit of "neglect" .. but maybe thats a good thing ! 

3. Is a good effort one that takes  w'bal close to 0?

Its certainly hard and really hurts. W' and CP are obviously estimates and not always nailed on. So getting near or past 0 for W' is an excellent sign that you went to your limits !

Cheers

Mark

[Russell Brown]

That's a great and comprehensive answer.

Many thanks

Russell