Some potentially useful links I have found whilst reading up on power:
From Freil’s Blog:
http://www2.trainingbible.com/joesblog/2009/03/wko-q.html
TSB = Training Stress Balance. This is often referred to as 'form.' It has to do with the athlete being rested before a race (or not). It may also help us to understand when the athlete is moving toward overtraining as a result of overreaching, which is necessary to achieve high goals. When well rested TSB is positive or at least trending strongly positive. When not 'on form' TSB is very negative and/or trending strongly negative.
CTL = Chronic Training Load. Referred to as 'fitness,' this is a marker of one's training stress over a long period of time, such as 6 weeks. The higher the CTL the higher the athlete's fitness. It indicates that the athlete can handle higher stress levels. Stress (workouts) are the reason we train as it produces adaptation which we call 'fitness.'
TSS = Training Stress Score. This is the heart of the system. The athlete's TSS is calculated for every workout by measuring intensity and duration. Intensity is measured relative to the athlete's Functional Threshold Power (FTP) which is the highest average power the athlete can maintain for 1 hour.
ATL = Acute Training Load. I call this 'fatigue.' It is the athlete's short term, rolling-average TSS. It is generally averaged over a 7-day period.
http://www.midweekclub.ca/powerFAQ.htm#Q1
http://www.midweekclub.ca/articles/coggan.pdf