Update 12/12/14 - Another look at at the Training Peaks Performance Management Chart in this article, "How Tinkoff-Saxo Manages Fitness and Fatigue Over the Season."
One of the best features of Training Peaks is the analytical software, the pick of the litter being the Performance Management Chart (PMC). The algorithm plots workout activity over time using a sliding scale, taking into account the activity type (swim, bike, run, etc.), intensity, and duration, and uses these data points to estimate the athlete's training load and training stress balance (fatigue). The idea is that the more an athlete trains the stronger they get, while at the same time the more fatigue they feel. Progress requires balancing training stress with recovery. Workouts tear down tissue. Rest signals the body to go into repair mode and, provided the necessary nutritional building blocks are available, the repairs will increase the strength of the damaged parts. Done right, these opposing forces do not quite cancel out, producing a gradual improvement.
This "result" line is called the Chronic Training Load. In a properly designed training plan the CTL line will wander up and down in response to alternating hard and easy workouts, but it should show an overall upward trend on the way to the goal, typically the athlete's "A" race. Typically an "A" race is followed by some recovery time, so the CTL line should fall. In fact, to be at peak performance the fall should begin just before the race, with training stress balance at a high point.
I have been paying particularly close attention to my PMC during my marathon training, because I designed my own plan. Now that I am in taper I took another hard look, and was puzzled why my CTL has not gone up much since the started my plan back in July. This is easy to see from the Century Ride on, a time when I really should have been improving. (Click on the chart below to see a larger version).
That looks much better. A nice gradual increase in CTL from mid-August. And what is all that stuff going on last winter (left third of the chart)? That is my build up to the Hapalua Half Marathon. That is a picture perfect build.
Notice how the blue CTL line is a lot lower during my marathon training? That is by design. Remember, my training plan is supposed to move a lot of the endurance training from the run to the bike. Now take a look at this year's bike data:
During my Hapalua Half Marathon training I did not ride much; there is one big spike for Sharon's ride, but after that I rode just enough to be ready for the Honolulu Triathlon; I focused much more on swimming for that.
It appears to me that the long Sunday bike rides that began in late July offset and smoothed out the run effort. As the runs increased in intensity, the bike rides held back. The run data taken alone shows a nice progression. When combined with everything else the progress is not as apparent. I interpret this as success in that the bike was supposed to reduce the run training volumn, and all you have to do to see that is to compare my build up to the Hapalu to my build up to the Honolulu Marathon.