In order to ensure your training is producing the physiological and psychological benefits you are seeking one must have baseline numbers. This is made possible by putting the body through a series of tests that quite frankly hurt, but are a necessary evil. One must put on the big boy/girl pants and execute this non-exhaustive list of tests below. It is important to note that there are many variations to the tests I mention here, but these are the ones I have taken a liking to:
CSS (Critical Swim Speed)
1000 yd time trial
CP20 (Critical Power)
Lactate Balance Point (LBP)
3 mile VDOT
1 hr TT
For the 2011 season I will be hitting these tests on a frequency range of every 4 to 6 weeks.
As mentioned above, there are plenty of testing options out there. The key is to own the ones you select and commit to them. This will allow you to adjust training zones and validate your progress (regression is not the goal) from month to month.
I look forward to sharing additional data as the season progresses to IML.