I've had this plugin installed in my copy of SportTracks for quite a while now but have only recently realised it's worth. This plugin uses data from your Garmin to give you a record of not only your workout but also how hard you've worked over the short term (ATL), long term (CTL) and how these workout affects your fitness.
Heres a chart of my recent cycling activities to illustrate;
Ok now to explain to the best of my knowledge.
TRIMP (Training Impulse), this is the vertical bars on the chart and correspond to your individual workouts which give a 'score' for your workouts based on time in various heart rate zones. As you get fitter two exact same workouts will have different scores. In the chart above the last two vertical bars are exact same workout based on speed over 1 hour but in my 2nd workout my heart rate had adapted from the previous workout and therefore slightly lower resulting in a lower score indicating an increase in fitness.
Red line is my ATL (Acute Training load). This is a measure of your fatigue and load over a period of the previous 10 days.
The blue area is my CTL (Chronic Training Load). This is an indicator of your fitness and takes into account all of your workouts over the last 45 days or so.
What that means
From the above chart you can see the effects my training had on my fitness starting 7th November when I started the first 3 week Base period of training ending 21st November. The chart shows that my CTL (blue, fitness) moved up 6 points, my ATL (red line) moved up towards 'epic' and then came week 3, a weeks rest where I recovered from the previous 2 weeks and my fitness in the remaining base periods from thereon remained fairly level (a slight dip over Christmas week). However just as I was about to take my training to the next level, I fell over and bust a few bones, This can be seen in the huge dip in my CTL (fitness, blue area) which corresponds with my hip fracture and lack of exercise in the weeks thereafter. Some more little raises as I attempt to get some fitness back, some gaps where I did nothing due to either despondency or after aggravating my hip. You can also see my ATL (red line) increasing as my workouts have increased in firstly length and lately intensity after my fractures. My very recent ATL (red line) tells me that my workouts are increasing in intensity (but not nearly as much as pre fractures workouts) and as result my fitness (CTL, blue) is also increasing in small steps. If I was to stop training this plugin also predicts how quickly fitness will be lost and can be seen in the pale blue area to the right of my last workout.
There's tons more stuff to learn from this plugin, I've just covered the basics. I can see this being of great use not only in viewing how my workouts affect my overall fitness but also I can see if my very recent workouts (ATL, red line) is leading me towards over training or getting close to it so I can back off to avoid illness. Everyone is different in how their bodies tolerate training loads but as most of us do at some point we over train without realising it until it's too late. If that should happen it would be easy to look at your ATL (red line) to see what load we have put on our bodies and take steps to ensure that we do not replicate that training load to avoid over training and possible illness.
I've not gone into the depths of what this plugin is capable of demonstrating, there's tons more but I have explained the basics as I understand it (feel free to correct me if I'm wrong) and how we can tailor our workouts to avoid over training.
A more detailed and dare I say a better blog on this plugin here