What is TSS and Why Should I Use It?

Training Stress Score (TSS) is a way of expressing the workload from a training session. It is the product of the workout’s intensity and duration.  As either of these increases, TSS also increases. Training Stress Score (TSS) is a composite number that takes into account the duration and intensity of a workout to arrive at a single estimate of the overall training load and physiological stress created by that training session. By definition, one hour spent at Functional Threshold Power (FTP) is equal to 100 points. Using Training Stress Score(TSS) you can find out just how hard your workout really was, track your fitness over time, and now predict your future levels of fitness. More and and more training devices are now implementing TSS scores as a measured metric, included in workout data.

For more information on TSS scores: 

http://support.trainingpeaks.com/personal-edition/training-stress-scores.aspx 

Coming Next: How to add TSS scores to your Weekly Summary