Load - Physiological Load ATL - Acute Training Load (aka, freshness) CTL - Chronic Training Load (aka, fitness) TSB - Training Stress Balance (aka, performance)
This chart is a well established standard format to help visualise training for a multitude of sports, with its use in running and cycling very common. A number of running and cycling applications and sites provide various this chart in various guises, often with a name variant, such as 'Fitness & Freshness' in Strava. The TrainAsONE chart tracks 4 data series:
Load - Your daily total physiological load.
ATL (Acute Training Load) - Often termed freshness, this represent the cumulative effect of loading on your body in terms of underlying fatigue. Increase the load, either as a large one-off or repeated small loads, your underlying fatigue increases.
CTL (Chronic Training Load) - Often termed fitness, this represents the cumulative effect of loading on your body and it's ability to 'withstand' further stresses. If you add more load, either as a large one-off or in repeated bouts this figure goes up - it says you're getting increasingly fitter, and can tolerate more load.
TSB (Training Stress Balance) - This is simply the difference between ATL and CTL. The response of CTL to a training load are much slower than that for ATL, i.e. a training load imparts an immediate fatigue response, with a concomitant slow fitness response. During training TSB will negative (with the possible exception of tapering). The often touted figures are -10 to -20 for general training, with intermittent drops as low as -30 'allowed'. However, don't expect to see such figures in TrainAsONE - but that's another whole story... and some of our users think we train them hard! (only joking)
As alluded to above, there are a number of (significant) flaws in the TSB model. The fact that training only reduces performance and never improves it for one! Still, it's often nice to look at, even if the system does not use it in training.