Chronic Training Load (CTL) is generally used to quantify an athlete’s long-term training stress or workload. It is the cumulative effect of training over an extended period. CTL is typically calculated as a rolling average of daily training loads over the past 42 days.
CTL is derived from training volume and intensity. One popular method to calculate CTL is through the Training Stress Score (TSS), a concept popularized by TrainingPeaks. TSS assigns a numerical value to each workout based on its intensity and duration relative to an athlete’s functional threshold.
For example, if you ride for 1 hour at your FTP, that’ workout will generate 100 TSS. Alternatively, if you run for an hour at your threshold pace (e.g.: 6:30min/mi), that would also generate 100 TSS. CTL updates daily by averaging with your prior CTL, weighted over the 42-day window.
Training Balance: Coaches and athletes use CTL alongside Acute Training Load (a shorter-term metric of 7 days) to calculate the Training Stress Balance (TSB). TSB=CTL-ATL. A positive TSB indicates recovery, while a negative TSB suggests fatigue.
