T-Score (TSS) , CTL , ATL and TSB explained by Today's Plan

What does T-Score mean?

E.g. 123 This value is a calculated score used to objectively measure rides completed with power data. The formula takes into account both the ride intensity and duration. If you are working to a plan, then a session will have a target T-Score – in which case you need to ride to both the specified duration and intensity to reach the desired goal. Generally speaking, a T-Score of 30 would be an easy hour recovery ride, 120 would be a solid 2 hour training ride, and 300 would be a massive Sunday epic.

 What is CTL? Chronic training load is a way of objectively measuring your general fitness. It is the long term, daily T-Score average of your rides. ie your daily T-Score average over a long period of time. To increase your CTL you are doing (on average) rides with a higher T-Score – this can be performed through either longer rides or more intense rides. CTL is a great way of tracking your overall fitness.  

What is ATL? Acute training load is a way of objectively gauging your current training load. It is the short term, daily T-Score average of your rides. ie your daily T-Score average over a short period of time. When compared with your CTL, you can see if you are currently riding above or below your long term average. By comparing your ATL and CTL you can track if you are building or recovering, and the comparison between the two values gives your TSB or freshness score.

 What is TSB? The training stress balance is really a freshness score. It is calculated simply by comparing your CTL to your ATL. A negative number will indicate you have been doing “harder” rides then your long term average. Harder could be either in duration or intensity. When your freshness score is negative you will likely feel tired and fatigued. In contrast a positive score indicates you are doing less load then your long term average. This is what you want for a taper or recovery period. In these periods you should start to feel refreshed and ready to knock out a personal best.

Today's Plan explains :Load and Performance charts CTL; ATL ; TSB

CTL/ATL/TSBLoad and performanceRider load tracking over time

The load and performance chart allows the rider or coach the ability to track chronic training load CTL, acute training load ATL and training stress balance TSB over selected time periods. CTL is really another way of looking at the rider’s current fitness level. CTL is derived from the weighted average of the last 42 days of the riders T-Scores. Correct ramp rates in terms of CTL build are different for individual riders, for some a ramp rate of 5 points/week may be achievable for a period of time during the base phase of a program. For others a 2-3 point rise will be enough without leading to declining performance and potential sickness. ATL is the weighted average of the last 7 days of the riders T-Scores. ATL is really a representation of the riders current fatigue level. A ride with a large T-Score will create a load and stress on the body that could take several days to recover from. This is represented by a sharp increase in the ATL line on the Load and Performance Chart. During periods of heavy training with consecutive hard day’s ATL will rise rapidly. TSB is the rider’s current CTL minus their ATL. TSB can be considered a riders freshness or fatigue indicator. Over time patterns and correlations between the interaction of CTL and ATL can be observed that can help distinguish the optimal TSB for an individual riders best performances.

When a rider has developed a high CTL and therefore fitness it doesn’t mean they are ready to race. The past weeks or months of training could have left the rider in a negative TSB and with a level of fatigue. By reducing the load in terms of ATL to below the current level of CTL a TSB rebound will occur. This rebound in TSB into a less negative or positive level will represent freshness and race/event readiness. For some riders this level of freshness TSB will be different for specific races. For a one day endurance race or event a simple trend of increasing TSB rebound can be enough to elicit a strong performance. This could see the riders TSB move from -20 to +1 or 2 and a strong performance will follow. For others this may not be enough rebound and this will depend on the length of time at or in the fatigued state and level of CTL. For stage races or very short intense efforts it may be necessary to allow for a larger TSB rebound and give away a little more fitness to be fresher. The accumulative days of racing or longer events will drive the TSB of a rider down and therefore coming into the event with a more positive TSB will allow the rider to better handle the load over the time/duration of the event. This might see the rider look to start the event with a TSB of +15 – 25 to elicit optimal performance over the coming race or event days. By toggling into the Load and performance chart the various performance and fatigue ratings from the rider in terms of peak W/kg, stress metrics such as sleep and fatigue patterns a greater understanding of the individual and their ability to handle load can be observed.

Certain trends can be seen that can help the rider or coach with selections for races and who in the team is handling the load and those that are not. Things to look for could be trends in poor sleep and high ramp rates for CTL as this could be a sign that the athlete is not handling the load and needs a small break to recover.