Training Stress Score (TSS)
Training results in stress on your body. Positive adaptations will occur when you are exposed to the proper amount of training stress and recovery.
If your workout produces too little stress, there will be no training adaptation. On the other hand, too much stress or lack of recovery in and between your rides may cause injury, illness, or prolonged recovery needs. Those hard-won gains will disappear with the incorrect amount of training stress.
TSS estimates the amount of stress placed on the body when you work out based on the training intensity and duration. For example, cycling at 100% FTP for an hour is equivalent to a TSS of 100. Training for longer than one hour can result in a TSS greater than 100, even if the intensity is less than FTP.
The formula used to determine TSS in your ride is:
(# of seconds of the workout x Normalized Power x Intensity Factor) / (FTP x 3600) then x 100
How much TSS should I have in my class?
Now that we have a base understanding of the concept of TSS, the big question is, how do I apply it to my classes. It depends. The length of the class and how much variance there is in efforts both over and above FTP will be major factors.
If a rider does a quasi-steady-state effort for a full hour, the TSS for that ride would be 100, whereas a quasi-steady-state 60-minute class at 80% would result in a TSS of 80.
Compared to the above examples, any ride that is less than an hour will automatically have a TSS of less than 100. A 45-minute class done from start to finish at 100% FTP would be 75 TSS. A quasi-steady-state 45-minute class at 80% would result in a TSS of 60.
The above examples are highly unlikely to occur because indoor cycling classes are typically 45-60 minutes long, have a warm-up and a cooldown, and have varying intensity intervals that include recovery.
A general rule of thumb would be that any 60-minute indoor cycling class would be less than 85 TSS, and a 45-minute indoor class would have a TSS that's less than 65.
But every ride can't be that hard. The whole concept of training is to progress intensity while being able to progressively overload all systems and get stronger over time.
As you can see, there's tremendous value in having access to the data and in understanding what that data means. As you become more comfortable with this information, you can see these concepts in action.
In general, based on the knowledge above, as well as the normal profile structure for Indoor Group Cycle Classes and our own experience, we recommend the following guidelines for Indoor Cycling Group Training (60 minutes).
Our guidelines for 60-minute classes
Base training: Go for 55-65 TSS.
Medium to hard: Go for 65-70 TSS.
Hard: Go for 70-80 TSS.
Below are examples of profiles with these three categories!
TSS 58 (note: 55-minute workout):
TSS 67 (note: 55-minute workout):
TSS 71 (note: 55-minute workout):
Many riders tend to focus on what happened in today's ride. It's a tremendous feat to hit your training goals in a single session; however, that is the equivalent of focusing on your diet for one day. A single day of dieting won't make a difference if the next six days are spent gorging yourself into a food coma.
While TSS can be helpful in your long-term training program, there are some things all coaches (and riders) should know:
- Management of exercise volume can increase training efficiency while helping you avoid overtraining. TSS is primarily used to determine the best combination of workouts and recovery over a mesocycle of 3-4 weeks. Therefore, your daily TSS information has limited value unless it's used to determine accumulated stress over a period of time (i.e. a microcycle within a microcycle).
- A training session with a high TSS does not mean high fitness. Subthreshold efforts lasting longer than an hour can result in a higher TSS than a shorter, more intense ride.
- Comparing your rides by TSS can be misleading. Effort type and workout structure are not factored into the calculation. Something as simple as a high cadence ride can increase the stress response if you ride outside your preferred cadence range. TSS doesn't factor in all physiological demands that impact you.
- TSS is only specific to the stress produced in that particular activity. It doesn't account for other stressors like your job, sleep quality, biomechanical issues, inefficiency, impending infections etc.
- The amount of training load that individuals can tolerate will differ. The goal of completing a higher TSS ride should fit within your overall training plan.