High Training Stress Score (TSS) is the only way to become a faster cyclist, right?

This can be true in many cases, but it’s largely dependent on the types of stress, when you apply it, and how well you manage it.

A lot of people get hung up on the numbers. And that’s not to say it’s a bad thing. Data is informative, but if used incorrectly can also be misleading. In a data-filled discipline like cycling, it can be hard to not get wrapped up in the numbers.

In this discussion, our aim is to clarify why comparing certain metrics can be misleading. In doing so, we’ll explain why certain types of training leads to particular trends in TSS. We also intend to dispel why comparing TSS from rider-to-rider is a mistake. The truth is that TSS is not comparable unless your physiology and rate of recovery are the same, and you’re consistently doing the same workouts as the rider you’re comparing yourself to.

Factors that Define Your Training Stress Score

TSS is a function of five things: workout duration (in seconds), Normalized Power, Intensity Factor, Functional Threshold Power and the number of seconds in an hour. The problem many athletes run into when boiling everything down to TSS is that not all TSS is made equal. In other words, TSS from one type of training means different things for your fitness and has differing effects on your body than another type of training. Your TSS total can be different depending on those forms of training while still being equally meaningful for your fitness. This explains Coach Chad’s most recent Sweet Spot Base training plans update.

Inherently built into the TSS equation is proportional weight on the unique composition of a workout. Inherently built into high-intensity interval training are shorter workouts with greater intensity. Presumably, the factors within TSS will increase with HIIT to create a TSS number equal to that of any other type of training.

It actually doesn’t always turn out that way. For example, you can have a 30-minute workout that’s super intense with an IF of over 1 but a low TSS. You can also have a 120-minute workout that is low intensity with a low IF but ends up with a higher TSS. What gives? Which workout is more beneficial for your training purposes?

That depends on your training goals and the system you’re trying to prompt adaptation within. Long story short: TSS, IF, and duration gives us the context we need to understand how a particular workout influences your body and training. Like any metric, TSS can’t stand on its own.

Comparing TSS

It’s critical to understand that the two types of workouts mentioned above will stress different systems in your body that need to be managed in different ways (e.g. 800 TSS at 60% FTP vs 400 TSS at 120% FTP and less time). Long-duration, low-intensity training exerts less strain on the body, hormonal imbalance, muscle damage, nutritional requirements, need for recovery, etc., than higher-intensity, higher-strain work. But the higher-strain work is a more potent form of training that produces more rapid fitness improvements.

While consistently high TSS can mean a lot of potential for fitness gains within the context of riding, slow for long durations, consistently lower TSS from HIIT can also translate into sizable fitness gains. But again, you have to manage the stress and may not have the ability to pack on the slow, long-distance miles that will attribute to a TSS score some coaches recommend.

The balance lies in following a training approach that best suits your time availability, how well you recover, and how much you want to train. Even TrainerRoad’s Sweet Spot Base plan can produce a high amount of stress inside a 5-hour training week, whereas it might take 15 hours of something like the Traditional Base plan (endurance work) to leave you with an equal or nearly equivalent level of stress.

Considering TSS is based on FTP, it’s clear why comparing TSS from one rider to another can be problematic. Furthermore, every riders’ physiology is different — rarely will athletes recover at the exact same rate. Even with similar FTPs — unless you’re doing the same training volume and workouts — comparing TSS is a crapshoot.

Note: If you’ve been tacking on loads of outdoor miles and notice a decline in TSS as you enter the indoor training season, don’t be overly concerned. Considering the different attributes to TSS scores, you can still be getting stronger despite a decline in weekly TSS.

Final Thoughts

While TSS scores are vitally important metrics for training, it doesn’t always tell the full story or clearly depict the type of work a rider might be doing to achieve their individual fitness goals. This is the reason TrainerRoad’s structured workouts and training plans are strategically designed to prompt meaningful adaptation relevant to your goals and endurance discipline. Take a look at them for yourself.

For more cycling training knowledge, listen to the Ask a Cycling Coach — the only podcast dedicated to making you a faster cyclist. New episodes are released weekly.

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Nick Kanwetz

Nick Kanwetz is a writer of all things cycling. Whether he's creating content, interviewing coaches or digging through studies, he's doing it all to make sure you become a faster cyclist and all around better athlete.