TSS – Training Stress Score – helps quantify the cumulative stress of your triathlon training to keep you progressing without overtraining.

As triathletes, we love to train. Often, the more training we can squeeze into a busy week, the more satisfied we feel. But without a metric like TSS to manage our workload, it can be all too easy to keep pushing without the rest that’s needed to allow our muscles to compensate for the training load and grow stronger.

By keeping an eye on Training Stress Score, we can get a clearer picture of when more is more and when it’s time to recover – helping us stay on the path of progressing fitness and avoid overtraining.

How Is TSS Calculated?

Developed by power training gurus Andy Coggan and Hunter Allen, TSS was first created for cycling and is calculated using Normalised Power (terrain-compensated average power), Intensity Factor (percentage of your Functional Threshold Power as a decimal) and your session duration.

The outcome of the formula is that an all-out effort sustainable for one hour is worth 100 points so sessions under an hour are always less than 100 TSS while longer workouts could be lower or higher based on intensity. If you’re training with power on the bike, TSS is calculated automatically in Training Peaks and is also available through other platforms like Garmin Connect.

But what about other sports? Though Coggan himself has been known to state that TSS is for cycling only on forums, triathletes need to take into account other types of activities. This can be achieved through a few other TSS-derived metrics developed by the Training Peaks team.

Running accumulates rTSS. This is calculated by taking into account run duration, your threshold pace and the session’s pace and elevation data. Meanwhile, sTSS provides a similar score for swimming based on your moving duration, distance and threshold swim pace.

There’s also hrTSS, which is employed when there’s not enough data for the above metrics to be calculated and is generated through heart rate data and threshold heart rate.

How To Use TSS Data

So what do you do with all this TSS data? Well, as your training volume or intensity steadily increases over days and weeks, so will your TSS. By keeping an eye on these daily and weekly figures and listening to your body, you can learn how much TSS you can handle before becoming fatigued and needing recovery. This gives you a good baseline for both the TSS you’re trying to accumulate and a way to judge increased fitness as your body adapts and you can handle higher weekly TSS scores without burnout.

If you’re on Training Peaks premium, much of the guesswork is relieved by the Performance Management Chart, which gives a simple graph overview of your TSS, current fitness level (called Chronic Training Load) and fatigue (called Acute Training Load).

This allows you to view the relationship between all these factors. So, a training camp would likely see all three spike, requiring recovery time afterwards to reduce fatigue. Meanwhile tapering for a race by reducing TSS will see a slight drop-off in fitness but a drastic reduction in fatigue as you freshen up for the big day, ready to put in your best performance.

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Triathlon Vibe is the home of triathlon training advice for beginner to expert triathletes. From sprint to Ironman, we share how to swim, bike and run stronger and faster.


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