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TRAVELLED TRIATHLETE

Stress is Stress: Why Training Metrics Alone Don't Tell the Whole Story

  • Writer: Rachel Faulds
    Rachel Faulds
  • May 21
  • 8 min read

We’ve all been seduced by numbers. Training Stress Score (TSS), power zones, heart rate -those precious digits that promise to unlock the ultimate training plan or race day fitness. But if you think your training load exists in some hermetically sealed bubble, I’m here to tell you: reality bites harder than your toughest interval (and so can a calf tear).


True story: my worst injuries to date (knock on wood) happened during a couple of really anxious periods in my life—times when my anxiety led to months of persistent insomnia and physical symptoms like a return of eczema flair ups after over 15 years. Instead of dialing back my training, I just kept pushing through like nothing was wrong. We’ve all been there (even when we know better).


A couple of calf tears later, I was reminded the hard way why it’s so important to come back to the basics. Your body doesn’t just track training load. It doesn’t differentiate between intervals on the bike, chronic sleep deprivation, or the emotional weight of an anxious mind. To your body, stress is stress. And it all adds up.


Cyclist in vibrant jersey rides a racing bike past ornate temple. Bright, sunny day with greenery in the background. Number 21 visible.

Photo from Challenge Taiwan

Stress + Rest = Adaptation


Yes, the fundamental formula is true (Banister, 1991). However, your body isn’t a simple machine calibrated to track only your intervals and FTP. Instead, think of your internal physiology as a complex network of competing stress signals -from work pressures and disrupted sleep to emotional ups and downs - all vying for your limited recovery capacity.


Your neuroendocrine system, autonomic nervous system, and immune responses constantly interact, integrating physical training stress with psychological and environmental stressors, affecting your overall adaptation process (Kellmann, 2010; McEwen, 2007).


Ignore this complexity, and you risk more than missing a personal best, you’re flirting with injury and burnout, and honestly, they both suck.



What Is TSS, and Why Do We Use It?


What Is TSS, and Why Do We Use It in Triathlon?

Training Stress Score (TSS) is a way to quantify the total physiological stress of a workout by combining intensity and duration into one easy-to-understand number. Developed by Dr. Andrew Coggan, TSS is widely used in triathlon training platforms like TrainingPeaks to help athletes and coaches manage training load across multiple disciplines-cycling, running, and swimming-and optimize recovery and performance.


Because triathlon involves three very different sports, TSS has variations tailored for each:


  • Cycling TSS (cTSS) is based on power data and measures how hard and how long your ride was compared to your Functional Threshold Power (FTP). For example, one hour riding at your FTP equates to roughly 100 TSS.

  • Running TSS (rTSS) uses pace or power data (if available) to estimate your running stress relative to your running threshold.

  • Swimming TSS (sTSS) uses pace and distance to estimate the training load from your swim sessions.


There are also heart rate-based TSS scores (hrTSS) for when you don’t have power or pace data available, which can help approximate training load from physiological effort.


TSS is incredibly useful for triathletes to balance training load across all three disciplines, but it doesn’t capture the full picture. Life stressors outside of training, like poor sleep, work pressure, or mental and emotional stress—also contribute to your total stress load and affect how well you recover and adapt. The thing is, they don't have a 'numerical score'.



Putting TSS Into Triathlon Practice

For example, if you complete a one hour bike ride at your FTP, that session will score about 100 cTSS. A shorter, higher intensity run might generate a similar rTSS, even though it’s half the duration, because it’s harder relative to your running threshold. Your swim might have a lower sTSS overall but still adds important training stress that your body needs to recover from.


Practical Tip: Use TSS scores from all three sports to guide your weekly and monthly training plans, but always listen to your body. If you’re juggling extra stress outside of training, your recovery demands increase, even if your TSS numbers don’t reflect that. Be ready to adjust your training load or increase recovery time to stay injury-free and maximize performance.



Training Load Is Only One Type of Stress


It’s easy to think of training stress as the main (or only) challenge your body faces. But the truth is, your body doesn’t separate stress into neat categories. Whether it’s the physical strain from your workouts, the psychological pressure from life, emotional ups and downs, or environmental factors like poor sleep or travel fatigue, your body responds to all of it through a shared biological system.


This concept isn’t new. Hans Selye’s foundational work on General Adaptation Syndrome (GAS), back in the 1950s, first described how the body reacts to stress in stages-alarm, resistance, and eventually exhaustion if the stress is prolonged (Selye, 1950). But since then, science has gone deeper. The allostatic load model refines our understanding by emphasizing the cumulative “wear and tear” that chronic stress places on the body’s regulatory systems (McEwen & Wingfield, 2010). Think of your body like a battery. Every type of stress-whether from training, work, or emotional strain-drains your energy. A single intense workout might use a big chunk of power, but ongoing life stress quietly chips away at your charge in the background. If you don’t give yourself enough time to recharge fully, your battery’s overall lifespan and performance will suffer.


For endurance athletes, this means that stress outside of training-like work deadlines, relationship challenges, financial worries, or even environmental factors such as poor sleep or frequent travel-can directly impact how well you recover and adapt to your training. In fact, a growing body of research supports this. A 2021 systematic review by Stults-Kolehmainen and colleagues found that psychological stress impairs muscle recovery and reduces the gains from training, even when the physical workload stays the same (Stults-Kolehmainen et al., 2021).


What does that mean practically? If your nervous system is already taxed by life’s stressors, even workouts that would normally feel manageable become much harder for your body to bounce back from. Your muscles take longer to recover, your performance plateaus or declines, and your risk of injury or illness increases.


So when we talk about “stress + rest = adaptation,” it’s crucial to remember: the stress part comes from all areas of your life, not just your training plan. To truly optimize your progress as a triathlete, you need to manage not only your workouts but also your overall stress load.



The Stress–Recovery–Adaptation Cycle


Training adaptations follow a predictable process:

  1. Stress – Exercise causes physiological disruption.

  2. Recovery – The body repairs damage and restores balance.

  3. Adaptation – Your system becomes stronger, faster, or more resilient.

This model has been a cornerstone of training literature (Bompa & Haff, 2009; Bourdon et al., 2017), but recovery is contingent on total stress load-not just what’s on your TrainingPeaks calendar.


If life stress is high, the body prioritizes survival over performance. And when the system is overwhelmed, adaptation stalls.



Coaching Is More Than Just Workouts


At Travelled Triathlete, coaching is both an art and a science. While we dive into TSS charts and training logs, we also watch for telltale red flags that numbers alone can’t detect:


  • Mood swings

  • Training dread

  • Unexplained aches or pains

Recent research supports this integrated approach. Individual responses to training stress can vary widely, even when external workloads are matched (Kiely, 2018). Coaches must look beyond data to identify signs of under-recovery or burnout.


Because even the most perfect data can’t reveal when you’re mentally fried or emotionally exhausted. The approach blends metrics with conversation helping athletes manage the full spectrum of stressors.


If you’re self-coached, you need to step into that same role. Start by checking in:

  • Are you dragging through sessions that should feel easy?

  • Is your heart rate unusually high at low efforts?

  • Are you dreading workouts you usually enjoy?

This may not be the time to ‘push though’ but rather signals that recovery isn’t keeping up with total stress.



Training Doesn’t Exist in a Vacuum


Trying to isolate training from the rest of your life is like watering only half a garden and wondering why nothing grows.


Work stress, sleep deprivation, emotional exhaustion-they all pour into the same recovery bucket. And when that bucket overflows? Your body hits a wall. You stop adapting. You stop progressing.



Practical Tips to Balance Training Load and Life Stress

1. Track Everything (Not Just Training)

If you are someone who tracks your training, consider keeping track of other things like:

  • Sleep quality

  • Mood and anxiety levels

  • Travel and jetlag

  • Work or personal stressors

Getting a fuller picture of your body’s signals can help you spot stress before it derails your season. And the best part? You don’t need fancy gadgets to do it. I’m super particular about sleep but I don’t wear a watch or any tracking device to bed. Instead, I just check in with myself each morning: How do I feel I slept? Not, What’s my sleep score?

2. Prioritize Sleep Like It’s Your Sport

Sleep boosts recovery hormones, clears brain fog, and repairs muscles (Fullagar et al., 2015). I would say treat it like a workout, but that’s insufficient. Treat it as more important than a workout.

3. Embrace Stress-Reduction Habits — Find What Works for You

Things like mindfulness, yoga, or deep breathing can lower cortisol and speed recovery (Goyal et al., 2014). But the most important thing is to find what works for you.

For example, I find journaling incredibly helpful for managing anxiety and mental clutter. Everyone’s different, though, so please know this is not medical advice, just my personal experience.

4. Adjust Your Training Load When Life Gets Heavy

Don’t be a hero. Dial back your volume or intensity, focus on recovery, and come back stronger.

5. Communicate

Talk to your coach, teammates, or even your dog if they’re good listeners.


Balancing all types of stress is key to sustainable progress and injury prevention in triathlon. Remember: your body only adapts when it has the right balance of stress and rest-and that stress comes from all parts of your life, not just your training plan.




TL;DR – The Whole Athlete Wins

  • Metrics matter, but they’re not the whole picture.

  • Stress is stress-your body doesn’t distinguish the source.

  • You don’t adapt from training; you adapt from recovering from it.

  • High life stress can completely stall physical progress.

  • Individualized, responsive training leads to sustainable success.

Training doesn’t exist in a vacuum and neither do you. The more you embrace that reality, the better your performance (and health) will be.




References

  • Baltzell, A. (2016). Mindfulness and Performance. Cambridge University Press.

  • Bompa, T. O., & Haff, G. G. (2009). Periodization: Theory and Methodology of Training. Human Kinetics.

  • Bourdon, P. C., et al. (2017). Monitoring Athlete Training Loads: Consensus Statement. International Journal of Sports Physiology and Performance, 12(Suppl 2), S2-161–S2-170. https://doi.org/10.1123/ijspp.2017-0208

  • Coggan, A., & Allen, H. (2010). Training and Racing with a Power Meter (2nd ed.). VeloPress.

  • Fullagar, H. H., et al. (2015). Sleep and Athletic Performance: The Effects of Sleep Loss on Exercise Performance and Physiological and Cognitive Responses to Exercise. Sports Medicine, 45(2), 161–186. https://doi.org/10.1007/s40279-014-0260-0

  • Kiely, J. (2018). Periodization Theory: Confronting an Inconvenient Truth. Sports Medicine, 48(4), 753–764. https://doi.org/10.1007/s40279-017-0823-y

  • McEwen, B. S., & Wingfield, J. C. (2010). What is in a name? Integrating homeostasis, allostasis and stress. Hormones and Behavior, 57(2), 105–111. https://doi.org/10.1016/j.yhbeh.2009.09.011

  • Mountjoy, M., et al. (2018). International Olympic Committee Consensus Statement on RED-S. British Journal of Sports Medicine, 52(11), 687–697. https://doi.org/10.1136/bjsports-2018-099193

  • Selye, H. (1950). The Physiology and Pathology of Exposure to Stress. Acta Inc.

  • Stults-Kolehmainen, M. A., et al. (2021). Psychological Stress Impairs Short-Term Muscular Recovery. Sports Medicine, 51(4), 675–692. https://doi.org/10.1007/s40279-020-01394-2


This blog post is based on personal experience and peer-reviewed research. It is not a substitute for individualized coaching or medical advice. Please consult a qualified professional before making major changes to your training or health routines.


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