How Life Stress Affects Our Training

A hard workout session hits us with two things at once. There's the work we did, meaning the weight on the bar or the distance on our watch, and there's what our body had to spend getting us through it. Much of the time, those two aspects track each other closely enough that the difference never comes up. Then the same workout that felt fine two weeks ago leaves us flattened for three days, and we start hunting for what went wrong with our training.

The common culprits are that we didn’t fuel right, rushed the warm-up, missed a session earlier in the week, or we've gotten sloppy about sleep. Any of those can be true, and maybe one or more of them is actually to blame, but there's a variable underneath all of them that rarely makes the list. Everything our system was already carrying when we started the workout (i.e. stress) can be the sneaky factor that weighs us down.

The Part of Training We Don't Log

For decades, sport science has been building the stack of evidence. External load is the work performed, measured by the sets, the reps, the kilometers, or the minutes on the clock. Internal load is our body's response to that work, and it's the internal side that actually drives improvement. The work is the stimulus; the adaptation is how our body responds. Two near-identical people running the same 10K are doing the same external load and, quite possibly, very different internal ones.

None of that is contested; heart rate, heart rate variability and how hard the session felt all exist as attempts to get at the internal number. What tends to get left out is that internal load doesn't begin when we start moving. Our stress response is already running on whatever the past few weeks have handed us, and the workout lands on top of that rather than on a clean slate.

Why Stress Slows the Rebuild

Getting stronger happens after training, not during it, and the rebuild is an active process that we usually have to pay for. Cortisol, the main stress hormone, is central to how that gets managed; its ordinary job is to free up energy and break tissue down so our body can use it, which is useful during a hard effort and hurtful when it sticks around longer than it’s needed.

The return to baseline after the cortisol response is the part life stress seems to interfere with. When elite athletes were sorted by how many stressful life events they'd been through and then put through an exhaustive exercise test, the high-stress group finished with higher cortisol than the low-stress group, and the difference held for up to twenty hours afterward. Those same athletes were more likely to report detrimental symptoms in the weeks that followed. This is from a small, older study, but the data is still useful in highlighting how long the effects stick around from just a single workout.

Two other experiments using a similar protocol came to the same conclusion. Trained participants were screened for chronic stress and then given an identical workout, and the ones carrying more stress recovered more slowly, both across the first hour and across the next four days. Perceived energy, fatigue and soreness followed the same pattern. Everyone had the same external load, but the internal cost was much different.

What Life Stress Looks Like Outside a Lab

Over a longer timeframe, the effects might show us as progress that doesn't match our effort. A twelve-week program run with 135 people training twice a week found that participants reporting fewer stressful life events improved significantly more in bench press and squat than those reporting more. Everyone was on the exact same program, and other variables, such as nutrition, were similar too.

How does this feel in real-time though? As a general reference, our normal weights we hit feel heavier than they should, our soreness sticks around a little longer than usual, and the workout we'd normally finish and feel hyped up on leaves us slightly hollowed out instead. It’s way too easy to confuse this feeling with detraining or worry that we’re getting lazy, so we often push harder to compensate, which adds load to our system that's already behind, or we slowly start second guessing ourselves. A review of 168 studies on stress and physical activity found that the second response is the more common one, with stress mostly reducing how much people train in the first place.

Two People, One Identical Session

The same workout is a different beast depending on who’s doing it and what they have going on in their lives. The obvious factors that make the workout different for everyone are fitness and training history, but some of it is the state the person was in before they started, which is often ignored. A session that builds one person up can dig a hole for another, and the cause isn’t usually visible on paper.

With all of this said, it's worth being careful about how far to push it. The effects vary by person, the source of stress, and by how long the stress has been running. Still, the impacts are consistent, and psychological stressors belong in the training load calculation. The idea is proven, it just sits awkwardly against the way we actually track training and how our tech measures load.

Nearly everything we can easily measure sits on the external side, so the training plan gets built from the tangible numbers in the physical world. Our mind, which plays a major role in how we perform, we're often guessing at. Two people finishing identical sessions can have paid wildly different prices to get to the finish.

With this in mind, we can upgrade how we think about recovery. It isn't only about what we did in the gym and what we did afterward. It's about what we’re also dealing with outside of training, and whether what we have planned takes this into account.

References

1. Bartholomew, J. B., Stults-Kolehmainen, M. A., Elrod, C. C., & Todd, J. S. (2008). Strength gains after resistance training: The effect of stressful, negative life events. Journal of Strength and Conditioning Research, 22(4), 1215–1221. https://doi.org/10.1519/JSC.0b013e318173d0bf

2. Impellizzeri, F. M., Marcora, S. M., & Coutts, A. J. (2019). Internal and external training load: 15 years on. International Journal of Sports Physiology and Performance, 14(2), 270–273. https://doi.org/10.1123/ijspp.2018-0935

3. Perna, F. M., & McDowell, S. L. (1995). Role of psychological stress in cortisol recovery from exhaustive exercise among elite athletes. International Journal of Behavioral Medicine, 2(1), 13–26. https://doi.org/10.1207/s15327558ijbm0201_2

4. Stults-Kolehmainen, M. A., & Bartholomew, J. B. (2012). Psychological stress impairs short-term muscular recovery from resistance exercise. Medicine & Science in Sports & Exercise, 44(11), 2220–2227. https://doi.org/10.1249/MSS.0b013e31825f67a0

5. Stults-Kolehmainen, M. A., & Sinha, R. (2014). The effects of stress on physical activity and exercise. Sports Medicine, 44(1), 81–121. https://doi.org/10.1007/s40279-013-0090-5