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Long-term stress cycles are important to consider in recovery and adaptation.
At the end of this article, there’s a breakdown of one way to incorporate rest throughout a year for a hypothetical athlete chasing their potential. Even assuming no serious injuries or layoffs, it adds up to 86 days resting each year. That seems like a lot, right? This article breaks down why resting 23% or more of the days in a year can support long-term growth.
The exact number isn’t important (it can be higher or lower), just the general principle: Adaptation happens in the empty spaces.
Let’s work through the logic of how consistent rest adds up for adaptation.
In March, I wrote an article on the science and theory of why breaks often lead to breakthroughs. The next day, I received a wonderful email, likely from the same type of person that reminded the teacher that they forgot to assign homework. “Given that breaks are good, do you plan long breaks for athletes you coach?”
This A-student caught me in a contradiction just when I was trying to get home for happy hour. While breaks are nothing to fear, I rarely plan extended breaks and long off seasons without specific stress-related reasons. I’m not a total hypocrite, though (just a partial one, when no one is watching). What gives?
It gets back to the main reasons that long breaks can be helpful.
The nervous system and endocrine system have some weakly-understood inflection points that work over weeks and months rather than days. For example, a 2018 article in the journal Hormones found that male distance runners training over seven hours a week had around a 10% reduction in testosterone levels after one year of training and over 30% reduction over five years training. A 2020 study on 21 high-level male athletes found that three months into the season when training levels were highest, testosterone levels dropped significantly, before rebounding when volumes were reduced.
While the relationship is more complicated for female athletes due to hormone fluctuations during the menstrual cycle, a 2019 article in the International Journal of Sport Nutrition and Exercise Metabolism reviewed the literature on low energy availability, finding that it could suppress sex hormones. Self-reported menstrual cycle dysfunction is as high as 60 percent among elite middle- and long-distance runners. And even without menstrual-cycle changes, hormone fluctuations are often measured in athletes across studies. For male and female athletes, the role of long-term, chronic exposure to cortisol from heavy training (and life stress) can wreak havoc.
A 2014 review in Current Sports Medicine Reports laid out the stakes: push too hard for too long and “the insidious onset of OTS (overtraining syndrome) slowly saps the efficacy of recovery times.” Wait to rest, and it may already be too late.
The nervous system acts similarly. Overtraining syndrome is a good case study, involving a series of dysfunctional adaptations to excessive training and inadequate fueling, with major nervous system impacts. A 2021 study in the International Journal of Sports Physiology and Performance found that a 12-week training reduction and increase in caloric intake could reverse some of the impacts of OTS in male athletes. In both male and female athletes, the stakes are high when it comes to balancing stress and rest. A 2014 review in Current Sports Medicine Reports laid out the stakes: push too hard for too long and “the insidious onset of OTS slowly saps the efficacy of recovery times.” Wait to rest, and it may already be too late.
Hard training is like putting the pedal to the metal in a car.
It’s fine, usually, in moderation, particularly when it’s 11:58 PM and the Taco Bell drive-through is a mile away. But keep the pedal down there too long, and the engine might sputter even if the car can avoid going into the nearest ravine. The endocrine system and nervous system act like the engine, ready to handle the stress as long as they’re not overloaded for too long.
The tricky part is what we mean by “too long.” Here is where individual response variation is so key. From seeing tons of elite athlete blood work over time, it’s clear that some athletes have endocrine and nervous systems that can withstand almost anything, like Monster Trucks in short shorts. Other athletes are more like Ferraris, able to push really hard, but also able to do damage and require a trip to the shop if pushed too much.
Independent of recovery and health, consistent rest is essential to avoid injuries and stagnation.
Most injuries start as something so minor that it barely even registers—a bit of inflammation around a bone, some frayed muscle fibers, a tendon with a weak strand. The hard part is that injuries are almost never isolated for lab study at that stage. An athlete might take a rest day or two and forget they ever had an issue. Conversely, an athlete might train through a small pain that erupts into a stress fracture, torn muscle, or ruptured tendon. Prophylactic rest can prevent athletes from needing a punch card at their nearest MRI joint, along with all the frustration that comes with it.
But what interests me most is how all of these elements combine to create the cellular-level context for long-term adaptation.
The body doesn’t know miles. It knows stress.
It’s possible to adapt through sustained high stress, particularly for athletes with anomalous genetics, but most need to take a step back to fuel a leap forward. Adaptation happens in the empty spaces.
A 2016 case study in the journal Physiological Reports showed what a perfect-world stress-balancing equation might look like. At a training camp for elite German runners, researchers took daily measurements of oxygen saturation of hemoglobin, resting heart rate, body mass, body and sleep perception, and capillary blood concentration of creatine kinase. Every other day, they measured venous serum concentration of blood urea nitrogen, venous blood concentration of hemoglobin, hematocrit, and blood-cell counts. If two or more values showed abnormal deviations for that individual athlete, then training load was reduced.
It worked. Running economy improved for those athletes on a strict load-management routine, and “no athlete showed any signs of underperformance, chronic muscle damage, decrease body and sleep perception as well as activated inflammatory process during the 21 days.” The athletes got faster because they felt good, which is the key takeaway in a culture that is permeated with the idea that you have to push until you feel bad to validate the work you are doing.
Building rest into the year prevents the runaway train effect of stress from taking hold of the endocrine system, nervous system, and/or musculoskeletal system. Plus, I think there’s a good argument that it’s the only way to progress over many years without burnout or regression outside of athletes that are genetic outliers or dopers. Here are five guidelines to consider when it comes to resting for performance.
One: Take at least one rest day every week
BYU has a powerhouse running program, exemplified by their women’s cross country team, which just won the national championship. While there are tons of reasons for their success, from wonderful coaching to badass athletes, one element that may be relevant is the prevalence of a weekly rest day. On Sundays, many BYU athletes don’t run (though that may be overstated, it’s tough to know exact training for most athletes). That doesn’t prove rest is needed, but it does add more evidence to the pile when it comes to rest not being a bad thing, even if it means fewer weekly miles.
I like to call the weekly rest day an “adaptation day.” The adaptation day (guidelines for activity here) can be once a week, once every 10 t0 14 days, or even twice a week for athletes with more stressful life contexts. Do the work, don’t chase the seven-day totals to satisfy ego, and let the body use the stress to reach new heights. Plus, it’s a great time to nap and eat your weight in nachos.
Two: Rest for three days at the first sign of any small potential injury
Something I have never heard in coaching: “Gosh, I wish I just didn’t take those three days off when my shin started hurting.” I am thinking of starting a store that sells a vacation-themed T-shirt for athletes that are forced to take six to eight weeks off that says “I Limped A Few Miles For Three Days And All I Got Was This Stupid Stress Fracture.” It’s better to be 99% too overprotective than 1% too underprotective. When in doubt, rest. And for all that is good in this world, please don’t poke it.
Three: Sprinkle extra rest on harder training cycles
The 2014 review in Current Sports Medicine Reports had one of my favorite lines ever: “Athletes and coaches understand the importance of rest days, but the insidious onset of OTS slowly saps the efficacy of recovery times so the athlete is no longer able to reach previously attainable goals.” Read that slowly, while clapping, for full effect. In other words, take too long to rest, and it may already be too late. Resting when you feel good (like the weekly rest day) helps you feel better. Resting extra when you start to feel bad for more than 24 to 48 hours helps you avoid a cellular-level sh*tstorm, while also supporting any longer-term bounce-back adaptation.
Four: Rest plenty after races and hard efforts
Hard races are the ultimate supercompensation stimuli, pushing many cells and systems in your body in new ways. Some empty space after races allows for the supercompensation adaptation to take hold, while avoiding negative impacts from the long tails of that level of major stress. In practice, almost every case of long-term regression I have seen (particularly in ultrarunners) involves races being stacked with training being stacked with races. It’s rarely the hours of the race, but the lack of recovery in the days and weeks after the race (or overtraining going into it). I like the general guideline of one to two days per 10 miles raced.
Five: Consider a short off-season, but no need to make it too long if resting throughout the year
Put it all together, and I like athletes to avoid planned offseasons of a month or two, simply because it’s not needed if we’re training sustainably the whole time. A week or two after the final hard race or effort is usually plenty because there is so much rest built in throughout the year. Let’s break it down for a hypothetical pro athlete racing consistently, staying healthy, and training for peak performance.
A rest day every week = 52 days of rest
A few rest days here and there for small injury scares = 9 days of rest
An occasional bonus rest day based on stress levels and unforeseen circumstances (like a vaccine shot) = 5 days of rest
Mini-rest blocks after hard races and efforts = 20 days of rest
That’s 86 days of rest! That seems like a lot, right? Especially for a pro athlete?
Let’s reframe it. That’s 23% of the year spent adapting to hard work.
Stress without rest and adaptation can become self-destruction. Consistent, strategic rest is a chance to become a highly-adapted athlete. And highly-adapted athletes can accomplish dreams that seem impossible.
David Roche partners with runners of all abilities through his coaching service, Some Work, All Play. With Megan Roche, M.D., he hosts the Some Work, All Play podcast on running (and other things), and they wrote a book called The Happy Runner.