A new and surprising study has shown that taking “time off” from training could produce unexpectedly positive results. If followed by appropriate re-training, the time off won’t diminish your fitness as much as you might have imagined. It could even make you a better runner in several important ways.
This unforeseen result increases what little we know about seasonal layoffs. It comes from a case report of a veteran 53-year-old triathlete,
The paper1Romuald Lepers, Mater, A., Assadi, H., Nadège Zanou, Gremeaux, V., & Place, N. (2024). Effect of 12 weeks of detraining and retraining on the cardiorespiratory fitness in a competitive master athlete: a case study. Frontiers in Physiology, 15. https://doi.org/10.3389/fphys.2024.1508642 concludes that, after re-training, the subject’s VO2 max improved beyond its prior level. Thus: “The masters athlete reached and even exceeded his baseline level of cardiovascular fitness.”
This measure–a higher VO2 max–is often a direct link to faster race times. However, the subject’s running economy and muscle mass “remained slightly depressed.”
When Scientists Become Their Own Experiments: Test Thyself First
The paper falls into a classic category of scientific advances wherein researchers use themselves as subjects in threatening experiments.
Everyone has heard about Marie and Pierre Curie exposing themselves to radiation in the 1890s. Ninety years later, runner-researcher Mel Williams blood-doped himself and found that he could run significantly longer. Williams’s work eventually led global authorities to ban blood-doping.
In the recent report, French physiologist-triathlete Romuald Lepers volunteered to stop training for 12 weeks. During that time, he did only 60 minutes of walking per week, and a little core work.
Lepers underwent a variety of body, performance, and muscle enzyme tests before de-training, after de-training, and again after 12 weeks of re-training.
The 12 weeks of de-training produced predictable results: He gained weight and body fat, while his aerobic fitness and running economy declined. He also lost muscle mass.
Prior to the layoff, Lepers had been training roughly 11 hours a week for 30 years. This gave him a cardiovascular fitness level in the 95th percentile vs other men his age. He competed in many triathlon championships including the Ironman World Championships.
The Remarkable Powers Of Re-Training
After de-training for 12 weeks, Lepers started a 12-week re-training period. He began slowly, and progressed gradually, aiming to avoid injury. As a result, his re-training period included less total mileage and less intensity than his regular program before de-training.
Despite this conservative approach, Lepers’s body and fitness changed in some remarkably positive ways. He lost weight (vs baseline), lost body fat, and increased his VO2 max.
These results would indicate that he was in better running shape than before the experiment. He lost muscle, mostly in the upper body, which was unlikely to diminish his running performance.
The paper concluded that “Twelve weeks of de-training boosted the physiological effects of training during the re-training.” In other words, de-training primes the body to improve rapidly once you begin re-training again.
Indeed, an accompanying article2Zanou, N., Gremeaux, V., Place, N., & Lepers, R. (2024). Cardiovascular and muscular plasticity in an endurance‐master athlete following 12 weeks of detraining and retraining: a case study. JCSM Communications, 7(2), 82–90. https://doi.org/10.1002/rco2.93 in a different journal concluded: “Re-training not only increased mitochondrial proteins but also glycolytic proteins all above baseline, likely improving skeletal muscle metabolism.” This suggests a broad improvement in how muscles process energy.
The Ups And Downs Of De-Training And Re-Training
The table below summarizes some of the key body and performance measures that changed when Lepers stopped training for 12 weeks, and then completed a 12-week re-training program.
Summary: He lost weight and body fat; lost some muscle (mainly in the upper body); improved his VO2 max; and had a decrease in running economy.
| BASELINE | AFTER DE-TRAINING | AFTER RE-TRAINING | |
| Body weight, lb. | 163 | 167.4 | 160.8 |
| Body fat % | 10.1 | 13.3 | 8.7 |
| Fat free mass, lb. | 147.2 | 142.6 | 145 |
| VO2 max (mL/kg/min) | 62.0 | 56.2 | 65.8 |
| RE @ 12k/hr (mL/kg/min) * | 186 | 227 | 219 |
* With running economy, the lower the number, the better.
Questions & Answers With The Researcher-Subject
In this section, Romuald Lepers explains what it was like to be the subject in this study, and what was learned from the experiment.
What is the most important message in this de-training study?
Athletes should not hesitate to take a training break when they feel physically and/or psychologically tired. You will lose some fitness, but you will be highly motivated to retrain.
In the past 25 years, I had never taken a break longer than two weeks. But now I believe I should have taken at least a one-month break each year.
Why did you volunteer for this case study?
I am a university physiologist and have been an active triathlete for 30 years. One summer, I read a scientific paper about de-training. Afterwards, I realized that I had never stopped training for more than two weeks–except for one month with a minor foot fracture.
So I decided that I would take a three month break after my next triathlon season. As a physiologist, I wanted to turn this into a personal case study with my colleagues where we would test everything we could.
Do you think de-training periods might be helpful in terms of major tissue recovery, and hence injury prevention?
It depends on the person. As I get older, I listen more and more carefully to my body. Now, I don’t hesitate to stop running when I feel even a small pain. Fortunately, as a triathlete, I can still swim and cycle.
However, if you train more than your body can handle, de-training is definitely an option to consider. The real question is always: How much is too much?
This study doesn’t tell us anything specifically about two weeks of de-training, or four or eight weeks. Do you have any thoughts about varying lengths of de-training and re-training?
There’s an adage that says, after a period of de-training, it takes twice as long to regain the same fitness level. This proved to be basically true in my case. But the process wasn’t linear. After three months of re-training, I’d say I reached about 80% of my previous level.
For my next de-training experiment, I think I’ll try stopping for a shorter period–maybe one month or two months. I definitely don’t want to go three months without training again. It was too long!
If veteran athletes want to try a de-training period, what would be your advice to them? Would you suggest they do at least minimal leg strengthening work? Or something else?
I would suggest stopping all training for one month. Do a couple of easy walks per week, and some core training. Of course, strength-training should be an essential part of a masters athlete’s routine, as I learned from a recent Hyrox experience.
I only recently discovered Hyrox events, and really enjoyed them. I realized that incorporating specific strength exercises (burpees, lunges, wall balls, etc.) into my training—in place of some cycling and swimming—had a positive impact on my running. I felt stronger on my feet.
I am now convinced that strength training should be an important component for master athletes. I knew this before, but I hadn’t really tested it. Now, I have proof.
What Can Runners Learn From This Paper?
#1: Don’t fear taking time-off.
You won’t lose as much fitness as you think, and you might come back fitter and faster. This paper didn’t look at injury-prevention or mental freshness, but all runners understand their importance. And they might be enhanced by “time off” periods.
#2: Be slow and patient when re-training.
Start at no more than 50% of your previous weekly mileage, and at a slower pace. Progress gradually from there, taking up to six weeks to reach your previous training level.
#3: Your VO2 max will likely return faster than your running economy.
Take this into account when planning the time you need to prepare for future races.
#4: Consider doing some lower-leg strength training during a time-off.
This could help maintain your leg strength, and speed your return to peak fitness when you retrain.
If you are looking for a strength routine to get started, check out our guide:
