Sunday, January 12, 2025

Take 12 Weeks Off And Come Back Stronger?

Consider the following scenario. You have trained well and have just taken part in the Swimrun World Championships. You then take 12 weeks off from training. You resume training again for 12 weeks and tests show your VO2 max levels exceeded those just before you took 12 weeks off

Too good to be true? Can a long break be that good for you? 

A French exercise physiologist and triathlete Romuald Lepers agreed to take 12 weeks off deliberately (for the sake of science) and allowed himself to be tested. With his colleagues' help, he underwent a whole bunch of tests straight after he competed in the World Swimrun Championships in 2022. After that he rested for 12 weeks and the tests were repeated. He then resumed training for 12 weeks and repeated the same tests. 

The results were published in 2 different journals last year showing what happened when you lose and then regain fitness, raising a possiblity that perhaps a long training break is actually good for you.

The first published article documents Leper's changing fitness. After 12 weeks of rest, his VO2 max measured in a treadmill running test dropped by 10.9 percent. In a similar test on an exercise bike, it dropped by 9.1 percent. That's a big drop equivalent to about 15 years of normal aging. For reference, Edward Coyle's famous paper from 1984 saw a 16 percent drop in VO2 max after 12 weeks of laying off training.

Here's the surprising good news. He gained 5.5 pounds of fat and lost 4.6 pounds of muscle during the 12 weeks rest. After retraining, he lost 9 pounds of fat and regained 2.4 pounds of muscle. His body fat levels  went from 10.1 percent to 13.3 percent then to 8.4 percent. A net loss of 5.7 percent at the end of the experiment. 

Cycling VO2 max levels
After 12 weeks of training again, his VO2 max did not just recover, it was better than before he stopped training (5 percent higher). The running test was 4 percent higher than before. In the cycling test it was 6 percent higher (pictured above). 

The fat loss will explain some of the improvement in his VO2 max as it is calculated relative to body weight, so losing weight can create the 'illusion' that you get fitter without changing your oxygen processing abilities. However, his overall oxygen processing capacity did improve, independent of his weight.

Another possibility documented in the second published journal is that something changed in his muscles making them more responsive to training. Lepers had muscle biopsies (ouch - they are very painful!) at each stage to measure the chemical changes occuring. Fast twitch muscle activity was ramped up during detraining while aerobic capacity and mitochondria function decreased. Retraining mostly reversed those changes and in his case resulted in better than baseline muscle properties.

Now, Lepers is an accomplished triathlete. In his younger days he placed in the top 150 at The Hawaii Ironman World Championships. At the time of the study, he was 53, training 10-12 hours a week and consistently placing near the front in his age category in Ironman 70.3 races. Lepers has trained consistently for more than 3 decades, and never missed more than 2 weeks of training at a time previously. 

Sounds good so far? Leper's results also seem to line up, declining with detraining and impoving to be even better with retraining.  If you're in your 20's, you can take 12 weeks off, train hard again and definitely regain your fitness and more. This case study suggest the same can be true in your 50's.

Note that this is just a case study, where n=1 where we may not get the same results as Lepers. This is different as missing 12 weeks through injury since you may not be able to start training full on especially if surgery was needed.

So here are the not so good bits if you read both articles in detail. Leper's cycling efficiency went down and his running economy worsened. He did not recover the muscle mass he lost and that is worrying (note to self : need to maintain strength training). Fortunately for him, his race results in the following season with similar with the previous season. Actually I thought that was remarkable given the fact that he took 12 weeks off.

I really liked Leper's experiment since I am in the same age group as him. Many of my older patients and friends take shorter and less frequent breaks from training because they are afraid they will lose their fitness from too long a break. I am definitely in the same boat. Now we can all be less paranoid about taking long breaks from training. Even if I do not get better than before, just the fact that one can get back to your previous level is reassuring enough.

Reference

Lepers R, Mater A, Assadi H et al (2024). Effect Of 12 Weeks Of Detraining And Retraining On The Cardiorespiratory Fitness In a Competitive Master Athlete: A Case Study. Front Physiol. DOI: 10.3389/fphys.2024.1508642.

Zanou N, Gremeaux V, Place N and Lepers R (02024). Cardiovascular And Muscular Plasticity In An Endurance-Master Athlete Following 12 Weeks Of Detraining And Retraining: A Case vStudy. JCSM Comm. 7:82-90. DOI: 10.1002/rco2.93.

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